A team of geologists from the University of Colorado Boulder (CU Boulder) found that ancient Mars likely experienced heavy precipitation in the form of rain and snow, potentially ending the debate regarding the role of water in the red planet’s formation.
Additional research will be required to confirm the hypothesis, but the team behind the proposed “rain and snow” model of ancient Mars believes their work could also help shed light on Earth during its early formation.
Rain and Snow on Ancient Mars is Still Controversial
Over the last three decades, a growing body of evidence has come to light suggesting that the Martian landscape seen today was formed in some part by the presence of water, including a massive ocean around 3 billion years ago. NASA’s Perseverance Rover and other missions have found several clues supporting the concept, including evidence that water may have given the planet its red color and data that a large lake may (or may not) exist beneath the polar ice caps. Still, scientists disagree on whether ancient Mars was warm and wet with regular precipitation that could potentially support life, or cold, dry, and lifeless, with frozen icecaps representing the only measurable water on the planet.
To help break the stalemate, former CU Boulder PhD student Amanda Steckel decided to evaluate the present geology of the red planet since parts of the planet appear strikingly similar to areas on Earth shaped by precipitation.
“You could pull up Google Earth images of places like Utah, zoom out, and you’d see the similarities to Mars,” said Steckel, who is now at the California Institute of Technology, in a statement.
An ongoing analysis of Jezero Crater by Perseverance has also revealed aspects of the landscape consistent with flowing water. For example, Brian Hynek, senior study author and a scientist at the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder, said large rocks deposited on the ancient lakebed offer tangible support of precipitation instead of ice caps.
“You’d need meters deep of flowing water to deposit those kinds of boulders (found in present-day Jezero),” Hynek said.
Digital Mars Recreation Supports Precipitation
Because going to Mars and studying the evidence for precipitation directly wasn’t an option, Steckel and Hynek decided to use advanced modeling software to create a simulated Mars landscape. Designed using the area around the red planet’s equator where the strongest evidence for precipitation is found, this ‘digital’ Mars allowed the team to explore several ancient Mars formation scenarios.
In one iteration, the team added water from falling precipitation, including rain and snow, to the simulated terrain. Another model replaced precipitation with melting ice caps. After running the two simulations for tens, hundreds, and thousands of years, the team compared the results. This effort was focused on areas of the landscape where headwaters feeding the red planet’s branching valleys emerged.
As expected, the two water scenarios created vastly different planets. For example, the ‘melting ice caps’ scenario resulted in valley heads, which the researchers say mostly formed at high elevations, “roughly around the edge where the ancient ice sat.” Conversely, the study authors indicate that ancient Mars’s precipitation model revealed more widespread headwaters, “ranging from below the planet’s average surface to more than 11,000 feet high.”
“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.”
A side-by-side comparison of the two scenarios with actual data captured by NASA’s Mars Global Surveyor and Mars Odyssey spacecraft also supported the precipitation model. According to the team, the ice cap scenario resulted in a landscape vastly different from the red planet seen today, whereas the precipitation model “lined up” much more closely.
“It’s very hard to make any kind of conclusive statement,” Steckel said of the comparison. “But we see these valleys beginning at a large range of elevations. It’s hard to explain that with just ice.”
Unlocking the Secrets of Ancient Earth
Although the new models support the concept of rain and snow on ancient Mars, the team warns that it is far from conclusive. For example, scientists still have difficulty explaining how Mars could have stayed wet and warm long enough for precipitation to mold the landscape to such an extent.
While the research does not end the debate on the role water played in forming the ancient Martian landscape, the team believes its findings are a significant piece of evidence supporting the precipitation theory. The team also says its work could help offer a snapshot of a remarkable period of Earth’s development, similar to Mars’.
“Once the erosion from flowing water stopped, Mars almost got frozen in time and probably still looks a lot like Earth did 3.5 billion years ago,” Hynek said.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.