ESA Rosetta mission: Philae lander - the sound of a Comet Touchdown

Image credit: ESA/ATG medialab – Audio file credit: ESA /Rosetta /Philae /SESAME /DLR

Sensors in the feet of Rosetta’s lander Philae have recorded the sound of touchdown as it first came into contact with Comet 67P/Churyumov-Gerasimenko. 

The instrument, SESAME-CASSE, was turned on during the descent and clearly registered the first touchdown as Philae came into contact with the comet, in the form of vibrations detected in the soles of the lander’s feet.

Focus on SESAME. Sensors are located in the three feet as well as in the units of the APXS (centre) and MUPUS-Pen (to the upper right of centre) instruments. Credits: ESA/ATG medialab

SESAME is the lander’s Surface Electrical Sounding and Acoustic Monitoring Experiment, and comprises three suites of instruments:

• CASSE – the Comet Acoustic Surface Sounding Experiment, which allows mechanical parameters of the surface to be deduced, along with details of the structure of the subsurface;
• DIM – the Dust Impact Monitor, which measures properties of impacting comet grains;
• PP – the Permittivity Probe, which determines one of the key electrical properties of the material beneath Philae, which is linked to the water ice content of the surface.

Klaus Seidensticker from the DLR Institute of Planetary Research says: “Our data record the first touchdown and show that Philae’s feet first penetrated a soft surface layer – possibly a dust layer – several centimetres thick until they hit a hard surface – probably a sintered ice-dust layer – a few milliseconds later.”