In June 2027, NASA will launch the long-awaited Dragonfly mission toward Saturn’s largest moon, Titan. By 2034, the 450 kg (990-lbs) nuclear-powered quadcopter will touch down at its target landing site (the Selk crater region) and begin searching Titan’s surface and atmosphere to learn more about this curious satellite. In particular, the mission will investigate the moon’s prebiotic chemistry, active methane cycle, and organic environment. These goals underpin Dragonfly’s main objective, which is to search for possible signs of life (aka. “biosignatures”) on Titan.
For years, scientists have speculated if life could exist on Titan since it appears to possess all the necessary ingredients (though not for life as we know it). This curiosity has only deepened since the Cassini–Huygens mission, which spent thirteen years exploring Saturn and its system of moons (from 2004 and 2017). Recently, a team of Cornell researchers combined and analyzed radar images taken by Cassini to determine the properties of the surface. The result is a detailed map of the Dragonfly‘s landing site, revealing a landscape of sand dunes and broken-up icy ground.
The research was led by Léa Bonnefoy, a postdoctoral fellow with the Cornell Center for Astrophysics and Planetary Science (CCAPS), the Carl Sagan Institute, and the Institut de Physique du Globe de Paris (IPGP). She was joined by multiple members from CCAPS and the IPGP, as well as researchers from the Johns Hopkins University Applied Physics Laboratory (JHUAPL), the Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS) at the University of Versailles, and the Institut Universitaire de France (IUF). The paper that describes their research and findings recently appeared in The Planetary Science Journal.
Bonnefoy was part of the research group led by Alex Hayes, an associate professor of astronomy and the Director of the Spacecraft Planetary Image Facility, which specializes in identifying and characterizing potentially habitable environments across the Solar System. Their work has included data from the Cassini orbiter, the Perseverance, Curiosity, Spirit, and Opportunity rovers, and the upcoming Europa Clipper mission. As Bonnefoy explained in a recent Cornell Chronicle release, Dragonfly will be investigating one of the most promising environments to date:
“Dragonfly – the first flying machine for a world in the outer Solar System – is going to a scientifically remarkable area. Dragonfly will land in an equatorial, dry region of Titan – a frigid, thick-atmosphere, hydrocarbon world. It rains liquid methane sometimes, but it is more like a desert on Earth – where you have dunes, some little mountains and an impact crater.
“We’re looking closely at the landing site, its structure and surface. To do that, we’re examining radar images from the Cassini-Huygens mission, looking at how radar signal changes from different viewing angles. “The radar images we have of Titan through Cassini have a best-resolution of about 300 meters per pixel, about the size of a football field and we have only seen less than 10% of the surface at that scale. This means there are probably a lot of small rivers and landscapes that we couldn’t see.”
During its many orbits of Saturn, the Cassini orbiter took multiple radar images of Titan and its many larger moons. On Christmas Day, 2004, the orbiter released its partner mission – the Huygens lander – which began its descent into Titan’s dense atmosphere on January 14th. During its two-hour descent, the lander gathered data on Titan’s atmosphere to determine what aerosols and chemicals are present (and in what amounts). It also returned pictures of the surface that showed river valleys not visible in the orbiter’s radar images.
For their study, Bonnefoy and the group used radar reflectivity from the Cassini images and angled shadows to map six terrains in the Selk crater, characterizing the landscape and gauging the height of its rim. Knowing the crater’s shape will provide insight into the region’s geology and help mission planners identify scientific objectives for the Dragonfly mission. Titan’s rich prebiotic environment contains organic compounds in its atmosphere and on its surface, where they resemble sand and form dune-like features.
Titan’s dense atmosphere, which is largely composed of nitrogen (around 95%), methane (~5%), and other hydrocarbons, is about four times as dense as Earth’s atmosphere. Combined with Titan’s low gravity (13.8% that of Earth), this will enable Dragonfly to remain airborne and perform like a drone, researching Titan’s atmosphere, surface, and methane lakes to learn more about the planet’s composition and its potential to support life. Said Bonnefoy:
“Over the next several years, we are going to see a lot of attention paid to the Selk crater region. Lea’s work provides a solid foundation upon which to start building models and making predictions for Dragonfly to test when it explores the area in the mid-2030s. Dragonfly is going to finally show us what the region – and Titan – looks like.”
Since Titan’s environment today is believed to be similar to primordial Earth, the data obtained by Dragonfly could help scientists learn more about how life emerged on Earth. There’s also the prospect that life emerged on Titan and is still there today, most likely in microbial form. The discovery and study of these potential lifeforms could shed light on how and where life emerged in the Solar System, not to mention how the building blocks might have been distributed billions of years ago (aka. lithopanspermia).