An image from the international spacecraft, Cassini, proves the presence of rainfall at Titan's northern pole, the largest of Saturn's satellites. Precipitation will be the first indication of the beginning of the summer season in the northern hemisphere of the Moon.
"The entire Titan community was eager to see clouds and rains on Titan's North Pole, which shows the beginning of the northern summer, but despite the climate models they predicted, we did not even see any clouds," said Rajani Dingra, a PhD student Physics at the University of Idaho in Moscow and lead author of the new study, accepted for publication in Geophysical studies, a journal of the American Geophysical Union. "People call it a curious case with missing clouds.
Dhingra and her colleagues identified a reflection function near the Titan northern pole of the image taken on June 7, 2016 by Cassini's near-infrared instrument, the infrared spectrometer and the infrared spectrometer. The reflecting feature covers approximately 46,332 square miles, approximately half the size of the Great Lakes, and does not appear on Cassini's previous and subsequent passages.
Short-term reflectivity analysis suggests that this is probably due to the reflection of sunlight on a wet surface. The study attributes the impact of methane rainfall followed by the likely evaporation period.
"It's like watching a sunny wet sidewalk," Dingra said.
This reflective surface represents the first observations of the summer rainfall of the Moon's northern hemisphere. If compared to the annual four-season Earth cycle, Titan's season lasts seven Earth years. Cassini arrived in Titan during the southern summer and watched clouds and precipitation in the southern hemisphere. Titan's climate models predicted that such a time would occur in the northern hemisphere in the years leading to the Northern Summer Solstice in 2017. But by 2016 the expected cloud cover in the northern hemisphere did not appear. This observation can help scientists gain a better understanding of the Titan seasons.
"We want our predictions on the model to coincide with our observations," said Dingra, "that precipitation detection proves that Cassini's climate follows the theoretical climate models we know about. – Summer is happening. It's funny but it's happening. But we will have to understand what caused the delay.
Additional analyzes show that methane rain has reached a relatively peg-like surface. The coarser surface generates an amorphous pattern as the liquid precipitates in crevices and gullies, while the liquid falling on a smooth surface would merge into a relatively circular pattern.
Dhingra uses the wet pavement effect to look for additional rainy Titan events as part of her research.
Source of History:
Materials provided by American Geophysical Union, Note: Content can be edited for style and length.