Scientists say that images from Mars show large slopes of ice — and provide a hint at how they were formed. One likely theory involves snowfall on the Red Planet.
The researchers say that the size and accessibility of the ice sheets, as well as the fact that they are made of relatively clean water, could be an important resource for astronauts who might travel to Mars in the future.
We've known for years that Mars has significant ice deposits. But this new research, published Thursday in the journal Science, reveals key information about the ice's layering, thickness and purity.
The researchers noticed that some of the cold, dry hillsides on Mars have naturally eroded to reveal vast deposits of ice, some of them more than 100 meters thick (around 330 feet). And because the steep slope showed the ice's vertical structure, the cross section also tells a story about their history.
Billions of years ago, Mars was likely much wetter than it is today. The ice has a series of layers, says Colin Dundas, a planetary geologist at the U.S. Geological Survey and the paper's lead author. Those newly detected layers suggest that the ice was laid down over a period of time, through a process that happened repeatedly.
"Something caused it to be deposited and then deposited again," says Dundas. That thing was likely snowfall, Dundas says, which was eventually compacted into these deposits. The snowfall could have happened as recently as tens of millions of years ago, he says.
Scientists are now talking about the valuable information they might learn by drilling a core out of one of these deposits and bringing it back to Earth.
"That preserved record would be of extreme importance to go back to," G. Scott Hubbard, a space scientist at Stanford University, tells Science in a separate article about the research.
The team studied eight scarps — the steep areas where the ice is exposed — by using high-resolution images taken by the Mars Reconnaissance Orbiter. All of the images were of sites in Mars' midlatitudes — some 55 degrees north or south of its equator.
The scientists think the exposed ice is not stable at the relatively warm surface temperatures. Dundas says ice at the surface is transforming from solid into vapor, causing the slopes to collapse and become further exposed.
There have also been significant questions about how pure Mars ice is. But Dundas says that "at these locations its quite a thick ice sheet of rather clean ice."
"There's certainly some amount of dust and debris in it, and there can be small amounts of salts or other things as well, but what we're seeing at the scarps are predominately ice," he adds.
This news could be vital for potential human trips to Mars. The sites, with their easily accessible ice, are drawing attention as possible places to construct future bases. As Science reports, "Water is a crucial resource for astronauts, because it could be combined with carbon dioxide, the main ingredient in Mars's atmosphere, to create oxygen to breathe and methane, a rocket propellant."