A Brown University study, led by doctoral candidate Ariel Deutsch, identifies three large surface ice deposits near Mercury's north pole, and suggests there could be many additional small-scale deposits that would dramatically increase the planet's surface ice inventory. The scorching hot surface of Mercury seems like an unlikely place to find ice, but research over the past three decades has suggested that water is frozen on the first rock from the sun, hidden away on crater floors that are permanently shadowed from the sun's blistering rays.
The study, published in Geophysical Research Letters, adds three new members to the list of craters near Mercury's north pole that appear to harbor large surface ice deposits. But in addition to those large deposits, the research also shows evidence that smaller-scale deposits scattered around Mercury's north pole, both inside craters and in shadowed terrain between craters. Those deposits may be small, but they could add up to a lot more previously unaccounted-for ice.
"The assumption has been that surface ice on Mercury exists predominantly in large craters, but we show evidence for these smaller-scale deposits as well," said Deutsch, who is in the Earth, Environmental, and Planetary Sciences department. "Adding these small-scale deposits to the large deposits within craters adds significantly to the surface ice inventory on Mercury."
The idea that Mercury might have frozen water emerged in the 1990s, when Earth-based radar telescopes detected highly reflective regions inside several craters near Mercury's poles. The planet's axis doesn't have much tilt, so its poles get little direct sunlight, and the floors of some craters get no direct sunlight at all. Without an atmosphere to hold in any heat from surrounding surfaces, temperatures in those eternal shadows have been calculated to be low enough for water ice to be stable. That raised the possibility these "radar-bright" regions could be ice.
Read more of Kevin Stacey's article about ice on Mercury's poles.