Think again. Our seas are not alone — Oceanography is no longer just an Earth science. Saturn’s giant moon, Titan has been surveyed for the last decade by the formidable Cassini-Huygens mission. That
$4B project (on which I started my career a quarter
century ago as an aerospace engineer straight out
of college, working for the European Space Agency,
ESA) saw a launch from Florida in 1997 and a seven
year journey past Venus (twice), Earth, and Jupiter —
epic before its science mission even started!
Shortly after arrival at Saturn in 2004, the four
ton orbiter spacecraft (built primarily at NASA’s Jet
Propulsion Laboratory in Pasadena, CA) released the
319 kg Huygens probe to parachute down to Titan’s
surface. It did so 10 years ago (January 14, 2005),
hitting the ground near Titan’s equator in what
turned out to be damp sand.
However, it was damp with something other
than water. Titan — being ten times further from the
Sun than is the Earth — is a frigid 94K (-189°C),
where water is ice and is as hard as many rocks on
Earth. Instead, it was damp with hydrocarbons,
liquid methane, and ethane, which we know on
Earth as the main components of natural gas.
Indeed, natural gas is transported around the Earth
in large refrigerated ships which keep the gas in
liquid form at conditions rather close (~100K, 1.1
bar pressure) to Titan’s surface conditions.
Among Titan’s many remarkable features is that
it has an atmospheric pressure somewhat larger
than Earth’s (1.5 bar), with the atmosphere made
mostly of nitrogen like our own. That composition,
temperature, and pressure mean the air on Titan is
four times denser than air on Earth, making Titan an
easy place on which to fly. Easier still, because
Titan’s gravity is about the same as that of the
Earth’s moon, or 1.35 m/s — a seventh of Earth’s.
Titan is the only moon in the solar system on which
a parachute is of any use!
The atmosphere has no oxygen, but does have
a few percents of methane vapor — much like the
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Figure 1. Titan at lower left (infrared false-color view, showing dark dune
fields near equator), compared with the Earth and moon at the same scale.
Figure 2. The author in 2005 at the European Space Operations Center in
Darmstadt, Germany for Huygens' historic descent to Titan's surface. This full-scale model of the Huygens probe was used in a stratospheric drop test to
verify the heat shield separation and parachute performance in 1995.
Part I — Probing Saturn's
By Ralph Lorenz