NASA / JPL / BROWN UNIVERSITY / SCIENCE PHOTO LIBRARY NASA / JPL / BROWN UNIVERSITY / SCIENCE PHOTO LIBRARY
Mars in an ice age, illustration. Simulated view showing Mars as it might have appeared during the height of a possible ice age in geologically recent time. During a period about 2.1 million to 400,000 years ago, increased tilt of Mars' rotational axis caused increased solar heating at the poles. This polar warming increased dust in the atmosphere, triggering an ice age. Mars has been in an interglacial period for about the last 300,000 years. Here, the simulated surface deposit is superposed on a topography map based on altitude measurements by Mars Global Surveyor and images from NASA's Viking orbiters of the 1970s.
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