Research activities on Titan
Global views of Titan with Cassini ISS and VIMS data. Left: In ISS true colors at visible wavelengths, TitanMiddle: ISS ultraviolet and near infrared color filters render a hazy perception of TitanRight: The Cassini VIMS mapping spectrometer allows to penetrate the atmosphere in a number of windows at infrared wavelengths. The white ellipse indicates the location of the Huygens landing site. Image Credit: NASA/JPL-Caltech/ASI, modified
Global views of Titan with Cassini ISS and VIMS data. Left: In ISS true colors at visible wavelengths, TitanMiddle: ISS ultraviolet and near infrared color filters render a hazy perception of TitanRight: The Cassini VIMS mapping spectrometer allows to penetrate the atmosphere in a number of windows at infrared wavelengths. The white ellipse indicates the location of the Huygens landing site.
Titan, Saturn’s largest moon, has been the subject of intensive research since the arrival of the Cassini-Huygens spacecraft at Saturn in 2004. Titan is especially interesting because it is the only satellite in the Solar System with a dense atmosphere. Despite its long distance to the Sun and, consequently the low temperature of the atmosphere and surface, Titan is a very interesting target for geological studies. It features the same geological processes found on airless moons. However, due to the presence of the atmosphere, additional processes play a role that we know from planets with an atmosphere, like Earth and Mars. For example, aeolian processes involve erosion, transport, and deposition of surface materials through the action of wind, while fluvial and lacustrine processes involve erosion, transport, and deposition by liquids present on the surface.
Cassini observes Titan with a RADAR, spectrometer (VIMS), and camera (ISS). The dense atmosphere is opaque at visible wavelengths, and VIMS and ISS can only see the surface through several spectral windows at near-infrared wavelengths. Data from the Huygens probe, which landed on Titan on January 14, 2005, also provided valuable insight in the processes that shape Titan’s surface.
Titan’s dense atmosphere harbors a volatile cycle that is responsible for phenomena like the formation of clouds, rainfall, and the incision of valleys. The water cycle on our home planet is the only other volatile cycle known in the Solar System. The cycle on Titan is based on liquid methane, which not only shapes the surface but also stimulates a debate about the habitability of Titan. Besides methane, a wide variety of other organic molecules e.g. hydrocarbons are present in the atmosphere.
Titan is regarded as an analogue to the early Earth. Many of the conditions for the emergence of life are apparently fulfilled, when we apply our 'terrestrial standards'. The surface of Titan also shows many other similarities to our home planet, and offers an excellent opportunity for studying extraterrestrial geology. Valley networks of rivers and lakes are a major landform on Titan. In addition to rivers, the Cassini RADAR revealed dunes, mountains, canyons, and karst landscapes. A small number of impact craters has been identified, which implies that the surface is relatively young.
A major topic of interest for our research group is the formation of Titan’s valley networks and the action of liquids on the surface, with several projects carried out in the frame of the Helmholtz Alliance “Planetary Evolution and Life”. Valleys are formed by precipitation and runoff of carbohydrate rain, most likely methane. We identified different morphological types of valleys, including dendritic valley systems and dry valleys reminiscent of terrestrial desert washes created by episodic precipitation. By comparing the valley morphology as seen by Cassini RADAR and VIMS with terrestrial fluvial channels we find high erosional rates and discharges which are comparable with those on earth.
Cassini ISS, VIMS, and RADAR found evidence for lakes, especially near the poles. Many lakes appear dark to the RADAR, which implies that they are physically smooth. This strongly suggests that we are looking at a liquid surface. We were finally able to unequivocally confirm the presence of liquids when we detected specular reflection a VIMS image taken on July 8, 2009, of the polar lake Kraken Mare. Not all lake basins contain liquids. Huygens, for example, landed in a dry lake bed.
Dendritic valley systems seen with Cassini RADAR data. The valley systems formed by precipitation and runoff of methane rainfall. Image Credit: NASA/JPL-Caltech/ASI, modified
For further information see also:
NASA – Saturn http://saturn.jpl.nasa.gov/CICLOPS http://ciclops.org/