> On the other hand, both Mars and Venus no longer have functional magnetic fields, which may explain their lack of atmosphere -- with no magnetospheres, their atmospheres may have been stripped long ago by the ablation of the solar wind.

There has been discussion before of seeding Mars, first with some types of anaerobic bacteria which could survive and gradually change its atmosphere, and then with others in a progression I don't remember. I saw an amusing show where scientists experimented--played--with a certain species of scorpion by subjecting it to all manner of extremes. They concluded that it could easily survive on the current Mars, if there were food. Big "if," I think. I'll guess there are particularly hardy species of plants that could live there now, as well. In any case, I think we ought to try it. Concern about destroying native life seems overrated to me, and it may help with any plans of sending humans to Mars if there is even a meager supply of food already there.

> The "alternating magnetic strips" which record magnetic reversal are never surface phenomena. The paleomagnetic record is locked into rocks of the ocean floor and in some deep lava flows: it is created when molten paramagnetic magma cools slowly, and the directional "dipole moments" of the iron-rich mineral crystals -- within the cooling lava -- align themselves along the existing field lines of magnetic force. Alternate (reverse) dipole alignments in subsequent lava strata indicate exposure to reversed magnetic fields, at some point in planetary history.

I'm not arguing with this evidence here, but it is worth mentioning that the above is a circular argument. Also, there are other manners of creating dipole alignments which should be considered. For example, in magma which is exposed and hardens sporadically and quickly, the first band aligns to the earth's magnetic field and the subsequent, later flows align opposite the most recent one, in a natural opposites-attract way. There may be others: contrary to high-school-textbook belief, the matter is not entirely confirmed.

> The example of lake drainage ...

Hm. I was thinking of the Lake Missoula Flood, and, searching around, the 1996 jökulhlaup in Skeidarárjökull, Iceland. [Woah. Nifty names.]

>Species like birds and water-dependent mammals (which have special sense organs in their noses or brains for detecting changes in the force of magnetic flux) may not be so lucky if magnetic reversal starts happening again.

It'd be cool if the monarch butterflies came here for summer.

gab"Then again, insects seem to have an irresistable fetish to die in my car."by