[X] My Assistant

[Guest_paulanderson_*]

This is the first source I've come across for this, an interview with Carey Michael Lisse, member of the Deep Impact Science Team and Principal Investigator for the Chandra X-Ray and Spitzer telescope Deep Impact spectrometer results:

http://www.earthfiles.com/news/news.cfm?ID...ategory=Science

Interesting results, including 50% + water ice, limestone-like carbonates and amino acid precursors, just presented at the 9th International Asteroids, Comets and Meteors Conference in Brazil.

[Bob Shaw]

This is the first source I've come across for this, an interview with Carey Michael Lisse, member of the Deep Impact Science Team and Principal Investigator for the Chandra X-Ray and Spitzer telescope Deep Impact spectrometer results:

http://www.earthfiles.com/news/news.cfm?ID...ategory=Science

Interesting results, including 50% + water ice, limestone-like carbonates and amino acid precursors, just presented at the 9th International Asteroids, Comets and Meteors Conference in Brazil.

Paul:

Some of the other articles are, er, 'interesting'. Let's hope the Deep Impact reportage is accurate!

NB, the Carbonates were explicitly described as being the result of a long, cold, watery process - nothing biological there, chaps!

Bob Shaw

[Guest_Richard Trigaux_*]

Paul:

Some of the other articles are, er, 'interesting'. Let's hope the Deep Impact reportage is accurate!

NB, the Carbonates were explicitly described as being the result of a long, cold, watery process - nothing biological there, chaps!

Bob Shaw

The very first data showed hot water. At least 50% of Comet Tempel I is water ice. The spectra also showed carbon dioxide and some yet unidentified organic material like graphite or carbon black. And Spitzer spectral data showed some surprises such as precursors to the aminos in amino acids. Those are hydrogen cyanide and methyl cyanide. Surprisingly, Deep Impact spectra also show carbonate - think limestone; and polycyclic aromatic hydrocarbons (PAHs) - think carbon Bucky Balls and nanotubes. I asked Dr. Lisse about his conclusions so far.

Nobody seriously hoped that their would be life on comets! But the fact is that we are now sure that they contain massive amounts of life precursors. That makes a ground for the theories as what comets may bring organic materials on planets, and even be the main or sole source of it.

There are arguments from looking at Hale-Bopp that the oceans can be no more than 30% to 40% comet-derived.

On the other hand, life precursors could also form on planets themselves, and anyway it is not sure that the complex chemicals brought by a comet may survive the impact. They may rather be burned by the heat or scattered in space. Only simple chemicals like water, cyanides, carbon and carbon oxydes would remain.

So the theory of comets providing organic matter is now possible, but not exclusive of others. For instance on Earth (and also Venus and Mars) there was an massive outgasing of mantellic carbon dioxyd (still going on on Earth) which certainly provided most of the today organic matter.

[Guest_RGClark_*]

Paul:

Some of the other articles are, er, 'interesting'. Let's hope the Deep Impact reportage is accurate!

NB, the Carbonates were explicitly described as being the result of a long, cold, watery process - nothing biological there, chaps!

Bob Shaw

But the key fact is that carbonates require liquid water to form. On Earth everywhere we find liquid water we find life.


Bob Clark

[Guest_RGClark_*]

On the other hand, life precursors could also form on planets themselves, and anyway it is not sure that the complex chemicals brought by a comet may survive the impact. They may rather be burned by the heat or scattered in space. Only simple chemicals like water, cyanides, carbon and carbon oxydes would remain.

So the theory of comets providing organic matter is now possible, but not exclusive of others. For instance on Earth (and also Venus and Mars) there was an massive outgasing of mantellic carbon dioxyd (still going on on Earth) which certainly provided most of the today organic matter.

I wouldn't d say "nobody" believed it. That's the main tenet of the theory of Panspermia. Note that there doesn't have to be current life on comets, just past life.
Note also that if this life only existed on comets early in the solar systems history, complex biological molecules may have decayed after millions or billions of years.



Bob Clark

[volcanopele]

But the key fact is that carbonates require liquid water to form. On Earth everywhere we find liquid water we find life.
  Bob Clark

On EARTH, everywhere we find liquid water we find life. Comet Tempel 1 is nothing like earth and one should be very careful comparing grapes to pumpkins.

[Guest_paulanderson_*]

Paul:

Some of the other articles are, er, 'interesting'. Let's hope the Deep Impact reportage is accurate!

NB, the Carbonates were explicitly described as being the result of a long, cold, watery process - nothing biological there, chaps!

Bob Shaw

Yes, I know, but I do think it is accurate as the quotes are from Mr. Lisse himself and I did hear the broadcast interview itself that this report is based on (Coast to Coast AM) where he is stating these results. I would just say the theory is that the carbonates are the result of a longer, colder process, but this will be debated for some time to come, I am sure...!

Paul

[Guest_Myran_*]

RGClark said; I wouldn't d say "nobody" believed it. That's the main tenet of the theory of Panspermia.

Somehow I just waited for someone to dig up poor old Arrhenius, but he wrote about his theory at a time when nothing was known about cosmic radiation and the charged particles of the solar wind. Precursors of life - yes! Our Suns T-tauri phase most likely cooked up one interesting stew of organic chemistry, but that would have happened in exposed places where they the same time were most exposed at to ultraviolet light (and you scientists can make a much better list than me about cosmic radiation etc than me.) So I view the chanse for life to develop on comets to be infinitesimal.

[Guest_BruceMoomaw_*]

It should be kept in mind that many of the carbonaceous asteroids had large amounts of WARM liquid water in their interiors, mixed with large amounts of complex organic biological precursors, for tens of millions of years -- much longer than the total liquid-water exposure time of the interior of any comet -- but show no sign of evolving life. As Chris Chyba says, that's one indication that the evolution of life may not be as easy and inevitable as is widely assumed nowadays, and it certainly speaks strongly against cometary life.

[deglr6328]

Ughhh I didn't even know that first link's association to THAT radio show until I got halfway down the page! Eeewwwwww, I feel all dirty now.

[Guest_BruceMoomaw_*]

Now, how can you say that? The item on the mystery of large numbers of "mutilated, bloodless kangaroos" being found in Australia was fascinating. If there's a pack of vampire kangaroos hopping around in the Outback, wouldn't YOU like to know about it before camping there?

Meanwhile, Hawaii's Jeffrey Bell tells me he's very skeptical of the carbonate detection, because carbonates aren't being found in the cometary dust particles collected by U-2s from Earth's stratosphere. Question: could vaporized carbonates have been formed on the spot in the very high-temperature gases produced by the Impactor's impact, out of the carbonaceous-chondrite dust and CO2 in the comet? Indeed, could both carbonates and the detected CO2 have been formed out of a quick reaction between the chondrite dust and the oxygen released by the high-temperature breakdown of water ice? (He also tells me that "Linda Moulton Howe... is a regular on the Art Bell show and has a long history of zany pseudoscientific beliefs. Back in the 1980s she pretty much created the modern myth of cattle mutilations by UFOs and/or black helicopters." However, I don't see any obvious BS in her quotes from Lisse, and Paul Anderson tells us he heard Lisse saying the same things in person.)

[Guest_Richard Trigaux_*]

Carbonates does not necessary need liquid water to form. They can also form in volcanoes, and there are several instances of carbnate lavas, in Africa and even in Europe. Carbonate lavas may form from phase separations in magmatic chambers, being not mixible with silicate lavas. I must confess I do not really understant how carbonates may sustain such high temperatures: when you heat limestone, it does not melt, instead it decomposes and form lime and carbon dioxid. Maybe carbonatite lavas are mixtures which melt at about 400-500° without decomposing.

And when we look at Temple II it really looks like a complex body exhibiting layers and varied structures. So it may be a part of a much larger body where many chemical reactions were possible. It may happen that even the coldest bodies in the Kuyper belt or Oort belt may have experienced ennough heat during their accretion to have liquid water inside. BruceMoomaw also have arguments to have some caution about carbonates.

That does not mean life, as life requires a constant source of energy to evolve, even the simplest living being consume high energy food and release low energy wastes. They need a medium with somewhere an energy source. Living beings are thermal machines (more complex, but the overal working of a food chain is that of a thermal machine) so they cannot exist in a medium in thermal equilibrium such as the hot inside of a newly accreted body. At best they could oxyde reactive chemical items, but this could last only a while, when the appearance of life may require millions of years.

Ughhh I didn't even know that first link's association to THAT radio show until I got halfway down the page! Eeewwwwww, I feel all dirty now.

I did not noticed no more. Personnally I am not closed to such matters as UFOs, crop circles and the like, but I must admit that most of the stuff published in these domains are only rumors and baseless statements. An example is that serious amateurs groups never found any real base or witness for the famous and infamous Roswell story. This was published in a french UFO review "Ovni presence" n° 54, on a study from the Centre for UFO Studies from Chicago, in 1989, and an inquiry by the US General Accounting Office in 1994. But what did you heard in the medias? That there was a movie with a Roswel corpse!! The owner of this movie awowed afterward it was fake, but the dollars he earned with it were not fake. So who is to blame? And who has the more reasons to be angry? The ones who try to search for the truth, whatever it is, who often spent years to inquire on baseless stories.

This was just a side remark, I do not intend to start a discution on these topics. Please start another topic if you are interested to reply.

[paxdan]

I've started a thread over in the commmunity section of the website to deal with hoaxing....

[Bob Shaw]

Bruce:

We don't have Art Bell here, I'm glad to say (yes, I know you *can* find him on the WWW if you want, but he's not corrupted the general public here in the UK in the same way as in the US). The trouble with even quite well-meaning people on the fringe is that they tend to have absolutely zero in the way of judgement, and similarly exhibit an inability to tell fun speculation from hard, established fact. It's always sad to see individuals with creative and enquiring (but often, er, 'unformed') minds having their intellectual processes corrupted. So I was rather wary myself of the original carbonate article, once I saw the company it was keeping...

I blame a lack of good (written) science-fiction in adolescence! Or, in my case, too much!

Bob Shaw

[edstrick]

There's a <deleted>-load about comets we don't know..but there's a lot we do know which gives us pieces of the puzzle.

There has never been a meteor photographed as part of a comet's meteor shower that lasted long enough and penetrated low enough into the atmosphere to have been a rock that could have survived entry. Decades ago, shower meteors were described as "having the mechanical strength of cigarette ash".... which makes loads of sense if they're bits of dessicated <well.. devolatilized> cosmic dust-bunnies.

Small comets like a comet Linear a couple years ago can disintegrate all on their own with nothing left other than dissipating dust clouds big enough for Hubble to see. Clearly, those objects don't have melted-and-refrozen slushball cores.

The parent object of the Kreutz <sp?> Sungrazer comets is believed to have been a monster to have split into so many substantial comets... Bigger than Hale-Bopp which was big.... Maybe it had a core that last rounded the sun in Cro-Magnon time and isn't coming back for another 5000 years, but the pieces it broke up into don't seem to have any more guts than Shoemaker Levy did. Kuiper Belt objects 200.. 500 km across proabaly did heat up inside, but how much is model dependent.. and a big unknown in the model is if any of the short lived radio-isotopes in the early solar system were still around when they accreted.

We have almost no idea how fine the ice grains in comet insides are, below any "rind" or "mantle" heated when a comet is in short period orbits. We have almost no idea of vapor transport within the comet.. barely know how volatile some of the ices are since we don't have any real inventory of the volatiles.... the Deep Impact flash data, and the plume data, both from the spacecraft and remote observations are telling us a lot.

Some of the ices may even be explosive. Take simulated Triton surface ices.. Water/Nitrogen/Methane frosts... Irradiate the mix with charged particles, it turns yellow with new compounds..... and it explodes when heated. There are crackpot therories of exploding asteroid/comet parent planets or ice-moons, with electrolytic chemical products in their interior making them timebombs waiting to go off... The theories overall are crackpot, but bits and pieces of them may well be valid. If we ever do get a cryogenic core sample return from a comet's interior, there's lab safety reasons to be sure it stays cold, besides science-value reasons!

[Bob Shaw]

There are crackpot therories of exploding asteroid/comet parent planets or ice-moons, with electrolytic chemical products in their interior making them timebombs waiting to go off... The theories overall are crackpot, but bits and pieces of them may well be valid.  If we ever do get a cryogenic core sample return from a comet's interior, there's lab safety reasons to be sure it stays cold, besides science-value reasons!

Edstrick:

Hey, that's *my* kind of crackpot! Any, er, URLs or whatever (hold your nose when you type!)?

Bob Shaw

[Guest_Richard Trigaux_*]

Some of the ices may even be explosive.  Take simulated Triton surface ices.. Water/Nitrogen/Methane frosts... Irradiate the mix with charged particles, it turns yellow with new compounds..... and it explodes when heated.  There are crackpot therories of exploding asteroid/comet parent planets or ice-moons, with electrolytic chemical products in their interior making them timebombs waiting to go off... The theories overall are crackpot, but bits and pieces of them may well be valid.  If we ever do get a cryogenic core sample return from a comet's interior, there's lab safety reasons to be sure it stays cold, besides science-value reasons!

Not explosive in the common sense of this word. But they could, when heated, say, boil. There is an example of this right on Earth, in the bottoms of the oceans, where "methane ice" can form, a common water ice with methane molecules into the hollows between water molecules. And this stuff can form ices in the bottom of the ocean (and fill pipe lines too). When brough to the surface, this ice-looking stuff melts like ordinary ice, but it boils in the same time while releasing the methane. So similarly such products such as ammonia-water eutectics (In Titan?) could boil when the pressure is released. If there are ice volcanoes (Enceladus, Titan, Triton...?) there could be explosions similar to our lava volcanoes where dissolved gasses drive the lava and project it very violently. But basically all this is just violent outgassing, eventually supersonic, but not detonations with a shock wave and the like.

[edstrick]

"Not explosive in the common sense of this word. But they could, when heated, say, boil."

No.. ... I mean kablooie explode.. there's all sorts of nitrogen double and triple bonds in the radiation induced reaction products and the stuff disassembles itself violently, and I think some lab equipment, as it's warmed up.

Like "Nitrogen-Tri-Iodide", which you can make by soaking iodine grains in household ammonia.. dry the stuff out and it's a contact explosive. Anything bigger than a grain of rice can hurt... big volumes aren't safe even when wet.

<fond memories>

[djellison]

Like "Nitrogen-Tri-Iodide", which you can make by soaking iodine grains in household ammonia.. dry the stuff out and it's a contact explosive.  Anything bigger than a grain of rice can hurt... big volumes aren't safe even when wet.

<fond memories>

VERY fond memories.



Doug

[Bob Shaw]

Not explosive in the common sense of this word. But they could, when heated, say, boil. There is an example of this right on Earth, in the bottoms of the oceans, where "methane ice" can form, a common water ice with methane molecules into the hollows between water molecules. And this stuff can form ices in the bottom of the ocean (and fill pipe lines too). When brough to the surface, this ice-looking stuff melts like ordinary ice, but it boils in the same time while releasing the methane. So similarly such products such as ammonia-water eutectics (In Titan?) could boil when the pressure is released. If there are ice volcanoes (Enceladus, Titan, Triton...?) there could be explosions similar to our lava volcanoes where dissolved gasses drive the lava and project it very violently. But basically all this is just violent outgassing, eventually supersonic, but not detonations with a shock wave and the like.

Methane-Water clathrates are actually fairly widespread on Earth, and are implicated in all sorts of less-than-desirable possibilities, among which are:

- Clathrate layers beneath melting permafrost may release large quantities of methane into the atmosphere, making global warming accelerate

- Oceanic clathrate decomposition may sink ships with no trace (release gas in sufficient quantities on the ocean floor and boats just drop once the density of the medium falls below that of water)

Ah, Thomas Gold, where are you when we need you!

[gpurcell]

Not explosive in the common sense of this word. But they could, when heated, say, boil. There is an example of this right on Earth, in the bottoms of the oceans, where "methane ice" can form, a common water ice with methane molecules into the hollows between water molecules. And this stuff can form ices in the bottom of the ocean (and fill pipe lines too). When brough to the surface, this ice-looking stuff melts like ordinary ice, but it boils in the same time while releasing the methane. So similarly such products such as ammonia-water eutectics (In Titan?) could boil when the pressure is released. If there are ice volcanoes (Enceladus, Titan, Triton...?) there could be explosions similar to our lava volcanoes where dissolved gasses drive the lava and project it very violently. But basically all this is just violent outgassing, eventually supersonic, but not detonations with a shock wave and the like.

My physics teacher made up a batch of this on a sheet of paper. As he was shifting the sheet, it blew...BIG sound, BIG purple cloud of smoke!

[tty]

Methane-Water clathrates are actually fairly widespread on Earth, and are implicated in all sorts of less-than-desirable possibilities, among which are:

- Clathrate layers beneath melting permafrost may release large quantities of methane into the atmosphere, making global warming accelerate

- Oceanic clathrate decomposition may sink ships with no trace (release gas in sufficient quantities on the ocean floor and boats just drop once the density of the medium falls below that of water)

Ah, Thomas Gold, where are you when we need you!

Methane hydrates are indeed widespread on (and in) the ocean floor. It is very likely that the sharp "spike" of very warm climate at the Paleocene/Eocene border was caused by a large methane hydrate "burp".

Here is an image if anyone is interested what the stuff looks like:

www.usssp-iodp.org/ Images/flaming_hydrate.jpg

Methane hydrates are perhaps the most obvious example of a compound that exists on a large scale here on Earth but is unstable at "normal" temperatures and pressures. I am sure the same applies even more to extremely cold/reducing/high-pressure environments elsewhere so I agree that material from e. g. an asteroid or comet must be kept under very carefully controlled conditions both for scientific and safety reason.

An interesting thought: without that "methane burp" 55 million years ago we wouldn't be here. The oldest primates are exclusively North American, but that Paleocene/Eocene spike was warm enough so that primates got across to Europe by way of Canada-Greenland-Svalbard-Scandinavia. In North America primates became extinct long ago but some of those in Europe later migrated to Africa. The rest is history as they say...

tty

[Guest_BruceMoomaw_*]

Unfortunately, Gold's methane-burp theory for ship disappearances just proves again that he had a penchant for unscientific sensationalism -- like his straight-faced theory that the little blobs of glass photographed on the Moon's surface by Neil Armstrong might have been due to a gigantic solar outburst only a few tens of thousands of years ago, and that this might explain the myth of Phaethon. (Or his straight-faced statement shortly before dying that solar sails couldn't possibly work because photon pressure doesn't really exist, although spacecraft have been using it for attitude control since 1964 and it's the only thing that saved Mariner 10.)

We already have a perfectly good natural explanation for some ship disappearances, and IT'S been proven -- SAR satellites have recently proven that 30-meter freak waves (sighted occasionally by surface ships that survived the encounter) really do exist, and in fact are surprisingly common. By contrast, no one seems to have seen a methane burp of any size whatsoever.

[Bob Shaw]

We already have a perfectly good natural explanation for some ship disappearances, and IT'S been proven -- SAR satellites have recently proven that 30-meter freak waves (sighted occasionally by surface ships that survived the encounter) really do exist, and in fact are surprisingly common.  By contrast, no one seems to have seen a methane burp of any size whatsoever.

Bruce:

If you SEE an oceanic burp you're possibly not going to make it back to shore to tell anybody! It's a bit like those 'friendly' dolphins and porpoises who (allegedly) escort lost swimmers back to shore - you'd never hear from anyone who was carefully escorted out to sea instead!

There have been several North Sea trawler sinkings which have happened in good weather, in well travelled seas. The wrecks have been found in good condition, hatches closed etc, on the sea-bed. And considering the amount of natural gas around the near-surface geology in those parts it's probably not even necessary to put forward any of Gold's more outre notions as to the origins of the gas...

The point is, I suppose, that even our own 'stable' environment is subject to a whole range of unexpected but catastrophic changes - just like all the bodies we've looked at which still have any life in them! Well, perhaps not 'life'...

Bob Shaw

[edstrick]

"....By contrast, no one seems to have seen a methane burp of any size whatsoever"

I don't know whether methane blows are enough to sink ships, but several years ago, the Japanese lost a research ship and crew that was investigating the surface roil over a seamount-volcano that was burbling.. My understanding was that it chugged and the ship sank almost without warning in the roil.

[Guest_RGClark_*]

On EARTH, everywhere we find liquid water we find life.  Comet Tempel 1 is nothing like earth and one should be very careful comparing grapes to pumpkins.

Neither is Mars or Europa. But liquid water is the key search point for life on those worlds as well.


Bob Clark

[Guest_RGClark_*]

It should be kept in mind that many of the carbonaceous asteroids had large amounts of WARM liquid water in their interiors, mixed with large amounts of complex organic biological precursors, for tens of millions of years -- much longer than the total liquid-water exposure time of the interior of any comet -- but show no sign of evolving life.  As Chris Chyba says, that's one indication that the evolution of life may not be as easy and inevitable as is widely assumed nowadays, and it certainly speaks strongly against cometary life.

Bruce you should keep in mind that relic life has been claimed to have been present in some carbonaceous meteorites such as the Murchison meteorite.
Also note that some scientists believe comets are the source of carbonaceous meteorites. Strong evidence for this is the large amount of water and organics seen in such meteorites. Another fact arguing strongly in favor of this is that the meteoroids from meteor showers such as the Perseids contain organics and hydrated minerals and we even know the comets these showers stem from.


Bob Clark

[Guest_Richard Trigaux_*]

The stories of ships sunk by methane eruptions is not rumor: there was recently an article in a french science review explaining how it happens, in Northers Sea. You know there are huge gaz deposits there, and some of it slowly leaks through sediments on the ocean floor. AS there are clay layers and sand layers, the leaking is not homogenous, it can form pockets of gas, which can break and left a crater. They were exploring one of these craters, and they were intrigued by a "central peak". They found it was a fisher ship sunken straight on the bottom, still intact. We can imagine a kind of limnic eruption, like the too famous Nyos lake in Cameroun; suddenly the ocean turns red and boils. And, as explained Bob Shaw, the density of the sea lowers (with bubbles of gas) and a ship can sink in some seconds. This is worth the Bermuda triangle story, but with a natural (and frightening) explanation...

There are other parts of the word with undersea mud volcanoes (some are as big a their lava counterparts) emitting enough methane emit flames and even detonate when it reaches the air. Jules Verne described the ones in the Crimea.


The idea of a sun flare large enough to be visible in antic times is not impossible too, although not proven. Many stars emit large flares at intervals, some large enough to roast a Earth-like planet. We do not know why some stars emit large flares and other not, so we cannot be sure that some dis not occured in ancient times, of which ancient myth may remember in their usual symbolic way.


Back to comets, I think all the comets may not have the same history or origin. Some may be loose snow balls; but others may come from the breaking appart of larger bodies, and may thus contain hardened ice, or eventually compounds which formed under pressure, like chlatrates.

[Guest_RGClark_*]

Now, how can you say that?  The item on the mystery of large numbers of "mutilated, bloodless kangaroos" being found in Australia was fascinating.  If there's a pack of vampire kangaroos hopping around in the Outback, wouldn't YOU like to know about it before camping there?

Meanwhile, Hawaii's Jeffrey Bell tells me he's very skeptical of the carbonate detection, because carbonates aren't being found in the cometary dust particles collected by U-2s from Earth's stratosphere.  Question: could vaporized carbonates have been formed on the spot in the very high-temperature gases produced by the Impactor's impact, out of the carbonaceous-chondrite dust and CO2 in the comet?  Indeed, could both carbonates and the detected CO2 have been formed out of a quick reaction between the chondrite dust and the oxygen released by the high-temperature breakdown of water ice?  (He also tells me that "Linda Moulton Howe... is a regular on the Art Bell show and has a long history of zany pseudoscientific beliefs.  Back in the 1980s she pretty much created the modern myth of cattle mutilations by UFOs and/or black helicopters."  However, I don't see any obvious BS in her quotes from Lisse, and Paul Anderson tells us he heard Lisse saying the same things in person.)

Bruce, carbonate HAS been observed in interplanetary dust particles (IDPs):

Carbonate Mineralogy in Stratospheric IDPs: Compositions, Co-Existing Smectite and Comparison to CI Carbonaceous Chondrites.
D. J. Joswiak and D. E. Brownlee, Dept. of Astronomy, Box 351580, University of
Washington, Seattle, WA 98195, e-mail: joswi**@*****.washington.edu, brownl**@*****.washington.edu
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1998.pdf

Perhaps you could do an interview with Lisse to establish the validity of these detections.


Bob Clark

[Guest_RGClark_*]

Carbonates does not necessary need liquid water to form. They can also form in volcanoes, and there are several instances of carbnate lavas, in Africa and even in Europe. Carbonate lavas may form from phase separations in magmatic chambers, being not mixible with silicate lavas. I must confess I do not really understant how carbonates may sustain such high temperatures: when you heat limestone, it does not melt, instead it decomposes and form lime and carbon dioxid. Maybe carbonatite lavas are mixtures which melt at about 400-500° without decomposing.

And when we look at Temple II it really looks like a complex body exhibiting layers and varied structures. So it may be a part of a much larger body where many chemical reactions were possible. It may happen that even the coldest bodies in the Kuyper belt or Oort belt may have experienced ennough heat during their accretion to have liquid water inside. BruceMoomaw also have arguments to have some caution about carbonates.

That does not mean life, as life requires a constant source of energy to evolve, even the simplest living being consume high energy food and release low energy wastes. They need a medium with somewhere an energy source. Living beings are thermal machines (more complex, but the overal working of a food chain is that of a thermal machine) so they cannot exist in a medium in thermal equilibrium such as the hot inside of a newly accreted body. At best they could oxyde reactive chemical items, but this could last only a while, when the appearance of life may require millions of years.
....

Rich, thanks for the info on carbonate lavas. I had not seen that before. As a first guess perhaps it could be the high pressure deep underground allows water to remain liquid to allow carbonate to form. It is notable for instance these lavas, though far above 100 C, are still far cooler than most other lavas.
Actually this info on carbonate lavas may be useful for another idea I'm investigating. Let's just say it involves a very warm place in the Solar System.




Bob Clark

[Guest_RGClark_*]

...
Perhaps you could do an interview with Lisse to establish the validity of these detections.

  Bob Clark

Meaning the Deep Impact Chandra and Spitzer detections.


Bob C.

[Guest_Richard Trigaux_*]

Rich, thanks for the info on carbonate lavas. I had not seen that before. As a first guess perhaps it could be the high pressure deep underground allows water to remain liquid to allow carbonate to form. It is notable for instance these lavas, though far above 100 C, are still far cooler than most other lavas.

   Bob Clark

What I was meaning is that carbonates do not necessary require water to form. Here in the example they form in magmatic chambers. Perhaps there may be other reactions in comets or very cold environments. Pure water cannot be coldest than -10°C at 1000bars of pressure. But water could form eutectics with other products (In a discution I launched about Titan, I was told that ammonia eutectics can be liquid at -100, and brines were found at -50°C in the Antarctic). Even in very cold places like the Oort belt, accreting bodies could reach such temperatures, even for some days, and generate carbonates. There also exist very reactive radicals in interstellar clouds, which, once gathered in a body, may generate reactions and perhaps even heat.

Today there is only one volcano emitting sodium carbonate, the Oldoinyo Lengai, in Tanzania. Lavas are black, water-liquid, with a temperature of 500-540° and usually flow in very narrow channels so that we could walk above a lava flow. After some hours they turn white. Carbonatite ashes are responsible of the many interesting human fossils in this region.

Carbonatite magmas co-exist with ordinary silicate magmas.

Actually this info on carbonate lavas may be useful for another idea I'm investigating.  Let's just say it involves a very warm place in the Solar System.

  
   Bob Clark

... A place where liquid carbonatites may exist permanently?

[Guest_BruceMoomaw_*]

Bruce, carbonate HAS been observed in interplanetary dust particles (IDPs):

Carbonate Mineralogy in Stratospheric IDPs: Compositions, Co-Existing Smectite and Comparison to CI Carbonaceous Chondrites.
D. J. Joswiak and D. E. Brownlee, Dept. of Astronomy, Box 351580, University of
Washington, Seattle, WA 98195, e-mail: joswi**@*****.washington.edu, brownl**@*****.washington.edu
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1998.pdf

Perhaps you could do an interview with Lisse to establish the validity of these detections.
  Bob Clark

Thanks for the tip! And I'm inclined to think it's time I took your advice and talked to Lisse myself.

[Guest_RGClark_*]

...
... A place where liquid carbonatites may exist permanently?

A very warm place in the solar system where liquid water may nevertheless exist.




Bob C.

[Guest_BruceMoomaw_*]

The abstracts from the upcoming "Dust in Planetary Systems" conference are out...
http://www.lpi.usra.edu/meetings/dust2005/pdf/program.pdf

...and they include one (# 4105) in which Cary Lisse goes into more detail about Deep Impact's compositional findings. Hawaii's Jeff Bell has griped to me that this
"lacks all details and numbers ('fine sand' and 'talcum powder' are not
defined terms in planetary geology!). It almost looks like the real
comet scientists on DI are using her as a stalking horse.

"Most of the spectral changes seen in the thermal IR could be due to the
impact throwing out particles of a larger size than the small ones
lifted off by sublimation. This can radically change the strength of
the bands even if the composition is the same."

However, I myself still think it puts more substance into the carbonate claim:

(1) Apparently the spectral evidence for carbonates was a lot clearer than the "surprisingly weak" evidence of PAHs and solid CO2 (although the spectral lines of the latter two are interfered with by the strong silicate line).

(2) The temperature of the ejecta was only about 325 K (52 C), not remotely hot enough to manufacture the carbonates by the heat of the impact itself (as I had suspected).

(3) The failure to see signs of carbonates on the nucleus' surface before impact -- along with the indications of them being dug up from the subsurface by the impact -- may be meaningful, since there's considerable evidence that solar UV may break down carbonates fairly fast. See http://www.nature.com/nature/journal/v379/...FF2B08B318597E8 . (This may also explain the fact -- stated, as Bob Clark has noted, in http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1998.pdf -- that while there are some carbonates in interplanetary dust particles ("IDPs"), they're scarce.)

Also of interest in this conference's papers on comets is #4090, which makes the puzzling statement: "The surface of Wild 2 is appreciably different from the four other cometary nuclei that have been imaged -- Halley, Borrelly and Tempel 1. Tempel appears to be covered with impact craters and presumably retains a significant [portion] of its surface that was exposed in the Kuiper Belt. The remarkably complex and rough surface of Wild 2 is different from the other three comets, probably because of prolonged evolution in the inner solar system." But I thought that Tempel had been in the inner System longer than Wild 2. I still think the flat-bottomed, steep-sided craters on these comets' surfaces are not impact craters, but sublimation pits. It's very easy to see how such pits could form, growing horizontally outwards from an initial small impact crater or vent site as a lag deposit of dust, left behind by ice sublimating off the nucleus' surface, slides down the steep side slopes to expose more and more fresh ice but piles up on and shields the crater's shallower floor slopes.

There are also a few other interesting revelations in these abstracts, which I'll describe in the "Enceladus Flyby" and "What Up With Hayabusa?" threads.

[Guest_BruceMoomaw_*]

Explanatory note on Point #2 above: the low temperature of the ejecta DISPROVES my earlier suspicion that the carbonates had been formed by the heat of the impact itself. If they really do exist, they must have been there before the impact.

[dvandorn]

The only problem I have, conceptually, with the idea of dust lag deposits around vents is that a comet nucleus has an incredibly small amount of gravity. Such that the gas pressure of the sublimating ice would propel any entrained dust well away from the vent site (and likely completely off the nucleus).

I'm truly fascinated by low-gravity surface dynamics. The visual similarities between the low-G surfaces we've seen up close (Tempel 1, Eros) and moderate-G surfaces (Moon, Mars, Earth) has surprised me. I suppose that, given enough time, even very low-G surfaces end up pulling rocks and dust into familiar-looking landscapes...

-the other Doug

[Guest_BruceMoomaw_*]

I doubt that. While a lot of the chondritic dust would be propelled away at the comet's escape velocity, a lot of it WOULDN'T, and would thus fall back upon the comet's surface. (Indeed, a great deal of the dust from the vents must be sprinkled very widely over all the rest of the comet's surface.) But this would happen only on fairly flat surfaces. The steeper the slope, the less erupted dust would fall back onto it -- and, also, the less dust sprinkled onto it by other venting areas would stay there without sliding down to the foot of the slope.

Really, I would be amazed if this selective-erosion phenomenon isn't occurring. It's hard to see how it could NOT happen; it nicely explains those flat-bottomed "craters" on Wild and Tempel (which, I think, are actually gradually growing inside-out mesas); and it's just about the only way to explain the "mesas" on Borrelly and the very steep-sided pinnacles on Wild and (in the close-up views) on Tempel. In fact, most interpreters of Stardust's Wild 2 photos think they've seen one large OVERHANGING cliff on it. You certainly can't explain that through impact.

By contrast, the craters into loose material on asteroid Mathilde -- except for their huge size -- are just the sort of bowl-shaped impact craters we've seen everywhere else; and while we never did get a look at the Impactor's crater on Tempel, lab simulations into powdery material showed a standard bowl-shaped crater getting gouged out there too.

[Comga]

Here's a link to a fun NPR interview with several science team members.
Mostly they talk about NOT seeing the crater form because of all the dust.

http://www.npr.org/templates/story/story.php?storyId=4815934

Soon we should be getting the papers from the meetings last week in Brazil and next month in Cambridge, England.

[The Messenger]

The abstracts from the upcoming "Dust in Planetary Systems" conference are out...
http://www.lpi.usra.edu/meetings/dust2005/pdf/program.pdf

...and they include one (# 4105) in which Cary Lisse goes into more detail about Deep Impact's compositional findings.  Hawaii's Jeff Bell has griped to me that this
"lacks all details and numbers ('fine sand' and 'talcum powder' are not
defined terms in planetary geology!).  It almost looks like the real
comet scientists on DI are using her as a stalking horse.

"Most of the spectral changes seen in the thermal IR could be due to the
impact throwing out particles of a larger size than the small ones
lifted off by sublimation.  This can radically change the strength of
the bands even if the composition is the same."

However, I myself still think it puts more substance into the carbonate claim:

Difficult analysis.

The Lisse article bothered me on several counts: I don't think the presence or absences of complex carbon compounds elsewhere in the universe, as discussed in the article should be a factor used to weigh observational data from a comet. No one knows what the comet is made of: Read and interpret the data.

Notice Lisse also stated that the probe disappeared under a fluffy surface layer, but there is no data supporting this disappearance - as near as I can tell, this conclusion is based upon prior expectations - there is nothing in the article about the presences or absence of copper spectra. Vaporized or buried? Without data to justify the conclusion, for all we know Tempel 1 is made mostly of rubber, and the probe bounced off and is on its way back

Finally, Lisse gave a compositional breakdown of 50% water, 50% 'other stuff'. Other articles have indicated that there was no net increase in water vapor production during the Deep Impact event:

http://www.physorg.com/news5166.html

http://www.planetary.org/news/2005/deep_impact_tcm_0720.html

http://www.universetoday.com/am/publish/sw...act.html?672005

So far, after a set of eight observations each lasting about 50 minutes, Swift scientists have seen a quick and dramatic rise in ultraviolet light, evidence that the Deep Impact probe struck a hard surface, as opposed to a softer, snowy surface.

I think we need clearer, unbiased numerical data before drawing hard conclusions about Deep Impact.

(2)  The temperature of the ejecta was only about 325 K (52 C), not remotely hot enough to manufacture the carbonates by the heat of the impact itself (as I had suspected).

This was the temperature reported ~24 hrs after impact

http://www.on.br/acm2005/visualiza-abstrac...haracterization

Depending upon the particle size, ejecta volume, emissitivity, dispersion, kinetic energy and so forth, the 24 hr temperature varies greatly from scenario to scenario - we need much more information before critically analyzing impact chemistry.

Edit: Universe today quote added

[The Messenger]

Here's a link to a fun NPR interview with several science team members.
Mostly they talk about NOT seeing the crater form because of all the dust.

http://www.npr.org/templates/story/story.php?storyId=4815934

Soon we should be getting the papers from the meetings last week in Brazil and next month in Cambridge, England.

The scientists speaking in the NPR interview are also ignoring, or were unaware of, the 'bright ultraviolet flash'. This is NOT the signature of pudding, but of a very HARD impact. As for the delay between the flash and the "dust explosion", this does NOT require that the probe penetrated deep into the comet. If the probe was literally vaporized on or very near the surface, the radiant energy must first be transferred t the surrounding terrain - no matter the size of the cavitation.

From what I have read, the first dust explosion was highly vertical, and resolution from the near-sighted mother ship low. I can make a good argument for a very small impact crater. We need another look at this comet...maybe in another decade or so, after we have figure out how to proof space lenses. Perhaps a job for - god forbid - space lab?

[Guest_BruceMoomaw_*]

We can already proof space-telescope mirrors perfectly well, if you haven't got negligent boobs doing the job. Jeff Bell says most of the engineers he's talked to expected trouble of some sort when Ball Labs got the contract for Deep Impact, and they were right. (Bell was warning me about this in his E-mails a couple of years before the HRI mirror screw-up.)

[Bob Shaw]

Bruce:

It's probably more of a management process issue than an individual screwing up, but certainly there's no doubt that after an organisation screws up once then it should clearly NOT be allowed to do so again in the same manner - and it appears that certain organisations *have*...

'Fuzzy optics' and 'deconvolved images' should be long-term end-of-mission add-ons after the hardware is well out of warranty, not primary target descriptions., and yet we've seen such all too often...

Bob Shaw

[tedstryk]

We can already proof space-telescope mirrors perfectly well, if you haven't got negligent boobs doing the job.  Jeff Bell says most of the engineers he's talked to expected trouble of some sort when Ball Labs got the contract for Deep Impact, and they were right.  (Bell was warning me about this in his E-mails a couple of years before the HRI mirror screw-up.)

Of course, any engineer with the misfortune of encountering him probably just agreed with him so he would shut up and go away.

[Guest_BruceMoomaw_*]

According to him, Ball Labs' relative incompetence compared to most other aerospace firms has been a legend in the industry for years. After this stunt, it's hard not to reach the conclusion that something might be a wee bit amiss there.

[The Messenger]

According to him, Ball Labs' relative incompetence compared to most other aerospace firms has been a legend in the industry for years.  After this stunt, it's hard not to reach the conclusion that something might be a wee bit amiss there.

Well, optical coatings and any other known cause of lense distortion should pop-up during any and every NASA design specification review. (Somewhere in this process, the use of non-metric engineering terms should have triggered a campaign to rid not only NASA, but the entire USofA of arcane units.) BASIC QC101.

Meanwhile searching on Deep Impact, I came across Hoagland's log (http://www.enterprisemission.com/weblog/weblog.htm), and I was a little angry:

Bruce, I do sound like Hoagland, and what is worse, his take on the Lisse interview is very close to my own: Hoagland has highlighted the same counter-indicative evidence I am having a hard time digesting. He bends the evidence to match his own theory (he ignores spectral bandwidth resolution), but he is correct in questioning Lesse's 50% water release, when other scientist at other telescopes have reported that the net quanty of H20 was unchanged by the impact.

The surprising results of Deep Impact on one comet don't unravel basic theory. Tempel 1 could be a rouge, but the analysis should not be coached into the most supportive interpretation possible of any prior expectations: As near as I can tell, no one was right about Tempel 1.

Edited to admit: I guessed Tempel 1 would be high in METALLIC nickel and iron

[Decepticon]

I just read some of his blog and noticed that his upset with the lack of RAW images from the deep impact mission.

Is this true? No Raw Images made available to the public?

The deep Impact websites has no area containing Raw Images.

[djellison]

Of course, we all know that that's complete rubbish - because people HERE were making composites from the raw imagery put on the DI website.

What he's moaning about is spectral data I assume. But that's just not something joe-public understands and is probably being held back for a Nature / Science special.

Doug

[tty]

Well, optical coatings and any other known cause of lense distortion should pop-up during any and every NASA design specification review.  (Somewhere in this process, the use of non-metric engineering terms should have triggered a campaign to rid not only NASA, but the entire USofA of arcane units.) BASIC QC101.

Can anybody tell me why NASA didn't simply prohibit the use of non-SI units by their contractors after the MCO debacle?

tty

[mike]

I suspect that as the rest of the (metric unit-using) world becomes more and more economically powerful, the US will be forced by simple commercial pressure to switch over to SI units. The Olde World unit system is just too nonsensical to last much longer.. And of course, scientists in general have been using the metric system for quite some time, and guess who discovers all the things that are later used by Jim and Jill Everyperson U.S.A.-- scientists.

[djellison]

At this point - I'm going to register my objection to the use of the phrase "English Units" when describing feet, inches etc.

They are IMPERIAL units.

And you can be damn sure that there isnt an aerospace firm in the whole EU that would dream of using them for a second.

Of course, there is another form of units that NASA uses for describing things - it has 5 different units....Golf Cart, School Bus, 12 story building, Utah, and Continental United States. Anything space related can be expressed as fraction or number of one of these

Doug

[ElkGroveDan]

Of course, there is another form of units that NASA uses for describing things - it has 5 different units....Golf Cart, School Bus, 12 story building, Utah, and Continental United States. 

You forgot the unit of "Manhattan" which came into popular use during the Eros mission.

[djellison]

Ahh yes - Manhattan - and of course there's Volkswagen Beatle as well.

Of course, in the UK we have Phonebox, Double Decker Bus, Nelsons Column, the M25 and Wales

Doug

[dvandorn]

I think that's the new DDU measurement system -- Dumbed-Down Units.

-the other Doug

[Bill Harris]

Of course, in the UK we have Phonebox...

Ah, yes, didn't Doctor Who travel in one of those?

The Brits have quaint money, too...

--Bill

[Guest_BruceMoomaw_*]

It's going to take a lot more than a (current) disagreement over the amount of water vapor released by the impact to start making me throw current conceptions of comet nuclei completely out the window; there are more than enough ambiguities in the initial interpretations of the measurements from different spectrometers (in different places) to explain that, I think. Especially since there were several predictions from various people before the impact that the impact might actually do little to release water from Tempel 1, or to punch down below its outer mantle of dried rock dust.

As for the "UV flash" supposedly showing something unusual, I'll have to listen to that interview -- but the DI researchers have already said that the sequence of events from the impact was EXACTLY what their ground simulations had shown would happen if the Impactor hit a deep, loose, powdery surface. It would tunnel a short distance below the surface before exploding (like a bolide entering Earth's atmosphere), then there would be a brief, narrow jet of ejecta spurting straight up through the tunnel it had dug into the surface -- and then the shock from the shallowly buried explosion would fling a far bigger cloud of ejecta in every direction. As of yet, the carbonates remain the only major surprise that I think this mission has turned up, which is why I'm waiting to hear from Lisse on just how good the spectral evidence for them really is.

[The Messenger]

Can anybody tell me why NASA didn't simply prohibit the use of non-SI units by their contractors after the MCO debacle? 

tty

NASA has what can only be termed a pathologically impairing fear of making changes in the manned flight program. Both shuttle disasters can be directly traced to known failure modes, but NASA told engineers to stay the coarse...I think it has something to do with being based in Texas

[Guest_BruceMoomaw_*]

"Messenger" is right about the ejecta temperaure reported by Lisse in that abstract actually being that 24 hours after the impact. Since the temperature in the immediate vicinity of the impact was fully several thousand degrees, it would still seem possible that the carbonates were synthesized by the heat of the impact themselves -- depending on just how much of them ws actually detected by deep Impact. I have yet to hear from Lisse on these subjects, and it looks as though I'll have to phone him.

As for the press release about the "Swift" data supposedly indicating impact into a hard surface, however, I think the article's phrasing may be misleading. What it actually says is that Swift detected a UV flash indicating that the Impactor did not hit "a soft, SNOWY surface". The latter adjective can perhaps be interpreted as meaning that it did not hit easily volatilizable ices -- but it could still have hit fine rock powder that resisted flashing into vapor and in the process absorbing much of the heat of the impact , so that more of the energy of the impact went into heating local rock powder to the point of its glowing incandescently.

[The Messenger]

Hoagland took Lisse to task for saying the Deep Impact observer did not have the 'best angle' for viewing the results, but my take on that was that Lisse was implying that observer had a narrow view, that was also screened by dust. Hoagland is correct, though, the integrated patterns from earth can't distinguish between native and induced water vapor.

The question is, was there significant water vapor emitted by Deep Impact, or was the water vapor already being released elsewhere on the comet irradiated by a an extremely bright UV flash? I am also of the impression that only the DI observer witnessed the full intensity of the flash, as I have not found any reference to it in ground based observations.

In any case, it is back to the drawing boards: Perhaps an observer that will hang around long enough to figure out what is happening during impact, with a second passive observation platform, and a pair of stereo lenses...sigh...it is a shame when your local 7-ll is better equipped for radio observations than a space observation probe.

[Guest_BruceMoomaw_*]

I plan to call Lisse tomorrow to try to get the straight dope on the following questions:

(1) How firm is the carbonate detection, and how big a fraction (roughly) of the surface material does the team think they constituted?

(2) How can the near-absence of carbonates on the surfaces of comet nuclei -- and in interplanetary dust -- be explained?

(3) How does he explain the apparent disparity in the measured amounts of water released by the impact?

(4) Did they detect formic acid, or not?

(5) Can finer particles in the exposed subsurface material actually account for a lot of the IR spectral differences that are currently being explained as actual compositional differences? (Thanks to Jeffrey Bell.)

Cany anyone think of any more questions?

[Guest_BruceMoomaw_*]

Let me add to that list my previous question:

(6) Could the very high temperatures in the immediate vicinity of the impact have synthesized the detected carbonates after all?

[The Messenger]

One -

The dust no one expected - is this an indicator that the density of the comet, and therefore the gravitational attraction, was possibly greater than expected? Is anyone trying to quantify how much of the dust resettled on the probe, and how much was blown away by the solar wind? This has implications for how the comet became dusty in the first place.

As an asside - Rosetta -http://www.williams.edu/Astronomy/jay/chapter19_etu6.html

Samples of material supplied by the Lander's Drilling and Distribution system (SD2) will be placed in a small oven and heated in stages up to 800C. Gases released from the ices will then be analysed to determine their composition.

67P is characterized as a 'dusty' comet.

A successful landing may lead to a GC choked with dust, not ices. Yes?

Edited to add: I checked with a chemist who works with GC's in adverse environments. At particle sizes ~2u it becomes difficult to both filter and control flow rate, as frits quickly plug.

[elakdawalla]

I am sitting in the press room at DPS, having just finished pounding the keyboard for my first blog entry from the meeting, and I am witnessing some very strange behavior on the part of Carey Lisse. He has just come into the room waving spectra and boasting about data he has and talking about giving his press conference talk early, on Tuesday, instead of Wednesday as scheduled, and talking about all his connections with various people on the Deep Impact team. But this is not typical behavior for a scientist; he's definitely grubbing for attention, which immediately makes me concerned about what message he's trying to sell me, and why he's working so hard to sell it. I started writing some stuff down and he saw me start to type and told me not to write down anything that he was saying. The BBC radio guy iwho is here is trying to tell him about responsible behavior for scientists and the Science embargo. It's all really odd.

Emily

[The Messenger]

Deep Impact is touching a lot of raw nerves, and no matter what model emerges, it will have to be sprinkled with dust. Data, please data.

HASI recorded an increase in the permittivity of the Titan surface at 12 minutes after impact.

What It would take some serious outgassing / chemical compositional change / fluid movement to modify the permittivity. Perhaps there really is a mooning Titanian, and he is a sand worm

They don't know what it means, and are working first to rule out anything that might be coming from within Huygens to cause that observation...But to do that, they need data from all the other science teams, and individual teams are often reluctant or at least slow to share the necessary data.

http://planetary.org/blog/20050905.html

This is disheartening. I can understand why some data is being withheld from the public (but I don't like it). For the teams trying to analyse and reduce such puzzling data to not share every piece of the puzzle with each other is retarded.

Stardust is scheduled to land in the Utah Desert in January of 2006. I propose we get together and fund a helicopter to intercept and pirate the probe to a secret laboratory that allows complete internet access to all the data as it emerges. Otherwise, the PIs will spirit it off like Genesis, and disappear forever.

[djellison]

For the teams trying to analyse and reduce such puzzling data to not share every piece of the puzzle with each other is retarded. 

I totally agree. It almost seems that one instrument is happier to share data with an instrument on a foreign spacecraft, before sharing it with it's neigbours onboard it's own spacecraft.

Doug

[The Messenger]

O'Hearn is reporting basically the same interpretive model as Lisse.

http://spaceflightnow.com/news/n0509/06deepimpact/

In a couple of seconds the fast, hot moving plume containing water vapor left the view of the spectrometer, and we are suddenly seeing the excavation of sub-surface ice and dust,

I am having all kinds of problems envisioning how a solid body could be filled with dusty ice, and how a probe could excavate subsurface ice after a violent heat exchange at the surface.

I see a timpanic model as more consistent with the observed shallow craters: A dust laden, but resilent surface that absorbed some of the energy, then the surface rebounded, flexing a circular shock wave across the surface, liberating ambient fine dust and ice from the adjacent surface terrain.

If this is correct, there should be secondary surface waves, and at least one harmonic in the explosion of dust, roughly consistent with the first interval.

[antoniseb]

I see a timpanic model as more consistent with the observed shallow craters: A dust laden, but resilent surface that absorbed some of the energy, then the surface rebounded, flexing a circular shock wave across the surface, liberating ambient fine dust and ice from the adjacent surface terrain.

Do I understand correctly that you are suggesting that the comet's surface is like a sand covered snare drum, and that the probe's collision stretched the surface, and it rebounded elastically? That can't be what you mean, but it's what I keep reading.

It could be that the top layers are fluffy, but ice free, and that after penetrating several meters of fluff the probe hit something more like the icy dirt that we've been saying comets are made of. I think that's what the paper is trying to say.

[The Messenger]

Do I understand correctly that you are suggesting that the comet's surface is like a sand covered snare drum, and that the probe's collision stretched the surface, and it rebounded elastically? That can't be what you mean, but it's what I keep reading.

Yes, that is what I mean, only a surface more like the earth, or a meteor. Yes, I will agree the interpretation that the probe 'punched through' is more consistent with models of what a comet should be, but I do not see how the interior of any solid object could be composed of very fine dust. Notice that the probe cannot be responsible for creating the dust, because this would have elevated the temperature and produced a more consistent IR spectra. And why would dust and or ice be ejected? A dust-filled nucleus would absorb energy like a Kevlar vest. If not, the compression necessary for a kinetic rebound should have melted the internal ice and ejecting a cloddy, muddy slurry, not dust and ice.

It could be that the top layers are fluffy, but ice free, and that after penetrating several meters of fluff the probe hit something more like the icy dirt that we've been saying comets are made of. I think that's what the paper is trying to say.

"Several meters' of dust would have a very high surface area. This would almost certainly absorb significant amounts of the underlying moisture...[thinking out-loud here] without which, this dusty layer would have a high dielectric strength and charge loading potiential. Moving against the solar wind, look at the potential for 'lightning strikes' within a comet! What a great primary mechanism that explains why comets are comets!

How deep the probe penetrated: It all boils down to the intensity of the initial UV spike. I am wondering if the CCD saturated and the energy released cannot be quantified - this would explain why they have not released an impact temperature. But even a saturated signal would provide a lower limit.

Edited to add:
According to Emily's Blog today, the spectra at the moment of impact was missed, A'Hearn stating that it would have saturated. She also states that the probe hit on a glancing blow - 20-36deg ...Now I'm confused, because there were images released on July 4th that definitely recorded the impact in the visual spectrum - how could the IR have been cockeyed?

http://planetary.org/blog/20050905.html

The science team is not convinced that we have seen the crater yet...A'Hearn quickly slid through several dozen attempts by the imaging team to process the images in ways that would reveal the crater, but I will verify that there was absolutely nothing in any of the images that looked convincingly like a crater (or even much of anything at all).

Two possibilities: 1) The dust hid the crater. 2) There is no significant crater, just a big cloud of surface dust.

Jessica Sunshine talked more about the post-impact spectra. They contained evidence of "literally glowing water, carbon dioxide, and organics in C-H bonds. The gases all had temperatures on the order of a couple of thousand Kelvin."

That is awful hot gases for a probe penetrating an object with 75% void volume, and no appreciable surface strength. Something is not right.

[SigurRosFan]

NASA's Spitzer and Deep Impact Build Recipe for Comet Soup

http://www.jpl.nasa.gov/news/news.cfm?release=2005-144

--- When Deep Impact smashed into comet Tempel 1 on July 4, 2005, it released the ingredients of our solar system's primordial "soup." Now, astronomers using data from NASA's Spitzer Space Telescope and Deep Impact have analyzed that soup and begun to come up with a recipe for what makes planets, comets and other bodies in our solar system. ---

[Guest_RGClark_*]

NASA's Spitzer and Deep Impact Build Recipe for Comet Soup

http://www.jpl.nasa.gov/news/news.cfm?release=2005-144

---  When Deep Impact smashed into comet Tempel 1 on July 4, 2005, it released the ingredients of our solar system's primordial "soup." Now, astronomers using data from NASA's Spitzer Space Telescope and Deep Impact have analyzed that soup and begun to come up with a recipe for what makes planets, comets and other bodies in our solar system. ---

Thanks for the link, Sigur. Here's another article on it:

Composition of a Comet Poses a Puzzle for Scientists
By KENNETH CHANG
Published: September 7, 2005
"In the burst of light after the collision, Spitzer detected specific colors of infrared light that indicated that Tempel 1 contained clays and carbonates, the minerals of limestone and seashells.
"Clays and carbonates both require liquid water to form.
"How do clays and carbonates form in frozen comets where there isn't liquid water?" said Carey M. Lisse, a research scientist at the Applied Physics Laboratory at Johns Hopkins University who is presenting the Spitzer data today at a meeting of the Division for Planetary Sciences in Cambridge, England. "Nobody expected this."
http://www.nytimes.com/2005/09/07/science/...html?oref=login
[may require free registration]

I'm surprised Lisse would say nobody expected the aqueous minerals to be seen. It is a well-known theory among comet researchers that radioactive heating may have allowed liquid water to form in comets early on in the Solar Systems history.
This theory was probably only controversial because it raises the possibility of life in comets, especially given the large abundance of organics, also confirmed by Deep Impact, in comets.


Bob Clark

[Stephen]

This theory was probably only controversial because it raises the possibility of life in comets, especially given the large abundance of organics, also confirmed by Deep Impact, in comets.

"Life" or merely some rather complex organic biochemistry? On the face of it, life as such surely still seems unlikely to evolve in a comet, if only because sources of energy in the interior it might use must surely be few and far between while those on the exterior would swiftly exterminate it.

======
Stephen

[edstrick]

Messenger: "That is awful hot gases for a probe penetrating an object with 75% void volume, and no appreciable surface strength. Something is not right. "


Uh... think of the awfully hot gasses for a meteorite penetrating an atmosphere.. with a density 0.00000something of the fluff on the comet's surface. You do bore in a bit, but by the time the impator/penetrator's punched through a dozen meters or so of "freeze-dried-icecream" or fluffy dust, it's pushed into the same mass per square meter as it's made of, has vaporized, and the vapor is mixed with the same amount of vaporized dust by mass, and is still is travelling downwards into the surface, but some gas is starting to expand / blowback out the hole. Hell yess it's gonna be hot!

[The Messenger]

Hell yess it's gonna be hot!

The problem is where the heat is: An extremely hot spectrum on impact, followed by an extremely cold one. To evacuated a deep cavitation, wouldn't the energy have to be carried by the probe - or the vaporized probe, to the "bottom", generating steam pressure that lifts the mass and causing the evacuation? The thermal energy should be distributed and not limited to the initial peak.

"In the burst of light after the collision, Spitzer detected specific colors of infrared light that indicated that Tempel 1 contained clays and carbonates, the minerals of limestone and seashells.
"Clays and carbonates both require liquid water to form.
"How do clays and carbonates form in frozen comets where there isn't liquid water?" said Carey M. Lisse

The spectrum tells us this comet is clearly not composed of virginal molecules: This comet has a terrestrial (warm) history. There is no reason, other than the rather iffy density determination, to assume this comet has a primal structure. Occur's razor preferentually places dust on the surface of a rock with obvious evidence of surface impacts. Since we can see no deep cavitation, and based upon the differential spectral temperatures, particle size, composition, impact angle, and icy state of the dust cloud, I see no reasonable evidence for A'Hearn's model. It is incredible.

[SigurRosFan]

New Spitzer Press Release: Tempel 1's Secret Ingredients Revealed

http://www.spitzer.caltech.edu/Media/relea...c2005-18a.shtml

--- Astronomers were most surprised to see clay, carbonates, and crystallized silicates because these chemicals are thought have formed in warm environments, possibly near the Sun, but away from the chilly outer neighborhood of comets. How did these compounds get inside comets? One possibility is that materials in our early solar system mixed together before being sorted out into individual bodies. ---

[Guest_BruceMoomaw_*]

The evidence is simply overwhelming, it seems, that "Messenger" is wrong, and that Tempel does indeed have a very low density with a surface layer of sun-dried dust covering an interior that still has a lot of water ice. Money quotes from various sources:

http://planetary.org/blog/20050905.html : "The surface temperature was 326 degrees Kelvin, 'nowhere cold enough to be at the sublimation temperature of ice. So the ice is not at the surface, it's below the surface.'

"The crater formed in a gravity-controlled regime, meaning that the impact happened into a material that had no significant strength holding it together. Which is pretty obvious from the dustiness of the ejecta. 'This wasn't a surprise' to most of the team 'but we're happy that we guessed right,' A'Hearn said. Almost all of the ejecta that came out of the crater was in the form of particles smaller than 10 microns, which is really tiny. The total ejected mass was about 10 or 20 million kilograms, and the plume remained connected to the surface for hours (which also would be expected from a gravity-controlled crater). The trajectories traced out by the ejecta allowed them to measure the force of gravity on the comet directly, and it came out to 50 milligal, or 50 parts in a million of Earth's gravity. That, in turn, lets you back out the mass of the comet, about 7 x 1013 kilograms. That, with the shape model, lets you calculate a density, 0.6 grams per cubic centimeter, but the density has large error bars, about plus or minus 0.35. But if you believe the 0.6 g/cc number, A'Hearn said, 'the porosity of Tempel 1 must be at least 75%. The comet's empty.'

"The size of the dust particles were 'mostly less than 10 microns, a mix of rocky dust and volatile solids.' They have lovely spectra from both before and after impact. A'Hearn showed a graphic illustrating that the slit of their spectrometer actually mis-pointed off of the impact site (down-range, off the southern edge of the comet), but that was 'good news' because otherwise the spectrometer would have saturated. There is a lot of information in the spectra. Water, carbon dioxide, and the C-H bond of organic molecules are obvious. Less obvious and more tentative identifications include methyl cyanide, sulfur dioxide, acetylene. 'The methyl cyanide is going to be controversial, because it looks like there is a lot of it.'

"Jim Richardson talked a little bit about the paths that the ejecta took. 'Less than 10% of the ejecta escaped the comet.' The material that made up the ejecta is extremely weak, with strengths measured at around 100 millipascals. But given the weak gravity at Tempel 1, this weak stuff can still hold a scarp. 'You can make a 20 or 40 meter scarp on a comet, but you couldn't pile it up a millimeter high on Earth.'

"Jessica Sunshine talked more about the post-impact spectra. They contained evidence of 'literally glowing water, carbon dioxide, and organics in C-H bonds. The gases all had temperatures on the order of a couple of thousand Kelvin.' Comparing pre-impact to post-impact spectra, Jessica said, they saw a 10-fold increase in the amount of water and carbon dioxide visible; but a 20-fold increase in the amount of organics. So there was a dramatic change in the abundance of organics, which they can't explain yet but has to do with what they excavated from the comet's interior. It's not clear yet whether it means that the surface is somehow depleted in organics, or maybe the organics at the surface are tied up in large grains so they only became visible when the impact dissociated all the large grains into little sub-grains.

"Jessica also said that they have discovered relatively recently that 'almost immediately after the vapor plume passes, we identified water ice. We have very strong evidence that we have water ice near the surface.' Remember, water ice can't be at the surface because the surface is too hot for it. Evidence suggests that the thermal inertia of the comet is nearly zero, meaning that it heats and cools quickly in response to sunlight, but the heating and cooling doesn't propagate into the interior...

"Pete Schultz reported that the observations of the impact flash, the continuous ejecta, the low velocity central plume, and several other details indicated that the comet was very porous, like the impact experiments he'd done into perlite. From the impact ejecta volume, he calculated a crater size of around 150 to 200 meters. But, he cautioned, the same volume could give you a 100-meter crater that was deep. And that the volume (and thus the crater size) could be greater for a very low surface density. He thinks that evidence suggests--but does not prove--that there is a highly porous surface layer, which is underlain by a weakly bonded upper 30 meters of the comet.

"Finally, Carey Lisse reported on the Spitzer observations. They have beautiful pre-impact and post-impact spectra. The post-impact one is full of features, a direct result, he said, of the fineness of the dust that the impact produced. He said that the impact must have broken apart aggregates into their component tiny grains. The spectra contain 'huge silicate features, indicative of fine dust.' The models of the impact process indicate that the impact produced 'gentle excavation of cold ejecta' and that 'the vast majority of the material was disaggregated on impact.' Among the features, the silicate features from minerals like forsterite and enstatite 'swamp' the other features, 'so our first job will be to understand' the abundances of the silicates. They saw 'a little hint of water in the first spectrum after impact but not much afterwards.' In addition to the enstatite, forsterite, and PAHs, they are trying to model their spectra using a library containing dolomite (a carbonate), smectite (a clay), spinel/hibonite, pyrrhotite, iron oxide, and elemental carbon grains. Lisse remarked that 'PAHs have never been seen before in a comet, but we expected them.' At which point ESA scientist Bernard Foing, who was sitting behind me, muttered 'no, they were' detected before. Lisse pointed out that he didn't yet have a suggestion for where all the iron and sulfur you would expect to see could be found.

"The carbonate and smectite that Lisse sees are the most controversial. As far as scientists understand it, it takes an aqueous (liquid water) environment to make these minerals. Yet the textural evidence suggests that Tempel 1 formed in the outer solar system. A'Hearn remarked that 'The high porosity tells me that things came together at very low speeds, far from the Sun, where the Keplerian velocities are very low, and with circular orbits, because elliptical orbits lead to high-speed encounters' and less porosity and more chemical alteration of the components of the comet. It would be difficult to form carbonate and smectite in the inner solar system and migrate it out to the outer solar system and not have a more violent birth for comets. So Lisse is going to have to work hard to prove that the carbonates are there. A'Hearn said 'it's premature to try to take our data, which we've only looked at 10% of in any detail, and apply it to the rest of the solar system at this point.'

"Someone asked Mike A'Hearn, 'with Deep Impact, did we learn about comets in general, or just Tempel 1?' A'Hearn's answer was that 'nothing may be typical' of comets. But if the high porosity result is true, then 'it's really hard to understand how you are going to attach the Rosetta lander to the surface' of its comet. 'They really have to think about that seriously. How well that's going to work with this incredibly weak stuff, I'm doubtful. Uwe Keller said yesterday he thought it would sink in. But I don't think its gravity is strong enough for it to sink in.' "

http://www.spaceflightnow.com/news/n0509/06deepimpact/ : "Mission data indicates the nucleus of Tempel 1 is extremely porous. Its porosity allows the surface of the nucleus to heat up and cool down almost instantly in response to sunlight. This suggests heat is not easily conducted to the interior and the ice and other material deep inside the nucleus may be pristine and unchanged from the early days of the solar system, just as many scientists had suggested.

" 'The infrared spectrometer gave us the first temperature map of a comet, allowing us to measure the surface's thermal inertia, or ability to conduct heat to the interior,' said Olivier Groussin, the University of Maryland research scientist who generated the map.

"It is this diligent and time consuming analysis of spectral data that is providing much of the 'color' with which Deep Impact scientists are painting the first ever detailed picture of a comet. For example, researchers recently saw emission bands for water vaporized by the heat of the impact, followed a few seconds later by absorption bands from ice particles ejected from below the surface and not melted or vaporized.

" 'In a couple of seconds the fast, hot moving plume containing water vapor left the view of the spectrometer, and we are suddenly seeing the excavation of sub-surface ice and dust,' said Deep Impact co-investigator Jessica Sunshine, with Science Applications International Corporation, Chantilly, Va. 'It is the most dramatic spectral change I've ever seen.' "


http://skyandtelescope.com/news/article_1589_1.asp : "The mass of Tempel 1's nucleus is around 72 trillion kilograms. The density is about 0.6 gram per cubic centimeter. That density, along with the gravity-dominated nature of the nucleus, has led team members to conclude that Tempel 1 is a porous rubble pile. This very loose body must be very weakly held together by gravity...

"The comet's outer layer is dusty fine powder. No blocks or boulders were seen flying from the impact site; only talcum-powder-like debris was observed.

"The spectrometer watched the ejecta plume expand outward. The observations revealed a distinctly layered comet. After the first blast of hot gas and plasma shot past the flyby craft's spectrometer, the instrument recorded a large peak due to water ice. 'It's the first thing we see after the hot vapor goes past. It must be near the surface,' says team member Jessica M. Sunshine (Science Applications International Corporation). The water was soon followed by a strong signal of organic materials...

"Team members conclude that far too much dust was released for it to have ever been heated by more than a few degrees. That suggests the material excavated by the impact is primordial — representing the original raw materials present when the comet first formed at the beginning of the solar system. 'Comets are the dinosaur bones of planet formation,' says Lisse. [This seems to put the last nail in the coffin of my theory that the possible carbonates might have been formed by the heat of the impact itself -- Moomaw.]

"The observed molecules are giving some experts pause, however. The spectra also show hints that Tempel 1 contains unexpected compounds such as carbonates and clays. By conventional thinking, these materials only form by chemical processing in the presence of liquid water. Thus, it's possible that the comet's ejecta might not have been 'primordial' after all. It might have been processed over billions of years. Can carbonates form inside a comet over extremely long time periods without liquid water? Did the comet melt enough for water to form? Future studies may provide answers."

Finally, regarding possible mechanisms by which carbonates might form in the very early Solar System, see one paper from the 2005 LPSC which claims to have found a mechanism by which carbonates can form in pre-planetary nebulas even without the presence of liquid water, through purely gas-phase reactions (
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1894.pdf ) -- which seems to
match well with the apparent detection of carbonates in such nebulas. I still think that the apparent absence of carbonates on the surfaces of comet nuclei, as opposed to their interiors -- and their scarcity (though not total nonexistence) in interplanetary dust particles collected out of Earth's upper atmosphere -- may be due to the fact that they're broken down pretty quickly by solar UV.

[Guest_RGClark_*]

...
Finally, regarding possible mechanisms by which carbonates might form in the very early Solar System, see one paper from the 2005 LPSC which claims to have found a mechanism by which carbonates can form in pre-planetary nebulas even without the presence of liquid water, through purely gas-phase reactions (
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1894.pdf ) -- which seems to
match well with the apparent detection of carbonates in such nebulas.  I still think that the apparent absence of carbonates on the surfaces of comet nuclei, as opposed to their interiors -- and their scarcity (though not total nonexistence) in interplanetary dust particles collected out of Earth's upper atmosphere -- may be due to the fact that they're broken down pretty quickly by solar UV.

Thanks for that link to the article, Bruce. Note though that the authors had to include H2O for the carbonate to form (it did not form without H2O, whatever its phase) and they had to raise the temperature above freezing for the carbonate to form:

Experimental evidence for condensation of "astrophysical" carbonate.
"Temperatures of these ambient gases, i.e.
condensation temperatures were varied between 25°C
and ~150°C, and condensation times from ~40 to 464
min. The condensed material was collected on a
horizontal steel plate 2 to 10 cm above the target."
Lunar and Planetary Science XXXVI (2005) 1894.pdf, p. 1.
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1894.pdf

Nevertheless the authors concluded that liquid water could not be involved because of the low pressures used. However, a key fact is that water can become liquid at below its normal triple point pressure with the addition of soluble gases or solutes. That is, dissolved gases or solids can not only lower the temperature required for liquid water, it can also lower the pressure requirements. It would be interesting to find out if they observed the carbonate forming when the surrounding pressure (not just the water vapor pressure) was below that required for gas or solid water solutions.


Note also that there is now additional evidence for internal heating in comets that could have allowed liquid water to form: the finding of olivine on Tempel I.
On the space bbs uplink.space.com someone mentioned the detections of olivine in Tempel I and previously in other comets raise the possibility of more heating in comets than would be expected for objects formed far from the Sun. This would also be consistent with the theory of radiogenic heating in comets:

NASA Research Finds Green Sand Crystals Are in Comet Tempel 1.
Date Released: Thursday, September 15, 2005
http://spaceflightnow.com/news/n0007/20cometdust/

Time travel through a trail of comet dust.
NASA/GSFC NEWS RELEASE
Posted: July 20, 2000.
"We know that these dust grains change from amorphous to crystalline as they are heated, and our laboratory research revealed that the rate at which they change is extremely sensitive to temperature," Nuth added. "At the very low temperatures, where water-ice and the other volatile components of comets are frozen, the time required for amorphous silicate dust grains to change to the crystalline olivine found in comet Halley is many times longer than the age of the Universe."
http://spaceflightnow.com/news/n0007/20cometdust/

So there are at least three separate and independent indications of internal heating, likely radiogenic, in comets: carbonate/clay detected in Tempel I, olivine in Tempel I and other comets, and crystalline ice detected deep in the Kuiper belt:

Chilly Quaoar had a warmer past.
Mark Peplow
Crystalline ice suggests remote object has radioactive interior.
Published online: 8 December 2004.
http://www.nature.com/news/2004/041206/pf/041206-7_pf.html



Bob Clark

[Guest_BruceMoomaw_*]

It can't be very much liquid water, though, or the olivine would have turned into clays -- don't forget how vulnerable it is to water weathering (which, as you know, is also another reason to think that Mars has never had much surface liquid water). There do seem to be some clays in Tempel, but there's also a hell of a lot of unaltered olivine.

[SigurRosFan]

SWAS (water) observations of comet 9P/Tempel 1 and Deep Impact

http://arxiv.org/abs/astro-ph/0509850

[Guest_BruceMoomaw_*]

Jessica Sunshine has a new interview on this subject: http://www.astrobio.net/news/article1731.html

The big news is that -- while they certainly did detect a major release of organics (along with water and CO2), they're having serious trouble interpreting just what organics actually did come out: " We knew organics were going to be vaporized, and we were expecting to see each organic material have a peak at a specific wavelength, depending on what it was. But what we saw was that anything that had a carbon-hydrogen bond was vaporized, and we got a conglomerate peak. That means there were a lot of organics, and a lot of different kinds, but we couldn't tell what any of it was." Nor does she think there's any way for continued processing to tease out the different organics from DI's own spectra; the main hope lies in the higher spectral-resolution and longer duration spectra of the cloud obtained by ground-based spectrometers. "I think the ground-based data already shows clear evidence of some. They saw a tremendous change in ethane before and after; they saw a lot more ethane after. They're also seeing formaldehyde and methanol, but not large changes. But we still have a lot to do."

[ljk4-1]

Sunshine on Comets: Part I

http://www.astrobio.net/news/article1731.html

Jessica Sunshine is the Deep Impact mission scientist responsible for the
onboard infrared spectrometer. In the first half of this two-part interview, she
discusses what the comet's nucleus looked like before and after impact, and
explains why it's so difficult to piece together the spectroscopic data.

[ljk4-1]

Observations of Comet 9P/Tempel 1 made by ESA’s Rosetta spacecraft after the
Deep Impact collision suggest that comets are ‘icy dirtballs’, rather than
‘dirty snowballs’ as previously believed.

More at:

http://www.esa.int/SPECIALS/Rosetta/SEMUSK5Y3EE_0.html

[Guest_Myran_*]

That idea of 'Icy dirtballs' makes sense to me, it have been speculated that some objects we think of as asteroids might be former cometary nucleus. Most likely candidates for such former-comet asteroid nowadays are the sun grazing ones, best known example of those are Icarus.

[djellison]

I thought the move from dirty-ice-ball to icy-dirt-ball was already a popular theory before DI

Doug

[tedstryk]

I thought the move from dirty-ice-ball to icy-dirt-ball was already a popular theory before DI

Doug

Remember, this is an ESA press release. It is a totally new idea

[Guest_Myran_*]

I might be out of touch to some degree, but I thought it was the ‘dirty snowball’ theory that was mostly embraced up until the analysis of Deep impact.

[antoniseb]

I might be out of touch to some degree, but I thought it was the ‘dirty snowball’ theory that was mostly embraced up until the analysis of Deep impact.

I recall reading that description well before DI hit Tempel 1, though personally, I think that it is not realistic to assert that about all comets on the basis of this impact with one comet. I would guess that is we were to run another DI type mission at an incoming comet with a hyperbolic orbit (i.e. fresh material), that we would probably see a higher ratio of ices to silicates, and a much thinner layer of surface dust.

[Guest_BruceMoomaw_*]

There were indeed strong suspicions for years before DI that there might be more dirt than ice in comets -- there was, in fact, a two-page article on it in "Nature", which I have in my files and will track down.

[Guest_BruceMoomaw_*]

Yup -- and the article (by Mark W. Sykes) goes all the way back to the April 22, 1993 issue. It turns out that for about a decade before that, the consensus was growing among comet specialists that there was a lot more dirt than ice in the things.

The previous serious underestimates of dust mass in them had been due to visual observations, which are only sensitive to extremely fine dust a few microns or smaller -- but both Giotto's measurments during its Halley and Grigg-Skjellerup flybys, and the long-distance IR observations from the IRAS satellite in the mid-1980s, had already led to the conclusion that "short-period comets lose mass primarily in the form of refractory particles a few millimeters to centimeters in diameter", which are hard to detect visually. The average dust/gas mass ratio for short-period comets (including Halley) had already been calculated at 2 or 3 to 1, meaning that volume-wise dust and grit made up 40-50% of their nuclei. This nicely matches the rock/ice ratios for Pluto and Triton, which after all were made up an accumulation of such comets.

[ljk4-1]

"Moreover, the expanses of interplanetary space are not the forbidding barrier they once seemed. Over the past 20 years scientists have determined that more than 30 meteorites found on Earth originally came from the Martian crust, based on the composition of gases trapped within some of the rocks. Meanwhile biologists have discovered organisms durable enough to survive at least a short journey inside such meteorites.

Although no one is suggesting that these particular organisms actually made the trip, they serve as a proof of principle. It is not implausible that life could have arisen on Mars and then come to Earth, or the reverse. Researchers are now intently studying the transport of biological materials between planets to get a better sense of whether it ever occurred. This effort may shed light on some of modern science's most compelling questions: Where and how did life originate? Are radically different forms of life possible? And how common is life in the universe?"

http://www.sciam.com/article.cfm?chanID=sa...4FF83414B7F0000

[Guest_RGClark_*]

Further evidence for comets around other star systems.

--------------------------------------------------------------------------------

This was released today:

NASA's Spitzer Finds Possible Comet Dust Around Dead Star
For Release: January 11, 2006
http://www.spitzer.caltech.edu/Media/relea...4/release.shtml

Then this may support the idea that the carbonate seen in planetary nebulae indeed stems from comets in those those systems. So rather than the extrasolar detections providing an alternative origin for carbonate that does not require liquid water, they may support the idea the carbonate in comet Tempel I may indeed be due to liquid water.


- Bob Clark

Thanks for that link to the article, Bruce. Note though that the authors had to include H2O for the carbonate to form (it did not form without H2O, whatever its phase) and they had to raise the temperature above freezing for the carbonate to form:

Experimental evidence for condensation of "astrophysical" carbonate.
"Temperatures of these ambient gases, i.e.
condensation temperatures were varied between 25°C
and ~150°C, and condensation times from ~40 to 464
min. The condensed material was collected on a
horizontal steel plate 2 to 10 cm above the target."
Lunar and Planetary Science XXXVI (2005)    1894.pdf, p. 1.
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1894.pdf

Nevertheless the authors concluded that liquid water could not be involved because of the low pressures used. However, a key fact is that water can become liquid at below its normal triple point pressure with the addition of soluble gases or solutes. That is, dissolved gases or solids can not only lower the temperature required for liquid water, it can also lower the pressure requirements. It would be interesting to find out if they observed the carbonate forming when the surrounding pressure (not just the water vapor pressure) was below that required for gas or solid water solutions.
Note also that there is now additional evidence for internal heating in comets that could have allowed liquid water to form: the finding of olivine on Tempel I.
On the space bbs uplink.space.com someone mentioned the detections of olivine in Tempel I and previously in other comets raise the possibility of more heating in comets than would be expected for objects formed far from the Sun. This would also be consistent with the theory of radiogenic heating in comets:

NASA Research Finds Green Sand Crystals Are in Comet Tempel 1.
Date Released: Thursday, September 15, 2005
http://spaceflightnow.com/news/n0007/20cometdust/

Time travel through a trail of comet dust.
NASA/GSFC NEWS RELEASE
Posted: July 20, 2000.
"We know that these dust grains change from amorphous to crystalline as they are heated, and our laboratory research revealed that the rate at which they change is extremely sensitive to temperature," Nuth added. "At the very low temperatures, where water-ice and the other volatile components of comets are frozen, the time required for amorphous silicate dust grains to change to the crystalline olivine found in comet Halley is many times longer than the age of the Universe."
http://spaceflightnow.com/news/n0007/20cometdust/

So there are at least three separate and independent indications of internal heating, likely radiogenic, in comets: carbonate/clay detected in Tempel I, olivine in Tempel I and other comets, and crystalline ice detected deep in the Kuiper belt:

Chilly Quaoar had a warmer past.
Mark Peplow
Crystalline ice suggests remote object has radioactive interior.
Published online: 8 December 2004.
http://www.nature.com/news/2004/041206/pf/041206-7_pf.html
  Bob Clark

[ljk4-1]

Astrophysics, abstract
astro-ph/0601709

From: Anthony Remijan [view email]

Date: Tue, 31 Jan 2006 16:02:51 GMT (39kb)

A Bima Array Survey of Molecules in Comets Linear (C/2002 T7) and Neat (C/2001 Q4)

Authors: Anthony J. Remijan, D. N. Friedel, Imke de Pater, M. R. Hogerheijde, L. E. Snyder, M. F. A'Hearn, Geoffrey A. Blake, H. R. Dickel, J. R. Forster, C. Kraybill, L. W. Looney, Patrick Palmer, M. C. H. Wright

Comments: Accepted for Publication in the Astrophysical Journal

We present an interferometric search for large molecules, including methanol, methyl cyanide, ethyl cyanide, ethanol, and methyl formate in comets LINEAR (C/2002 T7) and NEAT (C/2001 Q4) with the Berkeley-Illinois-Maryland Association (BIMA) array. In addition, we also searched for transitions of the simpler molecules CS, SiO, HNC, HN13C and 13CO . We detected transitions of methanol and CS around Comet LINEAR and one transition of methanol around Comet NEAT within a synthesized beam of ~20''. We calculated the total column density and production rate of each molecular species using the variable temperature and outflow velocity (VTOV) model described by Friedel et al.(2005).Considering the molecular production rate ratios with respect to water, Comet T7 LINEAR is more similar to Comet Hale-Bopp while Comet Q4 NEAT is more similar to Comet Hyakutake. It is unclear, however, due to such a small sample size, whether there is a clear distinction between a Hale-Bopp and Hyakutake class of comet or whether comets have a continuous range of molecular production rate ratios.

http://arxiv.org/abs/astro-ph/0601709

[Guest_AlexBlackwell_*]

Published online today in Science Express:

Exposed Water Ice Deposits on the Surface of Comet Tempel 1
J. M. Sunshine, et al.
Published online February 2, 2006; 10.1126/science.1123632 (Science Express Reports)
Abstract

[Guest_Sunspot_*]

From New Scientist too:

http://www.newscientistspace.com/article.ns?id=dn8670

[The Messenger]

From New Scientist too:

http://www.newscientistspace.com/article.ns?id=dn8670

The consensus model of a comet leading up to the Deep Impact experiment is no longer valid, says Don Yeomans at NASA’s Jet Propulsion Laboratory in Pasadena, California, US, a member of the mission science team. "It's certainly not a dirty iceball or an icy dirtball," he told New Scientist. "It's a very, very weak, dusty structure with interior ices."

Nice to see a flawed model finally laid to rest.

Edited to add: I am not sure where the conclusion that it is a weak structure comes from: We saw dust, we did not see the impact crater, the surface LOOKs like in has survived cratering impacts implies a resilent, hard layer under a lot of fine dust.

The mass of the nucleus was determined, according to an earlier article, by monitoring the settling of dust particles and calculating GM. Static electricity can exist in space, and therefore gravity may not be the only force involved in calculating the mass of the nucleus - even so the error bars reported are ~ 50%. If the mass is so low, how can it be so dusty?

I stand by my interpretation that the dust cloud MAY be the result of a timpanic response by a relatively resilient surface, revealing nothing about the nucleus interior.

[ljk4-1]

SPOTTED! ICE ON COMET NUCLEUS (Space & Astronomy News, 3/2/06)

Ice has been detected on the nucleus, or solid body, of a comet for the
first time, researchers report.

http://www.abc.net.au/science/news/space/S...ish_1561541.htm

[Guest_RGClark_*]

A report to be presented to the 37th Lunar and Planetary Science conference will argue that the Deep Impact results can not actually distinguish between the gravity-dominated or strength-dominated scenarios for the comet's make-up, despite the earlier reports the comet's make-up was gravity dominated and therefore very porous:

GRAVITY OR STRENGTH? AN INTERPRETATION OF THE DEEP IMPACT EXPERIMENT.
K. A. Holsapple1, K. R. Housen2
1Dept. of Aeronautics and Astronautics, University of Washington 352400, Seattle, WA 98195
2 Physical Sciences, MS 2T-50, The Boeing Co., P.O. Box 3707, Seattle WA 98124
Lunar and Planetary Science XXXVII (2006) 1068.pdf
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1068.pdf


If the comet was in fact strength-dominated then another explanation has to be found for its low density, rather than porosity.
One possibility is that the comet has hollow voids. This would be consistent with the theory that liquid water existed on comets early in the Solar Systems history due to radiogenic heating and this liquid water boiled off or evaporated over time:


Deep Impact Spectral Analysis Results, carbonates and amino acid precursors.
http://www.unmannedspaceflight.com/index.p...975&#entry20975


Bob Clark

[Guest_RGClark_*]

Lisse et.al. report on their detection of carbonate and clay from Deep Impact:

Spitzer Space Telescope Observations of the Nucleus and Dust of Deep Impact Target
Comet 9P/Tempel 1
C.M. Lisse1 and the Deep Impact Spitzer Science Team. 1 JHU-APL,
11100 Johns Hopkins Road, Laurel, MD 20723 ****@jhuapl.edu.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1960.pdf

They have submitted this for publication in Science.


- Bob

[The Messenger]

Lisse et.al. report on their detection of carbonate and clay from Deep Impact:

Spitzer Space Telescope Observations of the Nucleus and Dust of Deep Impact Target
Comet 9P/Tempel 1
C.M. Lisse1 and the Deep Impact Spitzer Science Team. 1 JHU-APL,
11100 Johns Hopkins Road, Laurel, MD 20723 ****@jhuapl.edu.
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/1960.pdf

They have submitted this for publication in Science.
- Bob

I have a problem with the logic here:

The overall temperature of the outflowing material appears to be very mild for such a violent event, about 340 degrees Kelvin, similar to the temperatures measured for the surface of the nucleus and small, semi-absorbing dust grains in the Sun's radiation field at 1.5 AU. There is simply not enough kinetic energy delivered by the impactor - approximately 2x107 kJoules - to heat the approximately 107 kg of material released by the impact more than a few degrees Kelvin. Thus the temperature excursions due to the impact are too low to alter the bulk of the ejected dusty materials...

We have measured the thermal capacity of Tempel 1, and it is very low: The 'dark' side cools almost immediately as the nucleus rotates. So the surface is not unlike a volcanic field desert in Idaho, where in mid August, the temperature a mere 4m under the surface can be less than 0C.

Now check out Lisse's conclusion:

...Thus Spitzer was directly measuring pristine cometary material from inside the comet, material that has been locked away since the beginnings of the solar system.

Why would the temperature of the material inside the comet be with a few degrees of the the surface at 1.5 AU? The Comet spends most of its existance at much greater distances, so I would expect, from the known properties of the surface, that the inner temperture should be much cooler, not within a few degrees of the surface temperature at the time of impact. A more reasonable conclusion would be that the dust lifted by the impact was very near the surface.

[edstrick]

The dust is so fine and powdery that once ejected, it very rapidly reaches thermal equilibrium with sunlight. The technical term is that it has extremely low thermal inertia.

In addition, partly determining the low thermal inertia, the dust has extremely low thermal conductivity. This means that the diurnal thermal heating/cooling cycle is very shallow, and even the annual (orbital) thermal heating/cooling cycle doesn't penetrate far. Centuries-long heating in a low-semi-major-axis orbit will penetrate only 5 or 10 times the depth of the annual thermal cycle. Deeper areas have hardly changed temperature in a thousand years.

These depths are shallow relative to the depth of excevation of any plausible crater whatever, so much of the material is inferred to have been relatively pristine.

[The Messenger]

The dust is so fine and powdery that once ejected, it very rapidly reaches thermal equilibrium with sunlight. The technical term is that it has extremely low thermal inertia.

In addition, partly determining the low thermal inertia, the dust has extremely low thermal conductivity. This means that the diurnal thermal heating/cooling cycle is very shallow, and even the annual (orbital) thermal heating/cooling cycle doesn't penetrate far. Centuries-long heating in a low-semi-major-axis orbit will penetrate only 5 or 10 times the depth of the annual thermal cycle. Deeper areas have hardly changed temperature in a thousand years.

These depths are shallow relative to the depth of excevation of any plausible crater whatever, so much of the material is inferred to have been relatively pristine.

Agreed the dust normally reaches thermal equalibrium quickly, but Lisse implies they would have been able to detect it if the ejecta was hot, and it was not: Remember, we are working in a vacuum here, and the only mechanism for transferring heat is radiation. It would take ejecta from inside the comet a significant amount of time to reach thermal equalibrium using radiation transfer mechanisms only, especially with the forground dust shading background dust relative to the only significant source of radiation: the sun at 1.5 AU. I haven't run the numbers, but my gut tells be using radiation transfer to equilibrate the temperature of a thick plume of dust could take days.

I don't see how, given the data in-hand, an unqualified statement can be made that the dust was 1) from the interior 2) pristine.