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Newly discovered layers of ice buried one kilometer below the north pole of Mars are the remains of ancient polar ice sheets and could be one of the largest water reservoirs on the planet, according to reports. scientists from the University of Texas at Austin and the University of Arizona.
The team made the discovery with the help of measurements collected by the Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter (MRO) of NASA. SHARAD emits radar waves that can penetrate up to one and a half kilometers below the surface of Mars.
The results, published on May 22 in Geophysical Research Lettersare important because ice sheets are a record of climate on Mars in the same way that tree rings are a record of past climate on Earth. The study of the geometry and composition of these layers could indicate to scientists if weather conditions were previously favorable to life, the researchers explained. The team found layers of sand and ice containing up to 90% water in some places.
If they were melted, the newly discovered polar ice would be equivalent to an overall water layer around Mars, with a minimum depth of 1.5 meters (5 feet).
"We did not expect to find so much ice water here," said lead author Stefano Nerozzi, a research assistant graduate of the Institute of Geophysics at the University of Texas (UTIG), who is completing his PhD. at the Jackson School of Geosciences. "This makes it probably the third largest reservoir of water on Mars after the polar ice caps."
The findings were corroborated by an independent study using gravimetric data instead of a radar, led by researchers at Johns Hopkins University. Nerozzi was a co-author. The articles were published simultaneously in Geophysical Research Letters.
The authors believe that the layers formed when ice accumulated at the poles during the last ice ages on Mars. Whenever the planet warmed, a portion of the ice sheets covered with sand, protecting the ice from solar radiation and preventing it from dissipating into the atmosphere.
Scientists have known for a long time the glacial events on Mars, which are due to variations in the orbit and inclination of the planet. Over periods of about 50,000 years, Mars leans toward the sun before gradually returning to a vertical position, similar to a spinning top. When the planet gets up, the equator faces the sun, allowing the polar ice caps to grow. As the planet slopes down, the ice caps may retreat and perhaps disappear completely.
Until now, scientists thought that the old ice caps had been lost. The document actually shows that important ice cap remains survived beneath the surface of the planet, trapped in alternating bands of ice and sand, like layers on a cake.
Co-author Jack Holt, a professor at the Lunar & Planetary Laboratory of the University of Arizona, said the study provided important new information about ice-cream exchange. 39 water between the poles and mid-latitudes, where his research group had previously confirmed the presence. widespread glaciers, also using the SHARAD instrument.
"Surprisingly, the total volume of water enclosed in these buried polar deposits is about the same as all known ice-water in glaciers and ice layers buried at low latitudes on Mars, and they are about the same age, "he said. .
Holt, scientist and research professor at the UTIG for 19 years before joining the University of Arizona in 2018, is co-investigator of SHARAD since the arrival of the probe in March 2006.
Nerozzi said that studying this record of past polar glaciation could help determine if Mars is still habitable.
"Understanding the amount of water available in the world compared to what is trapped in the poles is important if you want to have liquid water on Mars," Nerozzi said. "You can have all the right conditions for life, but if most of the water is stuck at the poles, then it becomes difficult to have adequate amounts of liquid water near the water. equator. "
The study was funded by a grant from NASA's March Data Analysis Program and the Jet Propulsion Laboratory's MRO Project Office. SHARAD was provided to NASA's MRO mission by the Italian Space Agency.
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