The NASA Cassini spacecraft recently discovered a massive cluster of ice, shaped like a cloud, at the south pole of Saturn's moon, Titan. Such a phenomenon has never before been observed.
This feature has already been seen decided to attribute to the part of the cloud system, known as the South Polar Vortex. Scientists suggest that winter in the southern hemisphere Titan will be even colder than originally predicted.
"At the beginning, the atmospheric signal was absolutely stable, and then BOOM began to grow sharply, thereby indicating the appearance of a completely new cloud," said scientist Carrie Anderson, who tracks Cassini's work from Goddard Space Flight Center in Greenbelt, Maryland. "I was so excited that I just fell out of my chair."
Anderson presented the Cassney spacecraft new results at a briefing held November 11 at the 47th annual meeting of the American Astronomical Society in Planetary Sciences in Oxen Hill, Maryland. She also discussed this at the morning conference that same day.
Ice Clouds
Titan is one of the most interesting for science Saturn satellites. It has a thick, atmosphere where nitrogen is most dominant. This is the only space object in our solar system, except the Earth, which has a stable liquid shell on its surface. But the so-called "sea" of Titan consists only of ethane and methane, but by no means of water. Many scientists consider this moon to be one of the most suitable for possible alien life outside the Earth, because there is some evidence that there may exist other organisms previously unknown to science.
Titan also boasts its own clouds in dense layers of the atmosphere. They are located completely at different levels: some lie close to the surface of the moon, and some are completely above the sky. In 2012, scientists found that the top of one of the "high" clouds of Titan is located at an altitude of about 300 km or 186 miles from the south pole of the moon in the stratosphere. This is the most stable part of the atmosphere outside the active "weather" layer.
"This is just the top of the vast stratospheric layer of the cloud system, which forms the most enormous" winter "cloud of the South Pole," said Anderson.
The second huge cloud, just recently formed, has already been found lying noticeably lower in the atmosphere. Scientists studied the composition of the cloud using a composite infrared spectrometer built into the Cassini comic, and conducted some laboratory experiments on Titan itself.
The team is absolutely convinced that it consists entirely of compounds of hydrogen, carbon and nitrogen. All elements periodically change their state, moving from liquid to gaseous and, conversely, depending on temperature. The composition of a similar cloud, discovered in 2012, changes quite often in the ratio of the number of elements, creating a completely new formation.
This image, taken in 2012, shows atmospheric changes in the south pole of Titan. Cassini's camera saw this impressive cloud floating at an altitude of about 186 miles (300 kilometers).
"Our cloud is new. It is completely different when compared with the previous one," said Anderson.
Freezing process
The newly formed cloud is located much lower (at an altitude of about 200 km or 124 miles from the surface). This is very unusual for such a massive object. There are guesses that the temperature under it on Titan is even lower than minus 150 degrees Celsius or 238 degrees Fahrenheit. Here there is a significant difference with the data from 2012.
On Earth, they are formed by the evaporation of water into the atmosphere. At sufficiently high temperatures, water vapor condenses into clouds. Ultimately, rainfall also returns to the surface through rain. Most of the hydrocarbon clouds of the moon Titan form in a similar way.
But a completely different story with its poles. There, the atmospheric circulation of the movement of gases occurs from the warm spring hemisphere (now from the northern hemisphere) to the colder - southern one. When the gases reach the key area, they descend, colliding with cold temperatures. Some of them can form rain, and some can freeze at different layers of the atmosphere. Cassini arrived at Saturn in 2004 in the middle of winter in the northern polar region. The mission of the spacecraft should end in September 2017, after which it will go back to Earth.
Ice clouds around the north pole disappear with the arrival of spring. At this time, new clouds are beginning to form only at the south pole. The general indicators show that the direction of the atmospheric circulation of the movement of Titan's gases is slowly changing.
The change in direction indicates that fresh organic vapors in the atmosphere come to the surface and begin to interact with the clouds. The increased number of these gases means that most of them get to the surface, being already cooled in their path. This cooling leads to the formation of new clouds. Thus, the cycle continues.
According to Anderson, a general decrease in temperature warns scientists that the southern winter on Titan will be one of the most severe.
