An amazing amount of water has been discovered under the Martian North Pole

With the help of a radar penetrating the ground, scientists have detected a huge reservoir of ice water surrounded by layers of sand beneath the north polar ice cap on Mars. This tank contains so much ice that, if it was melted and brought to the surface, it would submerge the entire planet.

"It was even a surprise for us," Stefano Nerozzi, lead author of the new article and doctoral student at the University of Texas in Austin, told Gizmodo in an email.

The massive reservoir was detected in the Cavi unit north of Mars, a deposit of several layers of water ice mixed with sand that has formed over hundreds of millions of years. The cavi unit rests about 2 kilometers under the North Martian Pole and, before the new study, scientists thought that it was mainly composed of sand dunes and contained less than 50% ice. water in volume. These estimates are based on observations of visible outcrops, which revealed significant amounts of black sands mixed with small amounts of frozen water.

But now, in-orbit radar sweeps suggest that the Cavi unit contains more water ice than sand, making it probably the third largest water reservoir on the red planet, followed only by the two ice caps. Polar glaciers. The new article was published this week in Geophysical Research Letters.

These new observations were made by the Shallow Radar, or SHARAD, aboard NASA's Mars Reconnaissance Orbiter probe. SHARAD emits surface-penetrating radar waves that allowed Nerozzi's team to discern the internal structures and composition of the cavi unit.

Observations revealed ice-rich horizontal slabs, sandwiched by alternating layers of sand. The distribution of ice in water ranged from 61 to 88% by volume, which means that the cavi unit is mainly composed of frozen water. As stated in the press release, once melted and raised to the surface, "the newly discovered polar ice would be equivalent to a global water layer around Mars, a minimum depth of 1.5 meters (5 feet)" . It's a lot of water.

SHARAD data showed that the frequency and volume of ice patches increased with the proximity of the North Pole. For example, in one region, the researchers detected two sand sheets more than 40 km wide over an ice layer with a depth of 50 to 100 meters.

According to the newspaper, these buried structures are remnants of old ice caps that contracted and were buried during warm periods. Therefore, this cavi unit contains a historical record of the Martian climate. The layers of ice resemble the rings of a tree and show the growth and removal of ancient polar ice caps over the years. Like the Earth, Mars has experienced several ice ages. During warm periods, the sand enveloped the reduced ice caps, shielding them from the sun and preventing the ice from evaporating into the atmosphere.

"The only hypothesis that can reconcile our results with all previous studies is that the cavi unit consists of alternating layers of ice, remnants of ancient polar ice caps and layers of sand, which served as a protective cover and prevented the complete withdrawal of the old polar region. ice cream, "Nerozzi told Gizmodo." This is another big surprise in itself, because it means that we have a new, unexpected record of growth and retreat of the polar ice cap in the past, which goes back to hundreds of millions of years. years. "

Before the new study, scientists thought the old ice caps had been lost, but SHARAD's data suggest the opposite.

"These results are significant because they reflect past climate cycles in the northern polar region," said Matthew Chojnacki, a scientist in planetary sciences at the University of Arizona, who did not participate to the new research, in an email addressed to Gizmodo. "For tens of millions of years, perhaps longer, the wind has accumulated huge sand deposits that have been repeatedly buried with varying levels of ice. These intra-dune ice deposits occur on Earth, but I do not know as great an example as this unit of northern polar cavi on Mars. "

The new discovery could also tell us a little more about water ice elsewhere on Mars, especially at lower latitudes. Jack Holt, co-author of the study and researcher at the University of Arizona, had previously used SHARAD to confirm the presence of massive glaciers in the middle Martian latitudes, one of which is three times larger than Los Angeles. These glaciers are almost entirely composed of water ice, but they are masked by surface materials.

"Surprisingly, the total volume of water enclosed in these buried polar deposits is about the same as any ice-water known to exist in glaciers and ice layers buried at low latitudes on March, and they are about the same age, "said Holt. in the press release from the University of Texas.

As we learn, Mars contains a huge amount of water. This theoretically augurs well for future settlers needing the precious liquid.

"The ice sheets could be very pure, with only a few percent of dust impurities. However, this unit is buried under a polar ice sheet with a maximum thickness of 2 km, which makes it difficult to reach, "said Nerozzi. "It would be much easier to extract almost pure water from the ice on the surface of the polar ice cap. To make it drinkable or to turn it into fuel for rockets, it would be necessary to filter the impurities of the dust and perhaps certain salts. "

Nerozzi continues to study this cavi unit and uses SHARAD to read recordings of the past evolution of the polar cap. Given the available geological and climatic data, he may even be able to reconstruct the entire history of cavi formation.

"This would give us valuable information about the distribution of water on the planet in the past, and therefore if a quantity of liquid water existed near the equator and could have supported life," Nerozzi said.