The Moon and Mercury have a lot in common. They're roughly similar in size, have no significant atmosphere, and have dramatic temperature differences between their day and night sides. They also have ice deposits in polar craters, where the Sun never shines. Now, researchers think they could harbor a lot more water than previously estimated.
As reported in Nature Geoscience, the ice water deposits are hidden in the ground in those never-sunlit craters. Researchers looked at almost 15,000 sample craters ranging from 2.5 to 15 kilometers (about 1.5 to 9.3 miles) across on Mercury and the Moon. The ones closer to the Mercurian North Pole and the lunar South Pole were up to 10 percent shallower than those at lower latitudes.
“We found shallow craters tend to be located in areas where surface ice was previously detected near the south pole of the Moon, and inferred this shallowing is most likely due to the presence of buried thick ice deposits,” lead author Lior Rubanenko of the University of California, Los Angeles, said in a statement.
It is particularly interesting that these shallow craters have not been found on the North Pole of the Moon, where water ice is lacking. This suggests that the phenomenon is related to water rather than just the latitude of the crater.
The team used observations from the Lunar Reconnaissance Orbiter to study the craters and the surface ice deposits. On Mercury, ice deposits have been discovered by the MESSENGER spacecraft in craters at both poles. Researchers also found glacier-like deposits, something yet to be seen on the Moon.
“We showed Mercury’s polar deposits to be dominantly composed of water ice and extensively distributed in both Mercury’s north and south polar regions,” explained Nancy Chabot, instrument scientist for MESSENGER’s Mercury Dual Imaging System from the Johns Hopkins Applied Physics Laboratory. “Mercury’s ice deposits appear to be much less patchy than those on the Moon, and relatively fresh, perhaps emplaced or refreshed within the last tens of millions of years.”
The prospect of significantly more frozen water on the Moon is certainly exciting for various reasons, including human exploration. A large reservoir of ice could be ideal for making long-term lunar exploration cheaper.