The sounds of an alien world

October 22, 2004 - The sound of thunder, the patter of rain (not water but probably liquid methane) and the crunch (or splash) of a landing, all might be heard as Huygens descends to the surface of Titan on 14 January 2005.

Only for the second time a terrestrial probe records the sound of an alien world.

So far only the Russians took a microphone to Venus in the 1970s at the Venera Missions, but only a few scientific results could be recorded. A similar microphone for Mars was destroyed when NASA's Mars Polar Lander crashed at December 1999.

The new microphone is part of the Huygens Atmospheric Structure Instrument (HASI), one of six multi-functional experiments carried on the Huygens probe. Although there is only a small chance that the spacecraft will pass near a thunderstorm, it could help us to understand if thunderstorms are an important energy source for organic chemistry on Titan.

This may hold clues about how life began on Earth. Titan's atmosphere is laced with chemicals and many scientists think these are the same as those that formed the building blocks of life on Earth, 4000 million years ago. But how did they join together on Earth to ultimately become DNA?

One possibility is that sudden discharges of energy, as occur in lightning, could have forced the simple chemicals together, making more complicated ones. So Huygens will listen for thunder and for chemicals that might have been produced in lightning strikes.

In fact, a second microphone experiment can also be found on Huygens. It is part of the Surface Science Package (SSP) and contributes to an experiment to measure the speed of sound in Titan's atmosphere.

Marcello Fulchignoni, of the Universitè Denis Diderot, in Paris, says: "Combined with the camera images, temperature and pressure profiles, and altitude data, the "soundtrack" will provide a fascinating look at the details of the mission's descent. We will be working hard to bring the voice of Huygens to the public as soon as we can after the descent."

Quick facts: Cassini - Huygens Mission
Special feature:		Orbiter (Cassini - NASA) and Lander (Huygens - ESA)
Mission start:		15 October 1997
Launch vehicle:		Titan IV-B/Centaur
Entering Saturn orbit:		1 July 2004
Entering Titan atmosphere:		14 January 2005
Mission status:		Flyby at Iapetus