Craters at Moon’s Poles May Hold Millions of Tons of Ice

The moon is seen during a complete lunar eclipse over Jakarta, Indonesia, on Aug. 28, 2018. (AP Photo/Tatan Syuflana)

(CN) – By studying craters near the poles of Mercury and the moon, scientists have identified what they believe to be millions of metric tons of water trapped as ice according to a study released Monday.

Past studies of permanently shadowed areas of Mercury have shown ice deposits several meters thick in the craters near one of the planet’s poles. But Mercury and the moon have similar thermal environments, and so researchers from UCLA studied roughly 2,000 craters on Mercury and nearly 12,000 craters on the moon looking for evidence of ice deposits.

In an article published Monday in the journal Nature, authors Lior Rubanenko, Jaahnavee Venkatraman and David Paige explain that Mercury’s ice deposits were measured by comparing the diameter-to-depth ratio of polar craters against similarly sized craters elsewhere on the surface. Shallowing of the craters in the shadowed regions indicated that something had collected in the crater and that something appears to be frozen water.

The researchers built on evidence gathered by the Arecibo Observatory and later by the Mercury Surface, Space Environment, Geochemistry and Ranging spacecraft, which indicated that cold traps on Mercury harbor pure ice deposits several meters thick.

During the 2009 Lunar Crater Observation and Sensing Satellite (LCROSS) mission, an empty upper stage of the Lunar Reconnaissance Orbiter (LRO) launch vehicle was deliberately slammed into the floor of the Cabeus crater near the south pole of the moon. The cloud of debris resulting from the impact was observed and analyzed, with both water vapor and water ice particles detected, along with a variety of other components including carbon monoxide, ammonia, methane and simple carbon-bearing molecules.

Using data gathered by the LCROSS mission and the LRO craft, researchers found that polar craters on the moon show similar shallowing to that on Mercury, which implies that ice is present there as well.

If the cold-traps in the moon’s polar regions do in fact contain frozen water, the total mass of water on the moon could be estimated to be up to 100 million metric tons, approximately two orders of magnitude greater than previous estimates that are based on surface detections and the LCROSS impact results.

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