An international team of scientists has determined that Mars once had an ocean of water that covered nearly a fifth of the planet. Per the article:
"Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space," said Geronimo Villanueva, a scientist working at NASA's Goddard Space Flight Center in Greenbelt, Maryland, USA, and lead author of the new paper....By comparing the ratio of HDO to H2O, scientists can measure by how much the fraction of HDO has increased and thus determine how much water has escaped into space. This in turn allows the amount of water on Mars at earlier times to be estimated....Based on the surface of Mars today, a likely location for this water would be the Northern Plains, which have long been considered a good candidate because of their low-lying ground. An ancient ocean there would have covered 19% of the planet's surface -- by comparison, the Atlantic Ocean occupies 17% of the Earth's surface....The results appear online in the journal Science today.
The findings, of course, together with the evidence that Mars once had rivers suggest that Mars may have once supported life.
That's interesting because just within the last couple of weeks I read that they are wondering how the earth gained its water.
I'd never thought of it.
Great questions!! Shit!! Now I'll never get to sleep!!
There's a History Channel documentary: How the Earth was made. I don't like the soundtrack - too many explosions - but it's a good summary that also answers the water question.
Thanks, Plinius. I'll see if I can find it.