Biology! Don't see too many of these. Eurpoa missions.

[LordFerret]

The list of microorganisms that can survive the conditions of space is short. Many have been tested on the ISS and other programs. We were discussing the Jovian system... a high radiation environment. The everyday common bacteria we face are not something I would think will be an issue, I doubt they would survive the trip.

On the other hand, I'll acknowledge that life is very persistent. I've no doubt we've carried a number of things to the places we've been. In that light, I guess it doesn't matter much as we've then already contaminated half the bodies in our solar system. - http://en.wikipedia.org/wiki/List_of_landings_on_extraterrestrial_bodies

[sndrtj]

Busting proteins with heat isn't always a big deal. I actually have a bio degree and know how they deal with spaceship sterilizations and I've had to work in sterile environments for cell culture and such... left that out of the op. I've denatured plenty of proteins with heat for certain kidns of assays. Plus bacterial endospores can be fine with boiling water, as can other kinds of 'living' things. And I'm sure you all know about tardigrades or Deinococcus radiodurans. I know you can't be 100% sure of sterile anything. I'm just thinking, if there's potentially a bunch of liquid water there, you're going to have to think pretty hard to make sure you don't accidentally dump something that can live in there. I mean, it might not actually be able to live in there, but that's not really something you can chance.

Maybe we just gamma radiate the probe for a long time and hope the instruments are cool with it.

Dude, go back to biology class please. Just the fact that you whiff some ethanol in your fume hood before and after you work in the cell culture lab, does not mean anything is truly sterile there! Your lab coat, hair, gloves, basically _ANYTHING_ has bacteria adhere to it. Just one tiny flake of skin, a broken hair, a tiny thread of cloth, and it all contains several hundred of thousands of microorganisms. Everyone who's worked on a daily basis in a regular cell culture lab has at one point experienced a yeast infection in their cultured cells; that's not a shame, that's just part of the deal And just heating things... good enough to denature proteins if you're working with the raw material, but real living things have such things as heat shock proteins, chaperones, sugar-coated surfaces etc eetc. That's why your biological waste (probably the blue bins in your lab) are not just heated, they are autoclaved. Even then you still have the extremophiles; I've worked with archaea whose optimal growth temperature is actually 80 degrees C.

I once had a pet project where the goal was to kill a culture of simple E. coli without using chlorine. It's much harder than you'd think. It involved several cycles of water bathing at near boiling temperature, followed by flash freezing (liquid alcohol: approx -80C), repeat a few times, try incubating with lysozyme and more. Even with all these, there were still some nasty cells that just wouldn't want to die. Conclusion: killing bacteria is harder than you think.

[Dunbaratu]

If we went to Callisto and used it as a base of operations, surely we'd end up making an 'environmental' impact ... doing no less damage per say than we would if we went straight to Europa. I don't see how we could manage not to.

Spoiling the Callisto environment isn't the concern that's driving this issue. Spoiling the experiment's validity is the concern. An experiment to test if Callisto has life, that's designed to be extremely sensitive to find the tiniest trace of life, needs to be sure not to generate a false positive from the life the probe brought with it.

[numerobis]

Maybe we just gamma radiate the probe for a long time and hope the instruments are cool with it.

Not nearly enough; you don't need much to shield gamma rays.

Keep in mind that anything that will be killed by a trip through space isn't a worry when it comes to seeding another planet with our bugs. So, almost by definition, the only things to worry about are extremophiles. Those can survive much higher temperatures than what one normally deals with; a couple hundred degrees is required to be sure (I forget exactly the figure I read) -- but basically, if you're killing the bugs, you're seriously damaging plastic (melting? burning? chemically modifying? I forget) and likely you're throwing off calibrations. So all you can do is a best-effort, you'll never kill everything.

The bigger worry in my mind (and in that of many in the field) is whether any of the experiments designed to check for life are actually finding life, or just contamination from home. There, even dead bugs are a problem: finding dead bugs on Mars would be huge news; it would be disappointing if they actually were stowaways that got zapped dead during the trip.

[LordFerret]

Spoiling the Callisto environment isn't the concern that's driving this issue. Spoiling the experiment's validity is the concern. An experiment to test if Callisto has life, that's designed to be extremely sensitive to find the tiniest trace of life, needs to be sure not to generate a false positive from the life the probe brought with it.

Understood. The absolute guarantee of such is the thing I'm not so sure we can bank on - all things considered. We would need to somehow manage total decontamination, or at least expect to see and account for such contamination in the samples... (This rings a bell with me in past experiences with applied liquid and gas spectrography/chromatography.) Europa was the initial target/topic. Callisto was brought up after the fact (by Bill Phil), as an alternative option place to seek, and as a good option to base Europa tasks from.

[fenderzilla]

what if we make the probe fall super close to the sun before heading out to jupiter?

[EzinX]

One nasty problem is that anything that will kill an extrophile for certain will probably damage the sensitive parts on the probe - the plastics, circuit boards, etc.

[KerikBalm]

Dude, go back to biology class please. Just the fact that you whiff some ethanol in your fume hood before and after you work in the cell culture lab, does not mean anything is truly sterile there! Your lab coat, hair, gloves, basically _ANYTHING_ has bacteria adhere to it. Just one tiny flake of skin, a broken hair, a tiny thread of cloth, and it all contains several hundred of thousands of microorganisms. Everyone who's worked on a daily basis in a regular cell culture lab has at one point experienced a yeast infection in their cultured cells; that's not a shame, that's just part of the deal And just heating things... good enough to denature proteins if you're working with the raw material, but real living things have such things as heat shock proteins, chaperones, sugar-coated surfaces etc eetc. That's why your biological waste (probably the blue bins in your lab) are not just heated, they are autoclaved. Even then you still have the extremophiles; I've worked with archaea whose optimal growth temperature is actually 80 degrees C.

I once had a pet project where the goal was to kill a culture of simple E. coli without using chlorine. It's much harder than you'd think. It involved several cycles of water bathing at near boiling temperature, followed by flash freezing (liquid alcohol: approx -80C), repeat a few times, try incubating with lysozyme and more. Even with all these, there were still some nasty cells that just wouldn't want to die. Conclusion: killing bacteria is harder than you think.

*edit* note there is a big difference between a fume hood and a cell culture hood. Also note that a culture hood has more than just ethanol to reduce the biological load (mainly lots of UV light, plus filtering the air))

At the same time... the conditions a microbe can tolerate for short periods, are not the same as those where it can proliferate.

It is very hard to culture many things in the lab. Many of these extremophiles which will tolerate all these extreme conditions, won't do well on a normal agar plate at room temp.

Deinococcus has truly impressive DNA repair capabilities, but it needs a source of energy to operate.

Prolonged radiation exposure, coupled with "starving" the microbes, should render it sterile... but "prolonged" in this case could be years.

That said... only the surface of the probe needs to be sterile. If you had a sphere of iron, hollow inside with insulation, you could heat the exterior until it was red hot, without damaging the insides, and the surface would be quite sterile.

I'm also not aware of anything that would survive being doused in paraformaldyhyde, or even just ethanol or isopropanol. However, then you always need to worry about little cracks/crevices/pits where the PAF didn't reach.

back to the microbes though... *IF* there is life on Europa, it is highly likely that it would outcompete any extremophile that managed to survive the sterilization procedures and the trip there, because it is not adapted to the conditions on Europa. The salt concentrations/the other nutrient concentrations, the temperature, the dissolved gas concentration, pressure, etc, will all be different from what the hitchhiker evolved in.

Many microbs are quite selective about what conditions they grow in. Many of these microbes develop very durable spores that can wait a long time in very harsh conditions until the right conditions are present again.

Just because you failed to kill it, doesn't mean it will grow on Europa.

Of course, the risk is there.

If Europa has life, I think the few spores that would get there would be outcompeted (particularly if the alien biochemistry is sufficiently different, the Earth microbe would have an even harder time adapting)

Then there is the other question:

If Europa has no life... should we try to seed it with life?

Should we try and seed mars with life? I'm thinking those geysers/ "spider features" are a good candidate... theres water ice there, I could imagine some earth organisms germinating during the warmer periods...

Of course, you can't do much in the way of analysis like that.

Edited December 10, 2014 by KerikBalm

[YNM]

*edit* note there is a big difference between a fume hood and a cell culture hood. Also note that a culture hood has more than just ethanol to reduce the biological load (mainly lots of UV light, plus filtering the air))

At the same time... the conditions a microbe can tolerate for short periods, are not the same as those where it can proliferate.

It is very hard to culture many things in the lab. Many of these extremophiles which will tolerate all these extreme conditions, won't do well on a normal agar plate at room temp.

Deinococcus has truly impressive DNA repair capabilities, but it needs a source of energy to operate.

Prolonged radiation exposure, coupled with "starving" the microbes, should render it sterile... but "prolonged" in this case could be years.

That said... only the surface of the probe needs to be sterile. If you had a sphere of iron, hollow inside with insulation, you could heat the exterior until it was red hot, without damaging the insides, and the surface would be quite sterile.

I'm also not aware of anything that would survive being doused in paraformaldyhyde, or even just ethanol or isopropanol. However, then you always need to worry about little cracks/crevices/pits where the PAF didn't reach.

back to the microbes though... *IF* there is life on Europa, it is highly likely that it would outcompete any extremophile that managed to survive the sterilization procedures and the trip there, because it is not adapted to the conditions on Europa. The salt concentrations/the other nutrient concentrations, the temperature, the dissolved gas concentration, pressure, etc, will all be different from what the hitchhiker evolved in.

Many microbs are quite selective about what conditions they grow in. Many of these microbes develop very durable spores that can wait a long time in very harsh conditions until the right conditions are present again.

Just because you failed to kill it, doesn't mean it will grow on Europa.

Of course, the risk is there.

If Europa has life, I think the few spores that would get there would be outcompeted (particularly if the alien biochemistry is sufficiently different, the Earth microbe would have an even harder time adapting)

Read here (not the best out but least it cites papers). Granted that Voyagers didn't really sterilized (so we just avoid crashing onto any planet or bodies). I do agree that it might be outcompeted, but look at that Voyager again : 30 years in space, ~10000 still viable. With a shorter timescales (I mean, maybe just <10 years) it should have more viable bacteria. I don't know; Huygens landed on Titan. Maybe ESA already have the ways for it... NASA itself puts Cassini under Category II in it's scheme.

Then there is the other question:

If Europa has no life... should we try to seed it with life?

Should we try and seed mars with life? I'm thinking those geysers/ "spider features" are a good candidate... theres water ice there, I could imagine some earth organisms germinating during the warmer periods...

Of course, you can't do much in the way of analysis like that.

That'd violate the Outer Space Treaty Article IX.

Edited December 10, 2014 by YNM

[KerikBalm]

That is not entirely clear, the text in question:

States Parties to the Treaty shall pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter and, where necessary, shall adopt appropriate measures for this purpose. If a State Party to the Treaty has reason to believe that an activity or experiment planned by it or its nationals in outer space, including the Moon and other celestial bodies, would cause potentially harmful interference with activities of other States Parties in the peaceful exploration and use of outer space, including the Moon and other celestial bodies, it shall undertake appropriate international consultations before proceeding with any such activity or experiment.

The first part... its not clear if they mean contamination of the target body, or contamination of Earth:

"conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter"

Its not clear if the *and* should be read as applying like so

1) "harmful contamination"/"adverse changes in the environment" + "of the Earth resulting from the introduction of extraterrestrial matter "

or

2)"harmful contamination"/"adverse changes in the environment of the Earth" + "resulting from the introduction of extraterrestrial matter "

- which would be odd because the word extra-terrestrial means not from earth, but it wouldn't mean something from earth going to Europa (though I could see people interpreting it in a general sense to mean any material foreign to the celestial body in question)

or fully

3) "harmful contamination"/"adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter"

-which would be odd because they don't elaborate on what they mean about harmful contamination of the foreign body, and they take a more specific and narrow scope for the protection of Earth, which if anything you would expect to have broader protections out of self interest.

So I'm going to chose (1) as the correct interpretation, and we can parse it like so:

"conduct exploration of them so as to avoid their harmful contamination of the Earth resulting from the introduction of extraterrestrial matter"

and also

"conduct exploration of them so as to avoid adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter resulting from the introduction of extraterrestrial matter"

It could be read like that, where they don't really give a **** about the extraterrestrial body, they just don't want you bringing anything back to Earth that could cause trouble.

Maybe some translations should be examined, that don't have this ambiguity.

There is a reason that many acts of legislation are not written in this format.

Sometimes i think treaties are intentionally vague.. but lets not get into politics.

The other part would be "would cause potentially harmful interference with activities of other States Parties in the peaceful exploration and use of outer space"

If someone wants to study the pre-biotic conditions of Europa, or any native biota, spamming Europa with bacteria is going to interfere with that... but the treaty only requires " appropriate international consultations before proceeding with any such activity or experiment."

Edited December 10, 2014 by KerikBalm

[lajoswinkler]

Like we sterilize any spacecraft that's going beyond LEO. That's a big part of the cost of these missions, making sure everything is as sterile as possible.

Just look at Curiosity:

http://media3.washingtonpost.com/wp-srv/photo/gallery/100921/GAL-10Sep21-5799/media/PHO-10Sep21-253550.jpg

Everything is done in a clean room and I bet these dudes have to take very special measures to do their work.

What you see in the photograph is not a sterile environment, and the rover is certainly not sterile.

[Idobox]

There's something everybody overlooked about contamination:

If something can survive the sterilization process and the trip to Europe, it could very well survive being ejected from the atmosphere by a meteor impact.

Sure, it doesn't happen very often that rocks from one planet en up on one other, but we have several Mars rocks on Earth, so it does happen.

It means there must Earth rocks all over the solar system, carrying extremophiles, and some of them have already crashed on Europa. True, most of them will take a lot more than 10 years to get there, since they will require some gravity assist to get the deltaV, but that doesn't sound terribly harsher than what stowaways on a Europa probe would face.

Beyond that, I love the idea of a sealed probe that is scorched to insane temperatures. You could also use strong oxidizers like chlorine trifluoride to really be sure.

[KerikBalm]

yea, but the surface of Europa is no picnic either, it would need to get to the ocean underneath, and then when it gets there it will need to have chemical energy in a form it can use.

Its *possible* but I wouldn't take it as a foregone conclusion that its already happened, and thus what we do won't really matter.

I think if we sent a probe where we tried rather hard to sterilize it, it would be fine for similar reasons.

But if we sent a probe that deliberately released a biological package, it could cause quite a change.

Now, back to article IX of the outerspace treaty... even under different interpretations... you'd still have to argue that the "contamination" (its not really contamination if it is deliberate) is "harmful", which would be even harder to argue if you can present good evidence that Europa was initially sterile.

Lastly, if it is decided that we should seed life on a sterile body, the treaty could easily be changed if enough nations consent to it.

[lajoswinkler]

I will quote myself because I have nothing else to say.

People have s gross misunderstanding of the word extremophile, and that's obvious from the original poster's entry post.

Those aren't organisms that are capable of withstanding whatever you put in front of them. It means the qualities of their ecological niches are such that organisms we're encountering on regular basis (mesophiles) can't stand it.

If you put such organisms in a different niche, they will die. Being an extremophile doesn't mean your niche is wide, and I can't stress that enough.

http://academic.pgcc.edu/~kroberts/Lecture/Chapter%206/06-05_MicrobeTempRange_L.jpg

(this is just for the temperatures, there's pressure, pH, salinity, heavy metal content, etc.)

We do not have organisms on Earth that could live in space, Mars, Venus, or anywhere else. Why? Because they've evolved to live in their own narrow niches.

The only way we could seed another place in space is to genetically engineer an organism, but the problem is that such places are very rare. Interior pockets of Mars, Europa, and other icy bodies, where liquid water exists, are a candidate, but we'd have to investigate those niches and then tailor the organisms for them.

Other than that, any attempt is futile and laughable.

[-Velocity-]

There's something everybody overlooked about contamination:

If something can survive the sterilization process and the trip to Europe, it could very well survive being ejected from the atmosphere by a meteor impact.

Sure, it doesn't happen very often that rocks from one planet en up on one other, but we have several Mars rocks on Earth, so it does happen.

It means there must Earth rocks all over the solar system, carrying extremophiles, and some of them have already crashed on Europa. True, most of them will take a lot more than 10 years to get there, since they will require some gravity assist to get the deltaV, but that doesn't sound terribly harsher than what stowaways on a Europa probe would face.

Beyond that, I love the idea of a sealed probe that is scorched to insane temperatures. You could also use strong oxidizers like chlorine trifluoride to really be sure.

It's very unlikely for any Earth organism to survive an impact on Europa. It's a long trip in a harsh environment, and the surface is harsh too, with very strong radiation. Europa has no atmosphere to cushion an impacting rock- they just smash into the surface at full velocity. Jupiter's high gravity also makes things even more difficult, because an incoming space rock is accelerated to even higher velocities. No extremophile can survive being vaporized on impact.

[-Velocity-]

We do not have organisms on Earth that could live in space, Mars, Venus, or anywhere else. Why? Because they've evolved to live in their own narrow niches.

The only way we could seed another place in space is to genetically engineer an organism, but the problem is that such places are very rare. Interior pockets of Mars, Europa, and other icy bodies, where liquid water exists, are a candidate, but we'd have to investigate those niches and then tailor the organisms for them.

You simply cannot know this as it requires knowing all the extremophiles of Earth, all their characteristics, and all environments available on extraterrestrial bodies. Underground niches on Mars may very well exist. And they don't have to be exactly the same as those on Earth, there are a lot of environmental factors that are irrelevant to an organism, and even within those environmental factors that DO matter, there is of course an acceptable range. Given the huge number of environments on Earth, if there is a place on Mars that has the proper chemicals, energy source, and reasonably fresh water, then there's a reasonable probability that there is at least one organism on Earth that could live there. We need to get to one of those recurring slope lineae and find out for certain whether they are water, and if so, find out if there is anything already living in it, and measure the pH, salinity, etc. THEN we'd have a better idea.

Edited December 10, 2014 by |Velocity|

[lajoswinkler]

You simply cannot know this as it requires knowing all the extremophiles of Earth, all their characteristics, and all environments available on extraterrestrial bodies. Underground niches on Mars may very well exist. And they don't have to be exactly the same as those on Earth, there are a lot of environmental factors that are irrelevant to an organism, and even within those environmental factors that DO matter, there is of course an acceptable range. Given the huge number of environments on Earth, if there is a place on Mars that has the proper chemicals, energy source, and reasonably fresh water, then there's a reasonable probability that there is at least one organism on Earth that could live there. We need to get to one of those recurring slope lineae and find out for certain whether they are water, and if so, find out if there is anything already living in it, and measure the pH, salinity, etc. THEN we'd have a better idea.

We have a pretty good picture of the extremophiles we find on Earth. The only harsh environment we haven't probed yet is below the deepest holes, and that close to the mantle is sterile environment because no fluids are capable of ensuring the continuous flow of matter, and the temperature is so high the building blocks of living beings are coagulating and hydrolizing.

If there are hydrothermal vents on Mars that can offer the nutrients Earth has, then our extremophiles could survive there, but it would require Mars to have tectonic activity and underground pools with free water. There might be free water pockets deep below the surface, but tectonic activity is gone. Vents capable of delivering nutrients can't exist in passive environments as they're are transient features of very active regions. They form, they clog and collapse. No plate activity, no new vents. No vents, no nutrient flow. No nutrient flow, no life.

Chances are high nothing from Earth could live there without modifications. Maybe for a while, but it wouldn't be sustainable.

Regarding the surfaces, all of them except Earth's are either airless (no matter flowing in dynamic equilibrium = no life in vaccum), extremely cold (no complex chemical reactions) or subjected to hard ionizing rays. Europa is bombarded with 5.4 sieverts each 24 hours. That is 0.225 Sv/h, which is roughly 1.125 million times the dose in my room. Even the most radioresistive bacterial strains could not endure that even under 1 atmosphere. They can survive large acute doses, but that's one exposure and then back to normal levels for repairing, taking up some time. Constant high exposure doesn't give them the time.

Only the subsurface pockets would be shielded. Even if spores could survive vacuum and high ionizing radiation of Jupiter, they couldn't reach it so if there's anything in Europa, it's Europian.

The question is if there are niches on Mars or other bodies which are substantially similar to our niches here. So far there is not only one evidence for that, but also nothing says it could be like that. There's more to a niche than just temperature, as you know.

Also, mind that extremophiles can only live in their niche. Putting such strains into "normal" environment causes them to die like flies.

[NERVAfan]

In general, yes, Earth life would have trouble on extraplanetary environments. Europan hydrothermal vent environments might actually be very similar to Earth hydrothermal vent environments, though. (OTOH I don't think you are going to find hydrothermal vent bacteria on humans working on spacecraft assembly, so it is probably fine).

Some Earth endoliths might be able to survive in the Mars subsurface, if there is ever any trace of liquid water at all, but again these are not human-commensal bacteria.

There are "polyextremophiles" though... but I would expect Mars or Europa bacteria to be better adapted to a Mars or Europa environment than terrestrial generalists.

Spoiling the Callisto environment isn't the concern that's driving this issue. Spoiling the experiment's validity is the concern. An experiment to test if Callisto has life, that's designed to be extremely sensitive to find the tiniest trace of life, needs to be sure not to generate a false positive from the life the probe brought with it.

Add a metagenomics experiment (analyzing environmental DNA samples). If it falls anywhere on Earth's tree of life, it's contamination; if it doesn't, or if there is no DNA at all, it's native.

[NERVAfan]

We have a pretty good picture of the extremophiles we find on Earth. The only harsh environment we haven't probed yet is below the deepest holes, and that close to the mantle is sterile environment because no fluids are capable of ensuring the continuous flow of matter, and the temperature is so high the building blocks of living beings are coagulating and hydrolizing.

Yes, there will be a depth limit defined by temperature, but I think the extremophiles there are very poorly known since there are very few holes that deep. We don't know what microbes, if any, are 2 miles below most of the land; only when there's already a way to get there, like the super-deep mine in South Africa, do we get a chance to see what's there.

Also, we don't know what the temperature limit (and thus depth limit) for life is. Clearly there is one -- enough heat will destroy any molecule -- but these environments are not well sampled and the current record holders (Methanopyrus reproducing at 122 C and "Strain 121" reproducing at 121 C/surviving at 130 C) are recent (2000s) discoveries. So there may be more discoveries to come. Also, these are hydrothermal vent organisms; the deep endoliths are AFAIK even less known.

Regarding the surfaces, all of them except Earth's are either airless (no matter flowing in dynamic equilibrium = no life in vaccum), extremely cold (no complex chemical reactions) or subjected to hard ionizing rays.

Titan might be workable. Not for Earth-type life, but it does appear to have complex chemistry.

Only the subsurface pockets would be shielded. Even if spores could survive vacuum and high ionizing radiation of Jupiter, they couldn't reach it so if there's anything in Europa, it's Europian.

I agree it is highly unlikely, but there does seem to be some surface/ocean interaction on Europa (plumes, and salts found on the crust) so it wouldn't be entirely impossible for a life-bearing meteorite to enter Europa's oceans if it hit in just the right place and time. And being inside a meteorite would provide some shielding, at least.

I'm not sure if anything would survive the actual collision, though, with no atmosphere to brake it.

[sndrtj]

That'd violate the Outer Space Treaty Article IX.

As I understand it, pretty much any colonization effort would violate that treaty. This has been written during the Cold War - perhaps it's time to revise it. I'm all in favor of seeding lifeless planets, and seeding those with life is going to be pretty unavoidable since those planets are the most likely we will colonize anyway. A human presence anywhere means seeding; the human body contains approximately 10 trillion bacterial cells (10 times more than actual human cells); just touching the ground with your index finger means several hundred of thousands of microbes touching that soil. Sometimes I believe that seeding planets with life is perhaps even a moral goal: we owe everything to our little ball of rock with its myriad life forms - we humans might be the best hope it has for "reproducing".

@ KerikBalm:

Ah, thanks, I forgot about the UV radiation (been two years ago since I last did tissue culture).

[lajoswinkler]

Yes, there will be a depth limit defined by temperature, but I think the extremophiles there are very poorly known since there are very few holes that deep. We don't know what microbes, if any, are 2 miles below most of the land; only when there's already a way to get there, like the super-deep mine in South Africa, do we get a chance to see what's there.

Also, we don't know what the temperature limit (and thus depth limit) for life is. Clearly there is one -- enough heat will destroy any molecule -- but these environments are not well sampled and the current record holders (Methanopyrus reproducing at 122 C and "Strain 121" reproducing at 121 C/surviving at 130 C) are recent (2000s) discoveries. So there may be more discoveries to come. Also, these are hydrothermal vent organisms; the deep endoliths are AFAIK even less known.

There certainly is limit and those holes are sterile. It's organic chemistry. Complex molecules fall apart, they hydrolize.

Titan might be workable. Not for Earth-type life, but it does appear to have complex chemistry.

Only its atmosphere. It provides the photolytic molecules which then contaminate the surface, but it must be very, very slow. It's a chemically extremely slow environment (physical changes are pretty fast as we see) with unbelieveably inert solvent at cryogenic temperatures. Vast majority of the atmosphere is nitrogen. Amount of tholins on Titan is very low. It's the thickness of the atmosphere and the color of the compounds that fools us into thinking it's a rich soup. Maybe rich by composition, but not by amount.

If there are some interesting chemical reactions on Titan, they are deep beneath its surface where it's warm enough and water exists. The surface is just a wasteland of ices and low hydrocarbons at temperatures used at labs when you want to stop a reaction in organic chemistry.

I agree it is highly unlikely, but there does seem to be some surface/ocean interaction on Europa (plumes, and salts found on the crust) so it wouldn't be entirely impossible for a life-bearing meteorite to enter Europa's oceans if it hit in just the right place and time. And being inside a meteorite would provide some shielding, at least.

I'm not sure if anything would survive the actual collision, though, with no atmosphere to brake it.

Ice can flow under pressure.

As Europa is squeezed by tidal forces, it does allow intricate "roads" on its surface, but there's lots of ice underneath. At such low temperatures and vacuum, free liquid water would quickly find its way to the top... like on Enceladus.

In any way, any viable spore, not destroyed by vacuum will be sterilized by Jupiter. Lots of ionizing rays around it.

Edited December 11, 2014 by lajoswinkler

[NERVAfan]

There certainly is limit

Of course there is; nothing made of complex molecules will survive at arbitrarily high temperatures.

But we don't know what that limit is.

I'm pretty sure it's no higher than the critical point of water since supercritical water is, from what I've read, really good at destroying organic molecules; but that leaves quite a big range.

and those holes are sterile.

What holes? Desulforudis audaxviator, a sulfate-reducing bacterium, has been discovered 2.8 km underground in the Mponeng mine, one of the deepest mines in the world. There just aren't that many holes that deep.

Did any of the super-deep drilling projects (Mohole/Kola Superdeep Borehole) look to see at what depth they stopped finding microbes? I never heard of anything like that, and chemosynthesis wasn't discovered at the time of Mohole.

Only its atmosphere. It provides the photolytic molecules which then contaminate the surface, but it must be very, very slow.

Compared to Earth, yeah, but the individual photochemistry reactions can be quite energetic (due to high-energy UV photons).

But this still provides a way to store energy (solar energy -> chemical energy by photochemistry in the upper atmosphere). These chemicals could then fall down to the surface and feed living things.

It'd be a very energy-starved, limited ecosystem compared to what we have on Earth's surface, but compared to low-energy endolithic biomes where a microbe might divide once every century? I don't think it's unworkably low-energy.

Vast majority of the atmosphere is nitrogen. Amount of tholins on Titan is very low. It's the thickness of the atmosphere and the color of the compounds that fools us into thinking it's a rich soup. Maybe rich by composition, but not by amount.

Well, low compared to what? IIRC Titan's sand dunes are supposed to be organic stuff, so the amount of complex compounds isn't that low. Plus whatever higher hydrocarbons might exist mixed in the methane/ethane seas (and the atmosphere has several % methane vapor). There are plenty of organics around, not just nitrogen.

The surface is just a wasteland of ices and low hydrocarbons at temperatures used at labs when you want to stop a reaction in organic chemistry.

Well, sure, but you've got that photochemistry feeding more energetic/reactive substances into the mix, so it's not really analogous to your classic lab organic chemistry.

(Plus the possibility of weird catalysts/enzymes. Life absolutely depends on enzymes as catalysts. Nitrogen-fixing bacteria can do nitrogen fixation at room temperature and pressure; the industrial process is done at something like 400 C and 200 bar).

I'm not saying Titan does have life, but I think the possibility is definitely there, and would be worth looking for if we could find a way to identify it (its processes would necessarily be very different from ours; even the basic chemistry would be different since there is a serious lack of available O atoms - at Titan temperatures water is a pretty inert rock - so you wouldn't find stuff like carboxylic acids [as in amino acids] and sugars playing a major role.)

As Europa is squeezed by tidal forces, it does allow intricate "roads" on its surface, but there's lots of ice underneath. At such low temperatures and vacuum, free liquid water would quickly find its way to the top... like on Enceladus.

Apparently it does, thus the plumes on Europa too.

But if a meteorite landed in the throat of a plume-geyser, or landed on a part of the surface that then cracked open to become "chaos terrain"... and there are those salts on the surface... there does seem to be surface-ocean interaction.

I think it's very unlikely that it would happen (I'm pretty skeptical of even Earth-Mars transfer of life by meteorites, and that doesn't have the intense radiation environment, ice shell, and lack of a braking atmosphere) but maybe not impossible.

[NERVAfan]

As I understand it, pretty much any colonization effort would violate that treaty. This has been written during the Cold War - perhaps it's time to revise it.

Oh, certainly; I don't think the Outer Space Treaty is a particularly good idea. If nations were allowed to claim land on celestial bodies, we might well have a base on the Moon now, and economic exploitation of space resources would be much farther advanced.

Without that, there was really nowhere to go after Apollo.

"Common property of mankind" sounds high-minded, but it leads to either abuse of resources (as in the oceans) or lack of ability to use them in the first place (as in Antarctica or space) in practice.

[RainDreamer]

I think the reason that we have the "common property of mankind" part is to prevent nations fighting each other over the new resources and may ultimately ruin them due to warfare. If only we have a way to expand without killing each others over new lands.

[NERVAfan]

I think the reason that we have the "common property of mankind" part is to prevent nations fighting each other over the new resources and may ultimately ruin them due to warfare. If only we have a way to expand without killing each others over new lands.

I'm sure that was the purpose.

But it's unnecessary from a modern perspective, IMO; only high tech, wealthy nations can exploit space, and those nations don't go to war with each other (not overtly anyway) anymore. It would be too destructive, and not worth it anyway.