There is now tantalizing proof of rainfall and of changing seasons on Titan — Saturn’s largest moon — after the Cassini spacecraft provided scientists with a fresh new image of methane rain falling down over the north pole of the moon.
As Phys.org have reported, the image of rainfall on Titan would signify the beginning of the summer season along the northern hemisphere, which is something that lead author Rajani Dhingra, from the University of Idaho in Moscow, was elated to see — especially after scientists had failed to even spot clouds there in the past.
“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.”
The image that was taken, one which shows rainfall on Titan, was originally captured on June 7, 2016 — and was grabbed by the Cassini’s special Visual and Infrared Mapping Spectrometer. Scientists noted that there was an area on Saturn’s moon, in this particular image, that was particularly vivid and reflective. This reflective area covered an enormous span, and stretched for 46,332 square miles.
This large-scale reflection had never shown up on previous images of Titan, and scientists quickly deduced that it was actually an image of sunlight bouncing off of a shiny and wet surface of the moon. As Dhingra stated, “It’s like looking at a sunlit wet sidewalk.”
— Phys.org (@physorg_com) January 16, 2019
The reflective surface that was captured by Cassini is the first time that rainfall in the northern hemisphere during the summer has ever been directly observed on Titan. This is a big deal, as unlike on Earth — where there are four seasons each year — on Titan a single season continues for a full seven years, at least by Earth standards.
When the Cassini spacecraft first began observing Titan, it did so while it was summer along the southern hemisphere of the moon. The craft did spot both clouds and rain there. Yet, this was not the case for the northern hemisphere — at least initially — even though scientists had speculated that the summer season should be showing itself well ahead of the 2017 northern summer solstice.
However, as it turns out, Cassini did capture an image of rainfall during this summer season along the northern hemisphere. The season appears to have been delayed, however, as Dhingra noted.
“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.”
The new study, one which found evidence through the Cassini spacecraft of rainfall and changing seasons on Titan, Saturn’s largest moon, has been published in Geophysical Research Letters.