Titan, Saturn's moon, is a prime target in the hunt for extraterrestrial life, and NASA plans to put a flying robot there as part of its newest planetary scientific mission.
The project called Dragonfly will be the first of its type. NASA plans to launch a car-sized quadcopter in 2026, arrive at its final destination in 2034, and then fly to several spots hundreds of kilometres apart. It will be outfitted with devices that can recognise huge organic compounds.
“The science is compelling and the mission is bold,” Thomas Zurbuchen, NASA’s associate administrator for science. “I am convinced now is the right time to do this.”
Why Titan?
Titan is as geographically diverse as Earth and larger than the planet Mercury. The only surface oceans in the solar system outside those on Earth are found on this big, frigid moon, which also has mountains of ice and a dense atmosphere rich in methane.
On Titan, however, liquid hydrocarbons are sloshing across the rivers and lakes. If there is water on the moon, scientists believe it is hidden under the frozen surface of an ocean.
It’s a world utterly unlike our own, and yet “we know it has all of the ingredients that are necessary to help life form,” said Lori Glaze, NASA’s planetary science division director.
Complex carbon rings and chains on Titan may mimic the first building blocks of life on Earth since they are essential to many fundamental biological activities.
Dragonfly will provide “the opportunity to discover the processes that were present on early Earth and possibly even the conditions that might harbour life today,” Glaze said.
New Frontiers
The NASA New Frontiers programme, which provides funding for medium-sized planetary scientific initiatives that don't exceed $1 billion USD, has now funded its fourth mission.
It follows in the footsteps of the asteroid-explorer OSIRIS-REx, the Juno probe, which is presently circling Jupiter, and the New Horizons mission, which just passed by Pluto and the Kuiper belt object MU69.
It was one of the two programme suggestions being thought about since December 2017. The Comet Astrobiology Exploration Sample Return (CAESAR) mission, which would have circled Comet 67P/Churyumov-Gerasimenko, was the other contender.
In November 2038, the spacecraft would have met with the enormous space rock, sucked up a sample from its surface, and brought it to Earth.
Dragonfly will touch down close to Titan's equator among solid hydrocarbon snowflake dunes. Similar to NASA's adventurous Mars rovers, it will be fueled by the heat from radioactive plutonium.
However, with eight rotors, it will be able to travel up to nine miles every hop, which is significantly further than any wheeled robot has ever been able to.
Elizabeth Turtle, a researcher at the Johns Hopkins Applied Physics Laboratory and the mission's chief scientist, said at a press conference on Thursday that flying on Titan was actually simpler. The gravity of that planet is weak, yet its atmosphere is thicker than Earth's.
However, the craft must be capable of independent movement. Dragonfly is substantially more complex than a typical drone since it takes 43 minutes for light signals from Earth to reach Titan.
A navigation system had to be created by scientists so that the spaceship could recognise risks and fly and land on its own.
Where will Dragonfly land?
It will take samples of Titan's hazy atmosphere during flight and transmit overhead pictures of the ground below. However, the ship will spend the majority of its time searching for biologically significant elements on the ground.
Selk Crater, the site of a historic meteor strike, is where it will eventually arrive. Here, researchers have discovered signs of liquid water, organic compounds, and energy that might power chemical processes.
The audacious design caused NASA to ask two separate teams to review the mission plan and determine if the project could be carried out at the permitted cost, according to Zurbuchen. In the end, the organisation judged that the idea was feasible.
Although this is a novel kind of planet exploration, Turtle pointed out that this technology is already extremely advanced on Earth.
“Really what we’re doing with Dragonfly is innovation, not invention.”
Since 2005, when the Huygens probe peaked through Titan's murky orange clouds to show an incredible picture, NASA hasn't been able to glimpse the surface of the moon. On this odd moon, each Earth-like feature has a distinctly chemically foreign twist.
“Instead of liquid water, Titan has liquid methane,” scientists reported in the journal Nature. “Instead of silicate rocks, Titan has frozen water ice. Instead of dirt, Titan has hydrocarbon particles settling out of the atmosphere.”
Its planet is very cold, with an average temperature of minus 290 degrees Fahrenheit (-180 degrees Celsius) on a nice day. It is about 1 billion miles from the sun. More oxygen would cause those plentiful hydrocarbons, which make up the majority of gasoline, to ignite.
Scientists are primarily interested in the existence of all that methane, a chemical that is typically destroyed by sunlight after a few million years. Its persistence raises the possibility of an ongoing mechanism that replenishes the supply of Titan.
With the exception that its clouds are comprised of hydrocarbon gas and its precipitation is in the form of organic compound rain and snow, scientists currently think Titan has weather that is quite similar to that of Earth.
Life as we don’t know it
Turtle said on Thursday that Titan has similarities with the early Earth, before life developed and permanently altered the planet.
“Titan is just a perfect chemical laboratory to understand the chemistry that occurred before chemistry took the step to biology,” she said.
A member of Dragonfly's scientific and engineering team named Sarah Hörst from Johns Hopkins University previously likened Titan to a cosmic kitchen where researchers have discovered all the elements necessary for life.
“But you weren’t there when they got mixed, so you don’t know what they got mixed up to do. You don’t know what will happen when you bake it,” she said in 2017.
The sum of all those parts can be zero. Or, she said, they may be indicators of "life as we don't know it"—a kind of species that relies on hydrocarbons rather than water.
Since the Huygens landing, scientists have discovered even more molecular treasures, including negatively charged molecules linked to intricate chemical reactions, rings of hydrogen, carbon, and nitrogen that can be used to build amino acids, and molecules that can group together to form an envelope that resembles the membranes that surround cells.
“We are pretty darn sure that everything in these broad, big-picture categories that’s required for life exists on Titan,” Hörst said. “At some point it just comes down to, well, shouldn’t we go check? ”
Reference(s): NASA