Earth Ejecta Could Seed Life On Europa

KentuckyFC writes "Various astronomers have studied how far rocks can travel through space after being ejected from Earth. Their conclusion is that it's relatively easy for bits of Earth to end up on the Moon or Venus, but very little would get to Mars because it would have to overcome gravity from both the Sun and the Earth. Now, the biggest ever simulation of Earth ejecta confirms this result — with a twist. The simulation shows that Jupiter is a much more likely destination than Mars. So bits of Earth could have ended up on Jovian satellites such as Europa. Astrobiologists estimate that Earth's hardiest organisms can survive up to 30,000 years in space, which means that if conditions are just right, Earth ejecta could seed life there."

Comments

Impossible

[Rosco P. Coltrane]

However long life may survive in space, when the organisms reach Europa, they get a message saying "DO NOT ATTEMPT TO LAND THERE" and get blasted out of the sky.

Re:Impossible

[eclectus]

It already reached Europa, thrived, and is attempting to stop anything else from landing. Why else do you think it spoke english?

Re:Impossible

[Anonymous Coward]

Is this just a troll, or a misguided advertiser? Nobody on this site is going to fall for the mydritypc scam.

Re:Impossible

[Mr. Guyman]

I live in europea but i dont see organisms no where not even sound but they says theres in sky should i be worrie. i herd on the webs that organism has invaded but i dont see them no where wats going on.

Re:Impossible

[Anonymous Coward]

Pedantic note:

"ALL THESE WORLDS ARE YOURS EXCEPT EUROPA. ATTEMPT NO LANDING THERE."

Sadly, the lameness filter prevented me from simply posting the above (apparently the fact that it's a direct quotation doesn't override the capital letters).

Re:Impossible

[Anonymous Coward]

How fascinating! Tell me more about your slower gigabits which became faster afterwards!

Latest evidence

[symbolset]

The latest evidence has fossil life appearing on Earth so soon after the LHB that it is implausible it evolved here.

Re:Latest evidence

[ginbot462]

I'm too tired. I read that as "as evidenced by LRH (L. Ron Hubbard), it is implausible life evolved." And, i agree with that. Course, the counter argument is he was a highly evolved gibbon (no offense towards gibbons).

Re:Latest evidence

[MBGMorden]

Without some basis for seeing it arrive elsewhere, it's pretty hard to proclaim any timeframe as "implausible". Until we get good date from other examples there's just no way to get an estimate on the normal time it would take for life to evolve from scratch to know whether it was accelerated or not in our case.

Re:Latest evidence

[Anonymous Coward]

no it doesn't.

Even if it did... You're suggesting that it'd be more plausible if....?? 0.o

Re:Latest evidence

[Anonymous Coward]

Ah the dangers of doing statistics with only one data point.

Re:Latest evidence

[Latinhypercube]

Agreed. I actually just posted a reply on the oldest fossils thread that says the same thing:-
http://slashdot.org/comments.pl?sid=2391904&cid=37171484

Re:Latest evidence

[Latinhypercube]

Wrong. We can try to experimentally re-recreate the origins of life (FAIL). Or look for a second genesis (FAIL).

Re:Latest evidence

[osu-neko]

The latest evidence has fossil life appearing on Earth so soon after the LHB that it is implausible it evolved here.

Interesting. That's pretty much the exact opposite of what the scientists discussing the latest evidence said on the interview I heard. Latest evidence has fossil life appearing on Earth so soon after the LHB that it seems implausible that it takes life very long to evolve, given the right conditions. Lacking evidence that it takes life much longer to get going than it did, and further that some more hospitable place for it to evolve existed, and further still that it then managed to get transplanted from there to here, it seems highly implausible that it evolved elsewhere, in some even less hospitable environment compared to the relative paradise that is Earth, even in its early days.

Re:Latest evidence

[Coren22]

You know, we in the west are trying our damndest to destroy all life on the planet. If only the rest of you would help, we may be able to test this theory...

Re:Latest evidence

[RockDoctor]

The latest evidence has fossil life appearing on Earth so soon after the LHB that it is implausible it evolved here.

Having just downloaded the paper to read over lunch and siesta, I'm wondering what makes you find the idea of life evolving on Earth so implausible that you're willing to accept the severe difficulties of panspermia, and the unresolved difficulty of having to have somewhere that life did originally evolve at. Not forgetting of course that there is only time for a limited number of panspermia cycles before you're back into a galaxy too metal-poor for life (as we know it) to exist.

I do agree that the timetable is getting a little crowded, but not enough to make me think "implausible". For example, I look at modelling that suggests that in a word with oceans and something resembling plate tectonics, even major impactors are not necessarily effective sterilising agents. Which makes the timing of the LBH less of an issue. And the advances in study of plausible pre-biotic chemistry are continuing apace.

(Afternoon, because we lost internet connection and I'd pulled another long shift.)

Read the paper. Doesn't much relate to the LHB, except pointing out that, for the ejecta considered, a significant fraction - several percent - re-impacts with the Earth within 30ka of a major impact. 30ka is their line in the sand for survival of viable organisms on a piece of ejecta. Which they take as plausible for re-seeding the Earth after a sterilising impact. Which, as I said above, reduces the significance of the LHB as a line before which life could not have evolved.

Re:Latest evidence

[symbolset]

I did download and read the paper as you suggested. They seem to be quite thorough. It's a good paper. As my opinion mattered I don't disagree with it, and it does lay out some specific conditions likely to have occurred where an impactor might have landed earthly life in still-viable condition on Mars and other planets. I suppose I'm going to have to read the referenced paper on the 30ka. I'm not sold on the idea that the "nonviability" of the organism is the end of the story here. Even a thoroughly dead ball of organic material dumped in the ocean might jump-start the process.

OK, I'll give some theories. None of these are mine:

1a. (abiogenesis) Life arose on Earth before (400My) or during (300My) the Late Heavy Bombardment and survived because not all of the crust was molten at any given time. The simultaneous re-melting of the entire surface is still debated, right? As bacteria are known to exist miles beneath the Earth's surface and huge impactors move stuff around, this is fairly plausible.

1b. (abiogenesis) Life arose on Earth before (400My) or during (300My) the Late Heavy Bombardment and survived because large rocks knocked large chunks of the Earth off but they landed back to seed life again within 30,000 years. This is fairly plausible also, but seems less likely than 1a. When we start mining some Earth Trojan asteroids perhaps we'll find evidence one way or another.

1c. (abiogenesis) Life arose on Earth within about 300My of the end of the LHB. This one seems less likely to me than either of the above, though I confess I have no data.

2a. (abiogenesis/panspermia) Some time in the span of 7 billion years span between the sun's precursor Population II star's explosion life arose in the detritus, perhaps in a natural nuclear fission reactor in an Earth sized agglommeration of debris, or in a small body orbiting a brown dwarf. The solar system's mass being slowed enough by the shockwave from another supernova, infall occurs and as chaos becomes order the genesis rock gets powdered and sprinkled all over the entire solar system, the brown dwarf swallowed in the infall to become the sun. Although unviable as lifeforms some essential complex compounds jump-start life on Earth.

2b. (panspermia) The above condition occurs, but the building blocks for life are in the shockwave rather than native.

2c. (panspermia) Somewhere in the vast cooling mass of the expanding supernova shockwave from a Population II star (up to 130 solar masses) the chemical reaction that creates amino acids occurs with a certain very low frequency so some very small fraction of interstellar dust is littered with the stuff. Cosmic rays are harsh, but enough samples survive to fall on the right environment and interact. Perhaps, being sticky, the molecules tend to preferentially attract water and become comets.

3. (Universal panspermia) One of the preceding three option occurs with such frequency in the Universe that every time a planet forms with the right (very wide) surface conditions, life takes root with essential materials fairly immediately. I like this one because it means that every place life could ever have been, we'll find evidence that it was.

4. (deliberate panspermia) Some joker on a minor planet like Ceres builds a railgun and starts deliberately shipping off particularly hardy life to nearby stars in the hope that if his race should find a way to get there, his spores would have made life more habitable when they arrive - or at least that life would have some hope of surviving the death of his sun.

5. Something else.

Interesting theories all, and an amusing way to spend a cloudy afternoon pondering abiogenesis as the waves roll in. With more experiments like Hayabusa perhaps we'll know one day for sure. Maybe even in my lifetime. That would be nice.

Re:Latest evidence

[symbolset]

That was supposed to read "as if my opinion mattered" - as in, "I am not a rocket scientist."

Re:Latest evidence

[RockDoctor]

Some points as they occur to me - then I've got EoWR to write.

• 1a - consider the Jack Hills and Acasta detrital zircons with the oxygen isotope compositions appropriate to an active hydrological cycle ... and which seemingly date back as far as 4300Ma, if not older. The work is replicated, from multiple areas. The belief that the planet had a thoroughly molten surface any significant time after the Moon-forming Giant Impact ... is in serious trouble form material evidence. It always had difficulty from an energy balance point of view - the flux of radiation varies as the 4th or 5th (I forget) power of the absolute temperature, so to have sustained fusion of a primitive crust requires a seriously greater whole-planet temperature than a planet with localised fusion around impacts, out-gassing volcanoes, etc. So the global magma ocean idea has long had difficulties. Putting a hydrological cycle onto the surface at 4300Ma give it real difficulty.
• 1b - 1a, 1b, and 1c are not mutually exclusive. Surface reseeding from remnant deep ocean basins, from lithophagic ("rock eating") organisms, and from re-impacting small debris could all happen sequentially or simultaneously (at which point, "re-seeding" becomes a dodgy concept). I note that "deep genomics" is seeing the deep roots of the "tree of life" as being a ring of organisms interlinked by considerable horizontal gene transfer, but with many of the most deeply-rooted genes being related to modern hyperthermophile genes. Which is what you'd more-or-less expect from the rather messy model above.
• 2a,b,c - ALL panspermia models have the problem that life has to originate somewhere, either in space or on a planet. Then it has to get here without being destroyed through space. Then it has to proliferate in the extremely different environment on a planet's surface. That is at least one major environmental change (space->planet) which is going to be a bottleneck, along with a (probably) low probability step (non-life->life). That is a pair of low probability events happening pretty independently, so you multiply the probabilities together and get an even lower probability.
  Life exists here ; the Copernican Principle ("we don't live anywhere particularly unusual") then suggests that life is not terribly uncommon. So tieing together two low probability to get a relatively common event ... doesn't work.
  You seem to be moving towards what I'd call a "weak panspermia" : the generation of "pre-biotic molecules" as a normal part of (inter-)stellar chemistry leads to developing solar systems having large (relatively) amounts of interesting compounds available if any solvent-wetted variably-energetic environment develops. Plate tectonics on Earth (possibly, briefly on Mars, differently on Venus) ; vigorous volcanism on Io ; ice flexure above a water-ocean on Europa ; methane rainfall on Titan. All would have been peppered with ain interesting mix. Which may (or may not) have resulted in development of life.
  "Weak panspermia" you will note does not require the development of life to produce the various interesting chemicals. It is a non-biological idea. So calling it a "panspermia" is more to contrast it with the stronger panspermia daydreams people have, including the ones that are religion with modesty boards (to stop scientists looking up god's skirt).
• 3 - "Universal panspermia" probably isn't impossible (I use the term to mean what the term means, not "low probability"), but it's probability is pretty low and is extremely unlikely to be influenced by your likes and dislikes. After all, it probably happened before you were born to have ideas (odds less than 100:13,700,000,000, assuming that you're less than 100 years old).
• 4 - you've been reading plenty of SF (says the guy with a hard drive full of SF). Try working out just how you're going to do this. Your projectiles are going to be limited to survivable impact velocities (say 300km/s = 0.001c, very generous to

Re:Latest evidence

[symbolset]

First, you might want to consult with your physician about the dosage of your meds.

Second, nobody's reading this old thread except you and me, so we may as well have a private discussion.

2a,b,c - ALL panspermia models have the problem that life has to originate somewhere, either in space or on a planet. Then it has to get here without being destroyed through space. Then it has to proliferate in the extremely different environment on a planet's surface. That is at least one major environmental change (space->planet) which is going to be a bottleneck, along with a (probably) low probability step (non-life->life). That is a pair of low probability events happening pretty independently, so you multiply the probabilities together and get an even lower probability.

No. There are many panspermia models. I only gave a sample. This is slashdot, not an encyclopedia. Your problem is with the word "somewhere." If you replace that word with "Somewhen" and admit that we're 12 billion years in, the rest is easy.

4)I didn't say the projectiles came from Ceres. Naturally at that point Asteroid miners would trade there. But the bigger issues are the waste heat, and orbital dynamics. For each slug launched in one direction, they have to launch another one the opposite way.

Whatever. Time for nite nite.

Re:Latest evidence

[RockDoctor]

First, you might want to consult with your physician about the dosage of your meds.

What the fuck prompted that?

You made a comment about panspermia concepts ; I replied ; we're exchanging ideas civilly, then you come out with the typewritten equivalent of throwing a beer in my face. If anyone should be checking meds, it isn't me (BTW the doses are one set of tabs of a broad-spectrum antibiotic, one set of industrial grade antihistamines, and malaria prophylaxis ; and I competed the first two courses yesterday with the infected bite having shrunk away nicely, thank you. The malaria prophylaxis continues until after I finish this job.

Second, nobody's reading this old thread except you and me, so we may as well have a private discussion.

The thread is what - 5 days old? You never encounter discussions that continue for years? Weird planet you live on.

Anyway, in the spirit that you obviously think is appropriate, go fuck a creationist and make the world another retard.

Oh, and how do you know that no-one else is reading this thread?

Re:Latest evidence

[symbolset]

Sorry - I get a little cranky sometimes.

Re:Latest evidence

[RockDoctor]

(Slashdot seemed unhappy with it's existence earlier, but I saved my reply and will try again.)

Apology accepted. Now, where were we?

Summary of my position : Panspermia is not impossible, in the strict sense, but unnecessarily complex given that you've got to have an origin of life somewhere, and only a limited number of cycles available in a universe of finite age. So, if you want a Copernican universe ("we're nowhere unusual"), you'll still have to have lots of separate panspermia origins to put us in an average part of an average galaxy. At the very minimum, you need an origin of life in every galaxy, and really you need a lot more than that. So that's billions of origins in the observable universe.

At that number of origin of life events, it's much simpler to work on the assumption that life originated where you find it. i.e., on Earth. Fr Occam would approve.

The detailed theories about the chemistry of OOL (I'm getting tired of typing "origin of life") cover quite a wide range of chemistries, indicative of the fact that we don't really know WTF happened. But my reading is that it's not a serious problem. Chemistry can happen fast, and several of the chemical ideas are not mutually exclusive. To my mind, the most interesting likely result of penetrating the ice on Europa or the lakes of Titan is going to be giving us a better idea of what chemistries were actually plausible, even if these places didn't ever generate life. Or maybe some people's buckets will start generating bugs. It's worth watching.

I was forgetting that I (intermittently) have access to "the literature" through a formal library. I don't at the moment, so I'm only seeing marginal access to Origins of Life and Evolution of Biospheres but I recall finding it very interesting when I browsed it. I just checked, and I'd downloaded volumes 39 to 30, averaging 42 articles per issue. (Obviously, it's an incomplete project ; I'll get back to it one day.) Hmm, "panspermia" gets 6 mentions in volume 33 (after a conference?) pllus the TOC, and 3 more in volume 34 (but not the TOC, comments and references?), 1 in vol 35, 3 more plus a TOC in vol 37, five in vol 38 and a couple in vol 39. Two points from that : "panspermia" is not ignored by the scientific community (30 items in 10 years) but it isn't considered terribly important or interesting (7% of a relevant sample of papers mention it, and many of them will be tangential).

That's a 12MB zip file.

Annoyingly, I haven't got round to titling the PDFs with the title of each paper, so I'd have to read or at least scan each paper. Which I may do, but not today. (I had a quick scan, dumped about 1/5 of the files that contained book reviews etc. But the general picture doesn't much change.)

Interesting and annoying

[JoshuaZ]

Well this is interesting. The fact that it is easier for our ejecta to get to a moon of Jupiter than Mars when Mars is much further away is counterintuitive and cool. But, this means that even if we find life on Europa, unless that life's basic biochemistry is radically different from that on Earth, we won't be getting any useful data about how difficult it is for life to start. The Drake Equation http://en.wikipedia.org/wiki/Drake_equation and variants thereof try to get an estimate for how common intelligence life should be. Most of the non-biological parameters (e.g. rate of star formation, how common planets are in star systems) we've been able to pin down estimates for a lot better than we used to (thanks in a large part to the modern ability to detect exoplanets and especially the massive amount of data we've got from http://en.wikipedia.org/wiki/Kepler_(spacecraft) although we still don't have a very good idea of exactly how common Earth-like planets are and the Terrestrial Planet Finder got canceled underestimates the chance for life to arise.

Re:Interesting and annoying

[JoshuaZ]

Ugh, should pay more attention to preview. Last part got cut off from bad URL link. Mean to say:

Well this is interesting. The fact that it is easier for our ejecta to get to a moon of Jupiter than Mars when Mars is much further away is counterintuitive and cool. But, this means that even if we find life on Europa, unless that life's basic biochemistry is radically different from that on Earth, we won't be getting any useful data about how difficult it is for life to start. The Drake Equation http://en.wikipedia.org/wiki/Drake_equation [wikipedia.org] and variants thereof try to get an estimate for how common intelligence life should be. Most of the non-biological parameters (e.g. rate of star formation, how common planets are in star systems) we've been able to pin down estimates for a lot better than we used to (thanks in a large part to the modern ability to detect exoplanets and especially the massive amount of data we've got from http://en.wikipedia.org/wiki/Kepler_(spacecraft) [wikipedia.org] although we still don't have a very good idea of exactly how common Earth-like planets are and the Terrestrial Planet Finder got canceled http://en.wikipedia.org/wiki/Terrestrial_Planet_Finder. This strongly suggests that investingating Euorpa won't get a good estimate for this probability. However, it also suggests that Drake's assumption that the chance for life to arise on each planet or moon is independent underestimates the chance for life to arise.

Re:Interesting and annoying

[CrimsonAvenger]

The fact that it is easier for our ejecta to get to a moon of Jupiter than Mars when Mars is much further away is counterintuitive and cool.

Umm, Mars is actually much CLOSER than Europa.

Re:Interesting and annoying

[JoshuaZ]

Er yes, that's why it is counterintuitive that it is easier to get Jupiter. Wow. I really need to work on the whole preview thing a lot more.

Re:Interesting and annoying

[Anonymous Coward]

Mars is not much further away than Jupiter. Can you repost again with this fixed?

Re:Interesting and annoying

[CrimsonAvenger]

Er yes, that's why it is counterintuitive that it is easier to get Jupiter. Wow. I really need to work on the whole preview thing a lot more.

What's really sad is that you realized you'd made a mistake on your original post, reposted it with the correction, and left the "mars is farther away" thing in the revised one too. ;)

That aside, it is pretty cool that it's easier to reach Jupiter's satellites than Mars. Especially given that the ejecta can reach Venus, which requires only a tiny bit less deltaV to reach than Mars.

Re:Interesting and annoying

[cyberchondriac]

Well this is interesting. The fact that it is easier for our ejecta to get to a moon of Jupiter than Mars when Mars is much further away is counterintuitive and cool.

I can't say though I find this really surprising. I suspect the average Joe (layman, astronomically-speaking) tends to think of the planets in a linear precession, each further from the Sun than the previous one; we grew up in classrooms with posters depicting them like that ; the truth being, of course, the planets all orbit at individual rates, (sometimes I forget too) so at times, the Earth could be in an inferior conjunction with Jupiter, but Mars is all the way over on the opposite side of the Solar System - as you alluded to.
As to how far the ejecta travels outward,it doesn't seem that unlikely that solar gravity has such a limited effect, because the objects have so little mass to act on, comparatively, and if they were ejected with enough force to exceed escape velocity, then it seems intuitive that they would continue outward, and possibly, if they get close enough, eventually get captured by Jupiter's large gravitational field, especially should Jupiter happen to be in the "right place" after an asteroid impact on Earth. The Sun's gravitational pull gets weaker the farther out they go, but Jupiter's grows stronger.
But then, hindsight and all that..

Re:Interesting and annoying

[JoshuaZ]

Hindsight here is wrong. That's a typo. My point was that Mars is generally closer than Jupiter but that it is easier to get ejecta to Mars than Earth. That's what is counterintuitive. Even when Mars and Earth are opposite each other they are only about 15-20 light minutes apart. When Earth and Jupiter are near each other they are still farther away than that.

Re:Interesting and annoying

[Anonymous Coward]

Well it's all very well claiming that hardy simple life can survive 30ka in a rock in space, but how does such life survive being ejected into space in the first place? I doubt any life can survive being in impacted or even molten rock after a serious asteroid impact...

Re:Interesting and annoying

[Anonymous Coward]

I eagerly await version 2.0 of this post.

Re:Interesting and annoying

[Anonymous Coward]

Venus is slightly smaller than earth. The gravitational pull from Venus would be enough to pull the object rest of the way there once it arrived at a certain point in space. Just like with the moon, you don't have to hurl an object all the way to the Moon's surface, just a little over halfway before the gravity takes over pulling the object toward the moon. Mars is much smaller than earth therefore would have a lot less gravitational pull. So yes, it would be harder to get objects to this planet.

However Jupiter is the largest mass planet in our solar system. While only slightly larger than Saturn, it is much closer to us and is more plausible to be able to project an item to that planet. More than likely the object will wind up on Jupiters surface though and not a moon. The only creature that would survive is an organism that can survive super cold temperatures and breathe hydrogen.

Re:Interesting and annoying

[Froeschle]

Perhaps it depends on the size of the rock and how deep the life is embedded into it? Also in the course of the history of the Earth there was sure a lot more than just one rock ejected from thee planet's surface.

Re:Interesting and annoying

[cusco]

Don't worry, it's Monday.

Re:Interesting and annoying

[Anonymous Coward]

Sounds like someone has a case of the mondays!

sounds dirty

[Anonymous Coward]

could anybody come up with a dirtier title for a story?

-- posted as AC due to moderator violence.

Re:sounds dirty

[SniperJoe]

How about "The Earth's Life Giving Goo could land on Europa's Face"

Re:sounds dirty

[Anonymous Coward]

Or "The Earth's Rock Hard Parts Giving An Explosive Facial to Europa"

Re:sounds dirty

[Anonymous Coward]

Gaea was supposed to be a female deity....

Admiral Ackbar told me so.

Re:sounds dirty

[Nicolas.Calderon]

Or "Earth's Life Giving Goo could land on Earth's Own Face"

How about the opposite?

[petes_PoV]

If it's easier for rocks to come sunward, then does that mean there's a chance that life-bearing rocks from Europa could have seeded the Earth.

Re:How about the opposite?

[Bomazi]

What rocks ? Europa is covered in ice.

Re:How about the opposite?

[BetaDays]

I knew I wasn't from around here.

Re:How about the opposite?

[MBGMorden]

Possible - but realistically you're putting the cart before the horse there. There's no evidence as of yet that there even is any life on Europa - or ever has been. It's a possibility sure, but until we at least have evidence to support life in the past there then any speculation on it seeding a planet with abundant known life isn't very useful.

Or, put more simply: you should always look for evidence that something DID happen than to come up with some scenario that has no current evidence against it and assume it likely.

Re:How about the opposite?

[petes_PoV]

you should always look for evidence that something DID happen

True, but since this entire topic (that Earth could have seeded Europa) is conjecture, a little more doesn't hurt. And since we know there's life on Earth wondering where it came from is more fruitful.

Re:How about the opposite?

[RivenAleem]

I'm no expert on such things, so feel free to ignore these musings.

I've often wondered if life really originated on another planet in our solar system, then came to Earth, why would it never have developed into something like we have here.

If it happened elsewhere first, then would they not have been more advanced, or did they never get past a certain phase? Or would the life form there be so different that we'd never have anything common enough to be able to identify the other as a life form.

Obviously, if people were subscribing to the idea of seeding life from one rock to another, then you can't expect to have one carbon based model vs silicone based. So things would have to be close enough so that they develop along some common thread. This would mean that the environment never got to a stage on Europa so that the algae decided to become fish, or fish to become mammals.

But then considering the timelines involved, with animal life spanning millions of years, what are the odds that we'll have some form of sentient life capable of detecting eachother within the same 300 year period.

If life could have originated on Europa, then is it still behind Earth developmentally, or is it so far advanced that it's extinct, or moved on. The idea that it's more advanced, and has not contacted us seems unlikely. So it would mean that either we seeded it, or it developed life independently (if there's life there at all) and has not (or cannot) develop to a level equal to us.

So, to sum up:
If life began on Europa and seeded Earth, what happened to stop further development on Europa?

Re:How about the opposite?

[Anonymous Coward]

Wondering where life on Earth came from in that context would be pretty pointless. It still wouldn't answer the big questions, it would just move the possible start point of the process to another planet but that still doesn't address "did we spontaneously spring into existence or did something give us a helping hand". Personally I think it would be more interesting to consider the possibility of using this knowledge to actively seed Europa - surely we can come up with a cheap system of throwing rocks and use this to possibly spread life.

Re:How about the opposite?

[Anonymous Coward]

Europa is covered in ice.

And spooge, according to the title.

Re:How about the opposite?

[Anonymous Coward]

The fact that simple live could have been planted here/there does not mean that was the only life on that source planet. It was the only life that was able to make that trip. It does not represent the current state of all life past or present from that source. A mold could leave the earth 100 million years ago, today or in 100 million years from now. That does not prove humans lived here or we had dinosaurs in the past.

Re:How about the opposite?

[Anonymous Coward]

What rocks ? Europa is covered in ice.

Well, it is now. After all the rocks got sent to Earth and other places trying to seed life.

Re:How about the opposite?

[tophermeyer]

I think an unspoken assumption you are making is that the evolution of life "advances" toward intelligence linearly at a common rate. This isn't really accurate. Advanced life does not necessarily mean intelligent life.

Life may well exist on Europa, and may well have existed for just as long as life on earth. We can look for examples in the communities surviving around deep ocean thermal vents (which are likely the best analog we have for the environment in Europa's oceans). Those environments are teaming with life in a fairly small area. That life isn't intelligent, and may never face the evolutionary pressures that will lead to the development of intelligence, but is very very highly adapted to an extremely harsh environment. That level of evolution can be considered every bit as "advanced" as our intelligence.

Re:How about the opposite?

[sjames]

If life began on Europa and seeded Earth, what happened to stop further development on Europa?

A less conducive environment?

Re:How about the opposite?

[Thing 1]

If life began on Europa and seeded Earth, what happened to stop further development on Europa?

The sun got cooler?

Re:How about the opposite?

[RivenAleem]

Well, that's something I had thought about. But wouldn't the cooling of the sun happen slow enough for any intelligent race to do something about it? Like migrate inwards, to Mars or, ultimately Earth?

There's a lot of assumptions here, as I said I'm not expert. I'm only speaking for a very sketchy background of high-school physics, general interest, and a lot of sci-fi books :)

If we are to consider that some form of life existed on Europa, and there were conditions good enough for them to develop into something (spores) that would survive the trip through space to Earth to seed the planet, then it must be similar enough to the forms of life we have here. If temperatures were higher due to bigger sun, then we add in our assumption that they evolved into intelligent life.

Have they become extinct? Did they evolve enough to escape their slowly freezing moon/planet, and did they move inwards? How many billions of years are we talking about here for the Sun to be too cold to support life on Europa, but not too hot for life on Mars? Was migrating inwards even possible, like us trying to migrate inwards to Venus?

No, I think that if there is/was life on Europa, then it's never been able to develop to a stage where migration was possible, or if it did, it didn't happen at a time where inward migration was feasible. Also, it's been somewhat agreed upon that life started on earth as a primordial ooze. I do not think (again I'm no expert) that ooze would survive the trip on a rock from one planet to another. It would have to be something like a spore, thus bypassing the much simpler forms of life on Earth. There would be no history prior to plantlife if it had come from another planet.

And also, if there was life on Europa because the sun was hotter, then any rock that managed to get from there to here at that time would not have seeded life on this too-hot planet. If it orbited the solar system for long enough for the sun to cool enough to support life on Earth, then whatever life-form was on it, (spore or otherwise) would have died in the interim.

Re:How about the opposite?

[osu-neko]

Hate to throw a wet blanket on this whole thing, but... the Sun has not gotten cooler. Hydrogen burning stars (and the Sun is still in that stage) get hotter as they get older, burning their remaining hydrogen at an ever increasing rate as they age. The Sun gets about 10% brighter every billion years. What you'd want to do to stay in the habitable zone is migrate outwards.

Re:How about the opposite?

[RivenAleem]

How long before Mars becomes warm enough to be more habitable?

Re:How about the opposite?

[Coren22]

Never. You know life did come from other parts of the solar system. First we tried Mars, but we couldn't seem to keep an atmosphere, then we tried Venus and cooked the planet, then we moved here and have been happy ever since. :)

Re:How about the opposite?

[RockDoctor]

I think an unspoken assumption you are making is that the evolution of life "advances" toward intelligence linearly at a common rate. This isn't really accurate. Advanced life does not necessarily mean intelligent life.

Simon Conway-Morris would disagree with you on that. I don't necessarily agree with him, but he's a sufficiently respected figure in evolutionary theory and palaeontology (and arguing a contrarian point of view) that you've at least got to read his opinions.

We can look for examples in the communities surviving around deep ocean thermal vents (which are likely the best analog we have for the environment in Europa's oceans).

The assertion is often made that these life forms are independent of the surface, existing solely on chemical and geothermal energy. This assertion is wrong for many of the community : they use photosynthesised oxygen to oxidise geologically supplied electron donors. Photosynthesis at Europa, at around 5.2AU, will have at best 1/27.04 of the productivity of that on Earth, falling by another factor of [several] for every metre below the ice surface that the light has to go through. Hydrothermal vents may be the best analogue we have for possible Europan life, but it's not necessarily a very good analogue, and could certainly be over-played.

form where, to where: no meaning

[circletimessquare]

it is my opinion that the theory of comets seeding life on earth, or earth seeding life on europa or mars or elsewhere is completely besides the point:

the seeds of life are simply everywhere, inside and outside the solar system, and life is simply always lying dormant, everywhere in the galaxy, as bits of flotsam and jetsam of space debris, ready to seed something somewhere, at any time, in the distant future, and the distant past

this whole argument of where life came from is moot. the potential is simply always there, everywhere, ready to seed

Re:form where, to where: no meaning

[biodata]

Fred would have agreed with you: http://en.wikipedia.org/wiki/Fred_Hoyle See his great work Evolution from Space

Re:form where, to where: no meaning

[circletimessquare]

thank you, that's awesome, because like fred i believe the big bang theory is a load of bunk as well

the universe is infinite in space AND time. the expansion and contraction we see on the "edge" of the universe is a local phenomenon. it's like being on the crest or trough of a wave in the middle of the ocean: the expansion and contraction you see is only local, in an infinite expanse of contractions and expansions

that's just my opinion, but since we first started looking skyward (geocentric solar system debunked, etc.) we always seem to fall for the prejudice we are at the center of things happening. the big bang theory is simple an extension of this prejudice. the march of astronomical progress has always shown we aren't anywhere special, or any TIME special

Re:form where, to where: no meaning

[englishstudent]

I think you hit the nail on the head.

Re:form where, to where: no meaning

[Anonymous Coward]

Maybe you could make a movie about cosmological zombies. That would be great.

Re:form where, to where: no meaning

[Chris Burke]

that's just my opinion, but since we first started looking skyward (geocentric solar system debunked, etc.) we always seem to fall for the prejudice we are at the center of things happening. the big bang theory is simple an extension of this prejudice. the march of astronomical progress has always shown we aren't anywhere special, or any TIME special

Except modern cosmological theory, including and especially the Big Bang, are based on the assumption that we aren't at "the center", that we aren't at a special time or place.

Sounds like you just have misunderstood the theory and from that basis believe it to be bunk.

Re:form where, to where: no meaning

[Latinhypercube]

Right on ! Absolutely. I just posted this comment which is along the same lines:- http://slashdot.org/comments.pl?sid=2391904&cid=37171484 The concept of an infinite universe is new to me and quite interesting. I have always thought that the reasoning behind Dark Matter, to explain the gravitational anomaly of the galaxies rotating, is bunk also. If the universe is infinite, then the dark matter phenomenon could be explained by the gravitational pull of the rest of this infinite universe.

Re:form where, to where: no meaning

[Latinhypercube]

Thanks for the link. A great author and scientist for sure. Shame about the whole intelligent design angle he went with. To me, to critique that stellar carbon is so unlikely that it had to be tweaked by a divine intelligence is quite blind, in the same way that creationist cannot understand the theory of evolution. For me, it is obvious, once you understand evolution, that the universe evolved through many different generations before it resulted in a more stable state that was right for us to emerge. Lee Smolin's cosmological natural selection theory demonstrates these processes, largely based around black holes as the source of this evolution.http://en.wikipedia.org/wiki/Cosmological_natural_selection#Fecund_universes

And the Hardiest organism is?

[Busted1942]

Long live the Cockroach!

Re:And the Hardiest organism is?

[Rik Sweeney]

I think you'll find it's the Waterbear

the body or the subject

[Anonymous Coward]

yeah, we use to eject a lot on europe...

Why wait?

[odirex]

Why wait for nature and chance? Launch some seed rockets.

Re:Why wait?

[Anonymous Coward]

Just help people to live on asteroids. They'll leak biologicals all over the Solar System for free.

Slashdot

[Anonymous Coward]

Porn for nerds, stuff that squirts.

Slight problem...

[advocate_one]

Surely any event that could eject material from earth with sufficient energy to escape Earth's gravity well would tend to melt the ejecta at the same time, so the bacteria would have to be seriously hardy...

Re:Slight problem...

[Anonymous Coward]

A lot of material may become molten or vaporized, but some solid material gets moved around.

Re:Slight problem...

[mbone]

Surely any event that could eject material from earth with sufficient energy to escape Earth's gravity well would tend to melt the ejecta at the same time,

No. Some, but not all. Here is a mechanism - impacting object hits, penetrates, and is stopped and imparts spherical shock wave into the Earth (or other planet) some depth inside the planet. (In simple terms, it explodes inside the crust of the Earth.) Some part of that shock wave is propagating near vertically up, away from the planet (including, maybe, parts that reflect from internal structure). These shocks lift material up out of what becomes the crater. For a 2 km crater (such as the Great Meteor Crater in Arizona), these shocks turn the layers in the near surface material upside down, just lifting and flipping them over in much the same way you would flip over a pancake, moves a mass of material maybe 1 km, without vaporizing any except for a small fraction near where the impactor stops. For a 100+ km crater, that some process pushes the some of the surface layers off the planet entirely (and also causes long rays, such as are found on the Moon). While some of the ejected material is vaporized, most isn't, and some is treated quite gently (for a massive explosion), gently enough that biological spores and the like could survive the experience.

Re:Slight problem...

[climb_no_fear]

IANAP (I am not a physicist) rather only a lowly geneticist. However, one question for someone that sounds like he understands the physics involved here:

I'll accept your assertion at face value that a rock containing spores could be ejected in such a way that some hardy spores could survive.

Now tell me this: This rock has to have the right amount of energy to reach Europa. Does it get blasted to bits upon impact and incinerate our little friends? The seeding hypothesis purported here sounds like the rock smashes through 20 km of ice to reach liquid water, where, presumably, conditions will allow the bugs to reproduce, etc (although maybe the tectonics of Europa would suck in rocks on its surface, allowing rapid access to liquid water?)

Re:Slight problem...

[utkonos]

I think you may be quite surprised at how many extremophile archaea there are, and what kind of conditions they can survive in. Alternatively, humans have been sending rocket-assisted ejecta into space for years and years.

Future Tense

[Anonymous Coward]

I'm just a tad uncomfortable with the use of the future tense in the headline. While we're all at the bottom of our gravity well, I hope that we won't in the future be contributing enough ejecta to seed Europa.

LHB is Late Heavy Bombardment

[Anonymous Coward]

To save anyone else the bother of googling it to be reminded.

Europa and the NASA Twins

[Darth Snowshoe]

The problem with Europa is that the interesting bits we want to get at are under (at least) 20 kilometers of ice. Whoever figures out how to breach that without destroying the environment beneath is going to be a winner in the big NASA lottery, and enable a lot of exciting exploration. Callisto probably has a similar subsurface ocean, for instance -

Re:Europa and the NASA Twins

[ArcherB]

The problem with Europa is that the interesting bits we want to get at are under (at least) 20 kilometers of ice. Whoever figures out how to breach that without destroying the environment beneath is going to be a winner in the big NASA lottery, and enable a lot of exciting exploration. Callisto probably has a similar subsurface ocean, for instance -

If I understand what I've read about Europa, we may not need to get through the ice at all. Due to tidal tugging, Europa is full of cracks. When those cracks form, it is believed that liquid water cycles to the surface and freezes again. It's Europa's version of plate tectonics. We should be able to get an excellent idea of what is below the surface by taking a sample of the surface ice on the surface near these cracks or even within the cracks themselves. As a bonus, whatever we find will be pre-frozen. Kinda like the frozen veggie aisle at your local grocer.

Why we have not sent a probe to land on Europa by now is beyond me.

Re:Europa and the NASA Twins

[Thing 1]

Why we have not sent a probe to land on Europa by now is beyond me.

But, apparently, not beyond Arthur C. Clarke.

Mars life probably infected Earth early on

[peter303]

Being smaller, Mars stabilized geologically before Earth and life evolved there first. Then it probably infected Earth.

Lets just start the future argument now...

[Charliemopps]

Lets fill a probe with biological stuff we think might work there and seed the thing ourselves!

Re:Lets just start the future argument now...

[Baloroth]

Lets fill a probe with biological stuff we think might work there and seed the thing ourselves!

There is definitely a joke in there somewhere...

Re:Lets just start the future argument now...

[Anonymous Coward]

I completely agree! I don't see any reason to not spread life as far as we can. Humans will colonize space eventually, but in the meantime let's get some microorganisms and hardy insect and plant life out there. If we are the only life in the universe, it's imperative that we do what we can to spread it before our planet hits another major extinction event or is destroyed completely.

Not just Europa

[LordNimon]

I told my wife I wanted to use my ejecta to seed life in^H^Hon Uranus, but she said no way.

Scifi backwards

[Windwraith]

This is a classic scifi scenario, just entirely reversed.
Let's send our "alien" meteorites to crash on other planets and spread our biological monsters!
Now let's hope European(*) Bruce Willis doesn't try to nuke it before it arrives.

(*) I am obviously talking of the on-topic Europa, but the idea of Bruce Willis with stereotypical French attire kind of makes me giggle. You know the beret and stripped shirt and baguette thing (no offence intended to real Frenchmen. Salut!)

Re:Scifi backwards

[Sockatume]

I think there was something like that in Hudson Hawk. The Bruce Willis bit, I mean, not panspermia.

Waterbear

[ildon]

All glory to the waterbear!

Re:Waterbear

[ginbot462]

You must know of their http://science.slashdot.org/comments.pl?sid=2391554&cid=37167712">plans too and are trying to get on their good side. Like the Remora, a few lucky souls will be allowed to serve them in the Cave of Hops and Honey. It will involve a lot of temporal maintenance and cleanup; on the plus side, the Hilter Time Traveling Exemption (http://tvtropes.org/pmwiki/pmwiki.php/Main/ptitlekz83hawz) will be lifted and whole cottage industry will be setup to assassinate him over and over again (that's why they used the Ruskies to steal his body, it's part of the Fugacious Firmament Flow Faunt).

Re:Waterbear

[ildon]

Ha, that's what I get for getting distracted and reading the waterbear article before clicking submit.

Earth Ejaculates?

[Anonymous Coward]

Who knew!

Re:Earth Ejaculates?

[scuzzlebutt]

More like "Earth gets its rocks off"...

Elements are not seeds

[mangu]

the seeds of life are simply everywhere, inside and outside the solar system, and life is simply always lying dormant, everywhere in the galaxy

I'd say the elements of life are everywhere, but not the seeds. Having the material but not the proper information is not enough. Life is composed by amino acids, but those are merely the bricks used to make proteins. One must have a suitable floor plan to build a house.

What makes conditions on early earth so special is not the existence of organic chemistry, but the special circumstances, so far not known to us, that brought the formation of complex self-reproducing chains of amino acids.

Re:Elements are not seeds

[circletimessquare]

agreed 100%. except what we are talking about is indeed accurately described as seeds

we all understand we aren't talking about a literal plant based seed

we are talking about the most basic molecular units that have the potential to replicate in the right environment. seeds

i mean if you still find use of the word seed as confusing, i would counter that the use of the word element in this context is equally confusing, as we aren't talking about just literal carbon and nitrogen, but how those elements are arranged as basic replication blocks

Re:Elements are not seeds

[mangu]

The papers mentioned in TFA mention the probability of a rock ejected from Earth reaching Europa. I didn't see in the abstract anything about the probability of survival of a viable spore.

We must take into account that all life is dependent of an ecological niche. For earth to seed life on another planet or vice versa one would need a spore that can survive the extreme conditions of vacuum, temperature variations, and radiation found in space. Then those spores should find an environment where they landed that would supply the needed conditions for reproduction and growth of that life form.

One often sees people mentioning, "look, this bacteria can survive in hot springs under the sea", or "look, this bacteria spores can survive in vacuum", or "look, this bacteria can survive in highly acidic liquids". They are not the same bacteria.

Being able to survive in one specific condition that might be considered extreme for us does not mean it will survive in all the extreme conditions needed to survive and reproduce after being ejected from one planet and falling on another celestial body.

Re:Elements are not seeds

[circletimessquare]

we're not talking about organisms. we're talking about basic molecular units of replication

still, the chance of such units getting ejected from one place of life, and seeding another place of potential life, is, obviously, vanishingly small

but over vast stretches of space and vast stretches of time, it goes from tiny possibility to probability

Re:Elements are not seeds

[HiThere]

You are making some assumptions that may not be true. Amino acids work as elements of life at temperatures around the melting point/boiling point of water under what seem to be normal planetary atmospheres. It's not clear that they would work on, e.g., Titan. You'd probably want something a bit more active. Maybe life isn't possible there, but I don't think that's the way to bet. (It could, of course, be more improbable, but then we don't know just how likely life was to arise on earth. It seems, in retrospect, to have been quite likely, but this could easily be a mistake.)

So. Amino acids are AN element from which life can be built. Possibly, however, not the only one. And we probably don't know what else to go looking for.

I do agree, however, that given what is currently known calling the extant space-born molecules "seeds of life" is overstating the case.

Re:Elements are not seeds

[Thing 1]

I'd say the elements of life are everywhere [...]

Yeah, ever since the supernova...

What makes conditions on early earth so special is not the existence of organic chemistry, but the special circumstances, so far not known to us, that brought the formation of complex self-reproducing chains of amino acids.

Without the moon, nothing would have combined.

Solar System Bukakke

[scorp1us]

You've heard of panspermiation, but lets call it what it is, a massive organic molecule cross pollination, with everything coming from one's own solar system. I have a real hard time accepting panspermiation from interstellar space. And while it might happen, the odds of it are is virtually zero. I'd assume those events to be from supernovas which would likely destroy any organic bonds as the material gets distributed throughout the universe on the shockwave of the supernova. Then it has to survive stellar formation...

Anyway, I think We'll have to add galaxy and solar system to the taxonomical names of species. Ours would be wilky way : sol

Re:Solar System Bukakke

[Derek Pomery]

No need of a supernova, and no one has ever suggested that as a mechanism. There is the possibility of directed panspermia if you're into sci-fi, or just rocks flying free from their solar systems.
http://www.centauri-dreams.org/?p=188

All you need is a lot of material, to have decent odds.

One meteor speed listed there is 300km/s - at that speed, it would take 4000 years to get to Alpha Centauri. If life can survive reasonably well for 30,000 years, that gets to quite a few stars nearby. You just need a lot of ejecta.

Universe is a messy place, and our earth's history has involved a lot of stuff banging about. I don't see why the theory should be rejected out of hand.

Re:Solar System Bukakke

[scorp1us]

Oh, I completely, agree, that reaching a star system is possible, possibly even probable, given a direct course. However to contribute it must survive the journey and reach the right destination. Given that suns are the biggest attractor, and heavy Jupiters are next most attractors, these guys will suck up the majority of material and destroy it through temperature. Even after arriving on an planet of suitable composition, temperature and chemistry, it still has to wait around and last long enough to influence the chemistry there. Landing on the surface is not nearly as good as landing in an ocean. I don't expect it to play out like the movie "Evolution" where the ejecta was able to create its own micro climate.

The odds are low, but non-zero. And I find that very exciting.

Re:Solar System Bukakke

[Anonymous Coward]

The real problem with Panspermia is not that it's implausible so much as that it fails Occam's Razor.

A complete theory of the origins of life on Earth will have to explain how life forms from nonliving matter, and how that life ended up on Earth. Until there exists evidence to the contrary, the assumption that life came to Earth from an extraterritorial body, on which it originally formed is unnecessary and does not add any predictive power to the theory. As such it should be considered an inferior to the theory in which life simply formed where it is observed to exist (Earth).

In short, Panspermia attempts to answer a question no one asked ("where did life originate") while passing it off as the answer to one that was asked ("how did life originate").

Re:Solar System Bukakke

[Anonymous Coward]

http://www.atlasoftheuniverse.com/50lys.html

It is fun to think of all of these possibly being our relatives.

Re:Solar System Bukakke

[Derek Pomery]

I'm not arguing that panspermia necessarily explains life on earth, just that it isn't impossible.

But there are some things that panspermia is useful for.
One being that as the age of life on earth gets pushed ever back, there is less and less time for life to have formed on an increasingly hostile early earth. The standard response is that, well, since we are here, it must have happened, we just happened to win the lottery ticket, and since we did, are here to be aware of it.

But panspermia exands both the time and surface area for life to have arisen by billions of years and stars.

It is a more complex explanation, certainly, but it helps quite a bit with the probabilities.
It also expands the possible conditions under which life had formed. As the origins of life get pushed back, the possible environments on earth are more limited. But if panspermia is a possibility, that allows scientists to reasonably continue investigating conditions other than those on the very early earth.

There's been some effort to try and detect evidence of life in ancient rocks at 3.8 billion years back or earlier. That cuts the available time for *complex* life to form down to a mere ¾ of a billion years or less. One objection to this evidence has been the shortness of time and the hostile climate on earth at that time. So in this case, panspermia would help defeat that objection to possible geological evidence.

Totally true tale

[ginbot462]

They prefer the term Aquaursus. Bears' real name was originally in German which they spoke ... later they would go on to form ancient Slavic languages as well and star in Bugs Bunny cartoons. The Ursidae Cabal knew that knowing their real name with give power over them including being able to merge with one to become a werebear (you might heard of one .. ColBEAR). The story of owlbears is too gross, but Aquaursus were ancient protobears that evolved into a highly intelligent republic of entities - retaining individuality while having the benefits of a hive collective. They are waiting on humanity to fuck up and/or help them crack the Earth Egg releasing their next form: the Space Bear. (BTW, humanities real name, given to us by the Honeybadgers, is also lost. It translates to "Givers of Plastic" or "Suckers" depending on who believe.)

http://www.etymonline.com/index.php?term=bear

Also see, Hayao Miyazaki's "Howl's Moving Castle" which is an allegory for this tale.

"Winged bear? Oh My God it's the end times!" - crow, 814 - Riding With Death

Re:Totally true tale

[ginbot462]

"In May 2011, studies involving tardigrades[Aquaursus] were included on STS-134, the final flight of Space Shuttle Endeavour."

Should have read that earlier, these are advanced scouts for the Space Bear. I mean ... obviously.

Re:Totally true tale

[Yamioni]

Your ideas are intriguing to me, and I wish to subscribe to your newsletter.

Misleading summary

[mbone]

Mars rocks have been found on Earth, and it has been a standard assumption in planetary science for some time now that Earth rocks have also been going to Mars by the same mechanism. You wouldn't know it from the summary, but the actual paper also predicts a significant rate of mass exchange Earth -> Mars -

Gladman et al. (2005) estimated the collision rate with Mars to be about 2 orders of magnitude lower that found on the basis of our simulations. However, as also noted in their paper, our results for Mars are within the known typical errors of such probability estimations. ... Both results, definite collisions with Mars and Jupiter, are of astrobiological significance,...

Prepare for 2010 Reference!

[Anonymous Coward]

"All these worlds are yours to use, Except Europa, attempt no landing there."

Seed life?

[Anonymous Coward]

I'm pretty sure humans will have a colony on Europa before any Earth ejacta sprouts up anything of interest...

Re:Seed life?

[Yamioni]

Naysaying aside, you're likely correct. The composition of the ice shell around Europa is full of materials that could make for easy farming of hyrodgen for energy and oxygen for breathing. Depending on what ends up being underneath that ice shell (is it all ocean, or is there land mass?) it seems at least borderline plausible to terraform the entire moon, generating a considerable atmosphere and making the place comfortably livable by humans. One concern is if there is enough spare oxygen available to form an atmosphere thick enough to trap enough heat from the Sun to raise the ambient temperature to a comfortable point for humans, given the distance from the Sun. Another is dealing with the extreme cold that would be experienced in an eclipse from Jupiter.

I'm quite certain there are people smarter than I that could weigh in on the topic with more merit, but casual observation seems to point in the direction of 'possible'.

Re:Seed life?

[cusco]

One of the reasons that probes to Jupiter use RTGs rather than solar panels is because the amount of sunlight reaching that far out impinging on a solar panel is almost useless. IIRC around 95 percent of the mass of the spacecraft would have to be solar panels, even with a bare-bones scientific package. (Another reason is the gravitational shear and inertial forces from such a huge object in highly elliptical orbit around the planet, but that's a different topic.) So no, there won't be sufficient heat from the sun to terraform it, nor is there sufficient gravity to retain that atmosphere. Even if those two reasons weren't enough, we'd still be living in tunnels because of the enormous amount of radiation in the Jovian system. We'd need some really serious shielding just to reach Europa alive, and could never even venture onto its surface in a typical space suit without it being some type of kamikaze suicide mission.

Meh.

[jonadab]

Wake me up if it ever amounts to anything you don't need a microscope to see.

30,000 years?

[JoeRobe]

I've previously heard this quote of organisms surviving for up to 30,000 years in space, but does anyone happen to have a real scientific reference for it? I'm really wondering what can survive that long with no fuel at all, unless the argument is that the whatever rock the organism sits on during its travels through space happens to have some nutrients on it. Even the waterbear still needs some energy after it goes into a cryptobiotic state, right?

Re:30,000 years?

[Anonymous Coward]

I would assume the near absolute-zero temperatures would keep the organisms in a dormant state.

Re:30,000 years?

[osu-neko]

Life doesn't need nutrients if the life-process can be shut down entirely, then restarted when conditions are favorable, and this is the case for many microorganisms. The waterbear may still need some energy, but it's much larger than what we're talking about here, also much more complex, and way more fragile/less hardy than many microorganisms.

Re:30,000 years?

[JoeRobe]

Ok then in that case, is there a reference for single-celled organisms that can completely turn themselves off at ~0 K temperatures and in a vacuum, then turn themselves back on? Now I'm really curious about this. I'm also thinking that after 30,000 years, the organism will have an enormous amount of UV, X-ray, and solar wind exposure that would break down most chemical bonds. That kind of exposure may not be immediately deadly to a larger organism that has a skin or outer shell, but for a single cell, that spells some bad news.

Oh great

[neostorm]

Send a note with it, will you? I hate the thought of bringing up a whole planet of lifeforms just so they can bang their heads and kill one another over the confusion of where they came from and why. ;)

Re:Oh great

[osu-neko]

Send a note with it, will you? I hate the thought of bringing up a whole planet of lifeforms just so they can bang their heads and kill one another over the confusion of where they came from and why. ;)

Alas, all evidence suggests that lifeforms will bang their heads and kill one another in any case. What they may or may not be confused about only provides convenient excuses for doing and/or justifying what they wanted to do anyway...

Mars

[geoffrobinson]

In the 3+ billion years life has been on Earth I would guess that life from Earth could have gotten to Mars even if it has lower probability than other locales.

So if we find life on Mars, or some moon of a gas giant, do we assume it got their from Earth or not?

Re:Mars

[osu-neko]

In the 3+ billion years life has been on Earth I would guess that life from Earth could have gotten to Mars even if it has lower probability than other locales.

So if we find life on Mars, or some moon of a gas giant, do we assume it got their from Earth or not?

Depending on when the migration took place, that might be a trivially easy question to answer. A strange life based on chemical processes entirely unrelated to anything on Earth today may leave us questioning, but RNA or DNA-based microorganisms with identifiable gene-sequences from strains that evolved on Earth with a clear fossil record would leave no question at all. So the answer to you question is, it depends on what we find...

Its inconsequencial.

[Anonymous Coward]

Yes, Mars use to sit where the earth is now. The likelihood that it once contained life is most likely. Whats the big deal? It is not likely that any life or even signs of it will be found billions of years later. Its a pipedream for the space people to think its worthy of wasting precious earth's resources to colonize Mars. Its ludimacrous.

Apropos methinks ...

[Anonymous Coward]

All these worlds are yours except
Europa
Attempt no
Landing there
User them together
Use them in peace

-- 2010

I don't understand.

[Anonymous Coward]

Earth rocks, the ones closest to our gravity center, can reach far flung space, yet the floating debris above us can't seem to fall down? This does not compute.

DNA is thermodynamically unstable

[gregor-e]

DNA forms pyrimidine dimers when exposed to energetic photons of UV and higher. The way life keeps living despite the mild exposure to gamma radiation on Earth is through active repair. In space, not only will organisms not have any active metabolism to accomplish repair, cosmic radiation is constant, and the longer a specimen is drifting through space, the more likely it is to be exposed to a heavy burst of X-rays or gamma rays from a solar flare. If a human were out prancing around on the moon when a solar flare erupted, they could receive sufficient radiation to be fatal, despite their active metabolic DNA repair mechanisms. An inert stretch of DNA in space for even one complete 13-year sunspot cycle would be completely unreadable, let alone able to participate in any replication.