Seen from space, regions of Mars around the south pole have a bizarre, pitted “Swiss cheese” appearance. These formations come from alternating massive deposits of CO2 ice and water ice, similar to different layers of a cake. For decades, planetary scientists wondered how this formation was possible, as it was long believed that this layering would not be stable for long periods of time.
But in 2020, Peter Buhler, a Research Scientist at the Planetary Science Institute, and a team of researchers figured out the dynamics of how the Swiss cheese-like terrain formed: it was due to changes in Mars’ axial tilt that caused changes in the atmospheric pressure, which alternately produced water and CO2 ice. However, they were only able to deduce the rate of CO2 and water deposits over millions of years, which is about ten times longer than Mars’ orbit cycles.
Now, in a follow up study, Buhler was able to model how the frozen carbon dioxide and water deposits grow and shrink over 100,000 year-long cycles of Mars’s polar tilt. The model allowed the researchers to determine how water and carbon dioxide have moved around on Mars over the past 510,000 years.
When planning crewed missions to Mars, the key phrase is “follow the water.” When astronauts set down on the Red Planet in the next decade, they will need access to water to meet their basic needs. Following the water is also crucial to our ongoing exploration of Mars and learning more about its past. While all of the water on the Martian surface exists as ice today (the majority locked away in the polar ice caps), it is now known that rivers, lakes, and an ocean covered much of the planet billions of years ago.
Determining where this water went is essential to learning how Mars underwent its historic transformation to become the dry and cold place it is today. Close to twenty years ago, the ESA’s Mars Express orbiter made a huge discovery when it detected what appeared to be a massive deposit of water ice beneath the southern polar region. However, recent findings by a team of researchers from Cornell University indicate that the radar reflections from the South Pole Layered Deposit (SPLD) may be the result of geological layering.
Is Mars home to an underwater lake? Different researchers are reaching different conclusions. Some say remote sensing from the Mars Express orbiter shows liquid water in an underground lake at Mars’ south polar region. Other researchers say clays or minerals explain the data better.
Who’s right? Maybe none of them.
A new study says that volcanic rock can explain the Mars Express data and that it’s a more plausible explanation.