Mars Was Always Destined to Die

Mars is the solar system's near-miss world. Earth may have gotten everything right when it came to sustaining life—atmosphere, water, proximity to the sun. Mercury, Venus and the outer planets, with their extreme temperatures and inhospitable chemistry, may have gotten everything wrong. Mars, on the other hand, came so close, yet fell short. Thanks to data from rovers and other spacecraft, we know that the Red Planet once fairly sloshed with water—with dry deltas, riverbeds, and sea basins stamped into its surface. But 4 billion years ago, the Martian core cooled, shutting down the dynamo that sustained its magnetic field….