Organic matter storms discovered on satellite of Saturn Titan

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UNITED STATES (VOP TODAY NEWS) – Astronomers saw in the photographs of Titan clouds of organic dust raised by the wind. The discovery makes Titan the third body in the solar system after Earth and Mars, where dust storms are observed. Details are set out in a scientific article published in the journal Nature Geoscience by a team led by Sebastien Rodriguez of the Paris Institute of Physics of the Earth.

The images were taken by the Cassini probe, the glorious history of which Vesti.Nauka (nauka.vesti.ru) was described in detail . The device burned down about a year ago in the atmosphere of Saturn , but astronomers continue to process the data transmitted to them to Earth.

“Titan is a very active moon,” explains Rodriguez. “We already know this from its geology and exotic carbon cycle. Now we can add another analogy to Earth and Mars: an active dust cycle in which organic dust can be picked up from large dunes fields at the equator of Titan.”

Recall that Titan is the only satellite in the Solar System with a dense atmosphere and the only body other than the Earth, on whose surface there is a stable liquid. True, these lakes and rivers are not filled with water, but hydrocarbons, mainly methane and ethane. The fact is that on Titan is very cold.

In the upper layers of the atmosphere, under the action of the solar ultraviolet, a more complex organics is formed. She creates the famous orange haze. Some of the formed substances in solid form fall to the surface of the satellite. They form the equatorial dunes. The existence of dunes has long been known, but dust storms have never been observed.

Strange structures in the atmosphere were seen in infrared images of 2009 and 2010. First astronomers took them for methane storms, when a strong wind carries huge clouds of methane. This phenomenon is usually for the equator of Titan in the equinox (we recall that on this moon there are seasons). However, further research disproved this hypothesis.

“From what we know about the formation of clouds on Titan, we can conclude that such methane clouds in this area and at this time of year are physically impossible,” says Rodriguez.

The fact is that, according to the devices, the mysterious structures consisted of solid particles the size of several micrometers. At the same time, clouds of methane storms consist of much larger drops of liquid. In addition, the simulation showed that dust accumulations were at a height of no more than ten kilometers, and methane clouds would be much higher.

The researchers also excluded the version that they observe formations on the surface of the satellite, for example, frozen “moisture” of methane rains or cryovolcano lava . First, such objects would have completely different chemical composition, which was shown by observations. Secondly, the lifetime of the observed objects ranged from 11 hours to five weeks. Stable structures on the surface would remain visible for much longer.

The only plausible explanation was a dust storm. Moreover, strange clouds were observed right above the equatorial dunes of Titan in the season of strong winds. It was logical to assume that dust was raised from these dunes. By the way, dust in the atmosphere of Titan itself is not new to researchers.

“We believe that the Huygens probe , which landed on the surface of Titan in January 2005, raised a small amount of organic dust on arrival because of its powerful aerodynamic trail,” Rodriguez says.

However, scientists were impressed by the scale of what is happening.

“The near-surface wind speed needed to raise as much dust as we see in these dust storms should be very high. It is about five times higher than the average wind speed estimated from Huygens measurements near the surface and climate models”, – the scientist shares the details.

Such strong winds should not only raise the dust, but also move the organic sand of the dunes. This means that the dunes of Titan are “living”, they are constantly changing. In addition, there must be a global circulation of dust throughout the celestial body, both on Earth and on Mars.