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Dedman College of Humanities and Sciences Dedman College Research Earth Sciences Faculty News

Matthew Siegler, Earth Sciences, ancient lunar ice indicates the moon’s axis slowly shifted by 125 miles, or 6 degrees, over 1 billion years.

SMU Research

Originally Posted: March 23, 2016

NASA data leads to rare discovery: Earth’s moon wandered off axis billions of years ago

A new study published today in Nature reports discovery of a rare event — that Earth’s moon slowly moved from its original axis roughly 3 billion years ago.

Planetary scientist Matthew Siegler at Southern Methodist University, Dallas, and colleagues made the discovery while examining NASA data known to indicate lunar polar hydrogen. The hydrogen, detected by orbital instruments, is presumed to be in the form of ice hidden from the sun in craters surrounding the moon’s north and south poles. Exposure to direct sunlight causes ice to boil off into space, so this ice — perhaps billions of years old — is a very sensitive marker of the moon’s past orientation.

An odd offset of the ice from the moon’s current north and south poles was a tell-tale indicator to Siegler and prompted him to assemble a team of experts to take a closer look at the data from NASA’s Lunar Prospector and Lunar Reconnaissance Orbiter missions. Statistical analysis and modeling revealed the ice is offset at each pole by the same distance, but in exactly opposite directions. READ MORE