Just below the surface, Mars is full of ice. New observations have revealed steep cliffs cut out of thick sheets of ice, which may be able to tell us about the planet’s climate over the past millions of years.
We know from previous radar studies that ice abounds just under Mars’s dusty surface, but where exactly it is in the Martian crust or how deep it goes is still unclear.
at the US Geological Survey in Flagstaff, Arizona and his colleagues examined pictures from the Mars Reconnaissance Orbiter and found eight ice patches in steep cliffs, which formed as ice accumulated over millions of years just under the Martian surface. Erosion revealed these icy blue spots, and they’re still visible today.
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The ice sheets start less than a metre below the surface and the team estimates that they are at least 130 metres thick. Of that, less than 100 metres is exposed, while the rest is below ground. Dundas says that they likely formed in layers as snow or frost built up on the surface and was compacted into ice over time as more frost and dust piled up. Studying the layers may help us learn about the history of Mars’ climate, as we do with ice cores on Earth.
Ice, ice baby
The area around these ice deposits lacks craters from meteor impacts, which indicates that the ice may be relatively fresh – deposited in the last few million years, rather than billion. That means that studying the individual layers can’t tell us about the time when Mars lost its atmosphere and liquid water more than 3.5 billion years ago, but it may be able to help us understand more recent developments.
“Over the past few million years, it’s thought that the tilt of Mars’ axis has varied between 15 and 30 degrees, so that affects the temperature at different areas on Mars, and that affects the deposition of ice,” says Dundas. So, we can study the ice to learn about the planet’s temperature and how its tilt has changed.
Unfortunately, most of this study will have to be done from afar because the cliffs are quite steep. “They would be challenging to traverse,” says Dundas. “I don’t know if a rover could get there.”
Science
Read more: It could be snowing on Mars right now
