The moon has a more complex history than previously thought with at least nine subsurface layers, results from ground-penetrating radar aboard China's Yutu lunar rover shows, scientists said on Thursday.
Researchers suspect the layering is due to ancient lava flows interspersed with layers of the lunar soil, known as regolith, which is formed by the weathering of rocks and boulders.
China's Chang'e-3 spacecraft touched down on the moon in December 2013 and dispatched the Yutu, or "Jade Rabbit," rover for an independent study of the landing site.
After zigzagging 374 feet (114 meters) on the surface, Yutu stopped near a relatively fresh crater southwest of the landing site, in a region known as Mare Imbrium.
Compared to NASA's 1969-1972 Apollo landing sites and other locations visited by Soviet-era landers, the northeast region of the Imbrium basis is younger, with complex subsurface structures, lead researcher Long Xiao, with the China University of Geosciences in Wuhan, wrote in a paper published in this week's issue of the journal Science.
"There is more complex geological history than we had thought," the scientists wrote.
Early results from the mission suggest eruptions of lava filled the Imbrium basin at least five times, forming layers of basalt rock about 0.62 mile (1 km) in depth. Yutu's radar detected five distinct lava layers within the top 1,312 feet (400 meters) of the moon's surface.
"It is very likely that more episodes of volcanic eruptions have filled the basin at greater depths," the scientists said.
The results are the first detailed look at the moon's subsurface.
"The Apollo missions drilled the regolith up to only 3 meters [9.9 feet]," Xiao wrote in an email.
"The layering structures tell us the late-stage volcanism show different styles," Xiao added. "It [also] means volatile elements played an important role in the thermal history of our moon."