Stuck, but still hard at work (Image: China Stringer Network/Reuters)

The moon has buried scars from an explosive past. That’s the lesson from China’s Yutu or “Jade Rabbit” lunar rover, which has discovered layer upon layer of past lava flows and explosive eruptions not previously seen.

“When you look at an image of this area, there are no features,” says Long Xiao from China University of Geosciences in Wuhan. “But when we looked at the inside, there are many stories within it.”

Jade Rabbit launched in 2013 as part of the Chang’e 3 mission, China’s first lander on the moon and the first lunar lander at all in 37 years. It touched down on Mare Imbrium, one of the vast flat craters thought to have been formed long ago by a large impact and filled by a flood of lava about 3.8 billion years ago, which had not been directly sampled before.


As it zigzagged along the crater, Jade Rabbit’s ground-penetrating radar peered up to 400 metres below the lunar surface. It found evidence for five distinct volcanic events. Xiao says it was a surprise that there were traces left all the way down to that depth because some people have thought the flows may be less than 50 metres deep.

A lot of gas

An even greater surprise is that some traces appear to be from explosive eruptions rather than gentle lava flows. The third lava layer from the surface, about 240 metres down and about 3.3 billion years old, has a reflection texture that is similar to what is seen on Earth when violent eruptions eject large rocks known as pyroclastic rocks. Evidence from the Apollo missions and from orbiting spacecraft had only seen evidence of basaltic lava, which flows more gently.

For the eruptions to be explosive, a lot of gas must have formed. The surface rocks don’t contain enough chemicals with low boiling points to make such explosive eruptions. This suggests there might be volatile molecules like water in the moon’s interior.

Xiao says they’ve only started figuring out what the data collected by Jade Rabbit means. The next step is to look at more closely to figure out exactly how each layer formed and where the volcanoes would have been.

Unfortunately, Yutu is stuck: after 14 Earth days of operation – one lunar day – it encountered a problem and was unable to move, although it is still gathering some data.

Another rover is planned for launch this year, ahead of a sample return mission planned for launch in 2017.

“Chang’e 3 and 4 is testing the technology – landing in a specific area,” says Xiao. “Maybe they will select another landing site for the sample return.”

Journal Reference: Science, DOI: 10.1126/science.1259866