[X] My Assistant

[Guest_Richard Trigaux_*]

James Oberg Chimes in:
Let Us Drink from the Fountains of Enceladus

The idea is as follows: send a stardust-like mission to capture particules from the Enceladus plume.

I think it is the cheapest way to have infos on what is going on into Enceladus, if it has a biochemistry and how far it evolved.

I allow myself to better the idea: the probe could have three targets.


1) when passing near Saturn, catches ring particules
2) Using Titan as a gravitationnal aid, captures smog particules (fortunately they reach very high)
3) passes into Enceladus plume, captures eventual evidences of biochemistry in Enceladus.

And back to Earth! It even don't need to actually satellise around Saturn, if it is well aimed. The only difficulty is a precise navigation, to aim into a 10x10kms window into the plumes, and a bit of fuel.

The only serious problem is not to bring back some alien bacteria on Earth! Eventually the aerogel containing the Enceladus particules would be coated in something after use, so that there would be no possible contamination, in any way.

Even if the mission fails, a low pass over the Tiger Stripes would allow to obtain precise images of the vents (or more likely zones where the ice is sublimating, like in a comet), provided we have a special shutter compensating for motion blur. Such images would be anyway a necessary preliminary step before sending a lander on Enceladus, and even before designing it (depending on the geometry of the vents, which may be complicated or hazardoous).

[helvick]

1) when passing near Saturn, catches ring particules
2) Using Titan as a gravitationnal aid, captures smog particules (fortunately they reach very high)
3) passes into Enceladus plume, captures eventual evidences of biochemistry in Enceladus.

Can any of the rocket scientists out there comment on the likelihood of managing to do some (or all) of the above in a single pass that has the sampler rapidly returning to earth?

[scalbers]

Even if the mission fails, a low pass over the Tiger Stripes would allow to obtain precise images of the vents (or more likely zones where the ice is sublimating, like in a comet), provided we have a special shutter compensating for motion blur. Such images would be anyway a necessary preliminary step before sending a lander on Enceladus, and even before designing it (depending on the geometry of the vents, which may be complicated or hazardoous).

One constraint on the tiger stripe imaging is the approaching end of the southern Enceladean summer. The south polar regions will be mostly in shadow for quite a while, until we approach the next summer solstice around 2030.

[Guest_BruceMoomaw_*]

Drat. We would still, however, be able to use a thermal imager on the craft to map the precise location of the warm vents with great accuracy on a low-altitude flyby.

As for combining an Enceladus sampler with sampling flybys of Titan or the rings (or, as James Oberg suggests, Io during the craft's Jupiter gravity-assist): it's tempting, but DON'T OVERDO IT. Any of this -- except maybe the ring sampling -- would dangerously overcomplicate the mission.

[helvick]

One constraint on the tiger stripe imaging is the approaching end of the southern Enceladean summer. The south polar regions will be mostly in shadow for quite a while, until we approach the next summer solstice around 2030.

So that would be an imaging constraint but should not be a constraint on a sample return, right?

[scalbers]

Right, this is just a sunlight imaging constraint, though the spring equinox would be about 2025. There might be some seasonal constraints on the trajectories though I suspect it wouldn't be too much of an issue.

In visible light, there's always starlight if we can sit long enough over one place to collect those photons.

[David]

Well -- surely the most likely scenario is that there is no biochemistry going on in Enceladus, and so the probe would be coming back with what? It's a long way to go for a teaspoon of water. Such a probe ought to be prepared to get some science return even if the plume chemistry is uninteresting.

[Guest_BruceMoomaw_*]

Which is precisely why we need to know as much as Cassini can possibly tell us about the composition of the plumes. But they definitely are not just plain water -- the plume is about 3-4% each nitrogen and CO2, 1.5% methane, and probably smaller amounts of other organics (acetylene and propane are thought to have been detected) and other substance. We simply don't know how far organosynthesis may have gone in this environment.

It is certainly important, however, NOT to jump to the conclusion that there's a good chance Enceladus is a Fountain of Life, even if this wet and organic environment has existed for hundreds of millions of years. As Chris Chyba has pointed out, the carbonaceous-chondrite asteroids are very rich in both water and fairly complex organics (including amino acids) -- and during the Solar System's early days, they also contained enough Al-26 (known to have been scattered throughout the forming Solar System by a coincidental nearby supernova blast) to warm their interiors to the point that a lot of that water was liquid for tens or even a few hundred million years. But not one carbonaceous meteorite shows the slightest sign that biosynthesis went very far -- which, as Chyba says, is actually the strongest evidence we have that the appearance of life really MAY require a major stroke of chance luck even under favorable conditions, and that life may therefore be rare in the Universe.

In any case, I repeat that it's risky to try to make such a mission do too much else. Flying it by Titan or Io would require some additional clever (and risky) interplanetary billiards. Having it brush through the region outside Saturn's visible rings to collect ring particles might be more practical as a bonus. And I suppose it could not only make more IR observations of Enceladus during the sampling flyby, but perhaps carry ice-penetrating radar to try to get a better idea of just what is going on down there. (Edwin Kite and I have suggested this in the past for the Europa Ice Clipper, to test whether Janusz Eluszewicz is right in his fears that ice-penetrating radar on Europa Orbiter might not be able to punch deeply through it at all. But Bob Pappalardo and others have recently provided evidence that Eluszewicz's fears are unfounded -- and if we're going to send Europa Orbiter there anyway with a large payload of other instruments, it won't cost much to add the radar sounder to it in any case. Besides, even if the radar can't penetrate deeply at some locations on Europa, it may well be able to do so at other places.)

Sushil Atreya and the other scientists most interested in outer-planet entry probes have recently firmly reached the conclusion (which they announced at the November COMPLEX meeting) that you don't really need very deep entry probes (which are hard to design) for the first probes to Saturn, Uranus or Neptune -- although at some point later on they will have their uses, as they will for Jupiter. Instead, they recommend that the next mission after Juno that is specifically directed to study ANY of the giant planets should be a relatively simply New Frontiers mission to fly by Saturn and drop off only two (or maybe just one) comparatively lightweight and cheap Galileo-type vented entry probes to analyze the atmosphere down to about 20 bars, while the flyby craft uses a microwave spectrometer similar to Juno's to measure the water and ammonia levels at much great depths (with the entry probe also providing crucial calibration data for that, such as the Galileo probe has already provided for Juno). If we decide to defer Neptune Orbiter and instead return to Uranus and/or Neptune first with more flyby missions, the same thing could be done there -- although the main craft would carry more instruments to study the planet and its moons. But, again, I think that combining such a Saturn entry probe with an Enceladus sampler presents serious and probably insuperable trajectory problems.

[Guest_Richard Trigaux_*]

Thanks all for your interesting contributions.

helvick, I though again to the right trajectory this night. The best trajectory would be an hyperbolic trajectory into the Saturn system, which would result in a gravity assist sending back the probe to Earth. Centered into the Saturn referencial, the departing branch would be toward the Sun, at right the moment where Enceladus is on the way. As an important constrain of the mission is SEEING the plumes in order to aim on them, and this can be done only in looking at Enceladus from its dark side (unless the camera has some coronograph). At this moment the probe has to navigate autonomously and accurately correct its trajectory in order to aim at the plumes.

Catching particules of the ring is easy, and even mandatory, as the ringplane has to be crossed at a moment or another. Just the right place must be choosen, not to just catch the Enceladus products. But, as Bruce noted, also catching Titan haze may fairly complicate the mission: -pose serious constrains on the timing -need other corrections, as the probe will somewhat aerobrake, in an unknown amount -the science bonus is questionnable. Just see if it is possible. Perhaps it will be easy, if Titan happens to be on the departing trajectory too.

The overal idea is to make a relatively cheap mission. At least it would be cheaper than a flagship mission like Cassini or Juno, and so it would not impede the funding of Juno or another Europa project.

In order to be cheap, the ship must be as small as possible, knowing that the cost and the mass of fuel are multiples of the mass of a ship. For this reason the ship would have no large gain antenna. Only a small dish to slowly return the (large) amount of close Enceladus images. (Galileo told us that it is possible... ) So it would entirely rely on software and mass data storage.

The ship must have a camera, otherwise it could not navigate into the Saturn system. It must have a complex software, not just executing a program, but able to understand the situation and correct for any unexpected event. Software has no weight, and it can save many fuel weight and structural wheight.

A difficult moment would be the close imaging of the vents without motion blur, in an encounter of only some seconds. The camera has no time to change filters, so only one filter must be used (centered on likely organic compouds) or several cameras with different filters. Shutter must be very speedy, and several overlapping images of the same area must be taken, allowing for a super-resolution reconstruction.

As scalbers noted, there is a serious constrain about the tiger stripes going into winter darkness. I think we have still the time to catch them, but the design of the probe must be started at once. After, it will be more difficult, perhaps even the plumes will be extinct, it they need the sun heat. (Likely there would be no liquid water gushing, but just hotter ice, which would sublimate only when heated by the sun, like in a comet).

The main interest of Oberg's idea is that is seems the simplest and cheapest way to get a soon answer about a possible life in another place, even simplest than with Europa which will require at least a lander.



Bruce, about your reflexions on the appearance of life, I would say that the very first step, the 100% chemical step, seems rather common. But that don't imply that the following steps are as much common. These steps require stable conditions and liquid water, conditions which were likely never fulfilled in comets and asteroids, even with a heating by Al26, as these bodies are very small. On Enceladus, there is likely liquid water since millions of years, with a chemistry similar to that of comets (and no massive ammonia or sulphuric acid poisoning) so that it is likely that some evolution could take place. At what rate? That depends on the conditions, if for instance the water inside Enceladus is at -10°C (min allowed for relatively pure liquid water like in the plumes) then evolution of life may be very slow or absent. But some bit of evoulution could have taken place, with the creation of proto-cells or something. In what extent? Which stage it reached? Only finding in ple plume a bio-catalist made of amino acids and nucleic acids would confort the known models on appearance of life. On Earth we have no record of these steps in the appearance of life. So Enceladus may provide us with an unvaluable insight on our origins, even if we don't find a single bacteria or DNA chain. Finding bacteria would of course be an incredible philosophy result, but finding an intermediary step would learn us more about how life appeared.

[Guest_RGClark_*]

...
It is certainly important, however, NOT to jump to the conclusion that there's a good chance Enceladus is a Fountain of Life, even if this wet and organic environment has existed for hundreds of millions of years. As Chris Chyba has pointed out, the carbonaceous-chondrite asteroids are very rich in both water and fairly complex organics (including amino acids) -- and during the Solar System's early days, they also contained enough Al-26 (known to have been scattered throughout the forming Solar System by a coincidental nearby supernova blast) to warm their interiors to the point that a lot of that water was liquid for tens or even a few hundred million years. But not one carbonaceous meteorite shows the slightest sign that biosynthesis went very far -- which, as Chyba says, is actually the strongest evidence we have that the appearance of life really MAY require a major stroke of chance luck even under favorable conditions, and that life may therefore be rare in the Universe.
....

The problem is that both DNA and proteins breakdown quickly when outside of an organism continually producing them. There have been claims of fossilized bacteria in some carbonaceous meteorites.
Most of the water that is detected in meteorites is in chemically bound form, not free liquid water. However, surprisingly there have been found small liquid water containing inclusions in some meteorites:

Asteroidal Water Within Fluid Inclusion-Bearing Halite in an H5 Chondrite, Monahans (1998).
Michael E. Zolensky, Robert J. Bodnar, Everett K. Gibson Jr., Laurence E. Nyquist, Young Reese, Chi-Yu Shih, Henry Wiesmann
Science 27 August 1999, Vol. 285. no. 5432, pp. 1377 - 1379
http://www.sciencemag.org/cgi/content/full/285/5432/1377

A LPSC report also discussed observing fluid inclusions in Martian meteorites:

Bodnar R.J.
Fluid Inclusions in ALH 84001 and Other Martian Meteorites: Evidence for Volatiles on Mars.
http://www.lpi.usra.edu/meetings/LPSC99/pdf/1222.pdf

They were described as containing mostly CO2, but it's possible they contain some portion of H2O.

As far as I know the micron-sized inclusions in meteorites have not been searched for microbes.
However, a recent report discusses a method that may work for such small inclusions:

Evaluation of the LIVE/DEAD BacLight Kit for Detection of Extremophilic Archaea and Visualization of Microorganisms in Environmental Hypersaline Samples .
Applied and Environmental Microbiology, November 2004, p. 6884-6886, Vol. 70, No. 11
http://aem.asm.org/cgi/content/full/70/11/6884



Bob Clark

[Guest_Richard Trigaux_*]

The problem is that both DNA and proteins breakdown quickly when outside of an organism continually producing them. There have been claims of fossilized bacteria in some carbonaceous meteorites.
Most of the water that is detected in meteorites is in chemically bound form, not free liquid water. However, surprisingly there have been found small liquid water containing inclusions in some meteorites:
...

It was said long ago that celle-sized carbon spherules found in the Orgueil meteorite (carbonacous chondrite fell in France in late 19th century) could be bacteria. I don't believe this too much, and seemingly this prospect was abandoned. But those things could be some preleminary steps into the appearance of bacteria. But the life appearance process would have stop when conditions became too cold.

[Guest_RGClark_*]

Perhaps we could collect some of the 1.6% methane in the plumes to use as propellant. But you would need oxidizer. There is no oxygen in the plumes.
There is *very* tenuous molecular oxygen around Saturn rings. My guess is this would not be enough.
Is there a low energy method to get an oxidizer out of the water, nitrogen, and carbon monoxide in the plumes? (Separating oxygen out of H2O is energy intensive.)


Bob Clark

[Guest_BruceMoomaw_*]

There ain't even any significant amount of carbon monoxide in them, according to Cassini's UV spectrometer (which, unlike its mass spectrometer, can distinguish between CO and N2). There IS a few percent of carbon DIOXIDE -- but we're talking about extremely small, ghostly traces of total plume vapor anyway: not enough to extract any conceivably useful amount of propellant from in any case.

[nprev]

So that would be an imaging constraint but should not be a constraint on a sample return, right?

One crucial payload element should be a hi-res IR imager, regardless. A dark south pole might even be advantageous in this respect; hotspot localization would be greatly facilitated by removal of the ambient noise from sunlight.

[Guest_BruceMoomaw_*]

One crucial payload element should be a hi-res IR imager, regardless. A dark south pole might even be advantageous in this respect; hotspot localization would be greatly facilitated by removal of the ambient noise from sunlight.

Also, let's not forget that while Enceladus' south polar region would be shielded from direct sunlight, it would NOT be shielded from Saturnshine -- and we already know from Cassini that you can get some quite useful visible-light photos out of that.

[Guest_RGClark_*]

There ain't even any significant amount of carbon monixide in them, according to Cassini's UV spectrometer (which, unlike its mass spectrometer, can distinguish between CO and N2). There IS a few percent of carbon DIOXIDE -- but we're talking about extremely small, ghostly traces of total plume vapor anyway: not enough to extract any conceivably usefrul amount of propellant from in any case.

Yes I meant Carbon dioxide.


- Bob C.

[Guest_RGClark_*]

Perhaps we could collect some of the 1.6% methane in the plumes to use as propellant. But you would need oxidizer. There is no oxygen in the plumes.
There is *very* tenuous molecular oxygen around Saturn rings. My guess is this would not be enough.
...

This article in Science gives the estimated amount of molecular oxygen above the Saturn A ring:

Oxygen Ions Observed Near Saturn's A Ring.
J. H. Waite, Jr., T. E. Cravens, W.-H. Ip, W. T. Kasprzak, J. G. Luhmann, R. L. McNutt, H. B. Niemann, R. V. Yelle, I. Mueller-Wodarg, S. A. Ledvina, S. Scherer
Science, 25 February 2005: Vol. 307. no. 5713, pp. 1260 - 1262
http://www.sciencemag.org/cgi/content/abstract/307/5713/1260

It estimates the number of neutral O2 molecules as 10^4 to 10^5 cm^-3. However, they note it could be much higher than this range because of the limitations of the measurements. I'll take the upper number, 10^5 cm^-3. There are 10^15 cubic centimenters in a cubic kilometer so this amounts to 10^20 molecules per km^3.
The article gives the orbital velocity around Saturn at the radial distance of the A ring as in the range of 15 km/s. Actually the article explains there are magnetic effects that accelerate the various ionized molecules even faster which when exchanging momentum with the neutral molecules accelerate these faster as well. I'll use the 15 km/s number for simplicity. Then if we orbit the spacecraft in the opposite direction we would have a relative velocity with respect to these molecules in the range of 30 km/s. So if we had a scoop with a 1km x 1km opening we could collect 30 x 10^20 molecules of O2 per second. To calculate the mass of this oxygen, Avogadro's number of O2 molecules, 6.0 x 10^23, amounts to 32 grams. So 30 x 10^20 molecules is 5 x 10^-3 moles or (5 x 10^-3) x 32 grams = 160 x 10^-3 grams. This is the mass collected every second. There are 31,536,000 seconds in a year, so after a year we would have 31,536,000 x 160 x 10^-3 grams = 5,045,760 grams, or 5045.76 kilos of O2.

This article gives the density of water molecules around Enceladus:

Enceladus Eruptions Enceladus Eruptions
Larry W. Esposito Larry W. Esposito
Principal Investigator Principal Investigator
UV imaging Spectrograph UV imaging Spectrograph
http://saturn.jpl.nasa.gov/multimedia/prod...RM_Esposito.pdf

On page 21 is given the density of water molecules versus altitude. The greatest density shown is about 10^7 molecules per cubic centimeter at 200 km altitude. The methane is 1.6 percent of this amount, so 1.6 x 10^5 molecules/cc. However, you couldn't move at high velocity around Enceladus such as 15 km/sec because the orbital velocity around it is so low.
One possibility would be to put it at one of the two Lagrange points that is close to the satellite. The distance from the surface would be higher than 200km so the density of the methane would be lower. You would need pumps then to draw in the methane. You would also have to separate out the more prevalent water from the methane.

Getting back to the molecular oxygen found around the rings, the researchers also found monoatomic hydrogen and monoatomic oxygen. They give the amounts of the ionized versions, but not the larger neutral amounts.
Both of these are known to be very efficient for propulsion: pure monoatomic hydrogen has about 3 to 4 times the ISP (specific impulse) as H2 with O2 as an oxidizer. A problem though that still has not been solved is how to store the monoatomic propellants stably within a rocket.
If all you wanted to do was to accelerate the rocket from Saturn then you could just use the monoatomic hydrogen as it normally combusts by bringing the single atoms together. That is, you would not need to store it. You couldn't use it though as an onboard propellant to engage on trajectory changes or landings and launches form satellites.


Bob Clark

[The Messenger]

If all you wanted to do was to accelerate the rocket from Saturn then you could just use the monoatomic hydrogen as it normally combusts by bringing the single atoms together. That is, you would not need to store it. You couldn't use it though as an onboard propellant to engage on trajectory changes or landings and launches form satellites.
Bob Clark

A better choice, unless you need oodles of thrust, would be a simple hydrogen ion drive. Accelerating hydrogen is would be the most efficient way to replace spent fuel - assuming either solar or nuclear energy is still available.

[tty]

Anybody have any bright ideas about how to collect atoms coming in at 30 kms-1, sort them out and store the ones you want to keep? I don't say it's impossible, but methinks it's rather considerably beyond the state of the art so to speak.

Another problem nobody seems to have discussed. The material we want to catch from Titan and Enceladus is largely organics and volatiles, so it must be collected at rather low relative speed or it will melt or even vaporize on impact. Also it should be stored at low, preferably cryogenic, temperatures all the way back to Earth and through the landing. If we keep the collectors in an absolutely gas-tight container the temperature requirements could be less tight since the collected materials would still be around though in liquid or gas form. However many of the most interesting compounds, especially from Titan, might be changed beyond recognition.

tty

[dvandorn]

Anybody have any bright ideas about how to collect atoms coming in at 30 kms-1, sort them out and store the ones you want to keep? I don't say it's impossible, but methinks it's rather considerably beyond the state of the art so to speak.

I think it would be easier to simply build a Bussard ramjet-style system, where you take all of the mass you collect (via magnetic field scoops) and use it as reaction mass. No wasteful sorting of different elements -- just squeeze it all down, heat it all up, and shoot it all out the back end.

Of course, that's just as far beyond our current technologies as a scoop to collect all the atoms and molecules, sorting them out, storing what we can use and discarding the rest... but it might be a less difficult path to trod.

-the other Doug

[Guest_BruceMoomaw_*]

I do not see any conceivable way to collect enough gas from the Enceladus plume -- or any other part of the Saturn system -- to make a tinker's damn propulsion-wise. (That includes the methane from Titan's upper atmosphere, which is far denser at Cassini's altitudes than the Enceladus plumes -- which is why its mass spectrometer, which was designed to analyze the denser gas of Titan's exosphere, was limited to accuracies of a few percent in analyzing the Enceladus gas.) We really should stop this nonsense and concentrate on ideas that might have some engineering validity.

[Guest_RGClark_*]

I do not see any conceivable way to collect enough gas from the Enceladus plume -- or any other part of the Saturn system -- to make a tinker's damn propulsion-wise. (That includes the methane from Titan's upper atmosphere, which is far denser at Cassini's altitudes than the Enceladus plumes -- which is why its mass spectrometer, which was designed to analyze the denser gas of Titan's exosphere, was limited to accuracies of a few percent in analyzing the Enceladus gas.) We really should stop this nonsense and concentrate on ideas that might have some engineering validity.

It doesn't have to be Enceladus. It could be the Saturn ring system.
Also, it doesn't have to be the methane. It could be the water itself. If you had a power system on board you could heat the water to break apart the H2O. Admittedly this would be energy intensive.


Bob Clark

[Guest_Richard Trigaux_*]

Perhaps we could collect some of the 1.6% methane in the plumes to use as propellant. But you would need oxidizer. There is no oxygen in the plumes.
There is *very* tenuous molecular oxygen around Saturn rings. My guess is this would not be enough.
Is there a low energy method to get an oxidizer out of the water, nitrogen, and carbon monoxide in the plumes? (Separating oxygen out of H2O is energy intensive.)
Bob Clark

As the thread "owner" I would like you avoid discussing further this idea. Everybody is free to submit any idea or question, but this one was replied as completelly unfeasible in practice, and by very far. Eventually there is not enough material in the whole E ring to fill a rocket tank. At a pinch, I prefer the Greenpeace's idea (as an alternative to Cassini's nuclear RTG) of using very large solar panels and a ion drive.


Anyway with the mission discussed here, the probe just goes through Saturn's realm with an hyperbolic trajectory. No satellisation, no large delta V. It only needs a few trajectory corrections (especially if we abandon the idea of catching Titan) but in a short time (approach of Enceladus). It is what makes this mission cheap and simple: few fuel implies light probe, implies small rocket to launch, implies low cost. Much lower than Cassini or Europa lander, so that it could be done by the way, without impeding larger projects. Eventually a good start for other countries than the US or Russia. In the Hayabusa style.

[Guest_RGClark_*]

As the thread "owner" I would like you avoid discussing further this idea. Everybody is free to submit any idea or question, but this one was replied as completelly unfeasible in practice, and by very far. Eventually there is not enough material in the whole E ring to fill a rocket tank. At a pinch, I prefer the Greenpeace's idea (as an alternative to Cassini's nuclear RTG) of using very large solar panels and a ion drive.
Anyway with the mission discussed here, the probe just goes through Saturn's realm with an hyperbolic trajectory. No satellisation, no large delta V. It only needs a few trajectory corrections (especially if we abandon the idea of catching Titan) but in a short time (approach of Enceladus). It is what makes this mission cheap and simple: few fuel implies light probe, implies small rocket to launch, implies low cost. Much lower than Cassini or Europa lander, so that it could be done by the way, without impeding larger projects. Eventually a good start for other countries than the US or Russia. In the Hayabusa style.

As thread "owner", I'll accept that.


Bob Clark

[Guest_Richard Trigaux_*]

Another problem nobody seems to have discussed. The material we want to catch from Titan and Enceladus is largely organics and volatiles, so it must be collected at rather low relative speed or it will melt or even vaporize on impact. Also it should be stored at low, preferably cryogenic, temperatures all the way back to Earth and through the landing. If we keep the collectors in an absolutely gas-tight container the temperature requirements could be less tight since the collected materials would still be around though in liquid or gas form. However many of the most interesting compounds, especially from Titan, might be changed beyond recognition.

tty

This is an interesting question.

First, what is interesting in Enceladus plume, is not gas or water, but eventual larger solid particules, which would contain complex organic molecules, eventually proto-life. Aerogel would catch them easily. Of course, we cannot expect to find living bacteria in the aerogel (even if there are in the plume) but molecules like RNA, proteins, cell membranes, catalysts, would be easily recognizable. Even ribosomes or centrosomes would be. At a pinch, it would be safier not to bring back alien living bacteria on Earth...

Gas or water are not interesting to bring back, as every water is like Earth water. We just need the quantities. Eventually a good motive to bring them back on Earth would be isotopic analysis, or trace elements.

For this I think we don't really need a cryogenic (and it would be difficult to build, requiring a heavy coolant tank, to work for years). It would be enough to have an airtight container (eventually self-welding) with a small tap to examine gasses before opening the container. But from the experience of the unhappy Genesis probe, it would be better if this container would be able to survive without its parachute... especially if it contains alien bacteria.


I just wonder of an idea to safely receipt contaminated sample return capsules: using the Moon as a gravitationnal aid, to plave the capsule on an orbit around Earth in place of directly receiving it on the ground. Of course it would be costy to recover from its orbit, but much less costy than some devastative epidemy. Such a recovery would be a good use for a space station (at last one ). And if the crew is contaminated, we just sacrifice the station and crew to avoid contaminate the Earth.

[dvandorn]

Gas or water are not interesting to bring back, as every water is like Earth water...

Hmmm -- I'd think we would want to see ice and water from the outer solar system, to see what the oxygen isotope ratios are within it. Our understanding of the structure of the early solar nebula is limited at best -- we need a lot more data points in order to fully pin down origin locations within the nebula based on given isotope ratios.

-the other Doug

[Guest_Richard Trigaux_*]

after what they say, Enceladus has the composition of a soda.

[Guest_Myran_*]

Perhaps its time to ask one of those really stupid questions again.

The rings of Saturn have been thought to be rather shortlived.
Now we found that Enceladus is the source of the outer parts, would it not be logical to assume its the source of the entire ring system?
So would we not be able to get samples from Enceladus by getting samples from the rings then?

[Guest_Richard Trigaux_*]

Perhaps its time to ask one of those really stupid questions again.

The rings of Saturn have been thought to be rather shortlived.
Now we found that Enceladus is the source of the outer parts, would it not be logical to assume its the source of the entire ring system?
So would we not be able to get samples from Enceladus by getting samples from the rings then?

That the saturn rings are short-lived is yet just a theory. That Enceladus created them all seems far fectched: it is sure that it created the E ring with fine ice particules, but the main rings are formed of larger blocks, up to some metres. Enceladus cannot have formed them with just some snow.


Even if the rings were made of Enceladus matter, anyway this matter is exposed to cosmic rays and solar UVs for many years. If there are biological molecules (and eventually remnants of bacteria) they are burned from long ago, and they cannot provide decisive evidences.

From where, the interest of an Enceladus fly-by is to catch the fresh material, not yet exposed to radiations. If there are biological molecules or forms, we can gather them intact.

There was already a discution about how "fresh" would be the material gathered at, say, 50kms above Enceladus. It was concluded that the material would be gathered some minutes after emission, so that space radiations or solar UVs had not time to alter it. Eventual life evidences would be tell tale.

[ugordan]

That Enceladus created them all seems far fectched: it is sure that it created the F ring with fine ice particules

That would be the E ring. F ring is the narrow one shepherded by Prometheus and Pandora and has all those kinks and braids.

[Guest_Richard Trigaux_*]

That would be the E ring. F ring is the narrow one shepherded by Prometheus and Pandora and has all those kinks and braids.

Yes, thanks to correct, I was mistaking. I corrected in the original post.

[Guest_Richard Trigaux_*]

I would like to add that such a mission is much cheaper than a large Cassini-style mission. So perhaps it could fit into a private budget, like the first amateur rocket to space. If we use a falco rocket, the lauch could be cheaper (provided the Falcon demonstrates its capacity of course). But in this case, the ship will have to operate entirely in autonomous mode, as there would be no large DSN dishes available to operate it.

It could be too a first mission for a new state involving into space.

We must however think that such a mission, even if the ship is small, will however need all the gear of a large ship: attitude control, engines, radio transmitters... and a guiding camera. It will also have to carry an heatshield for re-entering Earth atmosphere.

We could save a RTG in using no radio transmitter and using high efficiency solar cells (still possible on saturn, but difficult) or a fuel cell activated when near Saturn.

[djellison]

I can't imagine anyone being able to do such a mission with anything less than a New Frontiers budget ( $750M+ ) - and it's just unrealistic to suggest it would be a new space fairing nations first mission into deep space - it's a mission that would require a LOT of experience with deep space tracking, and seriously accurate navigation.

Doug

[Guest_Richard Trigaux_*]

I can't imagine anyone being able to do such a mission with anything less than a New Frontiers budget ( $750M+ ) - and it's just unrealistic to suggest it would be a new space fairing nations first mission into deep space - it's a mission that would require a LOT of experience with deep space tracking, and seriously accurate navigation.

Doug

Yes you are right, but on the pro side the craft would be much lighter than a New Frontier or Cassini class. But it is true that such a project would need to hire an experienced team, with experienced persons, at least at technical management level.

Doing an entirely autonomous mission would also save the need and cost of a remote control tracking, but would also raise new robotic issues. Not so new, as we have the Cassini experience, and the craft would behave a bit like a homing missile (even if the navigation requirements are completelly different).

[djellison]

We just don't have the ability to do the very very fine auto-nav that would be required out there. It will require people in the loop throughout the mission.

Doug

[Guest_Richard Trigaux_*]

We just don't have the ability to do the very very fine auto-nav that would be required out there. It will require people in the loop throughout the mission.

Doug

In this case, we need a radio transmitter, a dish, a DSN radio link, a RTG, etc and true we have to deal with much of the cost of a larger mission, we save only at launching. Especially there will be no RTG in an amateur mission or even on any non-american mission.

An autonav mission would anyway need a smart program (not just executing instructions, but able to adapt to unexpected situations) and also some kind of camera to aim at Enceladus, as it is absolutely out of question to predict Enceladus position with an accuracy of 10kms or less.

I don't see a large agency like ESA or NASA trying the autonav version, given the incertitudes. They would do a more classical remote control, and they would be right. But for an amateur mission, this concept makes it much more challenging.

[Guest_Richard Trigaux_*]

Richard, nothing -- and I mean, absolutely nothing -- in the private sector world *ever* gets done without *any* positive cash flow. No one is ever going to put up a few hundred million dollars for a planetary probe just because they want to see what's out there. Not without some way of generating some income out of it.

Even if Falcon worked (which it has not, as of yet) and even if the Falcon developmental costs (suffering from little, seemingly unimportant expenses, like needing to launch six or seven of them before they get the bugs out, or building an oxygen liquifaction plant so they can actually launch the things without having to wrap them in blankets that flap back onto the thrust chambers and damage them) don't push the eventual costs of a Falcon launcher up into the same range as the currently available launchers, there are still a lot of significant costs you're overlooking. For example, the DSN isn't cheap. How are you going to command your private Enceladus probe, or get data back from it, unless you pay the $10,000 or more an hour that using the DSN costs? Gonna build a new DSN? If so, how are you going to make it cheaper than the current DSN (seeing as how, AIUI, the current DSN is already a private enterprise)?

There are *maybe* three people in the world who have enough money to do something like this, and even they can only do this once or twice, at most, without bankrupting themselves. Corporations simply will not undertake such missions, since there is no chance of ever generating any income from them to match the outflow, or even to pay for a tenth of the costs. Corporations simply do not spend out millions of dollars for no return.

It's a nice dream, Richard. But that's all it is -- a dream.

-the other Doug

(moved out of the SETI thread)

Yes, a dream... like the first amateur manned rocket to space. Yes, affordable to only three persons... and all this kind of arguments. But a dream worthy of mentionnin git, don't you think so? We cannot expect such amateur missions to really challenge the great space agencies on their own ground. At least not on the short run. But some amateurs showed that they have too abilities, and they could do some unexpected little things. Wait and see.

[ljk4-1]

(moved out of the SETI thread)

Yes, a dream... like the first amateur manned rocket to space. Yes, affordable to only three persons... and all this kind of arguments. But a dream worthy of mentionnin git, don't you think so? We cannot expect such amateur missions to really challenge the great space agencies on their own ground. At least not on the short run. But some amateurs showed that they have too abilities, and they could do some unexpected little things. Wait and see.

It is a nice sentiment - and easy to say - but where and what are all the stages
to make it a reality? It's one thing to have a few overly rich people with lots of
time and money on their hands make a couple of suborbital flights and then charge
absurd amounts of money for only a minority of the public to hop a quick ride, but
where does one go from there to make this accessible to the rest of the populace?
And is there going to be an actual destination besides a quick view of a curved Earth?

As Doug said, companies tend not to support such endeavors out of the goodness
of their hearts for the benefit of humanity.

To aim this at deep space probes, unless and until the day comes that these robot
explorers can build, launch, and run themselves, they will not be cheap projects and
no one is going to give all that money just to explore strange new worlds so a bunch
of scientists will have something to put in their papers to Science. I also do not think
a couple of bake sales will cut it.

As Henry David Thoreau once said: "If you have built castles in the air, your work
need not be lost; that is where they should be. Now put the foundations under them."
- Walden, 1854

http://en.wikiquote.org/wiki/Henry_David_T..._18:_Conclusion