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clean slate
super member
Reged: 01/16/06
Posts: 124
Loc: New York
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With all of this talk about what is and isn't a planet, I haven't heard anybody mention whether objects like pluto could support salt-water oceans (or ammonia-water such as Triton is suggested to have). Under the right conditions, shouldn't it be feasible that an icy planet with enough mass, and orbited by a large enough moon, could have a liquid water layer much the way of Europa?
I remember reading about a "super earth" exoplanet orbiting a red dwarf approximately 25,000 LY away. If I'm remembering correctly, it was 5.5 Earth masses. Obviously, at it's distance of 1 AU it would be much too cold for surface water. But, due to radioactive decay, I would assume a subsurface ocean would be possible, if not probable. Combined with the numerous bodies in our solar system that are supposed to have subsurface oceans, I don't think we're really that "alone" after all. Even if a tiny percentage of bodies able to support life actually do, using the basics of solar system formation we understand, that would leave billions of planets, moons, or other objects with *at least* microbial life.
Thoughts?
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10" Zhumell Dobsonian
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10898
Loc: Amargosa Valley, NV, USA
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I think that a 5.5 earth-mass body should be more than large enough to support an internal ocean, and keep it liquid through radioactive decay. I don't think having a large moon would be necessary at all.
The main thing that has been bothering me of late about the possible appearance of life on watery worlds is the chemistry of that water. If it's briny and/or acidic, such as Mars's ancient seas are reputed to be, would that make it more difficult for life to develop?
Earth has a large reservoir of carbonate rocks that buffer its oceans and keep acid from building up. Mars has only traces of carbonates, for some reason that I don't understand.
I think we need to high-tail it over to Europa as soon as possible, and see just what is being emitted from those broken ice-slab boundaries.
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"S.O.E." (Sauron's Other Eye) 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Next Project: The "Eye of Sauron" Observatory!
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clean slate
super member
Reged: 01/16/06
Posts: 124
Loc: New York
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Quote:
I think we need to high-tail it over to Europa as soon as possible, and see just what is being emitted from those broken ice-slab boundaries.
Another reason I don't understand the hype surrounding Pluto. Why is NASA wasting valuable resources sending New Horizons to Pluto? Why not invest that money and time in more flyby probes to Jupiter or Saturn's moons? I know I'm being selfish, but I'd like to see a lander/melter probe for Europa in my lifetime. Unfortunately, looking at things realistically, I will never see that (and I'm only 22). It's almost depressing to know so much discovery is going on, but at the same time, so little knowledge about many enormous questions is being gained.
Quote:
I think that a 5.5 earth-mass body should be more than large enough to support an internal ocean, and keep it liquid through radioactive decay. I don't think having a large moon would be necessary at all.
I thought so, too. For some reason, astronomers talking about the subject on TV and in print said life wouldn't be possible. And I don't think they meant multicellular surface -dwelling life. Strange.
Quote:
The main thing that has been bothering me of late about the possible appearance of life on watery worlds is the chemistry of that water. If it's briny and/or acidic, such as Mars's ancient seas are reputed to be, would that make it more difficult for life to develop?
That seems to be the consensus, but I'm not a biochemist, so I can't say what is possible. Of course, since we don't know exactly what conditions life first appeared in on Earth, it is all conjecture. Again, I'm not a geologist or chemist, so I have no idea why a warm salty brine is more conducive to the development of long chain carbon molecules (specifically nucleic acids) than hydrothermal vents or other areas. At some point I've read why, but it has slipped my mind.
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Earth has a large reservoir of carbonate rocks that buffer its oceans and keep acid from building up. Mars has only traces of carbonates, for some reason that I don't understand.
That's very interesting. I wonder if Venus is/was more similar to Earth or Mars in that respect.
In the same way, I've always wondered why Venus is a hellish world of runaway greenhouse, and if Earth could ever truly have a similar fate. Not to get political, but I doubt our effects on the environment could take such a toll. I believe we'll do severe damage to this planet before we go the way of 99.99% of the species before us. But, I'm sure eventually the Earth will recover to a state of ice ages and warming spells. I'm also convinced that multicellular life still has a long time (hundreds of millions of years) to go before the planet is too hot. I wonder, how long will microbes hang on?
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10" Zhumell Dobsonian
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LittleDob
Pooh-Bah
Reged: 12/10/04
Posts: 1443
Loc: Here or there
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Quote:
Earth has a large reservoir of carbonate rocks that buffer its oceans and keep acid from building up. Mars has only traces of carbonates, for some reason that I don't understand.
The Mars rovers have detected a mineral called jarosite, a sulphate mineral, that precipitated from ancient waterbodies. The presence of such a mineral indicates that the water would have been a very strong brine, which would inhibit the precipitation of carbonates. So despite the "warm and wet" past on Mars and the abundance of CO2, carbonates were unable to precipitate. The carbonate paradox is perhaps best explained by these new data.
Even more troublesome for life on Mars is that the dust storms that rage on the surface create an electrical charge that oxidizes the surface and produces corrosive chemicals such as hydrogen peroxide. Read more here.
Intense radiation, low temperatures, strong brines, corrosive chemicals.....perhaps not the kind of place that many hoped mars to be.
Jason
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Jason
"Civilization exists by geological consent, subject to change without notice." Will Durant
NexStar 11 GPS 
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10898
Loc: Amargosa Valley, NV, USA
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It's a catch-22. If there were enough carbonates there to begin with, the very strong acidic brine that inhibits its precipitation wouldn't be able to exist. So that raises the question of how carbonates were able to form on earth.
Both Mars and Earth formed with abundant carbon. Both formed with abundant water. Both should have formed carbonates, or neither. There's another missing piece of the puzzle, another chemical influence which either Mars or Earth possessed in excess of the other.
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"S.O.E." (Sauron's Other Eye) 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Next Project: The "Eye of Sauron" Observatory!
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LittleDob
Pooh-Bah
Reged: 12/10/04
Posts: 1443
Loc: Here or there
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Quote:
It's a catch-22. If there were enough carbonates there to begin with, the very strong acidic brine that inhibits its precipitation wouldn't be able to exist. So that raises the question of how carbonates were able to form on earth.
Hi Dave,
Mars didn't have the carbonates to begin with. At least not in aqueous form in the "oceans" that precipiated into carbonate rock. The atmosphere was CO2 rich, and the waterbodies there must have taken up some of the CO2, but not enough uptake to precipitate carbonates in mineral form. The salinity of these waters would serve to further prevent mineral precipitates. Also the volcanic degassing of sulphates in the atmosphere may have produced acid raid that would have dissolved any early formed carbonates. This is a good explanation.
Although there are no large outcrops of limestone on Mars, there are carbonates in the Martian dust. So maybe a little mineral precipitation did squeak through.
Alternatively, there are suggestions that carbonate outcrops did from early on, but were subsequently destroyed and the CO2 released back into the atmosphere.
Quote:
Both Mars and Earth formed with abundant carbon. Both formed with abundant water. Both should have formed carbonates, or neither. There's another missing piece of the puzzle, another chemical influence which either Mars or Earth possessed in excess of the other.
Biological catalyst? In addition to the chemical process, carbonates can form through biological processes (some biochemists argue that even the "chemical" process is mediated by microbes). Could it be that the great difference between Earth and Mars is that organisms in the oceans of Earth facilitated the precipitation of carbonates here?
Another thought is that Earth has it's carbon cycle, with biological processes forming carbonate rock and tectonic processes releasing the CO2 back in the atmosphere. Over the course of geological time, this cycle keeps a certain amount of limestone lying around. Perhaps Mars, lacking in such organisms and similar tectonic processes, has processes that are more unidirectional than the cyclical balance that is achieved on Earth?
Edited by LittleDob (08/17/06 02:09 PM)
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LivingNDixie
Lord of Ferrets
Reged: 04/23/03
Posts: 15913
Loc: Hoover, AL
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Well here was where they were looking into a Europa mission.
http://research.hq.nasa.gov/code_s/nra/current/AO-99-OSS-04/apendixb.html
More information:
http://centauri.larc.nasa.gov/outerplanets/datainterface.pdf
The other links I have found searching on NASA will not come up?!?! 
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Preston
Celestron 11" Nexstar GPS XLT
Tak FS 78
Lunt LS60T/Ha 60mm f/8.33 (on order)
Vixen Porta Mount
Edited by LivingNDixie (08/17/06 02:09 PM)
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10898
Loc: Amargosa Valley, NV, USA
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Quote:
Quote:
It's a catch-22. If there were enough carbonates there to begin with, the very strong acidic brine that inhibits its precipitation wouldn't be able to exist. So that raises the question of how carbonates were able to form on earth.
Hi Dave,
Mars didn't have the carbonates to begin with. At least not in aqueous form in the "oceans" that precipiated into carbonate rock. The atmosphere was CO2 rich, and the waterbodies there must have taken up some of the CO2, but not enough uptake to precipitate carbonates in mineral form. The salinity of these waters would serve to further prevent mineral precipitates. Also the volcanic degassing of sulphates in the atmosphere may have produced acid raid that would have dissolved any early formed carbonates. This is a good explanation.
Although there are no large outcrops of limestone on Mars, there are carbonates in the Martian dust. So maybe a little mineral precipitation did squeak through.
Alternatively, there are suggestions that carbonate outcrops did from early on, but were subsequently destroyed and the CO2 released back into the atmosphere.
Quote:
Both Mars and Earth formed with abundant carbon. Both formed with abundant water. Both should have formed carbonates, or neither. There's another missing piece of the puzzle, another chemical influence which either Mars or Earth possessed in excess of the other.
Biological catalyst? In addition to the chemical process, carbonates can form through biological processes (some biochemists argue that even the "chemical" process is mediated by microbes). Could it be that the great difference between Earth and Mars is that organisms in the oceans of Earth facilitated the precipitation of carbonates here?
Another thought is that Earth has it's carbon cycle, with biological processes forming carbonate rock and tectonic processes releasing the CO2 back in the atmosphere. Over the course of geological time, this cycle keeps a certain amount of limestone lying around. Perhaps Mars, lacking in such organisms and similar tectonic processes, has processes that are more unidirectional than the cyclical balance that is achieved on Earth?
All great explanations, Little Dob. And a nice link, too. We're left with two possibilities then, both of which seem to limit the conditions under which life can develop.
The first is that Mars' size was the limiting factor, and that there wasn't enough time to retain water and atmosphere while sulphates were still concentrating on Mars' surface. The second is the possibility that the amount of original sulphur incorporated into Mars was greater by percentage than in Earth, and the proportion overwhelmed the available carbon.
They both sound plausible -- Mars' greater distance from the sun might have meant its local environment was somewhat more enriched with lighter and more volatile elements such as sulphur.
If true, this introduces some pessimism to the idea of finding life on or in Europa, and may introduce the idea that carbonates are one of the essential ingredients of developing carbon-based life.
It's true that on Earth today the great majority of carbonate rocks is produced by biological processes. If carbonates are essential to counteracting over-acidity of planetary oceans, however, the mechanism for producing non-biologic carbonates must have been working during the pre-biotic era.
I think this is a real problem that needs to be resolved, then: How did earth avoid filling its basins with an acidic, saturated brine instead of the mildly salty, buffered seas it possesses?
The answer can't be plate tectonics alone, because that would recycle sulphur as well as carbon. I need to see what I can find on sulphur abundance for Mars vs Earth...
Sorry for doing so much thinking out loud lately!   
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"S.O.E." (Sauron's Other Eye) 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Next Project: The "Eye of Sauron" Observatory!
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