LCROSS detects life on Earth!

By Phil Plait | August 4, 2009 5:39 pm

The Lunar Crater Observation and Sensing Satellite (LCROSS), part of the Lunar Reconnaissance Orbiter mission, performed a routine calibration of its instruments a few days ago, pointing them toward Earth and seeing what it could see. And what did it find?

Life!

LCROSS spectrum of Earth

This spectrum covers part of the ultraviolet and visible range of light. The big dips in the line are due to absorption of light from certain molecules; these dips are like fingerprints for specific atoms and molecules. You can see that LCROSS clearly detected ozone (O3) and water, which you might see on any old planet. But it also saw a feature that is from free oxygen (O2) — it’s subtle but it’s definitely there — and that’s something you don’t see just anywhere. Why not?

O2 is pretty unstable; plop some of it in a random planet’s atmosphere and in a few weeks it’ll be gone, combusted, combined with other molecules to make carbon dioxide or rust or something like that. The only reason we have a lot of it in our air (more than 20% of the Earth’s atmosphere is O2) is because we have life in the form of plants. They make it as fast as animals and chemical reactions use it up, keeping it in equilibrium.

In fact, looking for free oxygen is one way scientists may eventually look for life on planets orbiting other stars. It’s an incredibly difficult observation, but not impossible, and in the future better technology may allow us to search for the elusive dip in a spectrum that tells us that aliens are breathing (or whatever aliens do) there.

Incidentally, the forest of little dips in the spectrum may be due to vegetation itself, which would be a direct detection of life. I’ll take that, too.

LCROSS also took these cool images of the Earth:

LCROSS IR Earth

The image on the right gives you the context; North America is on the right side of the Earth, Asia/Russia on the left, and the Pacific Ocean dominating most of the view.The upper two images on the left are in the near infrared (just outside our range of vision), and the lower two farther out, where warm stuff emits IR. Note the line demarcating day and night in the top images; I suspect that’s not as obvious in the lower ones because at those wavelengths the Earth’s oceans glow whether it’s day or night. Water is slow to warm and slow to cool, and the temperature doesn’t change much from day to night.

So there you go; proof of life on Earth. Maybe there are slightly easier ways of detecting it — going to the mall, for example, or poking a wasp’s nest — but this is one way that may eventually give us the answer to one of the great outstanding mysteries the Universe still has for us: are we alone?

Image credit: NASA/Ames Research Center. And you can follow LCROSS on Twitter, too, which is how I found out about this!

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA

Comments (46)

  1. What would be the easiest best test for intelligent life then assuming you can’t see artifacts from orbit or there are no radio emissions? Lights on the dark side of a planet?

  2. JSW

    Are we sure we want to test for intelligent life on Earth? I think the results might be a bit of a blow to our egos.

  3. but is it intelligent life?

  4. Alex

    I wonder if they removed the solar spectrum from those spectra.

    I’m TAing a “Search for Life in the Universe” course this fall and we plan to do a “vegetation red edge” detection experiment with the students. I’d be interested to see someone compare the LCROSS data to previous attempts at detecting the red edge in Earthshine.

  5. How do you get a vegetation signal if the FOV was the North Pacific?

  6. T.E.L.

    Lab Lemming Said:

    “How do you get a vegetation signal if the FOV was the North Pacific?”

    Very good question. First, it’s not all ocean in the image; the land masses are a considerable fraction of the whole hemisphere. Their contribution may be enough to skew the total luminance around the band of absorbed frequencies. And (perhaps), there may be a lot of simple plant life at the ocean’s surface.

    Second, it’s not clear that it is from vegetation; the band of absorptions is labeled “Vegetation?”, meaning that no firm claim is being made at this time. I’m guessing that the attenuated frequencies correspond to known plant absorptions, so it’s considered plausible ’til further notice.

  7. Hmm

    Next week’s tabloid headlines:

    “NASA WASTES TAXPAYER MONEY TO DISCOVER LIFE ON EARTH”

    complete with editorial about how NASA is useless, with maybe one line like “nasa spokesperson says it was a simple, routine test” tucked in somewhere.

  8. MadScientist

    You get a better O2 signal in the near infrared.

    Plants consume O2 as well. Algae in the sea are a huge contributor to oxygen; do you count them as plants?

    Where was the instrument pointing when it took the spectrum and how large a spot is it looking at on earth? I’d be cautious about your interpretation of vegetation; absorption in the near infrared is a more reliable indicator of vegetation; unfortunately all the interesting biological stuff happens in a region just beyond what is presented here.

  9. @Hmm

    I LOL’d. It’s probably gonna happen, too.

  10. John

    I can’t see that we would detect intelligent life, Ken Ham perhaps, but nothing more intelligent than an amoeba

  11. Neet

    It’s a hoax.

  12. if there is some intelligent life out there – hope it´s intelligent enough not to get detected by us ;-)

  13. Jeeves

    Quote:

    You can see that LCROSS clearly detected ozone (O3) [...], which you might see on any old planet. But it also saw a feature that is from free oxygen (O2) — it’s subtle but it’s definitely there — and that’s something you don’t see just anywhere.

    Don’t you need O2 to get O3 (which means that if there is O3 there must also be O2)? Or can it also be generated from H2O and/or CO2?

  14. Annon

    “Algae in the sea are a huge contributor to oxygen; do you count them as plants?”

    Hmm, I really don’t know, they generate energy by photosynthsys and are multicellular, so I would say they are, even though they lack alot of the other features that make a plant a plant.

    Blue-Green Algae/Cyanobacteria blur the lines even more, as they too use photosynthsis for energy, but each cell lives as an individual.

  15. DA

    What I dont understand is that who and where does it say that alien life form will need O2 to thrive. Maybe we are the only planet in the Universe where we need O2 for life. Probably in other Galactic systems it could be Hydrogen or Nitrogen or some completely new element. If detecting O2 is a sign of alien life than thats a wrong statement. It should be rephrased to ‘Another planet where humans can survive”

  16. Ettienne Hugo

    Really cool article man, appreciate it…

  17. sdh

    How do you get a vegetation signal if the FOV was the North Pacific?

    Please don’t forget that there is a ton (many many tons) of vegetation in the oceans: primarily plankton but also seaweed. I’m not saying that plankton is the source of the ‘vegetation’ signal, but just pointing out that the ocean, even the frigid ocean, is not devoid of photosynthesis.

    I have to say Phil, I find this pretty freakin’ awesome. Best.

  18. Reverend J

    I have to disagree with you that ozone is more stable than molecular oxygen. Ozone (in the chemical world) is known as a great oxidant for many different organic (and inorganic) compounds in which oxidation would not work in an oxygen environment. Also, that why ozone in the lower levels of the atmosphere is a pollutant, it reacts with everything it touches (including our DNA) due to it’s instability. Lastly, ozone can only be made through a radical reaction of oxygen so you have to have some levels of molecular oxygen in the environment in order to make oxygen.

    To Jeeves:
    H2O and CO2 cannot make ozone, CO2 is too thermodynamically stable to react in some way to make ozone, unless there was complete disassociation of the carbon and oxygen, but then it wouldn’t be able to form ozone anyways. H2O,in our atmosphere can produce hydroxy radicals from loss of one hydrogen, which quickly react with other molecules in the atmosphere. It would require to much energy to lose the other hydrogen atom to form an O- (which in itself wouldn’t react with another O-)

  19. jeff

    there will be intelligent life detected on earth, which ones?

  20. Just out of curiosity: For how many of the Earth’s 4.5 billion years would this test have shown life on this planet?

  21. DrFlimmer

    I think, this is good news! Life on earth! At first, I couldn’t believe it, but thinking about it, well, let me conclude that it could be possible. But we should check the results very carefully! One can never be sure of such results!
    :D

  22. Michelle

    Well that’s good news! I feel reassured now. :P

  23. Steve A

    Actually Hmm, this is the tabloid for the week:

    http://www.dailymail.co.uk/sciencetech/article-1204254/Has-mystery-Mars-Monolith-solved.html

    Buzz Aldrin stokes the mystery of the monolith on Mars

    *sigh*

  24. Gary Ansorge

    18. DA

    We have to look for what we already understand and what we know is that for energetic life to exist, O2 is essential.

    There are only 92 stable elements in this universe and only a very few seem capable of entering into biological processes. Silicon is chemically similar to carbon in it’s chemical reactivity and “as common as dirt” but life here “chose” to use carbon as it’s basis(DNA made from Carbon, Hydrogen, Oxygen and Nitrogen). One would think, if silicon were a possible basis for life, we would find examples of such buried somewhere, in a geothermal vent or deep mine or,,,well, you get the picture. The chemical processes of life are not exactly random. They depend on how stable molecular structures need to be in order to form a more perfect union as well as how easily they can be remade into other structures. Most of that reactivity is dependent on the particular atomic/molecular valence levels of life elements. Before life stumbled on O2 as a reducing molecule, it was dependent on slow chemical processes and evolution was equally slow. A billion years of one celled, anaerobic life went into evolutionary hyper-drive when O2 came along, which produced,,,us and that’s what we’re really interested in,,,critters similar enough to us that we would recognize them. H2, Silicon based or some other exotic life chemistry is likely beyond our ability to detect until we can actually hang out on such a planet long enough to figure out how these rocks manage to make more rocks. Ah HAH! it’s because they’re ALIVE,,,in other words, what is the sound of two rocks humping??? and do they produce more rocks???

    GAry 7

  25. Dunc

    DA:
    What I dont understand is that who and where does it say that alien life form will need O2 to thrive. Maybe we are the only planet in the Universe where we need O2 for life.

    Even Earth didn’t need O2 for life for the first billion years or so of life’s existence – all the O2 was originally a poisonous by-product of other biological processes.

    The point is not that you need O2 for life, it’s that you don’t get O2 without life. Which is not to say that all life must produce O2, merely that if you see O2, you can be pretty sure that there’s life there. There may be other forms of life which would not be detected by this approach.

    Probably in other Galactic systems it could be Hydrogen or Nitrogen or some completely new element.

    Probably not – the chemistry is rather different. And it’s not going to be “some completely new element”, because we already know what all the naturally-occurring elements are and there is nowhere in the periodic table for a new one. Chemistry is the same wherever you go, because physics is the same wherever you go.

    Oxygen is a particularly useful chemical for life because it enables all sorts of energetic chemical reactions.

    Gregg:
    Just out of curiosity: For how many of the Earth’s 4.5 billion years would this test have shown life on this planet?

    For at least the last 2.4 billion years, since the The Great Oxidation.

  26. Andrew Taylor

    Life as we know it, Captain.

  27. Jeff

    Kepler is not capable of spectroscopy but should find hundreds of earth sized planets.

    But a future space telescope, TPF, should by 2016 be able to do spectroscopy like LCROSS did, but for these exosolar planets, and it might be able to detect the signature molecules of life.

    Still, please remember that we do not know for sure two related things: (a) exactly how did life originate on earth, and how complex was the process (b) are there enough planets “out there” so that life would be statistically able to form on them, and that’s the rub, we just don’t know how likely or unlikely the formation of life is.

    A case could be made that there are enough planets so it’s inevitable that life is out there.

    A case could be made that the probability of the formation process of life is so infinitesimally small that all the planets in the universe times this probability would give a very low probability of life being out there.

  28. OregonMJW

    I note that LCROSS did not specify it had found “intelligent” life on Earth. Your report avoided that phrase as well. Hmmmm. Otherwise, it’s Little Green Men, you can run but you cannot hide!

  29. T.E.L.

    Jeff Said:

    “Kepler is not capable of spectroscopy but should find hundreds of earth sized planets.”

    Kepler will find nothing. He died dozens of years ago, killed by the stench of Tycho’s festering chopped-off nose!

  30. mike burkhart

    I thought we all redy knew ther was life on Earth and thats why we were looking for life on Mars(and havent found any) or on Venus (It would fry in the heat) or maybe on Europa ( Im keeping a open mind until a probe can explore under the ice) in fact we should be looking outside the solar system for life P.S. I did not list the Moon Mercury or the gas giants asteroids comets or Kupier blet objects or the Sun because it was highly unlikely that life could have formed on these objects and astronomers never thought we find life there

  31. Keith Harwood

    Those near infra-red images look awfully like Mars circa 1930. Do I see canals? Canals prove there is life on Earth!

    BTW there are only 81 stable elements, hydrogen to lead, less technicium. All the heavier elements are unstable, though some have long enough lifetimes they can still be found on Earth.

  32. 22. jeff Says:

    there will be intelligent life detected on earth, which ones?

    Mice and dolphins?

    42

    J/P=?

  33. Buzz Parsec

    My previous comment seems to have vanished, maybe because I tried to link to a previous BA blog in the website…

    I was trying to point out to DA that the presence of O2 in a planet’s atmosphere definitely indicates life on that planet, since the only processes we know of that can produce O2 in large quantities (which is extremely reactive and will go away very quickly if not replenished) are biological. However, the lack of O2 does *not* imply the lack of life. For the first 2 billion years of Earth’s history, there was no O2 in the atmosphere, even though there was life for most of this time, and O2-producing life for a good part of it. When cyanobacteria first started producing molecular Oxygen (in the oceans), it immediately combined with disolved Iron and precipitated out, resulting in the banded iron formations that are the most common iron ores on Earth. Only after all the disolved iron had been removed (about 2.5 billion years ago) did O2 start accumulating in the atmosphere.

  34. Torbjörn Larsson, OM

    So there are “life on other planets” after all. :-o Comforting that it’s so easy to get at the observation.

    I have to disagree with you that ozone is more stable than molecular oxygen. … Lastly, ozone can only be made through a radical reaction of oxygen so you have to have some levels of molecular oxygen in the environment in order to make oxygen.

    That’s what I thought, or at least that the ozone from oxygen was sufficiently different in scale to enable life detection. I’m quite sure that it has been proposed as an observation of life, because as we can suspect from the spectrogram it gives a huge signal.

    Maybe we should ask Phil in the skeptics spririts to produce another “old planet” where ozone has been observed but not an oxygen atmosphere?

    What would be the easiest best test for intelligent life then assuming you can’t see artifacts from orbit or there are no radio emissions? Lights on the dark side of a planet?

    I think that is a good guess. But also common pollutants such as anomalous large amounts of nitrous oxides and so forth.

    There was this astrobiology webcast where they looked at future detectors with potentially sizes comparable to the solar system (from separation of smaller units), and how they could resolve continental size areas on (some) exoplanets. Light pollution on continents was IIRC mentioned.

    @ mike burkhart:

    Of course, but we also have to develop remote observation methods of life. And we have only this one reference object to look at…

  35. Torbjörn Larsson, OM

    Hmm, I really don’t know, they generate energy by photosynthsys and are multicellular, so I would say they are, even though they lack alot of the other features that make a plant a plant.

    They can be counted as plants in two respects: for methods such as those discussed (where it is practical to glom all oxygen producers together), or phylogenetically as above (where it is practical to distinguish clades).

    Googling a phylogenetic tree, red algae is among the oldest separation early on after uptake of a cyanobacterium (primary plastids), together with or after glaucophytes (unicellular algae, I think, which have putative early remains from plastid bacterial heritage in the form of membrane components).

    Then green algae separates out, which some places among plants [TOL], others not [Plant Physiology Online].

    For how many of the Earth’s 4.5 billion years would this test have shown life on this planet?

    Depends on the sensitivity. Photosynthesizers leaves the earliest traces (both as stromatolites, now known to be organic all the way down, and as isotope traces). Oxygenating photosynthesizers seems to have been early too, see early BIF remains et cetera, but the reducing atmosphere quickly subdued the release oxygen.

    I’ve seen models published where oxygen slowly increased to a few tens of percent as ‘excess’ reducing hydrogen has been lost to space. And other models which then have a bistability, switching from these scarce amounts to a substantial part of the atmosphere. (The mentioned oxygen catastrophe.)

    But I’m a layman and don’t have insight into the full research here. Though IIRC at 0.2 % there is a “Pasteur limit” or something such, after which yeast finds it energetically favorable to switch to oxygen dependent metabolism. That is, I take it, the biological separation between a “non-oxygen” and “oxygen” atmosphere, and is consistent with the bistability models.

    we just don’t know how likely or unlikely the formation of life is.

    But we do know the order of likelihood, as life is observed in the oldest available rocks.

    It is very unlikely that such a short period of time was a coincidence, but instead shows that life is an easy process. That is also consistent with observations of organics processes in the universe, as well as with the many pathways to life now proposed.

    [So many pathways in fact that I've seen biologists claim that they expect the analysis will turn to which of them are the likeliest. The question of if any realistic pathways at all are possible seems passed.]

    If seen as a process instead of a coincidence a model would tell us how few habitable planets would be without life.

    At the very least a Poisson model would do it. Hmm, say 1 Gy as an upper limit for life on Earth. (Though, as I understand Miller, 10 ky is likely.) That would give P(no life on Earth analog) = P(no life at 5 Gy) ~ 0.7 %, unless I’m mistaken.

    Using Miller’s estimate, I get something like 10^(-250 000) as the no-life likelihood. Low enough unlikelihood for ya’? :-o

    Unfortunately, while we seem to know the likelihood, a test of these models correctness must await observations. So while we arguably know what to expect, we don’t know what we will actually find. But that is but another thing what makes science exciting!

  36. amphiox

    Oxygen respiration is the most high yield energy releasing reaction that carbon based life can take advantage of (per the laws of chemistry as we currently understand them). Not only that, but the main structural proteins of all large life on earth (collagen in animals, cellulose and lignin in plants) are riddled with oxygen atoms in their structures. Multicellular life on earth simply did not happen until after the O2 levels rose to near modern ones.

    While it is certainly not conceptually impossible for large, fast growing, fast moving and otherwise energetic lifeforms to arise exploiting chemistry without O2, using oxygen certainly seems to be the easiest way for life to accomplish these things, and so we would expect, that, if multicellular life is at all common, oxygen dependent multicellular life would be the most common among whatever variations are allowable.

    #1,2, etc: I suppose it might be possible to look for the signatures of pollutant gases produced by industry as a signature for technological intelligent life. One would have to distinguish these from the products of non-intelligent biochemistry, which would require knowing something about what is and is not possible for non-intelligent biochemistry – a tall order. Perhaps things like CFCs, maybe. One could also try detecting the absorption spectra of non-natural building materials, like concrete and asphalt, which would probably require a planet to be significantly more urbanized that earth is at present to work, or maybe to tease out uniformity in the vegetation signal that might represent agriculture monocultures, though again, distinguishing the signal from something produced in nature without intelligence would be difficult (as would defining ‘intelligence’ – if one detected a water/gas/vegetation signal produced by a planet with 90% of its land surface riddled with beaver ponds, would one call that intelligent?)

    Technically, also, life alone could not have produced the O2 signature of today’s earth, because photosynthesis and respiration are in chemical equilibrium – you can’t go from 0 O2 to 20% O2 just by having photosynthetic organisms evolve because when these organisms die and decompose, exactly 100% of all the O2 they produce is recombined with their organic remains to produce CO2 and water. You also need sequestration of organic carbon somewhere inaccessible to oxidation, which probably means some equivalent of plate tectonics and possibly a few chance events like global glaciations to reset the O2/CO2 equilibrium.

  37. Wendy

    That’s way cool, now let’s point it somewhere else!

  38. silent or dearth day , that day will very dangerous for every men NASA has found life on earth. No mention of where though.
    =========================================================
    neeraj kumar

    hallucinating sapience

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »