Tentatively, the lander sought contact with the orbiter.

Fifteen minutes after its unpackaging, the main chute was cut away, and a smaller stabilizer chute opened.

The probe began to fall faster, into the deep ocean of air. Vanes around its rim made it rotate in the thickening air.

Diaphragms slid back. A series of small portals opened in the protective shell of the craft, and sensors peered out.

At the base of Titan’s stratosphere, some thirty miles above the surface, the temperature began to rise a little. Gradually, the surface became visible. Downward-pointing imagers peered, in visible and infra-red light, and as the probe slowly rotated, mosaic panoramas were built up.

At last, the probe crashed into the slush. Slowed by Titan’s low surface gravity, and the density of the lower air — half as dense again as Earth’s — the impact was slow, as gentle as an apple falling from a tree.

The probe continued its battery of experiments, pumping telemetry up to the orbiter, which sailed onwards towards Saturn.

Huygens was primarily an atmospheric probe. It had not been certain that the probe would survive the impact. And the probe had actually been designed to float if need be, for none of its mission planners had been sure whether oceans or lakes existed here, or if they did how extensive they were, or whether the chosen landing site would be covered by liquid or not.

Just six minutes after landing, the probe’s internal batteries were exhausted.

Melted slush frosted over the buried portals of the inert, cooling lander. And a thin rain of light brown organic material began to settle on the upper casing.

The chatter of telemetry to Cassini fell silent. The orbiter passed beneath the horizon, and then turned its high gain antenna away from Titan, to Earth. Patiently, Cassini began to download everything the lander had observed.