Scientists with the National Aeronautics and Space Administration are seeing the moon in a different light, thanks to new images from two of the space agency's latest missions.

Combined observations from the Lunar Reconnaissance Orbiter, which has been exploring the moon since 2009, and Gravity Recovery and Interior Laboratory mission, two probes sent to investigate the lunar interior, revealed the moon has a lopsided shape and changes under the Earth's gravitational forces -- a phenomenon not seen before from orbit.

"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, Maryland, said in a news release.

While the moon's lopsidedness is caused by the gravitational tug-of-war with Earth, the mutual pulling action stretches the Blue Planet as well, so both bodies end up with oval shapes, like two chicken eggs.

The distortion of the moon caused by the pulling effect -- which is called the lunar body tide and is powerful enough to raise a bulge about 20 inches (51 centimeters) high on the near side of the moon and similar one on the far side -- is difficult to detect because the moon is solid, except for its small core.

Scientists explain that the bulge shifts a few inches over time; the bulge responds to Earth's movements like a dance partner, following wherever the lead goes.

Therefore, even though the same side of the moon constantly faces the earth, because of the tilt and shape of the moon's orbit, from our perspective it appears to wobble.

"If nothing changed on the moon, if there were no lunar body tide or if its tide were completely static, then every time scientists measured the surface height at a particular location, they would get the same value," said Mike Barker, a Sigma Space Corporation scientist based at Goddard and co-author of the new research, available online in Geophysical Research Letters.

"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.