The temperature on Europa is much lower than the temperature on Earth.

The amount of sunlight on Europa is far less than the amount of sunlight

on Earth.

The surface gravity on Europa is far lower than the surface gravity on

Earth.

And that's the point of choosing Tardigrada as a subject. Water bears survive in temperature range of -271 - +150 C. They also easily survive without sun and it's the only creature capable of staying alive in OUTER space. The only trick is that I did not find any research on Tardigrada survival in combination of all of that. Yes, we know Tardigrada is tough, but is it tough enough to be capable of surviving on Europa? If yes, it is sensational, because if Earth organisms are capable of surviving in moon environment - POTENTIAL biota of Europa can exist too. The question is - will it add that much to a data which already exists (tides discovery, analysis of Europa crust etc.). Thank you for the reply, Michael.

There was a project named TARDIS conducted

by the ESA. Water bears survive for a while

in space.

Regards,

Joachim

Which Europan conditions? The surface or the deep interior?

The surface of Europa is a very tough environment - cold, in vacuum, and with a high level of radiation. The radiation is all charged particles and the amount of radiation varies over the Europan surface. If you have access to a 10 Mev accelerator and a vacuum chamber, then a research program aimed at showing whether Tardigrada could survive (in an inert , dehydrated, state) on the surface of Europa would be very interesting, as it would indicate something about whether "live" spores could be possibly sampled on the Europan surface or even in orbit from an active Europan plume.

See http://onlinelibrary.wiley.com/doi/10.1029/2007GL030834/abstract and

https://www.researchgate.net/publication/261013906_Survival_and_Chemistry_of_Organics_on_the_Near_Surface_of_Europa_and_Titan

If you are talking about survival in the deep ocean of Europa, you need to think some about what you are trying to show. The oceans are presumably salty liquid water, so any salt-water organism adopted to deep-water conditions presumably could survive, at least for a while (whether it could find food and reproduce is of course another question). The surface radiation does not penetrate into the deep ocean, and I don't think the change in gravity would matter to a water-born organism.

There is, however, one thing that does come to mind with the ocean case. No one knows the composition of these icy moon oceans, but, at least for Titan, there is speculation that they might be a water-ammonia mix - see

http://www.sciencedirect.com/science/article/pii/S0019103500964005

If you could show that Tardigrada could survive in a water-ammonia mix, or what level of ammonia would be fatal to them, and at what temperatures, then that could be a solid advance in understanding the sub-surface biological potential of at least Titan, and probably other icy Moon oceans as well.

Article Survival and Chemistry of Organics on the Near Surface of Eu...

In case of Europan ocean - wouldn't pressure play a major role in a research too? Ice crust of Europa is approximately ~3 - 10km depth (according to Richard Greenberg and Kevin Plaxco), plus ocean itself can be up to 100 - 150 km deep. Which means the experimental conditions should be: water-ammonia mix + temperatures + pressure. Or would it make more sense to start with w-ammonia and temperature only? Too many factors might make it hard to analyse the data.

Dmitrij - I don't know how much work has been done on pressure, but it says in the wikipedia article that "tardigrades can withstand temperatures from just above absolute zero to well above the boiling point of water, pressures about six times greater than those found in the deepest ocean trenches,"

Suppose that is the true limit. The Mariana Trench is 11 km deep, so 6 x that is 66 km, and (with 1 bar = 10^5 pascals every 10 meters) that means they die at a pressure ~ 6600 bars or 7 x 10^8 pascals. Ice VI forms in cold water at 6.324 x 10^8 pascals, so I would wager money that the tardigrade limit is at the formation of Ice VI. (I suspect that this is in fresh water; I know that JPL is investigating how brine changes the formation of the higher order ices.) Since the _bottom_ of the ocean on Titan or Europa is suppose to be Ice VI (or maybe V or VII), that actually makes it easy - research has apparently _already_ shown that the tardigrades can survive the _whole_ depth of the Ocean.

Now, that doesn't mean that you shouldn't investigate the effects of pressure, but it does make me think that it might not need to be your first priority.

I am not really in this field, but more curious, however there might be a logical trap in here. If I understand you correctly you want to test out if a "tough bacteria" on Earth can exist in the even rougher conditions on Europa and by this support the idea of life on Europa. Well, only because you have a life form here that can survive this, does not tell anything about the likelyhood of life formation on Europa. Vice versa even if you do not find a life form on Earth that can actually life under these circumstances, it does not say anything about the possibility of it having formed on Europa. Maybe it never evolved in that way, because it never had to?

also the trap that I meant is: What attributes, traits make your bacteria capable of surviving this and could they have developed in an area unlike Earth? So maybe trait B, C, and D make your bacteria strong enough to withstand the harsh(er) conditions on Europa, but to evolve into a state to have these traits, the bacteria needed trait A, which might no longer be there, but could only have developed in conditions like here on Earth. Like, we needed somekind of writing utensils, paper, stone, etc. to do math to develope computers, which made all these obsolete. But still without paper, stone, whatever, we would have never developed computers in the first place. Or like humans evolved so far and adaptable that they can now survive basically anywhere on Earth, but this does not mean we could have evolved like this anywhere on Earth.

I think the only way to go is, learn more about formation of life, check if there is any universal condition about it and then review if this is violated by the conditions on Europa. Which is, I guess, basically what is done right now.

If we do not find Life forms deep inside Mars, I doubt we will find

life forms deep inside Europa.

On Earth, Life forms began as single celled organisms, and after a few billion

years, multi-celled organisms evolved to eat the single celled organisms.

The problem is " What is the food Chain ? " on any other planet that

allows life to exist and survive.

What is the Probability that what happened on Earth over billions of

years could, can, or will, occur on other planets.

Frankly, I am absolutely astounded that larger more advanced life forms

have made it on Earth for more than the Last 630 Plus million years,

and did not end up in a 100 % global extinction.

That means it took about 3,800 to 3,900 million years for evolution

to really get off the ground and produce larger multi-celled

ocean dwelling critters, and another 630 million years to get to

life forms that are fully capable of altering their environment .

You need to study how the Earth got where it is, and what narrow

temperature - pressure range of the atmosphere actually allowed

this to happen. That range is - 6 C to + 26 C average global temperature,

with a dominate temperature of + 22 C over much of the last

252 million years.

My gut instinct tells me we are a pretty rare planet in the Galaxy.

Speaking of food chain, there is the microbe Desulforudis audaxviator

whose ecosystem consists of this one species. D.a. feeds on

anorganic compounds like sulphate, CO2, and gets its energy

from hydrogen produced by water splitting by radioactivity.

Conditions that could be found anywhere, even on a rogue planet.

Regards,

Joachim

An excellent question, highlighting some epistemological and methodological issues one has to face in astrobiology. I'd suggest that the positive outcome of the tardigrada survival experiment should count as an indirect weak evidence for the hypothesis of life's continued existence in the Europan conditions, but as fully aware that it comes with some additional - and possibly unwanted - epistemological baggage. The reasoning, roughly, is that the positive outcome would prove the capacity of SOME lifeform to survive on/in Europa. Since survival is a precondition to being inhabited today, this will prove that Europa could indeed be inhabited today by SOME lifeforms. Which is closer to our goal than we were before. Now, this does not tell us anything, as Volker Maiwald correctly suggests above, about the inherent probability of abiogenesis on Europa, but then again, it is very hard to tell anything about the inherent probability of abiogenesis on Earth either (after we account for obvious observation selection effects). However, the survival experiment would indirectly add a small support to the hypothesis that life from Earth could be transported via interplanetary panspermia and then survive on/in Europa. Since that is one of the three logically exhaustive hypotheses about the origin of any conceivable life on/in Europa (in situ abiogenesis, transport from Earth, transport from hypothetical other habitats), support for one option counts as the support for the whole disjunction of hypotheses.

Of course, all kinds of difficulties await if we try to answer the question what kind of changes would the environment on/in Europa cause in lifeforms transported there via panspermia in deep evolutionary time. The survivors might not resemble the ancestors on any morphological level - only the basic biochemistry will stay the same. But then again, how are we to distinguish the hypothesis that basic biochemical similarity is the proof of panspermia from the hypothesis that basic biochemical similarity is just the proof of existence of universal "optimal" biochemistry dictated by laws of physics and chemistry? ;)

The problem with interplanetary panspermia is that even if this hypothesis is true (let's imagine) - it still does not answer the question of the life origins. Some people think life came to Earth from Mars. Therefore, if we imagine that life from Earth could be transported to Europa - it starts to remind me the movie "Inception" or STI. For now we do not know anything about interplanetary panspermia - no robust evidence yet. However, NASA (sorry, if I am wrong) did experiment with extremophiles, including Tardigrades and results showed that some organisms might be able to survive in highly hostile environment - space.

For the start - it is highly doubtful that life can exist on the surface of Europa (exposed to huge radiation, extremely low temperatures, no oxygen etc.).

What I'd like to check - ability of organism to survive on Europa (under the ice crust). If Tardigrades die there - probably, we lose the "last hope". It would at least expose a huge weak point of interplanetary panspermia posibility: if one of the most "tough" organisms cannot manage to survive, than whom can? We have no clue if there are tougher organisms on Earth or anywhere else (so far).

BUT if Tardigrade is able to survive for quite a long time - it would not only support the panspermia hypothesis, but it might support the existence of living organisms on Europa. Analysis of Voyager and Galileo data showed a relatively high activity of Europa crust, which means that ice on Europa, is probably not as thick as people thought before and it probably has a liquid ocean underneath. The biggest planet in the solar system + sun + Io / Ganymede / Callisto + mobile, relatively rapidly changing crust => incredible gravitational influence + evidence => high tidal activity. Such tidal activity should produce incredible amount of energy (heat) - maybe enough to support life. The question is - how tough the environment was throughout the existence of Europa. If it was moderate, it is possible that hypothetical life on Europa did not need any panspermia. However, without the evidence all this is just a number of theories, talks and dreams.

Sorry for spelling and weak text structure - in a rush right now. Thank you all for the replies, they are drastically helpful and give me a chance to look at the problem from different angles.

Dmitrij - I think that all sounds very reasonable. For solar system panspermia I would for sure not leave out Venus. It had an early ocean and probably a much thinner atmosphere. I suspect life may have arisen there and spread to Earth and Mars.    As for the outer planets, I always thought that the movement of meteorite ejecta from here to there was energetically unfavorable, but http://arxiv.org/abs/1311.2558 show that it is possible. 

You would need to calculate the Solar output required to have Venus

not be at 850 C as it is now.  The Sun would need to be much smaller,

and Venus waould also need to be smaller, and rotate faster on its axis.

I strongly suspect that the Earth may be more unique than we want to 

believe.  The correct distance, a Moon to act as a pump to move the Earth's

surface up and down to aid in a " Fractional distilation " of the Earth

elements and compounds.  And a relatively slow growth rate of

our planet that has allowed the continents to stay above the elevation of the 

top of the oceans for much of the last 630 million years.

The drake equation is missing several terms that would significantly

decrease the likelyhood of advanced life ever getting started, or 

evolving long enough to reach the point of technologically altering

their surroundings.

If Venus had early oceans (see http://www.lpi.usra.edu/meetings/venus2009/pdf/2021.pdf for a brief description) at that time the carbon now in Venus's atmosphere would have had to have been sequestered in the surface rocks (and maybe also the oceans). In that case, you do not have a strong greenhouse, and you do not need a substantially weaker Sun to have a temperate Venus.

Venus is about 2/3 of the distance , so the power output would need to 

be around 4/9 or less of the current Solor energy output to match the Earth's

current value or 341 watts per square meter.  I use or less as the power

output of the sun was supposedly less in the past, and has been gradually increasing.

gradually is a very good thing for longevity of life forms on a planet.

Note that the (current) Bond Albedo of Venus is 0.90, versus the Earth's 0.3 (on average, it varies), so it actually received substantially less solar energy than the Earth does ((3 x 10^16 W vs 1.2 x 10^17 W on average). If Venus had anything like that albedo earlier on, sustaining an ocean for a while would not have been a problem

When I look at the Earth, I ask, what is different about the Earth to allow

it to sustain larger surface life forms for the excessively protracted

period of time of the last 630 million years, since it was more like

Europa between 812 and 630 million years ago.  One thing is distance from the

Sun, and another is we have the Moon to mechanically pump the

surface of the Earth up and down, and to release the volatiles like

Hydrogen, CO2, O2, Nitrogen.  Another question I ask is, why did it take

over 3800 million years to reach the point  where larger life forms

could evolve ?  Why has the average temperature stayed between 

about 6 C and 26 C with the dominate average temperature 

remaining around 22 C, for much of the last 630 million years ?

So if you compare Venus, Earth, and Mars, the Temperature is 

Far higher on Venus, and much lower on Mars.

The question is.... was it always that way ?   I suspect there was

a period of time when the Sun was smaller, and its solar output was less

such that the life sustaining Belt ( Goldilocks zone ) passed thru Venus, as it 

is passing through Earth, and will eventually pass through Mars.  This would 

imply that Venus could have had oceans, which are now boiled away.  In fact,

it would not surprise me that much of earth's Surface water came from

Venus, and possibly even the Mars shallow oceans also came from

Venus.  This would give us a time frame as to when Venus lost its surface 

waters, and Earth, and Mars gained some surface waters.

This is of course highly speculative, but, speculation often leads to

new lines of investigations, and new results.

The more important question is, did Venus have enough time at

the correct temperature range and surface moisture to produce

life, and have it evolve and diversify?    And, Did Venus have a fast enough

axial spin rate to keep the planet from alternately broiling and freezing?

Dear Michael; 

I would actually favor a biological mission to Venus, to  the 55 km altitude level where liquid water could survive. That region is not in chemical equilibrium, which is generally regarded as a possible marker for life, and we now know that the Earth supports a biosphere aloft, so it by no means impossible. That region is also  fairly well mixed, so that one mission (presumably balloon based) could rule Earth-like life on Venus in or out, which definitiveness I do not think will be possible for either a single mission to either Mars or Europa.