Crippled space missions can produce great results. China's Yutu moon rover got stuck on the Moon's surface after a short circuit a year ago. But it still managed to chart the Moon's crust down to a depth of almost 500 m. Results have been published in Science last week.
Historically, failed space missions in many cases have been spectacular - and not just by failing. Apollo 13 made it safely back home in 1970 after a an onboard explosion, a tremendous feat given the circumstances. European star charting satellite Hipparcos ended up in the wrong orbit in 1989 but still achieved its objectives and more. Yutu is just another example. So there is hope for Europe's comet lander Philae, which may or may not switch itself back on in the coming weeks as it receives more power from the Sun.
Yutu, which means Jade Rabbit, drove off from its parent lander in December 2013 but in January 2014 a short circuit kept it from closing down its instruments properly for the lunar night (which lasts a fortnight). It has been stuck since, having traveled just 114 meters around the lander.
A sad fate for the first human mission to perform a soft landing since the Russian Luna 24 in 1976.
But fortunately Yutu's Lunar Penetrating Radar kept working. By sending radar waves into the ground and detecting their reflections, the rover could picture the Moon's crust at this location - and an interesting one it turns out to be. Ars Technica writes:
The first few meters are a mix of lunar dust, or regolith, and large boulders shifted by impacts. Below 10 m, things shift to a layer of what's likely volcanic basalt, which is followed by a second layer that runs from 35 m to 50 m. Below that is what the authors interpret as a buried lunar regolith that formed early in the Moon's history and was then submerged by later lava flows. Several layers of old volcanic floods are below that, and then the authors suggest a deep layer is likely a mix of erupted material and intrusions by magma.
All in all the rover detected at least nine different layers beneath the surface, proving that in the past the Moon was geologically and volcanically very active, and not the dead rock that it is now. Some observers note that the Moon has an onion-like structure here. Of course Yutu's measurements only apply to this location. If you know your way around the Moon, it's the northern Mare Imbrium. Just like on Earth, different places have different histories and therefore different structures. The Chinese authors of the Science paper (paid access) themselves note that the Yutu site is much more complex (not to mention more interesting) than the Apollo and Luna sites that were charted before.
Herbert Blankesteijn is a technology journalist from the Netherlands who has written for many prominent Dutch newspapers. He presented and directed television and radio programmes and has 10 books to his name. Herbert is interested in nascent fields such as 3D printing, drones, robotics and the private space business.