Between the years 2004-2007, 49 craters were identified on the surface of Titan. In this period of time, 22% of its surface was surveyed and it turned out that the Xando area has more craters than the other surveyed areas
Makhteshim
Between the years 2004-2007, 49 craters were identified on the surface of Titan. In this period of time, 22% of its surface was surveyed and it became clear that the Xandu area has more craters than the other surveyed areas (1). Shown here are several craters that are not found in Xandu.
1. A crater with a diameter of 100 km and its location W 2130 - S 0 76.5. Several possibilities for its formation have been put forward. According to one hypothesis, this is a caldera that was created after cryovolcanic eruptions. According to a second hypothesis, the crater was created by an asteroid or comet impact and at a later date was partially filled by sedimentary material. According to a third hypothesis, the crater was created following the collapse of the ground associated with the presence of methane underground (2).
2. A crater with a diameter of 40 km located W 0 45 - N 0 12 and around it material that was thrown out of it. Dunes are visible at the foot of one of its sides (3).
3. A relatively young crater called Sinlap and a weathered crater called Soi. The diameter of the two craters is 80 km each (4).
Compared to the other moons of Saturn which are covered with thousands of craters, their number on Titan is very small. There are several explanations for this. According to one explanation, the great density of the atmosphere causes small crater-forming bodies to burn up during their penetration into the atmosphere. According to the second explanation, those bodies that do reach the ground create craters, but these craters undergo erosive processes throughout geological periods and are filled with sand carried by the wind and creovolcanism (3).
Cryovolcanism
In a comparison between 3 photographs viewed in the same area west of Xandu in October 2005, January 2006 and March 2006, changes in the brightness of the ground were noted. According to the researchers' assessment, the reason for this is cryovolcanism - volcanoes that emit water ice, ammonia and methane. Supporting evidence for this is probably the presence of haze in several places where there was probably an eruption of cryovolcanism. during the observations. The emission of methane during the eruptions can explain the continuous supply of this gas to the atmosphere (5). Two radar images at Arcus Hotei identified flow formations. The edges of these formations in the radar images are dark and the top is bright. The thickness of these formations is 100-200 meters. On Earth such a thickness could imply a viscosity like that of basalt (6).
As for ammonia in Regio Hotei, infrared photographs raise the possibility of a temporary presence of ammonia frost that disappears after it reaches the surface or is covered by another material. According to several models, within Titan itself ammonia can exist for a long time, which indicates that the process of its delivery to the surface is continuous. Radar images show structures that resemble terrestrial volcanoes. Near places where ammonia is visible deposited (7). Another place where cryovolcanism has been detected is Sotra Facula (8).
dunes
Unlike on Earth, the origin of the dunes on Titan is carbonate particles that come from the clouds in the form of rain that falls continuously and are limited to the tropical regions between latitudes S0 30 - N 0 30. Most of the dunes are linear but their dimensions (length, width, the space between them and the thickness of the sand in these spaces that covers the ground) vary from place to place. The width of the dunes is usually 1-2 km, their height is 100 meters and the distance between them is 1-4. km and are shaped by zonal winds - winds that move along the east-west oriented latitudes. From testing the reflection of the radar waves from the dunes, it became clear that in most of Titan's territory, excluding the lakes at the poles, the dune fields are more emissive than reflective of these waves. As you move towards the poles, the trend reverses. The dunes emit less radio waves and become brighter at radar wavelengths. It is estimated that the increase in brightness in the radar images is caused by a large part of the interval between the dunes.
It is estimated that the increase in brightness is due to the increase in the radar signal in the intervals between the dunes. As you move towards the north, the dunes become thinner and/or wider than one another. According to the information gathered, they came to the conclusion that the amount of sand transported by the wind is small towards the north. This may have something to do with the increase in the amount of moisture in latitudes, probably due to the asymmetric change of the seasons. This is a characterization that originates from the geometry of Titan's orbit around Saturn. The eccentricity of the orbit means that today the southern hemisphere is warmer and the summer season is shorter than in the northern hemisphere. The fact that the northern hemisphere is less warm means that the amount of evaporation in it will be smaller in relation to the amount of precipitation (precipitation), which results in an increase in the amount of moisture in the soil. This probably has something to do with most of the lakes in the high latitudes of the Northern Hemisphere. This large amount of sediment means that the sand grains are more sticky and close to each other and the dunes lose a lot of material.
As for the dunes themselves, the conclusion reached by the researchers is that their morphology depends on the height at which they are located. It turned out that the main dune fields (Belet, Aztlan, Shangri La, Fensal) tend to cover large areas in low areas on the equator at heights between 0-400 meters. They are not found in higher places. On Earth, dunes are usually found in topographical basins, places where the air penetrates, disperses, slows down its speed and causes sediments to be deposited. Therefore, one gets the impression that similar aerodynamic conditions exist on Titan and influence the location of the dunes and their development. Seasonal currents probably also contribute to the movement of sedimentary materials into the basins and in the process lose moisture and dry out. The exception in this respect is Lake Xandu which does not receive sediments at all or these were taken out of it by the wind. In addition, dunes are not found in the lowest places of Titan. In these places the soil is moist due to interaction with a potential reservoir of underground liquid hydrocarbonates. As you go higher in the area where the dunes exist, they become thinner and/or the space between them increases. Most likely the sand becomes thinner in the spaces between the dunes. This discovery is consistent with the assessment that the sources of the sediments are found in low places, places where the supply of sand is smaller than in the heights. What can contribute to this is an increase in the investment rate of sediments. Caused by winds, rivers and rain in high places.
Although the wind speed is low, 7.2-1.8 km/h, it can transport light grains of sand. Most probably the massive dunes were formed under other climatic conditions. On Earth, major climatic changes were caused by changes in the geometry of the orbit around the sun. Many of the linear dunes on Earth were formed at the height of the last ice age 20,000 years ago due to changes in the geometry of the Earth's orbit around the Sun. Similarly, Titan's orbital cycle should reverse over 42,000 years as northern hemisphere summers become longer. Another possibility is that the dunes will be placed and represent dunes that we have grown fond of. in a completely different climate. In radar images, the dunes appear to cross other geological formations which means they are among the youngest geological formations on Titan (9).
Sources
1. Anuradha Herath K – “Counting the craters of Titan” 23.4.2010
http://www.spacedaily.com/reports/Counting_The_Craters_On_Titan_999.html
2. PIA12111: South polar basin on titan
http://photojournal.jpl.nasa.gov/catalog/PIA12111
3. PIA14744: A new crater for Titan
http://photojournal.jpl.nasa.gov/catalog/PIA14744
4. PIA16638: Titan craters, the old and the new
http://photojournal.jpl.nasa.gov/catalog/PIA16638:
5. PIA11700: Titan's chilly volcanoes?
http://photojournal.jpl.nasa.gov/catalog/PIA11700
6. PIA11831: Hotei
http://photojournal.jpl.nasa.gov/catalog/PIA11831
7. "Titan twisted in frigid imitation of Earth" 13.8.2009
http://www.saturndaily.com/reports/Titan_Twisted_In_Firigid_Imitation_Of_Earth_999.html
8. PIA13695: Flyover of Sotra Facula, Titan
http://photojournal.jpl.nasa.gov/catalog/PIA13695
9. "Cassini radar observed Titan's tropical dune fields" 26.1.2012
http://www.spacedaily.com/reports/Cassini_Radar_Observed_Titan’s_ Tropical_ Dune _Fields_999.html
