July 30, 2021

It rains on Saturn | Science

It rains on Saturn | Science

No one who reads these lines will witness what the probe saw Cassini before burning. Enceladus hiding behind the golden atmosphere of Saturn. The waves that Dafne – one of its more than 60 moons – leaves in the rings of the planet. The murky atmosphere in which the ship disintegrated on September 17, 2017 so as not to contaminate the icy satellites, where there may be life.

NASA's artifact spent its last hours sending information to Earth constantly. As a result of these transmissions, they are now published in Science six studies that explain, among other things, what is happening between the highest clouds of the gas giant and the interior of its rings, an area that had not been explored until now.

The data shows that this region is hit by rain that falls from the D ring -the closest to the planet- as a "downpour", in the words of Hunter Waite, principal author of one of the studies and leader of the INMS spectrometer that was on board of the ship. "If you were there you would hardly feel the impact of the small particles, but you could smell the gases," explains the physicist of the Southwest Research Institute (USA).

The rain on Saturn contains water – 95% of the rings are composed of ice – methane, ammonia, carbon monoxide, carbon dioxide and nitrogen, more or less than expected, but also – and this is a surprise – organic compounds, including butane and propane. "The organic compounds observed seem similar to those of comets, and it is postulated that these bodies brought these compounds to Earth at their origins," says Waite.

The researchers are surprised by the amount of material that falls on the saturnine atmosphere, about 10,000 kilos per second. But the impact of these "rains" is relative. "Saturn has 63 times the surface of the Earth. The material is spread over a surface so wide that if it had been raining throughout the history of the Solar System [unos 4.500 millones de años], the accumulation would be of hardly 2,5 millimeters ", explains Waite.

However, the rain of the D ring modifies the chemical composition of the upper layers of the planet's atmosphere and it is possible that over time also change the proportion of carbon and oxygen in the inner layers that are in contact with the surface. The spectacular ring system, which covers 300,000 kilometers but is only 10 meters thick, feeds back. The ring C discharges on the D and this on the planet, as shown by one of the studies.

Cassini He has delved into another rarity of Saturn: his magnetic field is something never seen. On Earth, the geographical and magnetic poles are 11 degrees apart, but on Saturn they are aligned with a difference of less than one hundredth of a degree. "Until now we thought there should be some misalignment [entre polos] for there to be a magnetic field, but its absence on Saturn seems to indicate that we have to rethink everything we knew about how some planets form magnetic fields, "explains Gregory Hunt, a researcher at Imperial College London and co-author of another work published today. . Studying the magnetic field of the planet is key, because it can reveal if Saturn hides a solid core in its interior, one of the biggest questions that remain to be answered.

The ship was launched in 1997 as part of a joint mission between NASA and the European Space Agency, which was responsible for the Huygens landing module. Since it made land on Titan, its data have confirmed the presence on this moon of an atmosphere, as well as lakes and rivers of methane that evaporates and forms clouds that then return to discharge on the surface.

Cassini It was the first ship that orbited Saturn. Since his arrival on the planet in 2004 he did incredible things, such as crossing the fumaroles of Enceladus geysers that sprout from an unknown ocean buried under the ice, one of the most propitious places for life in the Solar System. Shortly before disappearing, the mission also confirmed that in the equatorial areas of Titan, dust storms occur, such as those that occur in the deserts of Earth and Mars. With more than 13 years of data collected by Cassini, we will be analyzing and making discoveries for years, if not decades, "says Hunt.


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