Saturn's Moon Titan is a fascinating world covered with pale yellow smoke. Similar to the Earth, the atmosphere is mainly nitrogen, with weather, including clouds and rain. The weather with the Earth is driven by evaporation and condensation, while the ice-cold Titan has a methane cycle.
NASA's James Webb Space Telescope complements images of the Keck II telescope, finding evidence of cloud convection in lakes and ocean areas for the first time in Titan's northern hemisphere. Weber also detected a key carbon molecule that provides insight into the chemical processes in the complex atmosphere of Titans.
On Titan, methane plays a similar role in weather as the water on Earth. It evaporates from the surface and rises into the atmosphere, where it condenses to form a methane cloud. Sometimes it falls on a solid surface like cold oily rainwater, and water ice is as hard as rocks.
“The Titan is the only place in our solar system that has weather like Earth, and in a sense it has clouds and rainfall on the ground.”
The team observed Titans in November 2022 and July 2023, using Webb and dual-base WM Keck Observatories telescopes. These observations not only show clouds in the central and high northern latitudes of Titans – the current summer hemisphere, but also show that these clouds obviously rise to higher altitudes over time. Although previous studies have observed cloud convection at southern latitudes, this is the first evidence of such convection in the north. This is important because most Titans have lakes and oceans located in their northern hemisphere, and lake evaporation is the main potential source of methane. Their total area is similar to that of the Great Lakes in North America.
On Earth, the lowest layer of the atmosphere or troposphere extends to an altitude of about 7 miles (12 kilometers). However, on Titan, where the gravity of the Titan allows the atmosphere to expand, the troposphere extends to about 27 miles (45 kilometers). Webb and Keck use different infrared filters to detect different depths in the Titan atmosphere, allowing astronomers to estimate the height of clouds. The scientific team observed that the clouds appeared to move to higher elevations within a few days, although they could not see any precipitation directly.
Due to its complex organic (carbon-containing) chemistry, Titan is an object of high astronomy interest. Organic molecules form the basis of all life on Earth, and studying them in a world like Titans may help scientists understand the processes that led to the origin of life on Earth.
The basic component that drives most of the chemistry of Titans is methane or CH4. Methane in the Titan atmosphere is separated by sunlight or energy electrons in Saturn's magnetosphere and recombined with other molecules to make substances such as ethane (C2h6) and more complex carbon molecules.
Weber's data provide a key lack of work for us to understand chemical processes: a clear detection of methyl radical CH3. When methane splits, the molecule (called "free radicals" because it has "free" electrons that are not in chemical bonds") form. Detection of this substance means that scientists can see the chemical reaction to Titan for the first time, not just the starting ingredients and the final product.
“This is the first time we’ve seen chemical cakes rise in the oven, not just the starting ingredients of flour and sugar, and then the final ice cake,” said Stefanie Milam, co-author of the Goddard Space Flight Center.
This hydrocarbon chemistry has long-term impact on the future of Titans. When methane decomposes in the upper atmosphere, some of the recombination causes other molecules to eventually appear on the surface of the Titan in one chemical form or another, while some hydrogen escapes from the atmosphere. As a result, methane will run out over time unless there is some source to supplement it.
A similar process occurred on Mars, where water molecules decompose and the resulting hydrogen lost space. The result is the dry desert planet we see today.
"On Titan, methane is a consumption. It can be poured and croaked continuously from the shell and interior for billions of years," Nixon said.
[embed]https://www.youtube.com/watch?v=rrj7jhun12i[/embed]
Credits: NASA's Goddard Space Flight Center. Producer/Editor: Dan Gallagher. Chief Scientist/Narrator: Conor Nixon. Chief Animator: Jenny McElligott. Chief Visualizer: Andrew J Christensen. Scientist: Nicholas Lombardo. Animator/Art Director: Michael Lentz. The protagonist of the animation: Walt Feimer. Animators: Jonathan North, Wes Buchanan, Kim Dongjae, Chris Meaney, Adriana Manrique Gutierrez. Data visualizer: Mark Subbarao, Kel Elkins, Ernie Wright. Data provider: Juan Lora. Executive Producer: Wade Sisler. Social Media Support: Kathryn Mersmann. Public Affairs: Laura Betz.
NASA's Dragonfly Mission will investigate more of Titan's mystery, a robotic rotor planned to land on Saturn's moon in 2034. Its in-depth investigation will complement Weber's global perspective.
Heidi Hammel added: “By combining all these resources, including Webb, NASA’s Hubble Space Telescope and the ground-based observatory, we maintain the continuity between the former Cassini/Huygens’ Saturn mission and the upcoming Dragonfly Mission.”
The data is part of Hammel's guaranteed time observation plan to study the solar system. The results were published in the journal Natural Astronomy.
The James Webb Space Telescope is the world's leading space science observatory. Weber is solving the mysteries in our solar system, transcending the distant world around other stars, and exploring the mysterious structure and origin of our universe and where we are. Weber is an international program of NASA and its partners ESA (European Space Agency) and CSA (Space Canada).
To learn more about Webb, visit:
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View/download research results From the Diary Natural Astronomy.
Laura Betz -laura.e.betz@nasa.gov
NASA's Goddard Space Flight Center, Greenbelt, MD.
Christine Chicken -cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, MD.
Conor Nixon (NASA-GSFC), Heidi Hammel (Aura)
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