Ancient Magnetic Fields On the Moon Could Be Protecting Precious Ice

sciencehabit shares a report from Science.org: For years, scientists have believed frigid craters at the Moon's poles hold water ice, which would be both a scientific boon and a potential resource for human missions. Now, researchers have discovered (PDF) a reason why the ice has persisted on an otherwise bone-dry world: Some polar craters may be protected by ancient magnetic fields. Researchers have known about the anomalies ever since the Apollo 15 and 16 missions in 1971 and 1972, when astronauts measured regions of unusual magnetic strength on the surface. Some anomalies are now known to be up to hundreds of kilometers across. Although their origin is debated, one possibility is they were created more than 4 billion years ago when the Moon had a magnetic field and iron-rich asteroids crashed into its surface. The resultant molten material may have been permanently magnetized. Thousands of the anomalies are thought to exist across the lunar surface, but the team mapped ones at the south pole in detail using data from Japan's Kaguya spacecraft, which orbited the Moon from 2007 to 2009. They found at least two permanently shadowed craters that were overlapped by these anomalies, the Sverdrup and Shoemaker craters, and there are likely more. Although the remnant fields are thousands of times weaker than Earth's, they could be sufficient to deflect the solar wind. Craters with known anomalies could become prime targets for science and exploration. NASA is already planning to visit the south polar region with a rover due for launch next year, called VIPER, and the agency intends to send humans there later this decade as part of its Artemis program. Studying the ice could reveal how it was delivered, which may in turn shed light on how Earth got its water.

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