Scientists have combined observations from two separate NASA missions to check out the moon's lopsided shape and how it changes under Earth's sway, something that has never been seen from orbit before.
Scientists were able to examine the entire moon, not just the side that can be observed from Earth, based on the data from NASA's Lunar Reconnaissance Orbiter, or LRO, and the Gravity Recovery and Interior Laboratory, or GRAIL, according to a NASA release.
"The deformation of the moon due to Earth's pull is very challenging to measure, but learning more about it gives us clues about the interior of the moon," Erwan Mazarico, a scientist with the Massachusetts Institute of Technology, who works at NASA's Goddard Space Flight Center in Greenbelt, Md., said in a statement.
The lopsided shape of the moon is one result of its gravitational tug-of-war with Earth.
The pulling of the two bodies is powerful enough to stretch them both, according to the release. The activity has a strong effect on Earth's oceans, and is the driving force behind tides.
Even though Earth's distorting effect on the moon is difficult to detect, scientists have been able to detect a bulge about 20 inches high on the near side of the moon and a similar one on its far side, according to the release.
The position of the bulge shifts a few inches over time.
"Although the same side of the moon constantly faces Earth, because of the tilt and shape of the moon's orbit, the side facing Earth appears to wobble," NASA said, in the statement. "From the moon's viewpoint, Earth doesn't sit motionless but moves around within a small patch of sky. The bulge responds to Earth's movements like a dance partner, following wherever the lead goes."
Scientists used data provided by LRO's Lunar Orbiter Laser Altimeter, which maps the height of features on the moon's surface.
They chose spots that the spacecraft has passed over more than once, compared the measurements taken at the same spot, and calculated whether the height had risen or fallen from one satellite pass to the next.
A change showed a shift in the location of the bulge.
The new results are consistent with earlier findings as the estimated size of the tide confirmed the previous measurement of the bulge, according to scientists.
"Having confirmation of the previous values - with significantly smaller errors than before - will make the lunar body tide a more useful piece of information for scientists," NASA said.
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