Randy Isaac wrote:
> Thanks, Phil. That makes sense. Should plate tectonics therefore
> be on the checklist of necessary conditions as people study
> planetary astronomy and look for life bearing planets?
My guess is no. It is necessary to sustain life over geological
time in OUR world. However, that does not mean that other planetary
systems with different planetary cycles and processes might not
provide suitable conditions. Perhaps a system of vertical tectonics
would work. For example, Venus apparently has (had) active volcanism
and a system of vertical tectonics -- global elemental cycling might
be possible in such a system.
I think that attempts to make long checklists of NECESSARY physical
conditions for life are fraught with problems. The usual efforts
seem to simply list the conditions of our particular life-bearing
planet, with our particular biological system, and assume that that
is the only one possible. I suspect that conditions that could
possibly support life (both physically and chemically) are far more
flexible than we imagine. Afterall, the conditions on Earth now
known to exist that support life are far more varied than thought
possible only a few decades ago.
Keith
Keith B. Miller
Research Assistant Professor
Dept of Geology, Kansas State University
Manhattan, KS 66506-3201
785-532-2250
http://www-personal.ksu.edu/~kbmill/
Received on Sat May 20 15:38:38 2006
This archive was generated by hypermail 2.1.8 : Sat May 20 2006 - 15:38:38 EDT