Understanding the depth and composition of Kraken Mare will gradually
reveal more about Titan's mysterious chemistry, dominated by ethane and
methane that collects in pools, lakes and rivers on the surface,
researchers said. The importance of the lake stems from Kraken Mare's
immense size; if placed on Earth, it would cover all five of the Great
Lakes of North America.
"Kraken
Mare … not only has a great name, but also contains about 80% of the
moon's surface liquids," study lead author Valerio Poggiali, a research
associate at the Cornell University Center for Astrophysics and
Planetary Science, said in a university statement.
While
Titan's chemistry is alien compared to Earth's, the moon's geography is
reminiscent of swampy or lake-rich regions on our planet. Titan is also
the only known moon in our solar system to boast a thick atmosphere — a gaseous nitrogen shroud, compared to Earth's mostly nitrogen-oxygen atmosphere.
That
sets Titan apart from the numerous moons in our solar system with
tenuous exospheres or no atmosphere (like Earth's moon) and from the potentially life-friendly "icy moons" where water ice covers an internal ocean — such as on Jupiter's Europa or Saturn's Enceladus, which both spout water through the ice into space.
Data on Kraken Mare was collected during Cassini's 104th flyby of Titan on Aug. 21, 2014, about three years before engineers deliberately threw the aging spacecraft into Saturn to avoid the small chance of accidentally contaminating the moon's surface.
Kraken
Mare was just one of the lakes on the mission's survey list for that
flyby. Researchers also wanted to look at Ligeia Mare — the site of a
mysterious "magic island"
that regularly appears and disappears — and a smaller estuary called
Moray Sinus, which the researchers estimated to be 280 feet (85 m) deep,
about the equivalent of the Statue of Liberty's height. Cassini probed
the moon's surface with its radar altimeter from about 600 miles (965
kilometers) away.
Scientists calculated sea depth by figuring out
how long it took the radar signal to bounce back from the liquid
surface and from the sea bottom, comparing the difference between these
depths and taking into account the composition of the lakes' liquid,
which absorbs some of the radar signal's energy.
The composition
of Kraken Mare surprised scientists, along with its depth. It contains a
mix of methane and ethane, which differed from previous models
suggesting ethane would prevail due to the lake's size and geographical
position farther from the moon's poles. The unexpected chemistry in the
lake could help scientists better understand the precipitation cycle on
Titan, according to the researchers.
Scientists also hope to
figure out from where the liquid methane on Titan originates. Titan
receives about 100 times less energy from the sun than Earth, given it
is roughly 10 times farther away. (Read more.)