The strange origin of the Mercury ice

The strange origin of the Mercury ice

New observations made by NASA's MESSENGER mission show where water ice is, but do not explain its origin.

Although Mercury is the nearest planet to Sun, there is ice in the depths of some craters. But how many are he, and how did he get there? This is answered by a new study. It is assumed that its thickness is approximately 50 meters, but this is only an approximate calculation. But what types of comets brought him there remains a mystery.

The study was based on the information of the Mercurial Laser Altimeter - a device of the NASA MESSENGER mission, which crashed into the planet (as planned) in 2015. Previously, a combination of ground-based radar and neutron data suggested that water ice reserves should have been at least 1-2 meters thick. But the new data raise it to a possible 85 m.

But intrigues rather than quantity, but origin. Researchers are not sure that the ice came from long-period comets of type Halley (come from Oort clouds - collections of ice objects in the distant Solar System) or comets from the Jupiter family (from Kuiper belt - ice group beyond the orbit Neptune). “If we found the lower limit of ice thickness, which was significantly greater than zero, we would exclude the presence of a Halley comet or asteroids responsible for delivering water to Mercury,” said Vincent Ik, lead author of the article.

“Models for a micrometeorite stream reaching Mercury are rather uncertain,” he says. - “Some of the more modern models managed to bring 50m of ice to polar craters (like the comets of Jupiter). However, if the depth of the ice reaches 50 m in all polar craters, then this excludes the possibility that one recent blow brought them. But another study believes that the drummer who created the Hokusai crater may be responsible for the deposition of polar water ice. ”

The strange origin of the Mercury ice

The impression of the artist of the BepiColombo mission on Mercury

When asked about the significance of the results, Ick added that they are “still undefined”, since the thickness of the ice is not accurate. He said that he plans to use the final data of the MESSENGER to obtain the best samples of the polar regions, which will allow a closer look at the craters and, possibly, even small ones. And this will help to establish a more stringent limit on the depth of the ice. Or you can take advantage of the new BepiColombo Mercury mission, planned for the 2020s. It should be equipped with a laser altimeter.

“If BepiColombo flies low over the South Pole, and not the North Pole, like MESSENGER, then we would increase and improve the quality of the images of polar craters. But I am not sure that they have already decided with the orbit of the apparatus, ”said Ik.

“Individual height is measured by a laser with an accuracy of one meter. But the problem is that the craters have deviations from the axisymmetry up to 100 m. It will be necessary to perform averaging to ensure that the difference in height is due to ice, and not the nature of the craters, ”he says.

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