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‘Wet Sidewalk Effect’ Solves Mystery of Rain on Saturn’s Moon Titan



Titan
Image: NASA / JPL / University of Arizona.

Scientists have found evidence of seasons on the moon's surface of Saturn Titan, thanks to observations similar to sunlight reflecting off the wet floor.

We already knew that Titan had experienced methane rainstorms on his south pole, making it the only astronomical object we know where it rains on the surface. The moon tilts on its axis, but when its position has changed and the clouds have refused to form above the north pole, scientists have wondered if and when they would have seen the evidence of the change of seasons. Cassini's long-standing rainstorm observations finally arrived on 7 June 2016, marking the beginning of the northern polar summer of Titan.

"Everyone was confused as to why it was not happening," Rajani Dhingra, a doctoral student in physics at the University of Idaho, told Gizmodo. "This tells us that not only has happened, but that it has been delayed."

Seasons should work the same way on Titan as they do on Earth, as both bodies lean over their axes of rotation. The hemisphere that looks at the Sun experiences "summer", while the hemisphere tilts away from the Sun experiences "winter". When the Cassini mission arrived at Saturn in 2004, the southern hemisphere of Titan was experiencing the summer, and the spacecraft recorded evidence of rainfall in the polar south of the moon.

There are about 14 years between the solstices of Titan, or the times when each pole receives more sunlight. (On Earth, of course, the solstices are only six months away.) So while the southern summer of Titan ended and began the northern summer, researchers expected to spot clouds and rain in the summer. northern hemisphere. But the rain would not come.

Scientists today report the results of an analysis of data from a Cassini spectrometer: a distinct luminous point covering a & # 39; area of ​​Pennsylvania, or 120,000 square kilometers, but only on certain days. The researchers hypothesized that they had identified the liquid that filled up in the cracks on the surface of the moon, causing it to reflect more sunlight. In other words, they saw a vast humid region on the surface, like a large strip of wet pavement, the result of rain.

It is important to note that there are other hypotheses about what may have caused the bright spot, such as fog, according to the document published in Geophysical Research Letters. The researchers found, based on their analysis, that the surface wetting from the presumed rain was the most likely explanation, however, that would make this the first rainfall observation on the north pole of Titan. This "wet effect on the sidewalk" could now serve as a new way to watch this rain.

And now that the researchers have actually identified evidence of rain, they hope to understand why it has been so delayed. "This is a great piece of the puzzle," Dhingra told Gizmodo. "This observation will help our understanding of what has happened". Perhaps it will help researchers understand the geology of Titan through the roughness of its surface.

This result is yet another example of important posthumous science of the Cassini mission, which ended September 2017 when the probe immersed in Saturn. But scientists hope that other sciences will soon arrive – Saturn is currently without a probe, but NASA funded a project that would send a quadcopter to the surface of Titan.

But working on the science of Titan was a dream come true for Dhingra. He said: "It certainly makes every day useful to go to work."


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