Steep slopes on Mars reveal structure of buried ice


These eight scarps, with slopes as steep as 55 degrees, reveal new information about the internal layered structure of previously detected underground ice sheets in Mars' middle latitudes. What's more, bands and variations in color suggest that the ice contains distinct layers, which could be used to understand changes in Mars' climate over time (the ice sheets themselves likely formed as snow accumulated over time).

Currently, the ice sheets appear to be covered by a very shallow layer of dust that's frozen in place-the authors estimate that this is less than two meters thick. The ice is a critical target for science and exploration: it affects modern geomorphology, is expected to preserve a record of climate history, influences the planet's habitability, and may be a potential resource for future exploration.

"There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars", said the study's lead author, Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. Because the ice is only visible where surface soil has been removed, Dundas et al. say it is likely that ice near the surface is even more extensive than detected in this study.

Scientists, using a National Aeronautics and Space Administration (Nasa) spacecraft, have discovered thick deposits of ice beneath the surface of Mars. It is estimated that nearly one-third of the surface of Mars has ice just below its surface.

A close-up of the false colour portion of the above image focusing in on the scarp to reveal the details. Credit NASA  JPL-Caltech  UA  USGS
A close-up of the false colour portion of the above image focusing in on the scarp to reveal the details. Credit NASA JPL-Caltech UA USGS

Scientists have not determined how these particular scarps initially form. 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.

The scientists already knew that Mars has a subterranean frozen water, nearly completely clean. A check of the surface temperature using Odyssey's Thermal Emission Imaging System (THEMIS) camera helped researchers determine they're not seeing just thin frost covering the ground.

Erosion on Mars is exposing deposits of water ice, starting at depths as shallow as one to two meters below the surface and extending 100 meters or more. But of course it's hard to confirm the identity of the layers seen in radar echoes, and the instrument doesn't have the resolution to figure out how close the ice might be to the surface beyond "less than 20 meters". It is a huge discovery that could explain where all the water that Scientists believe used to cover the Red Planet have gone. "Astronauts could only go to these areas with a bucket and shovel and get all the water they need", said researcher Seiner Merne of the Lunar and Planetary Laboratory of the University of Arizona. Their lower reaches were covered in rubble, making it hard to determine the total thickness of any ice deposits. The tilt of Mars' axis of rotation varies much more than Earth's, over rhythms of millions of years. When Mars tilts more, climate conditions may favor buildup of middle-latitude ice. "It's part of the whole story of what happens to water on Mars over time: Where does it go?"