Like on Earth, a Martian glacier is useful as a record of past climate change. "That kind of cross-sectional information is valuable for history," Dundas said.
But the scientists cautioned that more observations are needed to learn about the layers, purity, and thickness of these ice deposits — which could show things such as the composition of the ancient atmosphere.
The authors raised the possibility of ancient habitability in their paper, but that remains a contentious topic for Martian exploration. Water used to flow freely on Mars. But billions of years ago, the water appeared to stop flowing on most of the planet, lessening the chances for life. Scientists usually say Mars must have had a thicker atmosphere in the past that was lost to space; NASA's MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft is at the Red Planet looking at atmospheric loss. Its data was recently used to extrapolate habitability for planets orbiting red dwarf stars.
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Scientists continue to search for ancient habitability on Mars. In 2020, both the NASA Mars 2020 rover and the ExoMars rover will set out for the Red Planet in search of signs of ancient life. But current habitability conditions are debatable. Scientists can't agree on whether Martian features called recurring slope lineae (RSL) are briny water — or not.
RSL appear as dark streaks on certain Martian slopes, and appear to change with the seasons. In 2015, a NASA-backed study announced that RSL is likely based on Martian surface water. Subsequent studies, however, argue that RSL may be due to dust, atmospheric water, or some other explanation.
Dundas's team first spotted some of the new ice deposits a few years ago in images from the Mars Reconnaissance Orbiter. The new data comes after follow-up work with the NASA spacecraft, which has been at the Red Planet since 2006.
The team used the High-Resolution Imaging Science Experiment (HiRISE) camera to look at the deposits up close in visual wavelengths. They also used MRO's shallow radar (SHARAD) to see how deep the deposits go, and the spacecraft's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) to see how the deposits change over a few years.
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