The Moon is full of craters that preserve billions of years of history ; We have learned a great deal about conditions in our early solar system by studying the composition, size, and distribution of these holes in the Moon’s surface, created long ago by asteroid collisions.
Now, a team based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, decided to try something different to understand our satellite’s history a little better. Using computer simulations, they ” erased” thousands of craters from the Moon’s surface, as if turning back the clock in time to 4.25 billion years before the craters formed. Specifically, they worked with some 5,200 craters ranging from 20 kilometers to 1,200 kilometers wide.
They designed computer models that took the coordinates and widths of all these craters from topographic maps of the Moon made with data from LOLA (Lunar Orbiter Laser Altimeter, which is on board NASA’s LRO spacecraft) and then found their corresponding gravitational signatures, or pockets of greater or lesser gravity, on a gravity map of the Gravity Recovery and Interior Laboratory (GRAIL). The simulations then removed the gravitational signatures of each crater sequentially by age, essentially rewinding the Moon’s evolution and pushing the poles back toward their ancient locations with each removed impact. What’s left is what the Moon was like before all those craters were formed.
What did they discover?
Somewhat surprisingly, the locations of the Moon’s north and south poles moved slightly during this time period. wandering poles. So, they inferred that ancient asteroid collisions moved the north and south arcs of the moon about 300 kilometers. Over time and because of these asteroid impacts, the location of the lunar poles drifted 10 degrees latitude, the researchers show in their study published in The Planetary Science Journal.
Why is this data interesting?
The geographic north and south poles are located where a celestial body’s axis of rotation intersects its surface. In this case, the moon’s axis of rotation, the imaginary line through its center and around which it rotates, stayed the same as the moon’s body moved. If the moon had drastically shifted its pole locations to a warmer, less shaded region such as the equator , it is possible that some of the frozen water would have changed state at the surface , and the new water would have had less time to settle. accumulate at the new poles.
“Based on the history of cratering on the moon, the polar wander appears to have been moderate enough that water near the poles has remained in the shadows and enjoyed stable conditions for billions of years,” Vishnu said . Viswanathan, a NASA Goddard scientist who led the study.
As NASA points out, this is the same force that causes pizza dough to stretch when a chef throws it and spins it in the air. The power of centrifugal force. It is clear that, treating them collectively, they have a great effect on the Moon.
The phenomenon behind the changing poles is known as True Polar Wander , and it is what happens under the laws of physics to an object, when in this case the Moon, tries to keep spinning when faced with obstacles, such as changes in the how mass is moved and distributed.
According to the scientists, their team is getting closer to determining the true degree of polar drift on the Moon, but scientists still need to refine the current estimate. How are they going to get it? . They plan to erase more small craters on the Moon and remove other features, such as volcanic eruptions and the like, that could have contributed to the pole shift.
Referencia: David E. Smith et al, The Contribution of Small Impact Craters to Lunar Polar Wander, The Planetary Science Journal (2022). DOI: 10.3847/PSJ/ac8c39