Scientists from Brown University in US have created first map of water trapped in uppermost layer of Moon’s soil. The was build using NASA’s Moon Mineralogy Mapper onboard of India’s Chandrayaan-1 spacecraft.
The map builds on initial discovery of water and related molecule — hydroxyl (consists of one atom each of hydrogen and oxygen) in lunar soil in 2009. It may prove useful to future lunar explorers.
Water Presence on Moon
The signature of water is present nearly everywhere on lunar surface and not limited to polar regions as it was previously reported. The distribution of waster on moon is largely uniform rather than splotchy. The way in which it is distributed across Moon gives clues about its source.
The amount of water on moon increases toward poles and does not show significant difference among distinct compositional terrains. It reaches a maximum average of around 500 to 750 parts per million (ppm) in higher latitudes, less than what is found in sands of Earth’s driest deserts.
However, its concentrations gradually decrease toward equator. This pattern is consistent with implantation via solar wind from Sun, which can form hydroxyl (OH) and molecular water once emplaced.
Bulk of water mapped in this study can be attributed to solar wind with some exceptions. For example, higher-than-average concentration of water was found in lunar volcanic deposits near Moon’s equator, where water in surrounding soil was scarce. In this case, it is assumed that water comes from deep within Moon’s mantle and erupted to surface in lunar magma rather than coming from solar wind.
The concentration of water also changes over course of lunar day at latitudes lower than 60 degrees, going from wetter in early morning and evening to nearly bone dry around lunar noon. The fluctuation can be as much as 200 ppm.