Huygens probe. Computer artwork of the Huygens probe landing on the surface of Titan, the largest moon of the ringed planet Saturn (left). The Huygens probe is being carried on the Cassini spacecraft that was launched in October 1997 and will reach Saturn in July 2004. The disc-shaped probe will enter Titan's atmosphere in January 2005. Heat shields will deflect heat from the probe during atmospheric entry, before a parachute opens to slow its descent. The probe is expected to transmit data from Titan for up to 30 minutes. It will take measurements of Titan's nitrogen and methane atmosphere. Titan may have seas of liquid methane and ethane on its surface.