January 30, 2021: The Dragonfly Mission May Bring Us Major Clues Upon The Origin Of The Methane Present On The Opaque Moon Titan
Thanks to the Cassini-Huygens mission, our level of understanding of Titan's environment has significantly improved. However, many mysteries regarding Saturn's largest moon have emerged thanks to the analysis of the huge amount of data gathered by the Cassini orbiter or the Huygens probe. Remarkable panoramic images of Titan's surface had been acquired from the parachuted probe during its historic atmospheric descent on January 14, 2005. The color view obtained from the surface captures our imagination. The aerial views obtained from the Huygens probe had unveiled a familiar landscape composed of bright hills containing a network of dark drainage channels and composed of a brown or dark plain reminiscent of a dried up sea or lake. The journey of the Cassini orbiter ended on September 15, 2017 with the final plunge of the spacecraft into the atmosphere of the Ringed Planet Saturn. A new mission to Saturn's largest moon Titan is starting to take shape. That mission which involves Elizabeth Turtle of the Johns Hopkins University Applied Physics Laboratory, the Principal Investigator of the mission, is known as the Dragonfly mission. That challenge is very ambitious since the mission will mobilize a rotorcraft to explore the environment of the Opaque Moon.
The data gathered by the Dragonfly rotorcraft may allow us to better understand the various chemical reactions taking shape on the ground or in the dense air near the soil or in the troposphere of the Orange Moon. The mission may provide major clues to the habitability of Saturn's largest moon. Can the environment of Titan engender complex molecules, prebiotic molecules or some typical molecules mobilized by our biosphere ? The Dragonfly mission may allow us to get a clearer understanding of the complex chemistry of Titan. The Dragonfly mission is expected to last at least 32 months and may last longer if the probe or if the instruments continue to correctly work in the harsh environment of the giant moon where the level of energy received from the Sun is much lower than the level of energy received at the level of the Earth. The flying robot or the drone will represent an "8-bladed rotorcraft". That drone will evolve in an environment where the air is several times denser than the air on Earth at sea level and where the gravity is much lower than on Earth. Therefore, it will need less energy than on Earth to fly. In other words, the rotation speed of the rotor can be slower on Titan than on Earth.
Saturn and Titan evolve at about 1.4 billion kilometers from the Sun which represents about 10 times farther from the Sun than the orbit of the Blue Planet. That relatively high distance implies that any command sent from the Earth to the drone takes a relatively long time. Let's recall that any signal travels at the Speed of Light. The relatively long time to send a signal from the Earth to Titan implies that we produce a drone or a probe that can be autonomous on the surface or in the air on Titan. In other words, the drone must have artificial intelligence. The drone will remain on the surface if the weather conditions are too bad or not good enough for instance. The drone will be able to identify key surface features during its flight. The probe will be composed of several instruments to measure chemical processes, geological processes or meteorological processes. It will contain a mass spectrometer to identify the various molecules or chemicals, a neutron and gamma-ray spectrometer for the analysis of the soil or surface, a seismometer to determine or evaluate tectonic movements, flight sensors and radars as well as several cameras. Thus, the probe will be equipped with a remarkable suite of instruments likely to tell us a lot regarding the exotic environment of the giant moon.
During its journey in the varied environment of Titan, the rotorcraft will collect and analyze some materials present on the ground. The analytical process will be performed onboard. If the analysis of any sample is fruitful, the probe will be in a position to return to places where the samples have been collected. Doctor Rosaly Lopes who is a Senior Research Scientist at NASA's Jet Propulsion Laboratory and who is currently analyzing geological data obtained during the Cassini-Huygens mission pointed out that the idea of sending a drone or rotorcraft to another world was completely new in the sense that the concept had never been proven when some researchers advanced the idea of sending a drone to Titan. A drone or flying robot is going to evolve very soon on the surface of Mars for the first time ever. That probe known as Ingenuity which is a helicopter proposed by NASA is likely to explore the Red Planet in spring 2021 as part of the Mars 2020 mission that will also mobilize the Perseverance rover. In the 2030's, another drone or flying probe known as Dragonfly will explore a world in the Outer Solar System. Sending a drone to Titan is clearly a complex challenge.
Titan is a captivating world due to its dense atmosphere and due to its complex haze rich in hydrocarbons or organics in particular. Titan is the second largest moon in the Solar System and is bigger than Mercury or Pluto for instance. The mean distance between Saturn or Titan and the Sun is about 1,433,530,000 kilometers or 890,754,245 miles so that one year on Saturn or Titan represents approximately 29 Earth years. Environmental temperatures can be as low as -179 degrees Celsius, -290 degrees Fahrenheit or 94 Kelvin at the level of the surface. Those environmental temperatures combined with a relatively high atmospheric pressure allow the presence of liquid methane or liquid ethane on the surface. Water can only appear in its solid form on the surface in the harsh environment of the giant moon. Therefore, can Titan engender life ? If there is a form of life on Titan, it can't be based on liquid water like on Earth. Chemical reactions can be accelerated in a liquid like liquid methane or liquid ethane. Doctor Elizabeth Turtle advanced that the Orange Moon has chemical similarities to early Earth. She pointed out: "There's organic material, water at impact craters, cryo-volcanoes, and sunlight as the energy driving the whole thing." She added: "All the ingredients for life as we know it exist and interact on the surface."
The Cassini spacecraft has clearly allowed us to identify seas, lakes or rivers in the high latitudes of Saturn's largest moon. Therefore, Titan appears to be the only extraterrestrial world in the Solar System known to harbor stable bodies of liquid on the surface. Titan demonstrates that there can be exotic worlds containing exotic liquids which remain relatively stable on their surface. Titan's lakes, seas or rivers are dominated by hydrocarbons. Their exact composition is unknown but they may be mainly composed of methane and ethane with concentrations which can vary geographically or seasonally. The Dragonfly drone is likely to bring us key information regarding precipitation cycles, moisture evaporation and cloud formation. Titan appears really familiar because the moon has a meteorology and geological features that we regularly encounter on Earth. Dunes, canyons, lakes, seas, rivers, mountains, hills, craters, eroded features or even volcanoes or calderas can be found on Saturn's largest moon. Some chemical reactions in the environment of Titan today may look like the chemical reactions on the Early Earth that led to our biosphere.
The history of Titan's environment can tell us a lot regarding the history of the environment of our planet. The study of the evolution of Titan's atmosphere can help us better understand our own atmosphere. How do atmospheres evolve over geological time scales ? Elizabeth Turtle pointed out: "We want to understand those early chemical steps and how far the chemistry has progressed on Titan." The origin of the methane found in Titan's atmosphere is a major research subject. Titan's atmosphere is dominated by molecular nitrogen like our own atmosphere but it also contains a relatively significant fraction of methane that is supposed to vanish over time. The methane molecules interact with ultraviolet light from the Sun to form new molecules, elements or ions. The methane molecules can also be accelerated by Saturn's magnetism. Thus, new hydrocarbons can form in the atmosphere and hydrogen can escape into outer space. Elizabeth Turtle considers, on the basis of the amount of methane present in Titan's atmosphere, that "the lifetime of that methane is on the order of 10 million years". The Dragonfly drone may allow us to gather key clues regarding the origin of that methane and regarding the level of stability of the atmosphere.
Some researchers advance the hypothesis that there may be internal sources to the methane found in the Titanian atmosphere. There may be reservoirs of methane within the crust or there may be cryo-volcanoes spewing methane or even underwater sulfuric vents. Doctor Natalie Grefenstette who is a postdoctoral fellow at the Santa Fe Institute and who holds a PhD in prebiotic chemistry argued that the scientific community is "excited to see what the environment [on Titan] is naturally producing." Has there been life on Titan ? Is there life on Titan today ? Will there be life on Titan one day ? Natalie Grefenstette hopes that the Dragonfly mission will allow us to identify key organic molecules or unexpected "evidence of proto-life or life-like systems". Can there be other lifeforms based on other solvents than liquid water on other worlds ? Titan is likely to allow us to significantly advance on that topic. Titan can allow us to better understand the mechanics of organic chemistry in the universe. Elizabeth Turtle concluded: "Being able to see what happened in [Titan's] environment will give us perspective on what happened in other environments, as well as on habitability in general." Titan is clearly a natural laboratory for the chemistry of organics and hydrocarbons.
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The image above represents a portion of a radar swath of Titan obtained from the Cassini orbiter on June 20, 2011 during the T77 Flyby. Each side of the portion is 100 km long. One can notice a relatively circular feature which may correspond to an impact crater or a cryovolcano. One can also notice relatively linear and parallel dunes in the left part of the view. The contrast between the area of the dunes and the area of the circular feature is remarkable. Credit for the original view: NASA/JPL/Cassini RADAR Team/Jason Perry. Montage credit: Marc Lafferre, 2021. |
- To get further information on that news, go to: https://astrobiology.nasa.gov/news/nasas-dragonfly-mission-will-seek-clues-about-titans-habitability.