Ice at Mercury's poles is a relatively new arrival — a finding that could help to resolve a debate about whether ice may have survived for billions of years on the planet closest to the Sun.

Using data from NASA's MESSENGER spacecraft, Nancy Chabot of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, and her colleagues studied how light scattered inside dimly lit polar craters. They found that in a northern crater called Prokofiev, highly reflective ice drapes over the underlying topography. This suggests that the ice has appeared on the surface relatively recently.

This ice was either delivered to Mercury, perhaps by comets, or churned up from below by impacts battering its surface, the authors conclude.

Geology (2014)