New research suggests that ancient Mars, despite its icy conditions, once had rivers, lakes, and even a vast Mediterranean-sized lake, all flowing under thick ice.
The study, led by Planetary Science Institute scientist Peter Buhler, shows that around 3.6 billion years ago, carbon dioxide (CO₂) froze out of Mars’ atmosphere, creating a layer over the planet’s water ice sheets.
This CO₂ layer acted like an insulating blanket, trapping heat from Mars’ interior and raising pressure on the ice, which melted large amounts of water beneath the surface.
Unlike Earth’s climate-dependent water cycle, this process didn’t need a warm climate.
Instead, Mars’ carbon dioxide deposits and its icy conditions combined to release and circulate water in a unique way.
Buhler’s team used a model of Mars’ CO₂ cycle, tracing CO₂ as it moved between Mars’ soil (regolith), atmosphere, and polar ice caps.
Their findings highlight a Martian cycle influenced by the planet’s tilt. Over long periods, Mars’ axis tilts back and forth.
When Mars is more upright, sunlight hits the equator intensely but barely reaches the poles, allowing CO₂ to escape from the regolith into the atmosphere. This CO₂ then moves to the poles, forming icy deposits over water ice caps.
During times of extreme tilt, the poles heat up, causing the CO₂ ice to change back to gas, which is then reabsorbed by the regolith.
Buhler’s model focused on a time when Mars had a thicker CO₂ atmosphere. The CO₂ ice cap, about 0.4 miles thick, rested on top of a 2.5-mile-thick water ice sheet, trapping Mars’ internal heat.
This setup caused massive melting at the base of the ice cap, creating rivers under the ice and saturating the surrounding ground. Similar to Earth’s glaciers, these subglacial rivers left behind gravel ridges, known as eskers, many of which have been observed near Mars’ south pole.
As these rivers flowed to the ice sheet’s edge, they formed slow-moving, ice-topped streams, eventually flowing into a massive lake in the Argyre Basin.
This lake, as large as the Mediterranean Sea, filled over thousands of years before overflowing, sending water thousands of miles north.
The model suggests this process could have repeated over millions of years, creating a Martian water cycle without needing a warmer climate.
If further research supports these findings, it could reshape our understanding of Mars’ ancient water history and offer clues to its mysterious past.
Source: KSR.
