NASA’s Cassini spacecraft spotted fresh rainfall on Saturn’s moon Titan

This rainfall detection proves Cassini's climate follows the theoretical climate models we know of.

New research provides evidence of rainfall on the north pole of Titan, the largest of Saturn’s moons, shown here. The rainfall would be the first indication of the start of a summer season in the moon’s northern hemisphere, according to the researchers. Credit: NASA/JPL/University of Arizona.
New research provides evidence of rainfall on the north pole of Titan, the largest of Saturn’s moons, shown here. The rainfall would be the first indication of the start of a summer season in the moon’s northern hemisphere, according to the researchers. Credit: NASA/JPL/University of Arizona.

The international Cassini spacecraft has captured an image that shows the rainfall on the north pole of Titan, the largest of Saturn’s moons. Scientists noted that the rainfall must be the first sign of summer beginning in the moon’s northern hemisphere.

Rajani Dhingra, a doctoral student in physics at the University of Idaho in Moscow said, “The whole Titan community has been looking forward to seeing clouds and rains on Titan’s north pole, indicating the start of the northern summer, but despite what the climate models had predicted, we weren’t even seeing any clouds. People called it the curious case of missing clouds.”

Scientists identified a reflective feature near Titan’s north pole on an image taken June 7, 2016, by Cassini’s near-infrared instrument, the Visual and Infrared Mapping Spectrometer.

The reflective feature secured around 46,332 square miles, generally a large portion of the extent of the Great Lakes, and did not show up on pictures from past and consequent Cassini passes.

Examinations of the short-term reflective feature proposed it likely came about because of sunlight reflecting off a wet surface. The examination ascribes the reflection to a methane rainfall event, trailed by a plausible time of evaporation.

This reflective surface represents the first observations of summer rainfall on the moon’s northern hemisphere. If compared to Earth’s yearly cycle of four seasons, a season on Titan lasts seven Earth years. Cassini arrived at Titan during the southern summer and observed clouds and rainfall in the southern hemisphere.

Climate models of Titan predicted similar weather would occur in the northern hemisphere in the years leading up to the northern summer solstice in 2017. But, by 2016, the expected cloud cover in the northern hemisphere had not appeared. This observation may help scientists gain a more complete understanding of Titan’s seasons.

Dhingra said, “We want our model predictions to match our observations. This rainfall detection proves Cassini’s climate follows the theoretical climate models we know of. Summer is happening. It was delayed, but it’s happening. We will have to figure out what caused the delay, though.”

Dhingra said, “Additional examinations propose the methane rain fell over a relatively pebble-like surface. A rougher surface produces an amorphous example as the fluid settles in precipices and crevasses, while fluid falling on a smooth surface would puddle in a moderately circular pattern.

Dhingra is utilizing the wet sidewalk effect to look for extra rain vents on Titan as a feature of her research.

The study is published in Geophysical Research Letters.