La strada che porta allo spazio passa per il nostro bel Paese.

ASI - Agenzia Spaziale Italiana - News ASI - Agenzia Spaziale Italiana - News
FROM CASSINI'S DATA

Titan, rainfalls at the north pole

An image from the Cassini spacecraft provides evidence of rainfall on the north pole of Titan, the largest of Saturn's moons. New study on Geophysical Research Letters finds evidence of changing seasons on Titan

An image from the Nasa-Esa-Asi Cassini spacecraft provides evidence of rainfall on the north pole of Titan, the largest of Saturn's moons. The rainfall would be the first indication of the start of a summer season in the moon's northern hemisphere. 

"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," said Rajani Dhingra, a doctoral student in physics at the University of Idaho in Moscow, and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. 

Dhingra and her colleagues 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, developed by the Italian Space Agency within the agreement with Nasa for this mission. Analyses of the short-term reflective feature suggested it likely resulted from sunlight reflecting off a wet surface. The study attributes the reflection to a methane rainfall event, followed by a probable period 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. 

Additional analyses suggest the methane rain fell across a relatively pebble-like surface, Dhingra said. A rougher surface generates an amorphous pattern as the liquid settles in crevasses and gullies, while liquid falling on a smooth surface would puddle in a relatively circular pattern.