2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Under the surface of Ceres, the dwarf planet closest to the Sun, there are large reserves of water ice, with the greatest amount concentrated at the poles. In addition, water ice is also found on the surface of a celestial body - it is hidden in craters, where the sun's rays penetrate poorly. This is discussed in articles published in the journals Science and Nature.
Last year, the Dawn probe, while approaching Ceres, discovered mysterious bright spots on its surface. Initially, the researchers assumed that these spots are ice, but later it turned out that they are composed of salt. Scientists believed that the salt deposits remained after the evaporation of most of the water that was once on the celestial body. A little later, the Dawn mission team presented evidence that water in the form of ice actually existed and still exists on Ceres. Planetary scientists even indicated where exactly it is worth looking for deposits. However, only now scientists have carried out an extensive analysis of the data and showed where water ice is hiding on the surface and in the depths of Ceres.
The first team of researchers studied Ceres using the GRaND neutron and gamma-ray detector aboard the Dawn probe. She mapped the distribution of iron, potassium and hydrogen on the surface of the dwarf planet. Scientists have noticed that hydrogen is present in large quantities in temperate and circumpolar latitudes. In their opinion, this indicates that water ice may be hiding in the near-surface layer of Ceres, at a depth of less than one meter. In the equatorial region, frozen water is likely to sublimate and be carried away immediately into space. “Here the astronaut would have to dig a hole about a meter deep to find ice, while at the North Pole it would be enough for him to sweep away a layer of dust,” one of the authors of the work comments.
Comparing Ceres with Vesta, one of the largest asteroids in the main belt, shows that the dwarf planet contains about a hundred times more hydrogen, and that it is more evenly distributed over its surface. According to scientists, this suggests that water once played and still plays an important role in Ceres. An analysis of the ratio of iron to hydrogen in the upper layer and a comparison of the dwarf planet with similar in composition carbonaceous chondrites also shows that billions of years ago, Ceres could have been warm inside and probably liquid water existed on it. The heavy particles in the water probably drowned and went deeper, perhaps even to the core of the planet, while the lighter ones, on the contrary, remained at the top. According to scientists, this explains why, for example, there is very little iron near the surface.
Another team of scientists explored the craters of Ceres. To do this, she used an infrared spectrometer and cameras from the Dawn probe. Planetologists have studied more than 600 cold craters, which are in the shadow most of the time - such objects are called ice traps, and the temperature in them reaches about -160 degrees Celsius. In ten of them, deposits of bright material that reflect light were found. Only in one crater was it possible to confirm the presence of ice on the bottom.
Ice traps similar to those found on Ceres have also been found on Mercury and the Moon. The tilt of the axis of rotation of these bodies is small, so their poles are very cold and covered with craters, where sunlight does not reach at all. Scientists believe that ice on Mercury and the Moon could have been brought by other celestial bodies, such as meteorites. However, researchers cannot be sure that he got to Ceres in the same way.“It remains to be seen how the ice got there and how it stayed on the surface for so long. It could have appeared thanks to the icy mantle of Ceres, or it could have flown from space,”says one of the authors of the study.