Dennis Overbye in The New York Times:
Ten thousand times a hundred thousand dusty years ago
Where now it stands the Plain of Gold did once my river flow.
It stroked the stones and spoke in tongues and splashed against my face,
Till ages rolled, the sun shone cold on this unholy place.
That was the planet Mars as channeled by the folk singer and science writer Jonathan Eberhart in “Lament for a Red Planet.” Ever since the Italian astronomer Giovanni Schiaparelli thought he spied lines that he called “canali” on Mars in 1877, earthlings’ romantic thoughts about our nearest cosmic neighbor have revolved around water and its possible consequence, Life as We Know It. We haven’t found life on Mars, but decades of robotic exploration have indeed strengthened astronomers’ convictions that rivers and perhaps even oceans once flowed on the red planet. Today Mars is an arid, frigid desert, suggesting that the mother of all climate changes happened there, about four billion years ago or so. The question that haunts planetary scientists is why? And could it happen here?
“I think the short story is the atmosphere went away and the oceans froze but are still there, locked up in subsurface ice,” said Chris McKay, an astrobiologist and Mars expert at NASA’s Ames Research Center. In September a new spacecraft known as Maven, the Mars Atmosphere and Volatile Evolution mission, swung into orbit around the planet. Its job is to get a longer answer to one part of the mysterious Martian climate change, namely where the planet’s atmosphere went. One idea is that it was sputtered away by radiation and particles from the sun, known as the solar wind. Maven was designed to test that theory by measuring how fast Mars is losing atmosphere today. The results could help scientists determine what the atmosphere was like four billion years ago, and just how warm and wet the planet was.