Spitzer data helped solve the mystery of silicate clouds

Terrestrial clouds, as a rule, consist of water. However, outside of our planet, they may have a completely different structure. For example, some Martian clouds consist of dry ice, while the clouds in the upper atmosphere of Jupiter are composed of ammonia and ammonium hydrosulfide. And in the worlds beyond our Solar System, there are even more exotic variations. One of them is silicate (sand) clouds — clouds consisting of small silicate grains.

Martian clouds. Source: NASA/JPL-Caltech/

Until recently, the mechanism of formation of such structures remained a mystery to scientists. But the results of a new study published in the journal Monthly Notices of the Royal Astronomical Society helped determine the range of conditions under which exoplanets can acquire silicate clouds. 

To solve the mystery of silicate clouds, astronomers turned to the archive of the infrared telescope Spitzer. In the early years of the mission, when three cryogenically cooled instruments were working on board the spacecraft, it studied the atmospheres of a number of brown dwarfs and revealed traces indicating the possible presence of silicate clouds in them.

Since the atmospheres of brown dwarfs are almost indistinguishable from the atmospheres of gas giants, the team of researchers reanalyzed the Spitzer data. They grouped the brown dwarfs, in whose atmospheres traces of silicate clouds were found, by temperature. It turned out that they all lie in the range from 1000 °C to 1700 °C, which exactly corresponds to the predicted range at which the existence of silicate clouds is possible. At temperatures above up to 1700 °C, silicates will remain in the form of steam, at temperatures below up to 1000 °C, they will fall out in the form of stone rain.

The relationship between the temperature of a brown dwarf and the presence of silicate clouds. Source: NASA/JPL-Caltech

According to researchers, silicate clouds may exist in our Solar system — in the bowels of Jupiter. Due to atmospheric pressure, the temperature there is much higher than at the top. Silicate clouds on Jupiter cannot rise higher, because at lower temperatures they will condense and fall down.

According to https://www.jpl.nasa.gov

Follow us on Twitter to get the most interesting space news in time