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by Perry Pezzolanella

One of the most interesting worlds in the Solar System is Saturn’s largest moon, Titan. It is larger than Mercury and the second largest of all the moons at 3200 miles in diameter, only slightly smaller than Jupiter’s moon, Ganymede. The fascination with Titan began in 1944 when an atmosphere was discovered containing methane. Paintings of Saturn in a blue sky above Titan’s snowy landscape inspired many to pursue a career in planetary science.

Voyager 1 flew past Titan during November 1980. Voyager 2 followed during August 1981, but an orange organic haze completely obscured the surface. The Hubble Space Telescope revealed large bright and dark areas on Titan’s surface in1994 by imaging in near infrared. The truth about Titan’s surface was revealed in July 2004 when Cassini arrived and began orbiting Saturn for the next 13 years. Cassini used radar and near infrared imaging at close range to map the surface revealing rivers, lakes, and seas of liquid ethane and methane along with mudflats, sand dunes, mountains, and possible cryovolcanoes. Cassini also detected a vast, salty ocean beneath the icy crust and confirmed two methane rainfalls that filled rivers that flow into lakes and seas. The Huygens probe landed on Titan during January 2005 on a vast mudflat and confirmed the humid and frigid environment of -290ºF. The atmosphere is about 95% nitrogen and 5% methane. Sunlight interacts with the atmosphere to create complex organic compounds that impart an orange haze. This has made Titan a high priority for planetary exploration as it is the only moon with a dense atmosphere that supports an Earth-like water cycle of methane clouds, rain, and liquid flowing across the surface to fill rivers, lakes, and seas, thus classifying it as an “Ocean World”. The objectives for exploring Titan as it relates to an ocean world are: 1) to understand the organic and methane cycle on Titan, especially as it relates to prebiotic chemistry and 2) to investigate the subsurface ocean and/or liquid reservoirs, their evolution and possible interaction with the surface.

Titan has an atmosphere that is four times denser than Earth’s, which would exert pressure against one’s body with a force equivalent to that at the bottom of an Olympic size swimming pool, and gravity 1/7th Earth’s, where a 200-pound man would weigh only 29 pounds, making it a perfect world for balloons and aircraft. With the rapid evolution of drones, a mission to return to Titan and explore it in a way that never seemed possible may come to fruition in 2019 if approved. Dragonfly is a rotocraft (drone) lander mission that can utilize the thick atmosphere to fly between sites up to hundreds of miles apart. It will search for interesting places to explore while aloft with its camera, and then land. It will actually spend most of its time on the ground exploring and analyzing the surface. Because it can fly, it will be able to pass over interesting landmarks including sand dunes and smaller lakes. It will not be able to land on liquid, but could land near a shoreline. The huge seas in the north will be experiencing a long winter and darkness when Dragonfly arrives during the mid-2030, so exploring them may not be an option. The main goals for Dragonfly are: 1) sample surface materials and determine chemical composition, 2) monitor atmospheric and surface conditions, 3) image and classify geological features using imaging, and 4) perform seismic studies to detect quakes and subsurface structure.

If approved, Dragonfly would launch by 2025 and arrive at Titan in 2034. The mission would last about two years, but possibly much longer running on nuclear power since solar power is ineffective near Titan’s murky surface. A day on Titan lasts 15.9 Earth days and the majority of the daylight, which lasts about 8 days, would be spent flying, landing, and exploring. Dragonfly would use its radioactive thermoelectric generator to recharge its flight batteries during the 8-day long night. This is an inspiring mission that, if it is approved and succeeds, would further our knowledge of Titan’s evolution and future, and most importantly, spark a new wave of interest in youth to explore the worlds around us.