Using archive data collected by the Arecibo radio telescope, astronomers have confirmed and refined the location of water ice deposits on Mercury.
The first information about the presence of ice on Mercury was obtained by the Arecibo telescope back in the 1990s. The characteristics of radio signals reflected from the planet's poles indicated the presence of bright regions there whose properties were similar to those of ice. Subsequent analysis of the data allowed scientists to confidently state that Mercury does indeed have ice, apparently delivered there by comets.
In 2019, the Arecibo telescope again conducted a radar scan of Mercury's poles. A team of U.S. researchers combined the data it collected with MESSENGER observations and created the most detailed map of water ice deposits on Mercury and even determined its degree of purity.
It turned out that deposits of almost pure water ice in permanently shaded areas of Mercury are surrounded by dirtier material consisting of a mixture of ice and regolith.