Moon’s poles shifted over 4 billion years due to asteroid impacts, study finds

Findings can be useful for understanding the evolution of the moon, scientists say

The moon’s north and south poles have moved slightly over a period of 4 billion years from the effects of asteroid impacts, according to a new study.

The research, published on Monday inThe Planetary Science Journal, estimates that asteroid impacts could have led to the location of the Moon’s poles changing by about 10 degrees in latitude.

Scientists, including those from NASA’s Goddard Space Flight Center in Maryland, say the findings can be useful for understanding the evolution of the moon, and the condition of resources like water, on its surface.

In the study, they used computer simulations to turn back the clock by over 4 billion years to “erase” thousands of craters from the moon’s surface to a time before they formed.

When researchers did this, they found that the locations of the moon’s north and south poles moved slightly over the time period.

A celestial body’s geographic north and south poles lie where its rotational axis intersects with its surface.

In the moon’s case, they say the rotational axis – the imaginary line that passes through its center and around which it rotates – stayed the same as the body of the moon shifted.

Previous studies have found frozen water in shadowed regions near the moon’s poles, however, scientists are unsure how much water could be present in these locations.

If the locations of its poles had wandered toward a warmer, less shadowed region, they say some of the frozen water may have sublimated.

Researchers explain that pole shift happens when centrifugal force brings locations on a celestial body with large numbers of craters and depressions on its surface towards the poles, while areas of higher mass move out toward the equator.

Scientists liken this force to one that acts on pizza dough as a chef tosses and spins it in the air to stretch it out.

But based on the new research, scientists say the Moon’s pole shift seems to be moderate.

“Based on the moon’s cratering history, polar wander appears to have been moderate enough for water near the poles to have remained in the shadows and enjoyed stable conditions over billions of years,” Vishnu Viswanathan, a NASA Goddard scientist who led the study, said.

Researchers are hoping to estimate the true degree of polar wander on the moon, but say they need to refine their estimate.

In further studies, they plan to erase more small craters from the moon, and remove other features like volcanic eruptions that contribute to shifting the poles.

“There are a few things that we haven’t taken into account yet, but one thing we wanted to point out is those small craters that people have been neglecting, they actually do matter, so that is the main point here,” said Sander Goossens, another co-author of the study.