Rainstorms batter and alter Titan's surface

The surface of Saturn's largest moon Titan is altered by methane floods brought on by heavy rainstorms. A study suggests these storms occur more frequently than expected.

A Cassini image showing Titan, Saturn’s largest moon, behind the planet’s rings. The smaller moon Epimetheus can be seen in the foreground. Image Credit: NASA/JPL/Space Science Institute
Published: October 18, 2017 at 12:00 pm
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Rainstorms of methane flood the terrain of Saturn’s moon Titan more frequently than expected, and may alter its icy surface, according to a new study by scientists at the University of California, Los Angeles.


Titan is surprisingly Earth-like for a moon. It has flowing rivers, lakes and seas, and clouds in its atmosphere, all operating much like the water cycle on Earth.

Also like Earth, Titan has intense rainstorms that flood its terrain and carve out its surface.

However, on this icy Saturnian moon the liquid in question is hydrocarbons like methane and ethane.

The methane storms on Titan occur fewer than once a Titan year, which is 29.5 Earth years.

While this may seem very rare, it is more than expected.

“I would have thought these would be once-a-millennium events, if even that,” says Jonathan Mitchell, UCLA associate professor of planetary science and a senior author of the research.

“So this is quite a surprise.

Methane clouds drift across Titan’s summer skies in this Cassini image. The darker patches are hydrocarbon lakes.Credit: NASA/JPL-Caltech/Space Science Institute
Methane clouds drift across Titan’s summer skies in this Cassini image. The darker patches are hydrocarbon lakes.
Credit: NASA/JPL-Caltech/Space Science Institute

The most intense methane storms in our climate model dump at least a foot of rain a day, which comes close to what we saw in Houston from Hurricane Harvey this summer.”

Just like on Earth, these storms generate flows of sediment that spread into Titan’s lowlands and create cone-shaped features called alluvial fans.

These fans were detected by the Cassini spacecraft, which recently ended its mission at the Saturnian system.

Seulgi Moon, a co-senior author of the paper, says this is also likely to be the case on Mars, a body that also displays large alluvial fans.

On Titan, according to the study, the alluvial fans are mostly found between 50 and 80 degrees latitude, near the centres of the moon’s northern and southern hemispheres.

This suggests the moon has regional variations in precipitation.


In fact, the study suggests that storms on Titan develop due to the differences between the wetter, cooler weather in higher latitudes and dry, warm conditions in lower latitudes, also like on Earth.


Iain Todd, BBC Sky at Night Magazine
Iain ToddScience journalist

Iain Todd is BBC Sky at Night Magazine's Staff Writer. He fell in love with the night sky when he caught his first glimpse of Orion, aged 10.

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