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> and from meatball-like to a kitchen sponge, some ! The seven new moons As for Saturn itself, the spacecraft witnessed a
planet-sized, others equivalent to the dimensions of discovered by Cassini. complex atmosphere on the cusp of seasonal change
a football stadium. More than a hundred flybys of L-R: Aegaeon, Anthe, as the planet progressed along its 29-year orbit.
Daphnis, Methone,
Titan uncovered hydrocarbon rivers, lakes and seas, Cassini occupied a ringside seat, observing exotic
Pallene, Polydeuces
as well as a potentially habitable subsurface ocean. storms and jet streams, including the 30,000km-
and S/2009 S1
“Methane plays the role on Titan that water plays wide north polar hexagon, whose winds peak at
on Earth, carving river channels and filling Titan’s 320km/h. It photographed violent lightning storms
lakes and seas, while a subsurface ocean resides by day and night, mapped the planet’s magnetic
beneath Titan’s icy crust,” says Spilker. field and observed the evolution of an annually
Cassini saw water-ice jets spurting from fissures recurring white storm in the northern hemisphere.
at the south pole of the moon Enceladus, providing Planning for goodbye
NASA/JPL/SPACE SCIENCE INSTUTE X 16 with all of the ingredients necessary to host some of-mission scenarios were considered, including
a reservoir of material for Saturn’s E ring and
betraying the existence of a deep global ocean,
Yet all good things come to an end. Several end-
a prohibitively long trek back to Jupiter, killing
form of life. Still other moons, including the
Death Star-like Mimas, with its prominent crater,
Cassini off through an impact with Saturn’s rings
might also possess oceans, whilst tenuous oxygen
or moons, or entering a semi-stable graveyard orbit.
For the aging spacecraft, none of them promised to
atmospheres, trillions of times thinner than our
be scientifically profitable. And as its fuel dwindled,
own, were found around Rhea and Dione.
TOUCHDOWN ON TITAN

How Huygens reached the most Earth-like moon in our Solar System

Deep beneath the murky atmosphere, a wake-up timer 150km
orange clouds of Saturn’s brought its six instruments
large moon Titan lies an online. Descending via
Australia-sized plateau parachute, it was buffeted
called Xanadu. Since 14 by vigorous eastward-
January 2005, it has blowing winds, which
been home to ESA’s tiny diminished to gentler 15km
Huygens probe. Until gusts as it neared the
then, the very nature of surface to land.
Titan’s surface – whether From an altitude of
liquid or solid – was open 15km, its images seemed
to considerable debate. As to indicate an area of
a result, Huygens was drainage channels, perhaps
designed to survive a landing leading to a liquid methane
on mountainous or flat terrain, ‘shoreline’, together with tendrils of 2km
and even in a lake or sea. ! Titan appears as hydrocarbon ground-fog.
The spacecraft separated from a fuzzy ball due to its However, Huygens landed on
Cassini on Christmas Day 2004 thick atmosphere solid ground, kicking up a cloud
and coasted for three weeks to of organic aerosols and leaving
its destination. Shortly before entering Titan’s a 12cm indent. It bounced, slid, wobbled a
few times, then came to a stop.
For 90 minutes, the probe took a look
On the surface, Huygens
spied fist-sized pebbles at its gloomy environs, littered with 0.4km
of water-ice hydrocarbon-coated water-ice pebbles,
typically rounded and fist-sized. Early
notions of a sticky, clay-like composition
were later revised to be a sort of icy ‘sand’.
Hauntingly, Huygens’ on-board microphone
provided the first audible sounds from
another celestial body, recording the roaring
of Titan’s wind during descent before its
batteries ran dead. ! Huygens’ view as it descended to Titan, our
first glimpse of the surface of this moon

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