söndag, september 19, 2004

Hard to kill in the Dead Sea

Everyone with a passing interest in biology knows that bacteriae can be tough critters; they have been found thriving in the core of nuclear reactors, inside antarctican rocks, and down in the Earth's crust several kms beneath the seafloor, among other places. Basically, you find them everywhere on Earth that is not molten rock.

Now Nasa reports of insights in DNA repair gained from Dead Sea archean Halobacterium (via the Agonist). Add this to the Mars rovers' clues of martian water with the Allan Hills meteorite, which is less than 0.5 billion yrs old (when Mars most certainly had the same climate as today), and next in the news will be actual living martian bugs.

Not so fast, says I. First, there are certain doubts if there ever was water on a global scale on Mars. Personnally, I find the "long-winded Mars Model" (word doc with pictures) much more elegant in explaining the floodvalley-like and other martian geological features. Second, the magnetite in the ALH 840001 meteorite could well be abiogenic; it then becomes a question of which process, biogenic or abiogenic, is more probable.

But whatever the propitiousness of Mars for the genesis of life in the early solar system, or its eventual survival to this day, one thing is clear. Life can spread through space. In fact, life appears so early in Earth's history that it is hard to see how it could had it made through the then common impacts huge enough to melt the entire planet's surface every few million years, unless bacteriae could survive on splinters that fell back after a while, when conditions were again liveable.

One could set up a function, similar to the Drake equation, P=N*fB*fL*fS*fT*fA where:
P: Probability of finding life on a solar system body.
N: Number of meteorites leaving earth's orbit
fB: fraction captured by body's gravity field
fL: fraction of them having life on them
fS: fraction of bacteriae that survive journey
fT: fraction of bacteriae that survive landing
fA: fraction able to adapt to local conditions
If someone more mathematically inclined and more astronomically knowledgeable is interested in putting some figures in this formula... let me know! Some of the most interesting bodies are Europa, Callisto and Titan (where Huygens is scheduled to crash on Jan. 14, 2005)

This would mean the panspermia theory is correct, if nothing else in the sense that Earth is the origo of life's dissemination through the galaxy.