I think that we shouldn't send humans to Europa as in the Europa report, even if it were technically possible to do it (at present it is totally impossible because of the radiation levels unless the spacecraft is unfeasibly heavy with radiation shielding). That's because life on Europa may be vulnerable to Earth microbes.
And I think great care should be taken even sending a robotic mole to Europa - though that may be possible. Though we could sample the Europan plumes - if they exist. Hopefully we have a great opportunity there to find out about the life in the Europa ocean in a non invasive way.
That's because Europa's ocean could easily have life in it that's evolved independently from Earth life, indeed it would be rather surprising if it is closely related to Earth life. So what would happen to an ocean of non Earth life if you add an Earth microbe to it? Just one microbe that starts to reproduce in that ocean, which has maybe never seen DNA based life before? The life there could be based on XNA - like DNA but with a different backbone.
I don't think we should do that experiment. Because surely one possible outcome is extinction of many or all species of life in the Europa ocean, if it turns out that DNA based life is more highly evolved, better adapted. Even if it doesn't take over right away - a small population of Earth based life, once established in the Europa oceans - it could evolve, or mutate, or change of gene expression and then it develops the capability to take over from whatever is the dominant Europa lifeform in the ocean. And then - it might be that Earth life is inedible to Europan life or toxic to it. And the whole food chain then would collapse, and be replaced, eventually, with one based on Earth life.
There could even be a civilization in the Europan ocean and we wouldn't know. Highly unlikely that they would develop elaborate technology without fire. And may be creatures like dolphins without hands. So we wouldn't know about them and they wouldn't know about us. And if we introduce Earth life to the ocean - they could be extinct before either of us knows that the other exist.
Those are like the worst case situations. Not saying any of that is likely, or indeed unlikely. We just don't know. Have no previous experience of anything like this, and have never found any life that isn't based on not just DNA but the whole elaborate complex machinery of the modern cell.
But theoretically we've shown that XNA based life can work. Life like Earth life but just change the backbone. And experimenters have successfully added extra nucleotides to DNA - to make a version of DNA with two new bases (an experiment done with many precautions - made sure the new bases couldn't be made "in the wild"), and that worked and was able to reproduce and the new bases continued to the next generation. So we know for sure, theoretically, and practically, that alternatives to DNA are possible.
Another possibility is that there is no life in the Europa ocean, just proto cells on the way to becoming life. Or an "RNA ocean" - replicating chemicals but no cells so it's not really life. In that case - that's enormously interesting because it could help fill the huge gap in our understanding of evolution, about what happens between chemicals and evolution of life. And in that case Europa could be even more vulnerable. In that case, even dead DNA, thoroughly sterilized, even bits of cells with some of the machinery of life could become templates that get used by the Europan life to evolve to the next stage and become life rather than protocells. So we could lose the chance to study it in its original state.
So - I think we should not only avoid all chance of introducing viable Earth life to Europa, but even, dead life as well. Until we know what is there.
The safest way is to study samples from the plumes, if Europa is sending plumes into the atmosphere. Or if we send moles down to the ocean, I think they have to be very thoroughly sterilized, more so than Viking. Because they could land in water, and because the ocean could be vulnerable even to dead life. So I think we need methods that remove every trace of organics from the exterior of the mole. That may be possible with high pressure liquid carbon dioxide, treating the spacecraft after it leaves Earth so no chance of re-contamination. The organics dissolve into the liquid CO2 and then when pressure is released, they are removed from the spacecraft, would just dissipate into space. Life would remain in the interior, e.g. on electronics components (unless we can find a way to sterilize those also) - if so - at end of mission, maybe have a source of ionizing radiation to thoroughly sterilize the interior.
At any rate - I think we simply shouldn't send a mole to the Europan ocean until we are totally sure that we can sterilize it sufficiently, or until we know a huge lot more about the ocean. Because - if we contaminate its ocean - it's not going to harm us, in any way. But - it could harm whatever Europan life there is, if there is there, and it also could prevent us from making great discoveries in the future.
Which could be very frustrating. But it is just what we have to do. The ocean can wait, and it may be that future generations will be the ones who have the technology to study it properly - it might be that by sending insufficiently sterilized moles to Europa - the main impact may be on our children or grandchildren's generation, robbing them of an amazing exciting discovery they could have made if we hadn't done that. Or might be that we are able to do it ourselves, just a decade or so into the future. Even now, I think we are close to this capability, we may even have this capability already but need to be sure before doing something like this.
Note that there is a possibility of meteorites from Earth hitting Europa after huge meteorite impacts on Earth. But the chance is tiny, and any meteorites would spend a long time in transit and be thoroughly sterilized - also sterilized by the Jupiter radiation as they approach Europa orbit. So not too likely that life has got to Europa in the recent geological past. It might have shared life in the early solar system - that is - if early life was both vacuum and cosmic radiation resistant enough already to survive the transit.
And the thing is anyway - that nobody has yet proved that any life has ever been transferred on a meteorite anywhere in the solar system. It remains a theoretical idea. And most microbes even, never mind higher animals or multicellular plants, have no chance at all of transfer on a meteorite, just a few highly radioresistant microbes (and also shock resistant for the transfer) might, just possibly, be able to do this.
There's still a decent chance that life on Mars (if it exists) is totally independently evolved from Earth life, jury is still out on that. Will only know when we get a chance to study it. And an excellent chance that Europan life is, either completely independent, or last common ancestor is in the very early solar system, say 3.9 billion years ago or earlier, back to the late heavy bombardment. I think that is probably what most scientists would think is the likely situation for Europa.
And I think great care should be taken even sending a robotic mole to Europa - though that may be possible. Though we could sample the Europan plumes - if they exist. Hopefully we have a great opportunity there to find out about the life in the Europa ocean in a non invasive way.
That's because Europa's ocean could easily have life in it that's evolved independently from Earth life, indeed it would be rather surprising if it is closely related to Earth life. So what would happen to an ocean of non Earth life if you add an Earth microbe to it? Just one microbe that starts to reproduce in that ocean, which has maybe never seen DNA based life before? The life there could be based on XNA - like DNA but with a different backbone.
I don't think we should do that experiment. Because surely one possible outcome is extinction of many or all species of life in the Europa ocean, if it turns out that DNA based life is more highly evolved, better adapted. Even if it doesn't take over right away - a small population of Earth based life, once established in the Europa oceans - it could evolve, or mutate, or change of gene expression and then it develops the capability to take over from whatever is the dominant Europa lifeform in the ocean. And then - it might be that Earth life is inedible to Europan life or toxic to it. And the whole food chain then would collapse, and be replaced, eventually, with one based on Earth life.
There could even be a civilization in the Europan ocean and we wouldn't know. Highly unlikely that they would develop elaborate technology without fire. And may be creatures like dolphins without hands. So we wouldn't know about them and they wouldn't know about us. And if we introduce Earth life to the ocean - they could be extinct before either of us knows that the other exist.
Those are like the worst case situations. Not saying any of that is likely, or indeed unlikely. We just don't know. Have no previous experience of anything like this, and have never found any life that isn't based on not just DNA but the whole elaborate complex machinery of the modern cell.
But theoretically we've shown that XNA based life can work. Life like Earth life but just change the backbone. And experimenters have successfully added extra nucleotides to DNA - to make a version of DNA with two new bases (an experiment done with many precautions - made sure the new bases couldn't be made "in the wild"), and that worked and was able to reproduce and the new bases continued to the next generation. So we know for sure, theoretically, and practically, that alternatives to DNA are possible.
Another possibility is that there is no life in the Europa ocean, just proto cells on the way to becoming life. Or an "RNA ocean" - replicating chemicals but no cells so it's not really life. In that case - that's enormously interesting because it could help fill the huge gap in our understanding of evolution, about what happens between chemicals and evolution of life. And in that case Europa could be even more vulnerable. In that case, even dead DNA, thoroughly sterilized, even bits of cells with some of the machinery of life could become templates that get used by the Europan life to evolve to the next stage and become life rather than protocells. So we could lose the chance to study it in its original state.
So - I think we should not only avoid all chance of introducing viable Earth life to Europa, but even, dead life as well. Until we know what is there.
The safest way is to study samples from the plumes, if Europa is sending plumes into the atmosphere. Or if we send moles down to the ocean, I think they have to be very thoroughly sterilized, more so than Viking. Because they could land in water, and because the ocean could be vulnerable even to dead life. So I think we need methods that remove every trace of organics from the exterior of the mole. That may be possible with high pressure liquid carbon dioxide, treating the spacecraft after it leaves Earth so no chance of re-contamination. The organics dissolve into the liquid CO2 and then when pressure is released, they are removed from the spacecraft, would just dissipate into space. Life would remain in the interior, e.g. on electronics components (unless we can find a way to sterilize those also) - if so - at end of mission, maybe have a source of ionizing radiation to thoroughly sterilize the interior.
At any rate - I think we simply shouldn't send a mole to the Europan ocean until we are totally sure that we can sterilize it sufficiently, or until we know a huge lot more about the ocean. Because - if we contaminate its ocean - it's not going to harm us, in any way. But - it could harm whatever Europan life there is, if there is there, and it also could prevent us from making great discoveries in the future.
Which could be very frustrating. But it is just what we have to do. The ocean can wait, and it may be that future generations will be the ones who have the technology to study it properly - it might be that by sending insufficiently sterilized moles to Europa - the main impact may be on our children or grandchildren's generation, robbing them of an amazing exciting discovery they could have made if we hadn't done that. Or might be that we are able to do it ourselves, just a decade or so into the future. Even now, I think we are close to this capability, we may even have this capability already but need to be sure before doing something like this.
EXCHANGE OF METEORITES AND LIFE ON EUROPA
Note that there is a possibility of meteorites from Earth hitting Europa after huge meteorite impacts on Earth. But the chance is tiny, and any meteorites would spend a long time in transit and be thoroughly sterilized - also sterilized by the Jupiter radiation as they approach Europa orbit. So not too likely that life has got to Europa in the recent geological past. It might have shared life in the early solar system - that is - if early life was both vacuum and cosmic radiation resistant enough already to survive the transit.
And the thing is anyway - that nobody has yet proved that any life has ever been transferred on a meteorite anywhere in the solar system. It remains a theoretical idea. And most microbes even, never mind higher animals or multicellular plants, have no chance at all of transfer on a meteorite, just a few highly radioresistant microbes (and also shock resistant for the transfer) might, just possibly, be able to do this.
There's still a decent chance that life on Mars (if it exists) is totally independently evolved from Earth life, jury is still out on that. Will only know when we get a chance to study it. And an excellent chance that Europan life is, either completely independent, or last common ancestor is in the very early solar system, say 3.9 billion years ago or earlier, back to the late heavy bombardment. I think that is probably what most scientists would think is the likely situation for Europa.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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