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Life on Mars

My Favorite MartianThis news has already made it around practically all of the science blogosphere, and I even saw it mentioned in a special breaking news type segment on the Science Channel last night, but it's so cool that I can't resist commenting on it.

NASA just announced that they've definitively found methane on Mars. This is the first time they've been positive - previous announcements of methane were tentative, requiring more examination of the evidence. Since methane gets broken down very quickly in the Martian atmosphere (through as yet unknown mechanisms), finding methane means it must have been released into the atmosphere fairly recently. From what I've been able to gather, there are three likely sources for this methane:

  1. Biology This is most exciting possibility, that living organisms beneath the Martian permafrost are creating the methane as waste.
  2. Geochemical While I don't find this quite as exciting as life, it would mean that Mars is still geologically active. There are several processes that this could be.
  3. Reservoir In other words, there's no current process producing new methane. It was previously generated either biologically or geochemically (or both), and became trapped, and all we're witnessing now are periodic leaks.

I'm trying to be reserved about this, since NASA got my hopes up before with the announcement of probable fossil microbes in a Martian meteorite, which turned out to be not as probable as they'd initially thought. It still could be microbe fossils, but it could also be from non-biological sources along with Earthly contamination. So, I'm trying not to get too excited about this announcement.

But, if the methane does turn out to be from biological origin, it means we've found aliens! Granted, life on Mars may be little green slime instead of little green men, but it would still be extraterrestrial life. From Carl Zimmer's blog coverage of the news conference, there were a few statements that do seem to indicate that biology is the most likely source of this methane.

2:18 Mumma points out that if volcanoes were making the methane, you’d expect other gases too, which they don’t see. NASA will look for other things that would be consistent with biology.
2:21 Mumma is explaining some of the backstory–first reports of observations were in 2003. We knew we had methane since late 2003, he says. But they’ve been working to make the data “unassailable.” We’ll see…
2:35 Back to the science: Lisa Pratt says methane from rock (serpentinization) is rare on Earth and actually plugs up active sites. This is why she takes biology seriously as “slightly more plausible.”

There are two possibilities I can think of for this life (if it does indeed turn out to be life):

  1. uses DNA or RNA
  2. uses something else

If the microbes use DNA or RNA, then it would seem extremely likely that they have a common ancestor with life here on Earth. From what I've read, scientists think it's more likely that life would have originated here on Earth, and then got transferred somehow to Mars. Though it's still possible that it went in the other direction - life originating on Mars and then seeding Earth.

If the microbes don't use DNA or RNA, then it would seem most likely that they originated independently from the life here on Earth. Now that would be super exciting. For one, it would mean that life probably is fairly common in the universe, and that we're not all alone. Heck, if so many solar systems have life, then other multicellular and intelligent life out there seems much more likely, maybe even other technologically inclined organisms capable of producing civilizations. However, it will be a long time before we can look into those possibilities. But, the possibility of independent life on Mars is exciting for another reason - it would show us another strategy for life to take. It would start to show what types of things common to life on Earth are that way because they're needed for life, or simply because of historical contingency.

This really is some of the most exciting news I've heard in a while. Now we just have to wait to see what the actual source turns out to be.

Further Reading:

Added 2009-01-19 Phil Plait of the Bad Astronomy Blog has finally weighed in on this topic. He's very reserved about the whole thing, stressing that we don't know exactly what's creating the methane, and that we just need to wait for more data. He also criticizes much of the media for over hyping the biology aspect of the story.

Revised 2009-02-13 to added the statement "(if it does indeed turn out to be life)." That section's been bugging me ever since I first posted this - I should have edited that a while ago.

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