1. How Scientists Are Searching for Life on Titan

    A false color, infrared view of Saturn's largest moon Titan, captured by NASA's Cassini spacecraft. Source: NASA/JPL-Caltech/University of Arizona/University of Idaho Image credit: None
    A false color, infrared view of Saturn's largest moon Titan, captured by NASA's Cassini spacecraft. Source: NASA/JPL-Caltech/University of Arizona/University of Idaho

    At the dawn of the new millennium, Titan was a mystery to the scientific community. The alien moon was known as the largest of Saturn’s 62 natural satellites, a Mercury-sized behemoth hidden beneath dense, nitrogen-rich smog. However, the arrival of the Cassini spacecraft in 2004 marked the beginning of an exponential increase in scientists’ limited knowledge of Titan.

    Thanks to the data compiled by Cassini, scientists have now identified Titan as one of the most Earth-like worlds in our solar system. It’s the only place besides Earth to feature liquid rivers and lakes on its surface, and the only known moon with a substantial atmosphere. Titan’s hazy shroud is comprised primarily of nitrogen and methane gases, which react to create a wealth of organic compounds, including hydrocarbon molecules that serve as the building blocks for life on Earth.

    Many of Titan’s atmospheric gases fluctuate with latitude and time over the course of Titan’s 29.5-year seasonal cycle. However, variations in methane- a key element in the formation of organic material in Titan’s atmosphere- remain a mystery. Despite extensive data obtained by Cassini, both the source of Titan’s methane and the process by which it is replenished are currently unknown.

    A recent breakthrough by a research team supported in part by Habitability of Hydrocarbon Worlds: Titan and Beyond, NAI’s JPL Team, may prove a crucial step in deciphering Titan’s methane cycle. As published in The Astronomical Journal, lead author Alexander Thelen and his team have singled out an isotope of methane (CH3D) in Titan’s atmosphere using the Atacama Large Millimeter /Submillimeter Array (ALMA)- the world’s largest radio telescope, located in the desert of northern Chile. Combining the forces of 66 radio antennas, ALMA provides scientists a unique opportunity to study electromagnetic radiation at millimeter and submillimeter wavelengths.

    The team’s discovery is the first definitive detection of CH3D on Titan at such specific wavelengths. In the post-Cassini era, observation of the CH3D isotope presents a promising means for monitoring Titan’s methane distribution from Earth, and will help scientists solve outstanding mysteries regarding the composition and variability of Titan’s atmosphere.

    Scientists using ground-based telescopes aren’t the only ones trying to puzzle out Saturn’s enigmatic moon. Titan’s thick atmosphere, the nursery of organic molecules that’s proved an astrobiological goldmine, also serves as the ideal realm for a rotorcraft explorer- specifically Dragonfly, the drone-like flagship of NASA’s recently announced New Frontiers mission. Scheduled to reach Titan in 2034, Dragonfly will advance the work of terrestrial research teams by scouring the moon’s surface and atmosphere for evidence of prebiotic chemical processes common to both Titan and Earth.

    In-depth exploration of Titan, made possible through the work of teams like Dr. Thelen’s and the selection of the Dragonfly mission, is a venture that stands to revolutionize our current understanding of life in the Universe. As Melissa Trainer, former NASA Postdoctoral Program fellow and the deputy PI for the Dragonfly mission, states in an interview with Voice of America, “We have this chance to explore a world that we know has all the ingredients for life, but how far did it get towards life?”