Re: life test for planets

From: Eugene Leitl (
Date: Sun Jan 27 2002 - 13:32:25 MST

On Sun, 27 Jan 2002 wrote:

> One other opinion. The notion that many educated people seem blase'
> about life previously existing on Mars (for example) to me seems
> wrong-headed. If life was ever demonstrated to have lived on Mars, it
> would surely alter humankind's' perspective on the universe. It would

Universe? No, just our solar system. There is vigorous (albeit
assymetrical) material exchange within the inner solar system through
impact ejecta, there's zero interstellar pebble capture, however. Dust is
too small, and travels too long to be fried thoroughly. Hence, stellar
systems are probably mutually isolated petri dishes.

> be like saying "Oh, I've always believed in alien intelligence's
> existing, because I have also believed in hobgoblins and mermaids."


> Dan Clemmensen aptly, noted:
> <<It's possible that the test can be made insensitive to the specific
> photochemical: Any life based on photosynthesis will leave a dark spot
> in the spectrum. The tricky part is to figure out what a lifeless
> spectrum should look like for planets of a particular star, so that
> you can look for the difference. If someone works out a methodology,
> it can be tested on the planets of the Solar system first.>>

The canonical test for life is looking whether the atmosphere is not in an
equilibrium. Of course, all this assumes vigorous activity, which e.g. is
currently impossible on Mars. But, yes, Mars has traces of life. I would
be very surprised if it didn't. Jovian and Saturnian system also looks
very interesting.

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