Ancient Mars Was Warm and Wet, Study Reveals – What It Means for Earth

Imagine ancient Mars as a surprisingly mild world where rain or snow fell from the sky, and rivers flowed into hundreds of lakes. A new study from the University of Colorado Boulder suggests the Red Planet was once warm and wet—very different from today’s frozen desert.

Geologists found that heavy rain or snow likely carved Mars’ valleys and channels billions of years ago. The research, led by Amanda Steckel, was published on April 21 in the Journal of Geophysical Research: Planets.

“You could pull up Google Earth images of places like Utah, zoom out, and you’d see the similarities to Mars,” said Steckel, now at Caltech.

Most scientists agree Mars had surface water during the Noachian epoch (4.1–3.7 billion years ago). But how? Some argue Mars was always cold and dry, with ice caps melting briefly. Others believe it was warm enough for steady rain or snow.

To test these theories, Steckel’s team used computer simulations to model water flow on Mars. They found precipitation best explains the widespread valley networks seen today.

“It’s very hard to make any kind of conclusive statement,” Steckel said. “But we see these valleys beginning at a large range of elevations. It’s hard to explain that with just ice.”

Today, Mars still shows signs of water. Satellite images reveal river-like channels near the equator, some leading to ancient lakes. NASA’s Perseverance rover is exploring Jezero Crater, once home to a lake fed by a powerful river.

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“You’d need meters deep of flowing water to deposit those kinds of boulders,” said Brian Hynek, the study’s senior author.

The team used Earth-based landscape modeling software to simulate Mars’ terrain. Some tests included rain/snow, others melting ice. Over thousands of simulated years, precipitation created valley patterns matching real Mars data.

“Water from these ice caps starts to form valleys only around a narrow band of elevations,” Steckel explained. “Whereas if you have distributed precipitation, you can have valley heads forming everywhere.”

While the study doesn’t solve how Mars stayed warm, it offers clues about Earth’s past. “Mars almost got frozen in time and probably still looks a lot like Earth did 3.5 billion years ago,” Hynek said.