US & World  Strange Greenhouse Gas Warmed Ancient Mars   At
first glance, Mars' 500-mile-long Nanedi Valles looks like the
Grand Canyon, with its steep-sided walls and plunging crevasses,
two features that indicate a history of water.  However, the
Mars we know today is one of freezing temperatures, arid
conditions and, most importantly, a paper-thin atmosphere — all
combined to create a hostile environment seemingly defiant of
any life at all, let alone water.  Scientists have floated the
idea that meteorites assaulted the Red Planet billions of years
ago, generating steam atmosphere to create the landscapes like
the Nanedi Valles, a large valley that stretches 1.5 miles wide
in some areas. However, it's more likely that an unusual
greenhouse gas raised the planet's temperature to allow for
flowing water.  A team of researchers at Penn State University
used a one-dimensional climate model to show that molecular
hydrogen, along with carbon dioxide and water, could have
generated a greenhouse effect 3.8 billio