Before China’s Yutu rover launched its lunar mission in 2013, rocks hadn’t been sampled from the moon's surface in 40 years. Now, as reported in Nature Communications [PDF], scientists have discovered an entirely new type of moon rock within these latest samples, proving we still have a lot to learn about our nearest celestial neighbor. 

The unmanned Yutu rover, whose name means “jade rabbit,” collected the special type of rock from the moon’s Imbrium Basin, one of the largest known craters in the solar system. The volcanic basalt rock sampled there was shown to have a mineral composition distinct from anything scientists have found on the moon before. Researchers suspect it originated from a relatively young region that sprang up approximately 2.96 billion years ago. 

The moon is believed to have formed 4.5 billion years ago when a Mars-sized object impacted the Earth, causing debris to fly into its orbit. The matter eventually fused together and cooled, but radioactive materials beneath its surface heated up the interior rock, causing “seas” of volcanic lava to form inside the moon’s craters 500 million years later. The Yutu rover’s geologic discoveries may help shed some light on the youngest of these lunar volcanoes. 

Previous volcanic rocks collected from the moon by U.S. and Soviet probes were shown to have either high titanium content or low titanium content. What makes this latest sample different is that it’s both intermediate in titanium and rich in iron oxide. Because different minerals in magma crystallize at different temperatures, the mineral diversity in these rocks could help scientists better understand the history of the moon’s interior.

"The variable titanium distribution on the lunar surface suggests that the Moon's interior was not homogenized,” Bradley Joliff, the only American researcher on the Chinese research team, said in a press release. "We're still trying to figure out exactly how this happened." You can find the full report here.

[h/t: The Guardian]