Warming Mars 
Mars is a bitterly cold desert. At times, though, conditions improve — the atmosphere gets thicker and warmer, and liquid water may pool on the surface.
The change comes about as the planet’s tilt on its axis changes. Right now, Mars is tilted at the same angle as Earth. But over a period of about a hundred thousand years, the tilt varies by many degrees. And observations by a Mars orbiter suggest the change can make the atmosphere thicker and warmer.
Today, the Martian atmosphere is a bit less than one percent as dense as Earth’s. But Mars Reconnaissance Orbiter has detected vast pockets of frozen carbon dioxide buried near the planet’s south pole. Changes in Mars’s tilt can direct more sunlight onto those pockets, causing the “dry ice” to vaporize and gush out into the atmosphere. That can nearly double the atmosphere’s thickness.
The thicker air traps more heat from the Sun. The combination of the extra density and higher temperature could make it possible for liquid water to pool on the surface. It could also create even bigger dust storms than are seen today.
The observations show that some of the frozen carbon dioxide is vaporizing today, slowly thickening the atmosphere of this cold desert world.
Mars is putting on quite a show right now. It climbs into view in the east by around 8 p.m., and climbs high across the sky during the night. It’s the fifth-brightest object in the night sky, glowing like a brilliant orange star.
Script by Damond Benningfield, Copyright 2011