Bouncing On Titan: Strange Pyramid Shapes And Other Finds By Huygens Probe

The analysis reveals that, on first contact with Titan’s surface, Huygens dug a hole 12 cm deep, before bouncing out onto a flat surface.

The probe, tilted by about 10 degrees in the direction of motion, then slid 30–40 cm across the surface.

It slowed due to friction with the surface and, upon coming to its final resting place, wobbled back and forth five times, with each wobble about half as large as the previous one.

Huygens’ sensors continued to detect small vibrations for another two seconds, until motion subsided nearly 10 seconds after touchdown.

“A spike in the acceleration data suggests that during the first wobble, the probe likely encountered a pebble protruding by around 2 cm from the surface of Titan, and may have even pushed it into the ground, suggesting that the surface had a consistency of soft, damp sand,” describes Dr Stefan Schröder of the Max Planck Institute for Solar System Research, lead author of the paper reporting the results inPlanetary and Space Science.

Had the probe impacted a wet, mud-like substance, its instruments would have recorded a ‘splat’ with no further indication of bouncing or sliding.

The surface must have therefore been soft enough to allow the probe to make a hole, but hard enough to support Huygens rocking back and forth.

“We also see in the Huygens landing data evidence of a ‘fluffy’ dust-like material – most likely organic aerosols that are known to drizzle out of the Titan atmosphere – being thrown up and suspended for around four seconds after the impact,” says Dr Schröder.

Since the dust was easily lifted, it was most likely dry, suggesting that there had not been any ‘rain’ of liquid ethane or methane for some time prior to the landing.

“This study takes us back to the historical moment of Huygens touching down on the most remote alien world ever visited by a landing probe,” adds ESA’s Cassini-Huygens project scientist, Nicolas Altobelli.

“Huygens data, even years after mission completion, are providing us with a new dynamical ‘feeling’ for these crucial first seconds of landing.”

1. Speeding through Titan’s haze
This recording is a laboratory reconstruction of the sounds heard by Huygens’ microphones. Several sound samples, taken at different times during the descent, are here combined together and give a realistic reproduction of what a traveller on board Huygens would have heard during one minute of the descent through Titan’s atmosphere. 
File 1 : acoustic during descent

2. Radar echos from Titan’s surface
This recording was produced by converting into audible sounds some of the radar echoes received by Huygens during the last few kilometres of its descent onto Titan. As the probe approaches the ground, both the pitch and intensity increase. Scientists will use intensity of the echoes to speculate about the nature of the surface. 
File 2 : radar conversion 

Contacts and sources:
Markus Bauer
European Space Agency