Should We Send Humans to Titan?

Universe Today recently examined the potential for sending humans to Jupiter’s icy moon, Europa, and the planet Venus, both despite their respective harsh surface environments. While human missions to these exceptional worlds could be possible in the future, what about farther out in the solar system to a world with much less harsh surface conditions, although still inhospitable for human life? Here, we will investigate whether Saturn’s largest moon, Titan, could be a feasible location for sending humans sometime in the future. Titan lacks the searing temperatures and crushing pressures of Venus along with the harsh radiation experienced on Europa. So, should we send humans to Titan?

“Yes!” Dr. Jason Barnes, who is a Professor in the Department of Physics at the University of Idaho, excitedly tells Universe Today. “Titan is the second-safest place in the solar system after Earth. It’s protected from radiation, pressurized, and has great science to be gained by crewed exploration.”

In addition to his academic duties, Dr. Barnes is also the Deputy Principal Investigator for NASA’s upcoming Dragonfly mission, which is a rotorcraft designed to explore Titan’s prebiotic chemistry and liquid methane lakes and seas, along with Titan’s atmosphere of 95 percent nitrogen and 5 percent methane. Powered by a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG)—which currently power NASA’s Curiosity and Perseverance rovers—Dragonfly will carry a suite of instruments to help determine the habitability potential for Titan, which, in addition to being the largest moon of Saturn, is is also the second-largest moon in the solar system—the largest being Jupiter’s moon, Ganymede.

While Dragonfly will conduct the most in-depth surface exploration of Titan, this will not be the first spacecraft to land on Titan’s surface, as that honor goes to the European Space Agency’s Huygens probe, which landed on Titan’s surface in January 2005 and transmitted data for approximately 90 minutes after touchdown before its batteries ran out. Additionally, Titan was studied in-depth by NASA’s Cassini spacecraft at various times throughout its mission between 2004 and 2017. But with all this science having already been conducted by these robotic explorers, what additional science could be conducted by a human mission to Titan compared to a robotic mission?

“Similar to Mars, human boots on the ground could accomplish more exploration science faster than robots,” Dr. Barnes tells Universe Today. “Additionally, should life or prebiotic chemistry be found on Titan, people on-site could more safely study such life without risk of backward contamination to Earth. Finally, because of its safety, Titan is a prime target for long-term human habitation as we progress outward into the solar system.”

In terms of an orbital versus a surface mission for humans to Titan, Dr. Barnes tells Universe Today, “Orbital missions with people don’t make sense for science. Robotic orbiters do a great job, and our experience has shown that human remote sensing doesn’t provide any advantages over the robots. But a long-term surface mission with a base and surface mobility could open up an entire world of science.”

This “world of science” includes up-close investigations of Titan’s prebiotic chemistry, biochemistry, and organic chemistry, along with how Titan’s atmosphere and seas and lakes of liquid methane could influence such chemical reactions for both the short and long term. However, living on Titan’s surface would also come with its myriad of challenges, as well. While Titan is well-shielded from harmful solar radiation, its surface is both unbearably cold and extremely dark, as surface temperatures have been measured at -179.2 degrees Celsius (-290.6 degrees Fahrenheit) and Titan’s surface is estimated to receive only 0.1 percent of the sunlight that Earth receives. But, how else could this “world of science” pose additional challenges to human explorers on Titan’s surface?

“Challenges on the surface could be that the very organic molecules that make Titan so interesting could prove carcinogenic to a crew if pains are not taken to avoid getting them into the habitat,” Dr. Barnes tells Universe Today. “Another challenge is generating power out there — you’d basically need to bring a nuclear reactor with you, because there’d be no native way to generate the power needed to drive crewed exploration.”

In addition to the challenges of living on Titan’s surface, there is also the concern of the distance and travel time to the Saturnian system from Earth, as several missions have taken a minimum of several years to reach the Saturnian system, even if they took a direct route. For example, NASA’s Pioneer 11 spacecraft launched in 1973 and needed six and a half years to reach Saturn after flying by Jupiter. Only a few years later, NASA’s Voyager 1 and Voyager 2 spacecraft were launched in 1977 and required three years and two months and four years, respectively, to reach Saturn after they conducted flybys of Jupiter. While NASA’s Cassini mission conducted the most in-depth investigation of Saturn and its many moons, the spacecraft still required six years and nine months to get to Saturn after conducting two gravity assists at Venus, one at Earth, and one at Jupiter.

Currently, the fastest spacecraft to reach Saturn is NASA’s New Horizons spacecraft, which only required two years and four months to reach the ringed planet on its direct trajectory to Pluto. Therefore, even if a human mission were to take a direct route to Titan, it would still require a minimum of two years to arrive. Therefore, this lengthy travel time could hamper any resupply or rescue operation to Titan for a human mission.

“The travel time would be so long that any such expedition would need to be a pretty massive undertaking,” Dr. Barnes tells Universe Today. “Although astronauts would be safe on Titan’s surface from radiation, they would be subject to damage from solar storms en-route, at least while in the inner solar system. They’d be so far away from home that there would be no possibility of rescue if their systems failed, so plenty of backups would need to be brought along.”

Will we ever send humans to Titan? Will we learn more science than from a robotic mission like Dragonfly, and what will such a mission teach us about living and working so far from Earth? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!