[X] My Assistant

[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.