JANUARY/FEBRUARY 2020. DISCOVER 77A New Tool Turns Up
Surprise Slash Across
Saturn’s Largest Moon
BY BILL ANDREWS
i
Astronomers found an entirely unexpected feature
on Titan, Saturn’s largest moon, this year: a ribbon
of exposed bedrock ice that wraps nearly halfway
around the satellite. This unique feature came into view
thanks to a recently developed analysis technique never
before used on Titan.
Researchers had previously spotted surprisingly
diverse landscapes on the moon, from broad plains
to sandy dunes and even rivers and lakes. Since the
world is so cold, these features are made up of liquid
methane and other organic compounds that slosh over
a bedrock of solid, rock-hard ice. But it’s tough to get
good observations of the surface, because the moon’s
atmosphere is so dense and hazy.
So instead of examining individual pixels from images
and scouring them for details and data, the researchers
used a technique called principal components analysis
(PCA). This lets them look at all the pixels in a given
area, helping to spot larger trends in the landscape while
bypassing the atmosphere’s obscuring effects.
The result: a hi-def imaging of water ice on Titan
that formed a noticeable pattern. “Our PCA study
indicates that water ice is unevenly, but not randomly,exposed across Titan’s tropical surface. Most of the
exposed ice-rich material follows a long, nearly linear,
corridor that stretches 6,300 kilometers,” or nearly
4,000 miles, the team wrote in their study, published
in April in Nature Astronomy. That’s about 40 percent
of Titan’s entire circumference. (For reference, the
continental U.S. stretches less than 3,000 miles from
coast to coast.)
The find is, in a word, weird. The team says it’s pos-
sible that the icy corridor formed sometime in the past
billion years when Titan was still geologically active. And
they specifically wonder if a sudden eruption of this ice
onto the surface was tied to a “major cryovolcanic event” —
a kind of icy volcanism — that astronomers had already
speculated was happening during that time. While the
answers remain unknown, future PCA work may help
astronomers learn even more about the mysterious moon.Saturn looms large
behind Titan, the biggest
of the ringed planet’s
satellites. In April,
researchers announced
the discovery of an
unexpected slash (below,
in blue) stretching across
the moon’s surface for
thousands of miles.