When Nasa’s LCROSS mission disappeared into the lunar crater Cabeus the initial data collected showed evidence of “a significant amount” of water vapour and water-ice in the impact plume. Now, as the BBC reports, “A radar experiment aboard India’s Chandrayaan-1 lunar spacecraft has identified thick deposits of water-ice near the Moon’s north pole” – estimated as “at least 600 million metric tonnes of water-ice”. And there’s been further analysis of the LCROSS impact plume. From the BBC report
Scientists have also reported the presence of hydrocarbons, such as ethylene, in the LCROSS impact plume. Dr Colaprete said any hydrocarbons were likely to have been delivered to the lunar surface by comets and asteroids – another vital source of lunar water. However, he added, some of these chemical species could arise through “cold chemistry” on interstellar dust grains accumulated on the Moon. In addition to water, researchers have seen a range of other “volatiles” (compounds with low boiling points) in the impact plume, including sulphur dioxide (SO2) and carbon dioxide (CO2).
The subsurface ice deposits extend for hundreds of kilometers, or miles, in the rugged region called Deuteronilus Mensae, about halfway from the equator to the Martian north pole. Jeffrey Plaut of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., and colleagues prepared a map of the region’s confirmed ice for presentation at this week’s 41st Lunar and Planetary Science Conference near Houston.
The Shallow Radar instrument on the orbiter has obtained more than 250 observations of the study area, which is about the size of California.
“We have mapped the whole area with a high density of coverage,” Plaut said. “These are not isolated features. In this area, the radar is detecting thick subsurface ice in many locations.” The common locations are around the bases of mesas and scarps, and confined within valleys or craters.
Plaut said, “The hypothesis is the whole area was covered with an ice sheet during a different climate period, and when the climate dried out, these deposits remained only where they had been covered by a layer of debris protecting the ice from the atmosphere.”