JOIN USA Nasa spacecraft has found compelling evidence to support the long-held hypothesis that Mercury harbors abundant water ice and other frozen volatile materials within its permanently shadowed polar craters. The new information comes from Nasa’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.
Its onboard instruments have been studying Mercury in unprecedented detail since its historic arrival there in March 2011. Scientists are seeing clearly for the first time a chapter in the story of how the inner planets, including earth, acquired their water and some of the chemical building blocks for life. “The new data indicate the water ice in Mercury’s polar regions, if spread over an area the size of Washington, D.C., would be more than 2 miles thick,” said David Lawrence, a MESSENGER participating scientist at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., and lead author of one of three papers describing the findings.
Spacecraft instruments completed the first measurements of excess hydrogen at Mercury’s north pole, made the first measurements of the reflectivity of Mercury’s polar deposits at near-infrared wavelengths, and enabled the first detailed models of the surface and near-surface temperatures of Mercury’s north polar regions. The new observations from MESSENGER support the idea that ice is the major constituent of Mercury’s north polar deposits. These measurements also reveal ice is exposed at the surface in the coldest of those deposits, but buried beneath unusually dark material across most of the deposits. In the areas where ice is buried, temperatures at the surface are slightly too warm for ice to be stable.
MESSENGER’s neutron spectrometer provides a measure of average hydrogen concentrations within Mercury’s radar-bright regions. Water ice concentrations are derived from the hydrogen measurements.