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Does anyone know of any missions planned or in progress that are searching in the very vacuum of space for the complex organic molecules that are key indicators of life (such as DNA, RNA, etc.), or perhaps even life itself (as currently defined; ie. one cell or multi-cellular), or even lifelike things such as viruses?

I know there are several missions in search of life or evidence of life on celestial bodies (eg. Mars), but I'm talking about just in the "emptiness" of space itself.

I'm envisioning some kind of vehicle with a solar-sail for propulsion and perhaps also some kind of sensors built into these vast areas of the sails that also looks for the presence of certain biochemical molecules or cells that may have come into contact with the sails and stuck there as the vessel swept through space.

That kind of a discovery would seem to me to represent a potentially major change in humanity's search for extra-terrestrial life.

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    $\begingroup$ I know we did collect samples from a comet's tail, and did found enzymes and other fun stuff. Don't know about the space itself. $\endgroup$
    – Madara's Ghost
    Jul 23, 2013 at 20:08
  • $\begingroup$ Space is so unimaginably vast and empty, it seems that it would be more fruitful to search on or near objects. $\endgroup$
    – Don Branson
    Jul 23, 2013 at 20:21
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    $\begingroup$ A student experiment I was on shared a platform with some students searching for life in the stratophere. I don't think they found any. Stratolife. $\endgroup$
    – gerrit
    Jul 23, 2013 at 20:53
  • $\begingroup$ Several long duration experiments showed that bacteria can survive vacuum... it was an unintended finding, as it wasn't the intent of the experiments in question. $\endgroup$
    – aramis
    Aug 2, 2013 at 9:01

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I don't know of any projects currently planned to find such materials in the "vacuum" of space - the problem with this is that due to space being inherently huge, you're lucky to pick up any molecules at all, let alone the complex organic ones. You also get the issue that if you find such a molecule, then what would it really tell you about where it may have originated from? If we pick up molecules from solid bodies (not necessarily just planets, but meteors / comets) then we've got a starting point we can use to make assertions about its origin, whereas such a molecule collected in deep space wouldn't really tell us a great deal (it could have separated from pretty much any comet, at any time, anywhere.)

However, this isn't to say that only planets are useful in this regard - comets and other such bodies are all good things to investigate. NASA is working towards harvesting material from comets more easily in the not too distant future with structures such as the comet harpoon - something like this should, statistically speaking, prove far more fruitful in its approach.

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  • $\begingroup$ Thanks for your answer. I don't know what the matter density of interplanetary or interstellar space is. I'm sure it varies tremendously. But organic molecules have been detected through optical means (absorption spectra, et. al.). So it's clear that there is some stuff up there. But just like Earth's oceans harbor a great deal of microbial life that is not apparent at first glance, what if space too held any life that was just up there floating around. That would seem to be a pretty "Earth-shattering" (no pun intended) result, no? $\endgroup$
    – Kevin Ford The Submariner
    Jul 23, 2013 at 20:59
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    $\begingroup$ @CopyrightX For the sake of argument, let's assume an average of about one atom per cubic centimeter in interstellar space. Cosmic dust is about 1000 times less common still (ref). In comparison, there's about 10,000,000,000,000,000,000 times (give or take) more atoms and other stuff the closer you get to your average rocky body due to gravity. So why search for a particularly rare brand of needle in the proverbial haystack when you've got the universe's largest collector needles gathering up the stuff for us in great quantities for eons? $\endgroup$
    – Robert Cartaino
    Jul 24, 2013 at 0:49
  • $\begingroup$ @RobertCartaino I think that's one very worthy perspective, but it occurs to me that maybe there are some types of molecules that can only form in zero gravity. Searching gravity wells for such molecules would certainly be a waste of time. I'm not saying that an entire mission should be devoted solely to the search for biochemical molecules in deep space far from gravity wells. But if you're powering a vessel with solar sails anyway, then why not check the sails for accumulation of interesting molecules. That's all I'm saying. Thanks for your insight, however. :) $\endgroup$
    – Kevin Ford The Submariner
    Jul 24, 2013 at 2:04
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You do get complex organics formed in dust clouds and comet tails and so on. Not enzymes, that would really be a big deal(on a level with finding a stainless steel 3/8th inch socket wrench in a comet), but nucleotides and amino acids and some even simple sugars are definitely out there.

It's one hypothesis that most of the precursor organic molecules needed to get life kickstarted just fell to earth over time, having formed out in space. And it's not implausible, you get all kinds of weird chemistry in interstellar dust. When there are only three carbon atoms, you get all kinds of strange ions and bonds that aren't stable if there are other things around to react with.

Life in a way we would recognize it cannot exist in the vacuum of space. It can survive(often for a surprisingly long time, especially inside rocks and things), but it can't be life in a way we recognize. Life is probably possible in space, but if it's there, it doesn't look like anything we know about or could test for. Checking solar sails for cells is like checking trees for elephant poop. It's a way of looking for life, but even if it's there, you're not going to find it that way.

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