Water on Ancient Mars? New Study Challenges the Cold Planet Theory

Despite being a vast and inhospitable planet today, scientists believe Mars, the Red Planet, used to look much like Earth, the Blue Planet. Over the last four years, NASA's Perseverance rover has wandered across an area of Mars where researchers believe a powerful river once poured into a crater, forming a sizable delta. According to computer models, ancient Mars most likely had frequent snowfall and rain, which shaped the enormous networks of lakes and river basins. In the Journal of Geophysical Research: Planets, a recent study found that the distribution of these land characteristics is more consistent with precipitation models than with only the consequences of melting ice caps.

Investigating Early Martian Climate Through Modeling

The researchers published their findings April 21 in the Journal of Geophysical Research: Planets. According to the research by geologists at the University of Colorado in Boulder, our planetary neighbour, on average 140 million miles away in space, was warm and wet billions of years ago. This challenges a long-held belief that early Mars was mostly cold and icy. However, there's a vital mystery buried in the story: It's unclear where Mars' water could have come from, and most climate models predict the world exhibits surface temperatures that are far too cold to sustain liquid water, raising questions about how those visible geological features could have formed.

"It's very hard to make any kind of conclusive statement," Amanda Steckel, a postdoctoral researcher at the California Institute of Technology's Division of Geological and Planetary Sciences, said in a statement. "But we see these valleys beginning at a large range of elevations. It's hard to explain that with just ice," she further added in the official blog posted by University of Colorado. 

Through computer simulations, Steckel and her team explored what Mars might have looked like during the Noachian epoch, when water may have drastically shaped the planet's surface, some 4 billion years ago. Initially created for Earth, their model was modified to simulate how Mars' landscape changed near the equator, where expansive channel networks extend from the highlands and drain into ancient lakes, possibly even an ocean. NASA's Perseverance rover is currently exploring one of these sites, Jezero Crater, where a once-powerful river poured into the basin.

Comparing Climate Models and Implications for Planetary History

The group explored two major simulation models, the ice-melt model and the wet and warm model for how precipitation might have created the valleys on Mars: one in which the planet was warm and humid, and another in which ice briefly melted at the edge of a huge ice cap, signifying a cold, arid climate. With valley roots showing up in radically diverse places, each scenario produced a very different Mars.

Their goal was to determine whether ancient Mars may have had a more Earth-like climate, at least for a while. While more evidence is needed and answers to questions, such as how the planet stayed warm enough for rain or snow, are part of an ongoing investigation. Still, Hynek said the study offers valuable clues, not just about Mars, but about the early history of Earth as well.