You know the story of the Princess and the Pea. What about the space probe and the pebble?

In 2005 the European Huygens probe landed on Saturn’s moon Titan and provided an unprecedented look at the surface. But what happened in the first seconds after touchdown wasn’t clear.

Now a re-analysis of Huygens sensor data has reconstructed the bouncing, skidding moments before the probe came to rest on Titan—apparently on top of a small rock. The report is in the journal Planetary and Space Science. [Stefan E. Schröder, Erich Karkoschka and Ralph D. Lorenz, Bouncing on Titan: Motion of the Huygens probe in the seconds after landing]

The parachuting probe hit the surface of Titan at about 10 miles per hour. According to the new study, the impact created a hole in the ground a few inches deep. But Huygens bounced out and slid across the surface before coming to rest with a wobble. The sliding motion implies that Titan’s surface was a bit like damp sand. And the speed of the probe’s wobble suggests that Huygens bumped against a rock less than an inch across.

Again, that’s a reconstruction based on sensor data, but the researchers contend it’s a likely scenario. Regardless, it makes a nice story. Like the Princess and the Pea.

—John Matson

[The above text is a transcript of this podcast.]