Surprising number of meteoroids hit moon’s surface

Lunar images reveal over 200 new craters and about 47,000 undiscovered ‘splotches’

map of craters on moon's surface

CRATER CRAZE Images captured by the Lunar Reconnaissance Orbiter from 2009 to 2015 revealed 222 new impact craters (in yellow) on the moon. Red dots are new craters whose impacts were observed from Earth.

GSFC/NASA, Arizona State Univ.

The moon is one tough satellite. With no atmosphere, it endures a barrage of incoming asteroids and comets that pit its surface with a constellation of craters. A new map (above) reveals 222 recent impact craters (in yellow), 33 percent more than simulations predicted. Scientists spotted the features by analyzing about 14,000 pairs of before-and-after images captured by the Lunar Reconnaissance Orbiter from 2009 to 2015. (Red dots note new craters whose impacts were observed from Earth.)

The craters — up to 43 meters in diameter — were probably formed by small meteoroids crashing into the crust. Using the image pairs, the researchers created ratio images, which highlight how the impacts alter the reflectance of the moon’s surface. That perspective illuminated the starburst debris patterns around the craters (below, left).

The scientists also found about 47,000 “splotches,” faint marks several to tens of meters across (below right, before and after shown). Most result from secondary debris being jettisoned by impacts and spattering the surface, the researchers propose in the Oct. 13 Nature.

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LRO images of moon's surface
CHURN BABY CHURN Scientists spotted over 47,000 “splotches” (right, before and after shown), which would rework the top two centimeters of lunar soil much faster than thought. Most of the faint marks are formed when small meteoroids crash into the crust, creating a starburst debris pattern around craters (left) and sending debris splattering across the surface, scientists propose. GSFC/NASA, Arizona State Univ.

Those splotches would “churn” the upper two centimeters of lunar soil in about 81,000 years, more than 100 times faster than previous predictions that didn’t include the smudges, researchers say. That revelation could improve interpretations of remote-sensing data and help engineers design equipment to better withstand the occasional speckling of soil, says study coauthor Mark Robinson, a planetary geologist at Arizona State University in Tempe. “All of the images we’re taking … and the discoveries we’re making are feeding forward into future human exploration of the moon,” he says.

Emily DeMarco is the deputy news editor. She has a bachelor's degree in English from Furman University and a master of environmental science and management from the University of California, Santa Barbara.

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