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Arizona Researchers Detect Change In Moon’s Axis, Indicates Water At Solar System's Birth

cross-section of the moon
(Photo courtesy of James Tuttle Keane - University of Arizona)
A cross-section through the moon showing the ancient spin pole (green arrow) to the present-day spin pole (blue arrow).

Researchers from the Tucson-based Planetary Science Institute have detected a change of the moon’s rotational axis and evidence of water being present early in the solar system’s history.

The findings were published Wednesday in the journal Nature, in conjunction with the Lunar and Planetary Science Conference in Houston.

Matthew Siegler assembled data collected by spacecraft orbiting the moon and analyzed by fellow lunar scientists. James Keane, a doctoral student at the University of Arizona’s Lunar and Planetary Laboratory, contributed to the research.

By studying the hydrogen near the poles, likely composed of water ice, the team concluded that the moon once spun on a different axis than it does today.                

Siegler said that means the shift occurred early in the moon’s history. That leads to a conclusion that water was present as the inner solar system was forming.

“We have now an explanation for potentially when the ice came to the moon, and then it also gives us a hint on the big picture geophysical evolution of the moon,” said Siegler, who also is on the faculty at Southern Methodist University in Dallas.

The study says the slight shift of the axis, called “true polar wanderer,” was caused by changes in the Earth’s satellite’s interior billions of years ago.

Model Shows How Moon Has Reoriented Over The Past 4.5 Billion Years

Sara Hammond has an extensive background in journalism as well as corporate communication. A graduate of the University of Arizona’s (UA) School of Journalism, Hammond interned at the Tucson Citizen and, after graduation, spent 10 years reporting for the Portland Press Herald in Maine.