The study proposes that during periods of Martian history when the planet was tilted more like 35°, and the poles were hotter than today, snow fell on Mars.
Locked away beneath the surface of Mars are vast quantities of water ice.
Additionally, the scientists discovered the ice sheets in eight difference places that could be future sources of water for astronauts.
Much like Earth, where thick ice deposits provide lengthy climatic records, the ice discovered on Mars could provide a window into the climatological changes the planet has undergone over millennia.
The deposits were found at seven geological formations called scarps, with slopes up to 55 degrees, in the southern hemisphere and one in the northern hemisphere.
The latitudes were the equivalent on Earth of Scotland or the tip of South America. The slopes appear to be the product of erosion along the edges of a broad, smooth elevated plain.
"Here we have what we think is nearly pure water ice buried just below the surface". Their lower reaches were covered in rubble, making it hard to determine the total thickness of any ice deposits.
The European Space Agency's ExoMars rover, also slated for a 2020 launch, will come outfitted with a drill created to sample geology at depths of up to two meters. That's thick enough for the orbiting camera to resolve different colored bands within the material.
Mars (over time periods of millions of years) wobbles on its axis; present day, it's at about 25°. A lack of craters indicates that some of that history could be quite recent.
Fortunately, land erodes. Forget radar and drilling robots: Locate a spot of land laid bare by time, and you have a direct line of sight on Mars' subterranean layers-and any ice deposited there.
"The take-home message is, these are nice exposures that teach us about the 3D structure of the ice, including that the ice sheets begin shallowly, and also that there are fine layers", he said. The slopes are probably being continuously exposed as the ice sublimates into the Martian atmosphere, likely to cycle up to the poles and end up frozen there. "Our research may be useful information but it will be up to them to determine how to use it".
These visible ice sheets are likely just a small representative of the total water ice on Mars. Most of this precious liquid escaped into space, but some of it stayed behind, transforming into ice and settling beneath the rocky surface. "You don't see a high-tech solution", Byrne added. Importantly, the water ice is only visible where the processes of erosion are taking place, and the researchers speculate that ice near the surface may be more abundant than what they were able to detect in this study. They could also make for accessible sites to extract water for human use, although that would obviously conflict with studying the ice's layers for clues to the past.