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Looking for Martian life that’s not like life on Earth October 18, 2010

Posted by Simon in Uncategorized.

Another day, another correction to my presentation!

I concluded my talk in class last week by talking about the expert problem associated with ALH84001 – how can anyone really be an expert on signs of life on a Martian meteorite? I also added that the whole thing is riding on the assumption that Martian life is similar to life on Earth.

Now I’ve listened to talk by Chris McKay from NASA (an interesting speaker – I’ve seen him on some documentaries before). He was talking to the Astrobiology and Space Exploration class at Stanford. It doesn’t seem to be on YouTube, but you can find it on iTunes – search for Astrobiology in the iTunesU section, find the Astrobiology and Space Exploration (Winter 2008) course, and it’s talk 16 – “Exploration and Colonization of Mars – Why and How?”

McKay makes it very clear that his goal is to find life on Mars that isn’t similar to life on Earth. Some quotes:

What we’re looking for is the possibility of a second genesis of life. We’re looking for an alternate type of life.

We’re not asking the question “Is there life on Mars?” We’re asking the question “Is there alien life on Mars?” And that’s an important distinction and it will influence where we ought to go look for life.

Why do we want to find aliens? The main reason we want to find aliens, scientifically, is that it would allow us for the first time to do what I would call comparative biochemistry.

But there’s also the broader issue of life in the universe. If we were to find out that in our own little solar system life start twice, separately and independently, that would be convincing evidence that life is common in the universe.

We’re going (to Mars) to look for evidence of a second genesis. So what exactly does that mean? Well first it means that fossils are not what we’re looking for. Fossils are evidence of life, but we’re not satisfied with finding evidence of life on Mars. We want to know what that life’s relationship is to life on Earth. Or asked another way, we’re saying “Is there life on Mars, and is that Martian life on our tree of life?”

What we’d like is to find an organism that is not part of our family.

It’s not clear how widely this goal is shared within NASA.

He goes on to make an interesting argument about how one might go about looking for life that’s not related to life on Earth. The argument involves Lego and Lincoln Logs, and well worth a listen.




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