The Cassini spacecraft that orbits Saturn and passes by its moons many times in the last decade has improved our knowledge about Titan, the enigmatic moon, and has also increased curiosity, so much so that there are proposals to send a balloon to Titan
atmosphere
Cassini's prolonged observations of Titan indicated the presence of aromatic hydrocarbons (PAHs POLYEYCIC) AROMATIC HYDROCARBONAT) in its upper atmosphere. These particles grow into larger clusters and eventually reach the ground like snowflakes and cause an increase in the amount of aerosols.
When sunlight or high-energy particles from Saturn's magnetosphere hit the upper layers of the atmosphere at an altitude of 1,000 km above the ground, the nitrogen and methane molecules break down. Due to this, positive ions and electrons are created in large quantities and these in turn create a chain of chemical reactions that create different types of hydrocarbons. These reactions ultimately result in the formation of carbon-based aerosols. Large clusters of atoms and molecules have been observed in lower layers in the haze that is less than 500 km above the ground (1). As for methane, a fundamental question is where does the current supply of methane come from due to the decomposition in the upper atmosphere. It is estimated that the source is geological in nature (2). An intriguing surprise in itself is the migration of pockets of organic molecules found high above the poles. The surprise was due to the fact that winds in an east-west direction at medium altitudes should fundamentally mix molecules formed there (3). In the lower part of the atmosphere, the plastic material Propylene was discovered, which is used to create plastic containers (a3).
ionosphere
The ionosphere is mainly made of organic compounds such as HCNH+ (PROTONATED HYDROGEN CYANIDE) and 5 H 2 C (ethyl group), although many molecules are found in abundance in tiny amounts. The main cause of the ionization of the atmosphere is the flux of ultraviolet radiation from the sun. Particles trapped in Saturn's magnetosphere play a small role on Titan's day side and have a larger effect on its night side. The highest density of the ionosphere is at an altitude of 1,000 - 1,300 km above the ground. The decrease in density is when the sun is high above the horizon line. The highest electron density was 3,000 particles per 1cm during the day and the lowest 1,000 particles per 1cm at night. A clear correlation was found between the extent of ionization in the ionosphere and the level of solar activity. The flux of ultraviolet radiation changes during the solar cycle and greatly affects the electron density in Titan's ionosphere. After 2010, the sun's activity increased rapidly, and data analysis during the spacecraft's passes near Titan between May 2012 and November 2012 showed an increase in electron density of 15% - 20% in the lower layers of the biosphere(4). As summer approached the Northern Hemisphere, the haze above the North Pole began to dissipate (5).
climate
As for Titan's climate, two models have been developed. According to one model - with the seasonal changes in the Northern Hemisphere, ripples will develop, cross the hydrocarbon oceans and hurricanes will begin to swirl around these days. According to the second model - warming in the northern hemisphere can also bring hurricanes known as tropical cyclones. On Earth, the tropical cyclones suck their energy from the evaporation of sea water, and small changes were indeed observed in Lake Huron (6). As the Northern Hemisphere receives more sunlight in early summer, cyclone-like hurricanes appear. In addition, with the transition to this season of the year, the northern lakes begin to glow with near-infrared radiation (7).
clouds
To the researchers' surprise, the observations indicated the presence of a methane ice cloud above the stratosphere. This cloud is denser than the previously identified ethane ice. They did not expect methane clouds at this height, a place that on the face of it seems impossible for the development of these clouds. What heightened the surprise was the fact that even a temperature of 203 degrees below zero in the Southern Hemisphere is not cold enough to allow methane to condense into ice in the lower stratosphere. The temperatures in the lower part of the atmosphere are not uniform along the vertical section of the stratosphere. The spacecraft's infrared and radio observations showed that the temperature near the North Pole is lower than that found in the Southern Hemisphere. It turned out that this difference of 12 degrees and more is enough to create methane ice. It seems that the process of creating these high clouds is different from the one that occurs in the atmosphere. The global circulation of the atmosphere is such that warm air in the summer in the summer hemisphere rises up into the stratosphere and slowly moves towards the pole where winter prevails. There the air sinks down as it cools and allows the formation of methane clouds. Similar to parallel processes on Earth and Mars. Methane clouds are found from latitude 65 north and above. It is estimated that these clouds develop at an altitude of 50-130 km. With the approach of winter in the southern hemisphere, the development of clouds of this type will be checked (8). These clouds were observed on July 20, 2014 and on July 22, 2014 over Lake Mare Ligeia. Measurements over the South Pole showed that the wind speed is between 14.2 and 16 km/h (9). In 2013, the formation of a new cloud over the South Pole was observed, although its composition is unknown. A similar haze of ice is also found at the North Pole. The season in it now is spring (10).
lakes and seas
The largest sea on Titan is the Kraken Mare, which is the size of the Caspian Sea and Lake Superior combined (11). Titan's second largest sea is Mare Ligeia with an area of 125,000 square kilometers (12). Titan's lakes have different shapes. There are some that are rounded and some that have steep slopes. These were probably formed by volcanic eruptions or the development of karst soil formed by the dissolution of soluble rock layers (13). During the observations, a way was found to measure the depth of the lakes with two radar measurements. In one measurement, the surface of the lake is checked and in the second test, its bottom is checked. The time difference between the two measurements makes it possible to calculate the depth of the lakes. It was found that the depth of Mare ligeia is 160 meters. Through laboratory experiments it is possible to learn about the composition of the lake (14). Observations made in 2013 showed that the surface is as smooth as a mirror, which indicates that winds did not blow at the place then.
During Cassini's observations, wind measurements showed that their speed was too small to create waves in lakes. Observations made for the first time this summer in the Northern Hemisphere showed that the wind speed is approaching the threshold necessary to create waves. Models built for this purpose have shown that a speed of two or three km/h makes this possible. When spring and summer come to the northern hemisphere, the speed is 3 km/h or more, depending on the composition of the lake and the speed of the winds. The height of the waves can reach 15 cm (6). It is estimated that the duration of the waves is very short (15).
topography
For the first time, the researchers produced a topographical map of Titan, albeit a partial one. Most likely, if the spacecraft had been put into orbit around it, the mapping would have been complete. The scope of the mapping is 50% of the surface like the Magellan spacecraft that circled Venus. It was found that the surface at the poles is flat and lower than the equatorial region (16).
dunes
The dunes in the equatorial region are made of plastic-like sand and the direction of their movement is west-east, the opposite of what they thought. The movement is slow, similar to the changes that occurred during the ice ages on Earth. On Earth, giant dunes change the direction of their movement for thousands of years. On the surface of Titan, the movement of the dunes in the equatorial region is slower due to the low speed of the winds (17). Following laboratory experiments that lasted two years in wind tunnels that simulated the surface conditions and atmosphere of Titan, it turned out that the wind speed is 50% greater than they thought. The conclusion reached by the researchers is that twice a year (a year of Titan - 30 years of the Earth) the wind changes the direction of its movement. This change occurs when the sun passes over the equator and causes the atmosphere and especially the wind to change its direction of movement. The duration of the change is short and the movement is west-east (18).
Sudden appearances of bumps
In one of the photographs of Mare Ligeia on July 10, 2013, a large body 9.6 km wide and 19.2 km long suddenly appeared and disappeared. It is not known what it is made of and it was named the magic island)). It could be the iceberg floating around, or material that has detached from the bottom (19). A similar phenomenon was observed between May 2013 and August 2013 in Kraken Mare (20).
plans for the future
Following the extraordinary success of the Cassini spacecraft, they are beginning to think about a follow-up spacecraft. The idea being discussed is to launch a balloon that will cruise through the atmosphere and explore Titan's surface and lakes or launch a lander. A drone will be attached to the balloon or lander that will descend to the ground, sample it and return to the balloon to recharge it (21). This is only an initial idea. It is not yet clear how long the balloon will stay in the atmosphere, what the power sources of the balloon or the lander will be and whether they will have a small laboratory that will test the soil samples and maybe they will be brought to Earth. In any case, this is a very complex challenge.
Comments
1. POLYEYCIC AROMATIC HYDROCARBONATE
http://www.thefreedictionary.com/Polycyclic+aromatic+hydrocarbons
2. PROTONATED HYDROGEN CYANIDE)
HCNH+ – Wikipedia, the free encyclopedia
3. ethyl group
http://en.wikipedia.org/wiki/Ethyl_group
Sources
1. "Cassini sees precursors to aerosol 'snow' on Titan" 6.6.2013
http://www.spacedaily.com/reports/Cassini_Sees_Precursors_To_Aerosol_Snow_On .Titan_999.html
2. "Ocean on Saturn moon could be as salty as the Dead Sea" 2.7.2014
http://saturn.jpl.nasa.gov/news/newsreleases/newsrelease 20142702
3. "Organic molecules in Titan's atmosphere intriguingly skewed" 24.10.2014
http://www.spacedaily.com/reports/Organic_Molecules_In _Titan’s_ Atmosphere intriguinty _Skewed__999.html
3a. "Cassini finds ingredient of household plastic in space" 7.10.2013
http://www.spacedaily.com/reports/Cassini_Finds_Ingredient_Of_household_ Plastic _In_Space__999.html
4. "The active Sun boosts Titan's outer atmosphere" 17.10.2013
http://www.spacedaily.com/reports/The_Active_Sun_Boosts_Titan’s_Outer_ Atmosphere__999.html
5. PIA17470: Titan's northern lakes : salt flats?
http;//photojournal.jpl.nasa.gov/catalog/PIA17470
6. "Wild weather could be ahead on Titan" 24.5.2013
http://www.spacedaily.com/reports/Wild_Weather_Could_Be_Ahead_On Titan__999.html
7. Stephan C. – “Cassini mission continues pulling back the veil on Titan” 5.3.2014
http://www.spaceflightnow.com/news/n1403/05titan/UxgiO00ULU
8. "NASA finds Methane ice cloud in Titan's stratosphere" 24.10.2014
http://saturn.jpl.nasa.gov/news/cassinifeatures/feathere20141024
9. PIA18420: Clouds over Ligeia Mare on Titan”
http;//photojournal.jpl.nasa.gov/catalog/PIA18420
10. "It's fall on Titan: Icy cloud Methane Saturn moon's season" 11.4.2013
http://www.space.com/20632-titan-ice-cloud-fall-photo.html
11. PIA17470 : Titan's northern lake : Salt flats?
http;//photojournal.jpl.nasa.gov/catalog/PIA1740
12. PIA17844: Titan Lake Country
http;//photojournal.jpl.nasa.gov/catalog/PIA17844
13. PIA17471: Dark lakes on bright landscape
http;//photojournal.jpl.nasa.gov/catalog/PIA17471
14. "Cassini nears 100th Titan fly by with a look back" 9.3.2014
http://www.spacedaily.com/reports/Cassini_Nears_100th_Titan_Fly_By_With_A _Look_Back__999.html
15. Stuart G. – “Waves' spotted on Titan's seas” 23.6.2014
http://www.abc.net.au/science/articles/2014/06/231/4030008.htm
16. "Cassini shapes first global map of Titan" 20.5.2013
http://www.spacedaily.com/reports/Cassini_Shaped_First_Gglobal_Map_Of_Titan__999.html
17. Blaine F. – "Plastic 'wrong way' dunes arise on Saturn moon Titan" 16.5.2014
http://phys.org/news/2014-05-plastic-wrong-way-dunes-arise-on-saturn-moon-html
18. "Tennesee research offers explanation for Titan dune puzzle" 0
http://www.spacedaily.com/reports/ University_Of_ Tennesee_Research_0ffers_Explanation_For_ Titan_ Dune_ puzzle__999.html
19. "Mystery object in lake on Saturn moon Titan intrigues scientist" 22.6.2014
http://theguardian.com/science/2014/jun/22/mystery-object-in-lake-on-Saturn- titan – intrigues -scientist-nasa
20. PIA19047: Bright feature appears in Titan's Kraken Mare
http;//photojournal.jpl.nasa.gov/catalog/PIA19047
21. "NASA considers sending quadrocopter drone to look for life on Titan" 23.6.2014
http://www.spacedaily.com/reports/NASA_Considers_Ssending_Qquadropter_ Drone _ To _ Look _ For_ Life _On _Titan__999.html
