Magazine article USA TODAY

Rainy Days on Ancient Mars

Magazine article USA TODAY

Rainy Days on Ancient Mars

Article excerpt

Mars is a cold, dry desert, but robotic satellites and rovers have returned evidence of a warmer and wetter climate that existed more than 3,500,000,000 years ago, when conditions may have been more favorable for life. Geologists at the Smithsonian National Air and Space Museum's Center for Earth and Planetary Studies, Washington, D.C., working with colleagues at the University of Virginia, Charlottesville, have discovered 21 river channels in the dry Martian valleys, which provide clues to the planet's ancient climate. The researchers have determined that Martian rivers were about the same size as their counterparts on Earth, suggesting similar amounts of runoff from thunderstorms or rapid snowmelt.

Until the discovery of channels, scientists could not determine the amount of water that had flowed through these valleys. Larger, periodic floods carve wider river channels, so by measuring the width of a channel, geologists can estimate the size of the flood that carved it. To explain the width of the Martian channels, some watersheds likely received an inch or more of rain per day during storms, or more than 10 inches of melted snow on particularly warm days. …

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