Dust storms on Titan spotted for the first time

September 25, 2018, NASA
Artist's concept of a dust storm on Titan. Credit: IPGP/Labex UnivEarthS/University Paris Diderot - C. Epitalon & S. Rodriguez

Data from NASA's Cassini spacecraft has revealed what appear to be giant dust storms in equatorial regions of Saturn's moon Titan. The discovery, described in a paper published on Sept. 24 in Nature Geoscience, makes Titan the third Solar System body, in addition to Earth and Mars, where dust storms have been observed.

The observation is helping scientists to better understand the fascinating and dynamic environment of Saturn's largest moon.

"Titan is a very active moon," said Sebastien Rodriguez, an astronomer at the Université Paris Diderot, France, and the paper's lead author. "We already know that about its geology and exotic hydrocarbon cycle. Now we can add another analogy with Earth and Mars: the active cycle, in which organic dust can be raised from large dune fields around Titan's equator."

Titan is an intriguing world—in ways quite similar to Earth. In fact, it is the only moon in the Solar System with a substantial atmosphere and the only celestial body other than our planet where stable bodies of surface liquid are known to still exist.

There is one big difference, though: On Earth such rivers, lakes and seas are filled with water, while on Titan it is primarily methane and ethane that flows through these liquid reservoirs. In this unique cycle, the hydrocarbon molecules evaporate, condense into and rain back onto the ground.

This animation, based on images captured by the Visual and Infrared Mapping Spectrometer (VIMS) on NASA's Cassini mission during several Titan flybys in 2009 and 2010, shows clear bright spots that have been interpreted as evidence of dust storms. Credit: NASA/JPL-Caltech/University of Arizona/University Paris Diderot/IPGP/S. Rodriguez et al. 2018

The weather on Titan varies from season to season as well, just as it does on Earth. In particular, around the equinox—the time when the Sun crosses Titan's equator—massive clouds can form in tropical regions and cause powerful methane storms. Cassini observed such storms during several of its Titan flybys.

When Rodriguez and his team first spotted three unusual equatorial brightenings in infrared images taken by Cassini around the moon's 2009 northern equinox, they thought they might be the same kind of methane clouds; however, an investigation revealed they were something completely different.

"From what we know about cloud formation on Titan, we can say that such methane clouds in this area and in this time of the year are not physically possible," said Rodriguez. "The convective methane clouds that can develop in this area and during this period of time would contain huge droplets and must be at a very high altitude—much higher than the 6 miles (10 kilometers) that modeling tells us the new features are located."

The researchers were also able to rule out that the features were actually on the surface of Titan in the form of frozen methane rain or icy lavas. Such surface spots would have a different chemical signature and would remain visible for much longer than the bright features in this study, which were visible for only 11 hours to five weeks.

In addition, modeling showed that the features must be atmospheric but still close to the surface—most likely forming a very thin layer of tiny solid organic particles. Since they were located right over the dune fields around Titan's equator, the only remaining explanation was that the spots were actually clouds of dust raised from the dunes.

This compilation of images from nine Cassini flybys of Titan in 2009 and 2010 captures three instances when clear bright spots suddenly appeared in images taken by the spacecraft's Visual and Infrared Mapping Spectrometer. Credit: NASA/JPL-Caltech/University of Arizona/University Paris Diderot/IPGP/S. Rodriguez et al. 2018

Organic dust is formed when organic molecules, formed from the interaction of sunlight with , grow large enough to fall to the surface. Rodriguez said that while this is the first-ever observation of a dust on Titan, the finding is not surprising.

"We believe that the Huygens Probe, which landed on the surface of Titan in January 2005, raised a small amount of organic dust upon arrival due to its powerful aerodynamic wake," said Rodriguez. "But what we spotted here with Cassini is at a much larger scale. The near-surface wind speeds required to raise such an amount of dust as we see in these would have to be very strong—about five times as strong as the average wind speeds estimated by the Huygens measurements near the and with climate models."

The existence of such strong winds generating massive dust storms implies that the underlying sand can be set in motion, too, and that the giant dunes covering Titan's equatorial regions are still active and continually changing.

The winds could be transporting the dust raised from the dunes across large distances, contributing to the global cycle of organic dust on Titan and causing similar effects to those that can be observed on Earth and Mars.

Explore further: Cassini's final view of Titan's northern lakes and seas

More information: S. Rodriguez et al. Observational evidence for active dust storms on Titan at equinox, Nature Geoscience (2018). DOI: 10.1038/s41561-018-0233-2

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9 comments

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rossim22
2 / 5 (2) Sep 25, 2018
I think this observation is very peculiar.

Unusual equatorial brightenings in infrared... features are atmospheric but close to the surface... and are occurring above dune fields...

https://doi.org/1...3.05.011
https://doi.org/1...6.12.018
wduckss
1 / 5 (3) Sep 25, 2018
Nothing weird.
The Titan Moon has the same or similar temperature (-179.5 ° C) as the Earth's Sahara (average annual temperature is + 31ºC) or the desert at Mars (max. 308 ° K (+ 35 ° C).

Liquid state of matter for nitrogen ranges from -210°C to -195,795°C.
CH4; Melting point -182.5 ° C, Boiling point -161.50 ° C. (H2O, 0°C, 100°C).

Is there dust on the Titan Moon or in the author's head?
dsylvan
5 / 5 (1) Sep 25, 2018
Is there dust on the Titan Moon or in the author's head?


What, in your mind, qualifies as dust?
blazmotronic
1.8 / 5 (5) Sep 25, 2018
Is the observation right or the narrative right? A 4 billion year old
solar system with a small active moon...or a extremely young solar
system with a small active moon? Screw the observation if it
upsets the narrative!
wduckss
1 / 5 (2) Sep 26, 2018
"Organic dust is formed when organic molecules, formed from the interaction of sunlight with methane, grow large enough to fall to the surface." from article

Metane CH4, Melting point −182.5 °C; Boiling point −161.50 °C; Titan Moon temperature -179,5°C.
If there is another kind of dust, it should be written in the article (that we a little laugh).

dsylvan
2.5 / 5 (4) Sep 26, 2018
Metane CH4, Melting point −182.5 °C; Boiling point −161.50 °C; Titan Moon temperature -179,5°C.
If there is another kind of dust, it should be written in the article (that we a little laugh).


Better. Thank you. But I will repeat the question. This time without commas so you might get the joke.
What in your mind qualifies as dust?

Answer: All the little ideas you use to define things all by yourself.
wduckss
1 / 5 (1) Sep 26, 2018
You have Internet, check it out. It will not be difficult for you.
The problem is for you., this is the Titan Moon.
There is no evidence of chemical composition.
Still the authors (and you are loudly applauding) claim that within the value, when CH4 is a liquid, there is dust.
I'm, in a commentary, quoted article ("Organic dust is formed when organic molecules, formed from the interaction of sunlight with methane, grow sufficiently enough to fall to the surface.").
You certainly want to add some of your irrefutable evidence?
Feel free to show yours. scientific thinking. What is the dust on Titan Moon (from which it is composed) for you and the authors?
torbjorn_b_g_larsson
3 / 5 (4) Oct 01, 2018
Is the observation right ... ? A 4 billion year old
solar system with a small active moon ...


Yes, read the paper. And the system is closer to 5 billion (4.56 billion years old), we know that from precision dating of meteorites.

There is no evidence of chemical composition.


Both the lander Hyugens and the long lived orbiter Cassini observed a lot on Titan's chemistry, as well as what can be complemented by telescope data et cetera.


wduckss
not rated yet Oct 01, 2018
NASA does not mention the chemical structure.
https://solarsyst...verview/

Wikipedia claims that it is on Titan Moon Water.
"The Huygens probe landed just off the easternmost tip of a bright region now called Adiri. The probe photographed pale hills with dark "rivers" running down to a dark plain. Current understanding is that the hills (also referred to as highlands) are composed mainly of water ice." https://en.wikipe...3Huygens

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