Figure 1: A 1024 x 1024 picture of Titan, taken by the Cassini Orbiter on the Cassini-Huygens mission to the Saturnian system. The photo portrays Titan as a fuzzy, orange ball.
Source Credit: Nasa Planetary Data System, Jet Propulsion Laboratory, Caltech (LINK)
For the past few years, humanity has given unrequited attention to Earth’s next door neighbor, Mars. With aerospace companies like SpaceX on the rise, and new rovers successfully landing on the surface of Mars, it is nearly impossible not to be excited about new discoveries. It has been three weeks since the landing of the most recent Mars rover mission, Perseverance, and this 3 meter long metallic beast has been capturing nearly 400 photos every single day, allowing scientists to thoroughly investigate the geographic features and habitability of the planet. However, it seems as if the spotlight is slowly shifting from Mars to a less known celestial body—Titan.
Titan, characterized by its murky atmosphere and its musty, pear-like color, is the largest of Saturn’s seven sizable moons. Discovered by Chirstiann Huygens with the help of his brother Constantijn Huygens, Titan was first spotted by the brothers’ 12-foot long telescope on March 25, 1655. Despite being only 3 times as large as and 1.8 times heavier than our moon, Titan seems to have gained much recent attention for its potential habitability. Robert Zubrin, an American aerospace engineer, asserts in his 1999 book “Entering Space: Creating a Spacefaring Civilization” that “in certain ways, Titan is the most hospitable extraterrestrial world within our solar system for human colonization” (Zubrin 163-166), citing Titan’s climate and geological activity for being some of the primary reasons for its possible habitability.
While Titan is primarily composed of ice and rock, its seas, lakes, rivers, and clouds are teeming with an abundance of organic molecules. Accordingly, it has been, for quite some time, predicted that Titan could possibly host some extraterrestrial organisms, although none have been found as of now. In talking about Titan’s potential habitability, we must talk about its atmosphere, climate, and its geographic features.
According to an article in the Planetary and Space Science journal, Titan’s atmosphere is a thick layer of nitrogen (96.3 percent), isotopes of nitrogen (1.08 percent), methane (2.17 percent), and a variety of other organic compounds, including but not limited to acetylene, ethylene, ethane, propyne, propene, propane, and diacetylene. Due to this chemical composition and Titan’s relatively small mass, the moon has a very extended, opaque atmosphere that blocks out nearly all visible light. Furthermore, Titan has both a greenhouse and anti-greenhouse effect: while its methane atmosphere traps a lot of light from the sun within the atmosphere, it also serves to reflect light back into space, keeping more from entering the atmosphere, and also helping regulate the moon’s temperature.
Titan is a cold, barren moon, but this might change in the future. Currently, Titan has a temperature of -180ºC. Contrary to our planet’s 70 percent, only 1 percent to 8 percent of Titan’s atmosphere is covered by clouds. With its clouds, it has non-frequent, liquid methane rains. However, with the Sun becoming a red giant, and Titan being within the habitable zone, it is predicted that it will have more suitable temperatures in the future.
Titan’s geology mainly consists of wide, rocky plains, with the occasional ice Ih, which is the hexagonal crystal ice we are used to seeing on Earth. But more interesting are the hydrocarbon seas—the Kraken Mare being the largest of them all—and the possible liquid water sea underneath the surface of Titan. This is very important in that firstly, water is obviously a vital component of life. Secondly, in devising possible forms of life on Titan, a hydrocarbon solvent-based model was proposed. While hydrocarbons are less useful as a solvent when compared to water, it is possible that, analogous to marine life on Earth, populations of organisms might thrive in the hydrocarbon oceans of Titan, feeding off ethane and methane. Furthermore, a form of methanogenic, oxygen free model of life has been proposed by a team of Cornell University Researchers, according to this 2015 Phys.org article.
Due to these valuable, possibly life-sustaining properties of the moon, several aerospace organizations have set forth to probe deeper into Titan. In 1979, Pioneer 11 first visited the Saturnian system. Later in 2004, the Cassini-Huygens aircraft arrived at the Saturnian system, and took close-up shots of Titan. On Jan. 14, 2005, the spacecraft landed on Titan, and since then, it has been probing the surface. The Dragonfly mission, consisting of a robotic rotorcraft designed to detect organic materials and discover new biochemical properties, will launch and head for Titan in 2027. According to one New York Times article, Valerio Poggiali, a researcher at Cornell University, claimed that a submarine is on the way. With increasingly sophisticated technology on the rise, the future for Titan exploration seems bright. While the habitability of Titan is uncertain at best, such global scientific interest has made an opportunity for the masses of people to work towards clearing that uncertainty, and perhaps making Titan a habitable moon.
Q&A:
Jiwon: In your article, you talked about Titan's potential habitability as a result of its atmosphere, climate, and geographic features. From what I understand, there have been traces of hydrogen on the surfaces and greenhouse effects in the upper atmospheres of certain planets. What differentiates Titan from these other discoveries?
Certainly, there are planets with significant amounts of hydrogen in the solar system. First, the gas giants: Jupiter, Saturn, Uranus, and Neptune. Because these planets have non-terrestrial surfaces, they aren’t suitable for colonization. Next, the planets within the asteroid belt: Mercury, Venus, and Mars. Although Mercury’s atmosphere does contain traces of hydrogen, its drastically fluctuating climate makes it inhabitable. Venus’s atmosphere is mostly composed of carbon dioxide, and its high atmospheric pressure makes it inhabitable. Mars is a viable candidate, but it lacks nitrogen in its atmosphere and lacks radiation protection, so it may only be a short-term solution due to its proximity to Earth. On the other hand, Titan has an abundance of elements crucial to life: nitrogen and hydrogen in the atmosphere, and hydrocarbons in its lakes.
Sally: What about the other moons of Saturn? Are there any possibilities for habitation?
Saturn has an astounding 82 moons. Out of these, Titan and another moon named Enceladus are of interest due to their potential habitability. Enceladus’s suspected hydrothermal activity makes it eject salt water riddled with elements crucial to life, but in trace amounts. Sadly, its conditions render the moon almost inhabitable - not only does it lack a surface pressure, but its gravitational field is very weak, and its temperature is even lower than that of Titan.
Xavier: You mention that humanity has given “unrequited attention” to Mars, and that attention is slowly shifting towards Titan. What makes habitability on Titan a more superior alternative to the colonization of Mars?
Again, Mars may be a short-term candidate for habitation due to its proximity to the Earth and the Sun (a source for solar power). However, it lacks some elements crucial to life. Furthermore, the atmospheric pressure on Mars is so low that our bloods would boil the moment we stand on its surface. Contrarily, Titan has a similar atmospheric pressure to Earth (1.45 atm) and contains in its atmosphere and lakes elements crucial to life.
Hannah: Based on your article, it seems as though the study of habitability in Titan began quite some time ago. Then why are most people still focusing mainly on Mars and why is this shift of attention towards Titan happening now instead of earlier?
That is mainly due to the proximity of Mars. Because Mars is much more close to Earth, with our current technological capacities, it is much more feasible that we colonize Mars first. While it is difficult to fully comprehend the trend and reasons behind the fluctuation of public interest, the shift of attention towards Titan is most likely because the recent Perseverance mission turned out to be a success, and much time will pass before we make the next significant step towards colonizing Mars.
Eric: How does the existence of organic molecules dictate livability for humans, and what steps would need to be taken to make Titan inhabitable?
The presence of organic molecules is necessary in order for other types of life to flourish in an ecosystem (e.g. via self regulating processes occurring in the environment). Because our sustenance mainly depends on the healthy continuation of other types of life, the presence of organic molecules are crucial in gauging habitability.
Josh: By the time Titan has a more suitable temperature due to the Sun’s changes, what would happen to Earth?
By the time Titan has a more suitable temperature due to the Sun turning into a Red Giant, Earth will already have been swallowed by the Sun’s increased radius. Thus, Earth will have become an inhabitable place. Thankfully, Titan will be within the habitable zone of the red giant, making it an optimal place for human survival.
Wooseok: Are there any benefits to the exploration of Titan other than finding a potentially suitable shelter for future use? (e.g. valuable metals / minerals)
The hydrocarbon lakes of Titan contain more than one hundred times the hydrocarbon in all the gas and oil reserves on Earth. Thus, in the future, it might be a useful source of organic chemicals.
Works Cited:
“Catalog Page for PIA14602.” NASA, NASA, photojournal.jpl.nasa.gov/catalog/PIA14602.
“Mars 2020 Perseverance Rover.” NASA, NASA, mars.nasa.gov/mars2020/.
“Huygens and the Improvement of the Telescope.” Digitaal Wetenschapshistorisch Centrum Huygens and the Improvement of the Telescope Comments, www.dwc.knaw.nl/biografie/christiaan-huygensweb/instrumenten-en-uitvindingen/huygens-and-the-improvement-of-the-telescope/?lang=en.
Zubrin, Robert. Entering Space: Creating a Spacefaring Civilization. Jeremy P. Tarcher/Putnam, 2000.
Magee, Brian A., et al. “INMS-Derived Composition of Titan's Upper Atmosphere: Analysis Methods and Model Comparison.” Planetary and Space Science, vol. 57, no. 14-15, 2009, pp. 1895–1916., doi:10.1016/j.pss.2009.06.016.
Gohd, Chelsea. “Methane Rain Falls on Titan's North Pole from Cloudless Skies.” Astronomy.com, 21 Jan. 2019, astronomy.com/news/2019/01/methane-rain-falls-on-titans-north-pole-from-cloudless-skies#:~:text=But%20while%20scientists%20aren%27t,gravity%2C%20the%20raindrops%20fall%20slower.
Shiga, David. “Titan's Changing Spin Hints at Hidden Ocean.” New Scientist, 20 Mar. 2008, www.newscientist.com/article/dn13516-titans-changing-spin-hints-at-hidden-ocean/.
Ju, Byanne. “Life 'Not as We Know It' Possible on Saturn's Moon Titan.” Phys.org, Phys.org, 27 Feb. 2015, phys.org/news/2015-02-life-saturn-moon-titan.html.
“In Depth.” NASA, NASA, 16 July 2019, solarsystem.nasa.gov/missions/pioneer-11/in-depth/.
“Cassini Orbiter.” NASA, NASA, 25 Apr. 2019, solarsystem.nasa.gov/missions/cassini/mission/spacecraft/cassini-orbiter/.
Overbye, Dennis. “Seven Hundred Leagues Beneath Titan's Methane Seas.” The New York Times, The New York Times, 21 Feb. 2021, www.nytimes.com/2021/02/21/science/saturn-titan-moon-exploration.html.
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