How the Moon Got its Scars

A new study on moon's scars shows that science might have overestimated the number of asteroids that hit the lunar surface.

The current research was based on data from lunar-orbiting twins of NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission.

Researchers found that both near and far-sides of the moon suffered the same number of cosmic impacts. However, the near side has more craters, due to its relatively thinner crust.

The craters on moon are a testimony to the violence that the solar system had to face during its infancy. Several hundred asteroids collided with Mercury, Venus, Mars, Earth and our moon. But this event- also called the Late Heavy Bombardment (LHB) occurred about 4 billion years ago. The sheer time period makes it impossible to detect signs of the damage earth bore ( tectonic activity along with weathering of rocks has wiped-out traces of the event).

Thus, the moon is a primary source for data about LHB. But, it turns out that the moon is double-faced, hiding crucial information on its other side. The latest study shows that the troughs on moon might have been created by relatively smaller asteroids than previously believed.

"This is very interesting, because we thought we knew the approximate sizes of impacting asteroids to make the bigger basins on the near side," said Maria Zuber, MIT's vice president for research and the E.A. Griswold Professor of Geophysics, in a news release. "What [this work] indicates is that the flux of large impacting bodies during the Late Heavy Bombardment has been overestimated."

"Impact simulations indicate that impacts into a hot, thin crust representative of the early moon's near-side hemisphere would have produced basins with as much as twice the diameter as similar impacts into cooler crust, which is indicative of early conditions on the moon's far-side hemisphere," noted lead author Katarina Miljkovic of the Institut de Physique du Globe de Paris, according to a news release from NASA.