Hundreds
of millions of miles away, in the orbit of Saturn, on the surface of Titan, the
planet’s largest moon, rests a piece of human-made technology. Huygens, a
nine-foot-wide, saucer-shaped probe, was dropped by the passing Cassini
spacecraft and parachuted down to the surface in 2005. For a precious 72
minutes after it landed, Huygens transmitted data back to Earth, including
image after image of its surroundings. There they were—gullies, the kind that
on Earth are etched into rocky terrain by flowing water. Scientists watched,
enthralled, as views of an alien land flashed across computer screens, marking
humanity’s first look at the surface of a moon that wasn’t their own.
Then
Huygens, out of battery power, went dead; its demise was, as grim as it seems,
part of the plan. Huygens remains in the spot where it landed, a dusty monument
to the desire to glimpse, even briefly, the worlds in our solar system.
But a
new piece of technology may be on its way. Not to land on Titan, but to
hover—getting just close enough to reveal secrets.
A
mission to send a drone-like spacecraft to study
Titan received approval and funding from nasa Wednesday. Dragonfly, a
dual-quadcopter, would launch in the mid-2020s and, upon arrival, hop from one
spot over Titan’s surface to the next, searching for signs of life.
The
funding comes from nasa’s
New Frontiers program, a competition for exploration proposals that has
produced several well-known and successful robotic missions in the solar
system: New Horizons, which flew past Pluto in 2015; Juno, which currently
orbits Jupiter; and OSIRIS-REx, which is on its way to an asteroid called
Bennu, where it will carve out some surface material and return the sample back
to Earth. The Dragonfly mission, led by Elizabeth Turtle, a planetary scientist
at Johns Hopkins University’s Applied Physics Laboratory, now has $4 million
and one year to complete its concept. So does the second mission nasa approved
today, the Comet Astrobiology Exploration Sample Return (CAESAR) that would
target a comet that approaches the sun about every six-and-a-half years. But
only one of these missions will actually launch—nasa will choose between
them in 2019.
Titan, the
largest of Saturn’s moons, has long mystified scientists. The moon is wrapped
in a dense, planetlike atmosphere mostly made of nitrogen. Spacecraft like
Voyager 1 and Cassini have detected a plethora of complex and organic molecules
in the atmosphere that are also found on Earth. Robotic missions have also
revealed Titan has a similar liquid process to the water cycle on Earth, but
with a different chemical compound: methane, the main ingredient of natural
gas. On Titan, methane clouds release methane rains that feed methane lakes and
seas and streams that can erode the rocky landscapes. This makes Titan, like
Earth, an ocean world. All together, these features mean Titan is one of the
best candidates for life in our solar system.
(Evangle Luo of TTFLY shared with you)
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