Making tracks

DESPITE being Earth’s nearest neighbour, the Moon has been a lonely place for the past three decades. Space probes have voyaged to the outer solar system, rovers have landed on Mars and orbiting telescopes have discovered thousands of worlds around other stars. But until this decade nothing, robot or human, had landed on the Moon since August 9th 1976, when Luna 24, a probe belonging to the Soviet Union, set itself down in Mare Crisium, just north of the lunar equator.

That changed on December 14th 2013, when China became the third power, alongside America and the USSR, to land successfully on the lunar surface. Chang’E 3, the craft that did so, then deployed a small rover called Yutu, or “Jade Rabbit” (pictured above), which travelled for 114 metres before getting stuck. This week, in a paper published in Science, a team led by Xiao Long of the China University of Geosciences, in Wuhan, laid out some of Chang’E 3’s early scientific results.

Beyond the constant pitter-patter of meteorite strikes on its surface the modern Moon is thought to be geologically dead. But it has not always been this way, and Yutu—which is equipped with a ground-penetrating radar—has shed some light on the body’s past. Chang’E 3’s landing site was Mare Imbrium, the remnant of a giant impact crater formed 4 billion years ago. Peering hundreds of metres beneath the mare’s surface, the rover was able to discern at least nine distinct strata. Some of these are remnants of recent impacts, which leave layers of fine, powdered rock across the surface. Others, deeper down, are lava flows from volcanoes that, according to data from Lunar Reconnaissance Orbiter, an American spacecraft, may have stopped erupting a mere 100m years ago.

Interesting, then, if not revolutionary. But space exploration has always been as much about Earthly PR as about science. On this front, the mission has been a big success. Its landing was flawless, and even when the rover got stuck China’s deft handling of the matter turned a scientific setback into a PR success, with Yutu broadcasting plucky messages from its official Twitter account.

Chang’E 3 will probably not be the last Chinese visitor to the Moon. Even if the country’s somewhat vague plans for a crewed landing and perhaps even a permanently occupied base fail to come off, several more robotic missions are planned. Chang’E 5—which is designed to return a sample of the lunar surface to Earth—is scheduled for launch in 2017.