Mars is a frigid world today, and all of its surface water is frozen solid. However, there’s ample evidence that liquid water once coursed over the Red Planet. That paradox has sparked an ongoing debate: What warmed up Mars’s climate billions of years ago? A team now has proposed that giant asteroid impacts—the kinds that carve out basins exceeding 1,200 kilometers in diameter—might have played an important role. The team reported its results in March in Geophysical Research Letters.
The gullies, streambeds, channels, and lake beds that pepper the Martian landscape are dead ringers, morphologically speaking, for water-sculpted terrain on Earth. The presence of hydrated minerals such as phyllosilicates and sulfates, which have been spotted spectroscopically by Mars-orbiting satellites, has provided more evidence that the Red Planet was once warmer and wetter. By dating geological features and water-altered minerals, scientists have determined that Mars must have been relatively balmy roughly 4 billion years ago.
