The Earth's Gravity Is Pulling So Hard At The Moon, It's Bulging

May 30 2014, 12:12pm CDT | by

Everyone knows that the power of the Moon’s gravity is what moves the oceans’ tides here on Earth, but that’s not all the gravitational tug-of-war between the two celestial bodies is doing.

The force between the two is so strong that each sphere is ever so slightly pulling the other into a lopsided egg shape that points towards the opposing body. But because the Moon is such a solid body with a small core and only one side of it is facing us at a time, it’s not the easiest thing for scientists to study./>/>

“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,” said Erwan Mazarico, a scientist with MIT who works at NASA’s Goddard Space Flight Centre.

To find out more about lunar body tide, researchers have combined data from two NASA missions, the Lunar Reconnaissance Orbiter (LRO), which has been investigating the Moon since 2009, and the Gravity Recovery and Interior Laboratory (GRAIL) satellites, which circled our night-time space rock for a year before impacting on its surface at the end of 2012. Using both missions allowed the scientists to take the entire Moon into account, not just the side that can be seen from down here.

Although the Moon is tough, the force from Earth is still enough to raise a bulge around 20 inches high on the near side of and a similar-sized one on the far side. Those bulges don’t always stay in the same place either. Although the same side of the Moon constantly faces Earth, the tilt and shape of its orbit makes the near side seem to wobble.

null , moving a few inches over time. A few studies have been able to see these subtle changes from Earth, but LRO and GRAIL have given scientists the opportunity to observe the lunar tide from orbit.

LRO used the Lunar Orbiter Laser Altimeter (LOLA) to map the height of features on the surface. By examining the data for locations the orbiter sighted more than once, the researchers could calculate whether the height had risen or fallen, indicating that the bulge was shifting.

GRAIL’s detailed map of the Moon’s gravity field allowed the team to pinpoint exactly how far over the surface LRO was for each measurement to help their calculations.

The researchers were able to confirm that both the estimated size of the tide and the overall stiffness of the Moon were similar to prior observed results – and improve the margin of error.

“This study provides a more direct measurement of the lunar body tide and much more comprehensive coverage than has been achieved before,” said John Keller, LRO project scientist at Goddard.

For more news on forces beyond our ken and other science and tech stuff, follow me on Twitter and Google +.

 
 
 

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