Why We Need Dragonfly
Life as we know it needs three things: an energy source like sunlight, aliquid solvent like water, and organics — a wide variety of carbon-basedcompounds that build the proteins for life as we know it. That’s apretty vague recipe; it’s like saying you make soup using a stove, a potof water, and some food.
Before life arose on Earth, our atmosphere was a lot different. Therewas hardly any oxygen and a lot more methane. In sunlight, thesemolecules formed organic chemicals that rained down on our planet. Wedon’t know exactly what those chemicals were, but when combined withwater and energy they probably formed the primordial soup from whichlife arose.
We can’t travel back in time and see exactly what happened, butfortunately, there’s a present-day location with a similar atmosphere:Saturn’s moon Titan. Like early Earth, Titan’s skies are clouded withmethane that forms organic molecules — the building blocks of life as weknow it. These molecules should be abundant on Titan’s surface, offering us a unique opportunity to study the possible starting ingredients for life.
NASA’s Dragonfly spacecraft is our next step in Titan exploration.Scheduled to launch in 2028, Dragonfly builds on thelegacy of NASA and the European Space Agency’s legendary Cassini-Huygensmission. Cassini orbited Saturn and buzzed the ringed planet’s moonsfrom 2004 to 2017, while Huygens landed on Titan in 2005. Together, thespacecraft mapped the moon, studied the composition of Titan’satmosphere, and discovered evidence for a water ocean beneath thesurface.
In addition to revealing new clues about the recipe for life onEarth, Dragonfly will help us explore possibilities for decidedlyun-Earth-like life. Like Earth, Titan has mountains, rocks, dunes,rivers, lakes, and seas, and a plentiful supply of organic chemicals.Unlike Earth, Titan’s mountains, rocks, and sand are made mostly ofwater ice, and its rivers, lakes, and seas are filled with liquidmethane and ethane instead of water. Dragonfly will study this bizarroversion of Earth to see what chemical processes are happening, and howthat relates to both life as we know it and forms of life that might beunlike anything we’ve ever dreamed.
How does Dragonfly work?
Usually, planetary landers can only explore one small region of theworlds they visit, but Titan’s low gravity and dense atmosphere willallow Dragonfly to take flight. The spacecraft, about the size of asmall car, has four arms that each hold two helicopter rotors stacked atopone another. This will allow it to make short flights around thesurface. Each flight will be meticulously planned, but must happenautonomously, since the one-way light-travel time to Titan is more thanan hour.
Titan’s gravity is about one-seventh that ofEarth’s — a little weaker than our Moon’s gravity. With an atmosphere four times denser than Earth’s — roughly the pressure you feel a meterunderwater — the conditions are prime for flight. If you strapped on apair of wings and flapped your arms, you’d be able to fly!
Dragonfly will initially land near Titan’s equator in Shangri-La, afield of dunes that are similar to the dunes found in Namibia here onEarth. The spacecraft will also visit the Selk impact crater, where the energy of the impact may have created a temporary liquid-water lake.
Everywhere it goes, Dragonfly will study Titan’s surface, whichshould have collected organic chemicals raining out of the atmosphere.Mounted to each of the probe’s two sled-like rails is a drill that willgrind up materials so they can be sucked into an instrument called amass spectrometer. The mass spectrometer will be able to measure themasses of molecules in each sample, including heavier organic compoundsthat are the building blocks of life as we know it.
At Saturn’s distance from the Sun, sunlight is only 1% as strong asit is on Earth. Titan’s haze blocks most of the rest. Therefore,Dragonfly can’t rely on solar power — it will operate on batteries duringthe day and recharge at nightfrom a nuclear power source similar to the ones used on NASA’sCuriosity and Perseverance rovers. Days and nights on Titan are eachabout 8 Earth days long, and Dragonfly will be able to fly once perTitan day.
Dragonfly also carries a suite of instruments that will directlyanalyze Titan’s atmosphere, allowing scientists to see how it changeswith the days and seasons. This could help us understand how Earth’satmosphere formed. The spacecraft will also measure any Titanquakeswith a seismometer. And, of course, Dragonfly has cameras to take aerialimages as it soars through Titan’s skies. These photos will help themission team scout for Dragonfly’s next destinations, and will also givethe public awe-inspiring panoramic views of this mysterious moon.
