Quote:
Originally Posted by CraigS
Yeah .. well here we go again … if the bulk of the water on Earth was present in this zone before the formation of the planet, then it must've been confined in an extremely tight zone ... given that Venus and, perhaps Mars, missed out on the similar volumes of it. (Ok .. ok .. I know .. there may have been big liquid water on Mars … that's open to debate, as far as I'm concerned, though ..  )
Cheers |
Actually, Venus didn't miss out on having a similar volume of water. The D/H ratio in the upper atmosphere of Venus points to it having a similar amount. It's basically lost most of it. Mars would've had a substantial amount as well. You also have to remember that the terrestrial planets also wandered about somewhat during their formation until they entered their present orbits.
It was most likely Venus losing its water that raised the surface temp up to where it is now. Creating a super greenhouse effect due to the presence of large amounts of water vapour in the atmosphere. Especially, once the Sun became hot enough at Venus' distance to evaporate the water quickly enough to drive the enhanced GH mechanism.