A Moon-orbiting camera briefly shuddered — then got back to work — when it was hit by a tiny bit of space rock no bigger than a pinhead.

LRO image during tiny impact
On October 13, 2014, as the Lunar Reconnaissance Orbiter Camera scanned the landscape 1,834 km below, a tiny bit of space rock struck the camera's external radiator and created this brief zigzag vibration.
NASA / GSFC / Arizona State University
It's inescapable that, left in space long enough, anything and everything will be struck by bits of interplanetary debris. And so it was that at 21:18:48.404 Universal Time on October 14, 2014, during its 23,986th orbit of the Moon, NASA's Lunar Reconnaissance Orbiter got whacked.

Fortunately, even though the attacking particle was moving very fast, perhaps 7 km per second, it wasn't large — just an estimated 0.8 mm across and 11,000 of a gram. In fact, LRO personnel back on Earth might never have known about the strike were it not for a swatch of zigzag jitter seen in one of its images — evidence that was only recently discovered once someone inspected the archived file. No other sensors recorded an anomaly at that moment, and the spacecraft wasn't moving its solar-cell panels or antenna.

Instead, it appears that the one of the craft's two telephoto cameras took a tiny hit on the big, scoop-shaped radiator that helps cool the camera's detector.

"The meteoroid was traveling much faster than a speeding bullet," says Mark Robinson (Arizona State University), who leads the Lunar Reconnaissance Orbiter Camera team. "In this case, LROC did not dodge a speeding bullet, but rather survived a speeding bullet!"

LROC's telephoto cameras build up images one line at a time as the spacecraft coasts high above the lunar surface. As shown here, the image scan started fine but then briefly recorded a zigzag pattern about 10 pixels wide. That corresponds to an angular jitter of roughly 1 arcsecond (13600°). At the time, LRO was recording a strip of lunar terrain on the Moon's farside, just to the northwest of Mare Orientale.

Read more about this barely-there impact in this ASU news release, and take some time to explore LRO's amazing photographic record using this interactive lunar map.


Image of Graham-Wolf


June 2, 2017 at 8:39 pm

Phew, Kelly!
That was almost too close to call.
The poor thing survived the experience.
Still doing wonderfully useful work.
Reminded me somewhat of the Giotto micro-impact of 1986, during the p/1 Halley flyby.

You certainly don't want one of those micro-fragments zipping through your space suit, in the middle of an EVA. Wouldn't be too good for morale or your personal health!

Graham W. Wolf
46 South, NZ.

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June 11, 2017 at 4:22 pm

why's this in the news if it occurred 3 years ago?

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Image of AB


June 14, 2017 at 11:02 pm

Because it was "only recently discovered once someone inspected the archived file." Read the second paragraph?

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