A count of new crater formations on the Moon has turned up 33% more than predicted, researchers at Arizona State University have found.

Meteors regularly impact the Earth but they usually burn up in the atmosphere. On the Moon, which has no atmosphere, they constantly form craters and impact basins. Bombardment by small meteors could post hazards to future lunar settlements.

Emerson Speyerer and his Arizona State colleagues compared 14,000 photos taken between Oct. 25, 2012 and April 21, 2013 by the high-resolution camera on the Lunar Reconnaissance Orbiter (LRO), reports New Scientist. They found 222 new impact craters more than 10 meters wide, a third more than predicted. They also found 47,000 new splotches, Speyerer’s term for splatter-like changes in reflectance on the surface caused by dust and rock thrown off by the initial meteoric impact.

The largest new crater was 43 meters in diameter. more “222 New Impact Craters Measured over Six Months”

In 1972 America’s astronauts left seismic sensors on the Moon. Gathering data for five years, they transmitted evidence of 12,000 moonquakes, reports The Atlantic.

Scientists have identified four classifications of moonquakes: deep moonquakes, thermal moonquakes, meteroid impacts, and shallow moonquakes. Deep moonquakes are the most common. Scientists counted 7,000 of them. Likely caused by the Earth’s tidal pulls, they occur about every 27 days and usually measure 2 or smaller in magnitude. Thermal quakes occur in response to the temperature changing from lunar day to night. Meteoric quakes are triggered by the impact of meteors.

The really interesting moon quakes are the “shallow” moonquakes. Seven of the 28 recorded up to 1977 exceeded magnitude 5. They last longer than earthquakes, where underground water helps dampen them. On the Moon, which is incredibly dry, seismic energy is more efficiently propagated.

Another factor differentiating shallow moonquakes from earthquakes: Unlike the Earth, the moon has no active tectonics.

The cause of shallow moonquakes remains a mystery.

Humans have long observed the effect of the Moon’s gravitational force on the ocean tides. it turns out that the Earth has a gravitational effect on the Moon as well. Earth gravitation is shaping formations of cliffs that form as the Moon slowly shrinks, reports C/Net.

The core of the Moon is cooling. As the core cools, the partially molten regions in mantle solidify and the Moon shrinks slightly, a process that wrinkles the crust. The wrinkles form a type of cliff called “lobate scarps,” usually less than six miles long and tens of yards high.

NASA’s Lunar Reconnaissance Orbiter has identified 3,200 scarps randomly scattered across the Moon’s surface.

“There is a pattern in the orientations of the thousands of faults and it suggests something else is influencing their formation, something that’s also acting on a global scale — ‘massaging’ and realigning them,” explained study lead author and Smithsonian senior scientist Thomas Watters of the National Air and Space Museum in Washington.

That force comes from the gravitational pull of the Earth.

Because the Moon’s core is still cooling, the scarps are likely still forming. Seismic activity is likely to peak when the Earth and Moon are furthest apart. NASA hopes to be able to monitor the hypothesized moonquakes with a lunar seismic network..