Venus, Mars Share Rare Molecule Options

[cndwrld]

Planetary scientists have detected a rare molecule in the atmospheres of both Mars and Venus. The molecule, an exotic form of carbon dioxide, could affect the way the greenhouse mechanism works on Venus.

More information is available at the ESA Venus Express web site at:

http://www.esa.int/SPECIALS/Venus_Express/SEMF8BV7D7F_0.html

[nprev]

I was thinking of accretional effects too, Doug, but couldn't think of a plausible sorting mechanism that would put Earth in an O-18 depletion region. Perhaps we're seeing an artifact of LHB here? Objects that originally accreted in different regions of the solar nebula got swept up, and random (well, assymetrically distributed) isotropic enhancements occurred on the final products...?

Actually, though, I like your thought that the discriminating mechanism might be Earth's magnetic field. That's the only erosion barrier that seems to exist on any of the terrestrial planets with atmospheres, and a paucity of O-16 seems more reasonable then an enrichment of O-18.