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If humans return to the Moon, they will need good maps. Luckily, one plucky little spacecraft has been making them. For the past seven years, the Lunar Reconnaissance Orbiter (LRO) has been painstakingly photographing almost all of the Moon’s surface. But the mission has not always gone to plan. One day, a photo came out all wiggly.

Diagnosing the shake

Before you get excited, no, there isn’t a spot on the Moon that happens to be wiggly. The photo is definitely an error. However, the cause of the error is quite interesting. And to understand where the wiggle came from, you first need to know about the LRO’s cameras.

The cameras on the LRO are a bit different to normal cameras. They don’t take a whole photograph all at once. Instead, they capture one line of the photo, then wait for the spacecraft to move. When it’s pointing at the right spot, they capture the next line, and then the next, until the whole picture is formed.

A bump in space

When the scientists in charge of the mission saw the wiggly image, they immediately realised what was happening. In between each line of the wiggly photo, something was moving. They quickly ruled out the possibility of a moonquake. Something must have bumped the camera.

Luckily, NASA has a very detailed computer model of the LRO. Using simulations and some measurements they took from the photo, they calculated that the spacecraft was hit by something very small and very fast. It was probably a meteoroid, a fleck about 0.8 millimetres wide, travelling at about seven kilometres per second. That’s roughly ten times faster than a speeding bullet!

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