The collision of two moons orbiting Earth may have resulted in the planet's present-day lopsided moon, scientists say.

Research published on Wednesday in the journal Nature states that in its younger years, Earth's moon was shadowed by a lightweight companion that was about one-thirteenth of its mass.

But as they both traveled through space, the moons began growing farther form the Earth. The moons' stability within the orbit was disrupted by Sun's gravitational force and they ended up crashing into each other, with the remnants of the smaller moon pancaking the bigger.

At least that's what Erik Asphaug, a planetary scientist at the University of California, Santa Cruz, believed caused the asymmetry of the Earth's current moon. He said the crash was slow and took several hours.

"By definition, a big collision occurs only on one side," Asphaug told Nature, "and unless it globally melts the planet, it creates an asymmetry."

When scientists observe Earth's current they find that the visible side is made of low-lying plains, while the farside consists of mountainous terrains and is about 50 kilometers thicker that the near side.

The near side also has a richer source of potassium (K) and rare-earth elements (REE) and phosphorus (P), which are known as KREEP.

Co-author Martin Jutzi of the University of BerneJutzi, told the UK Guardian that the impact produced a disc of debris around the Earth, which produced the current moon.

Both Asphaug and Jutzi created a computer model showing that a collision of the moons can be an explanation for why the moon is the way it is now.

Also Read: Earth had Two Moons Until They Collided: Claim Scientists [Photos]

Earth and Two moons
Artist's impression of a hypothetical collision between the moon and a companion moon Martin Jutzi/Erik Asphaug/Natu
Earth and Two moons
An artist's conception of two moons that could have collided to form into one moon. IBT
Earth and Two moons
Four snapshots from the computer simulation of a collision between the moon and a smaller companion moon show most of the companion moon is accreted as a pancake-shaped layer, forming a mountainous region on one side of the moon. M. Jutzi and E. Asphaug, Natur
Earth and Two moons
During its mission, the Galileo spacecraft returned a number of images of Earth's only natural satellite. Galileo surveyed the moon on Dec. 7, 1992, on its way to explore the Jupiter system in 1995-1997. This color mosaic was assembled from 18 images taken by Galileo's imaging system through a green filter. On the upperleft is the dark, lava-filled Mare Imbrium, Mare Serenitatis (middle left), Mare Tranquillitatis (lower left), and Mare Crisium, the dark circular feature toward the bottom of the mosaic. Also visible in this view are the dark lava plains of the Marginis and Smythii Basins at the lower right. The Humboldtianum Basin, a 400-mile impact structure partly filled with dark volcanic deposits, is seen at the center of the image. NASA/JPL/USGS
Earth and Two moons
The thick crust and highlands of the Lunar far side could have been caused by the splat of second moon in orbit around the Earth NASA / GSFC / Arizona State Un
California Rare earth California Space