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University of KansasTitan Studies |
Image courtesy of NASA/JPL-Caltech.
Titan Studies at the University of Kansas
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Titan is the largest satellite of Saturn with an orbital distance from
that
planet of 20 Saturn radii (RS), at which distance it will usually
find itself within Saturn's outer magnetosphere, where it will interact with
the magnetospheric plasma. Titan is, after Jupiter's satellite Ganymede, the
second largest satellite in our solar system. Titan possesses an extensive
neutral atmosphere consisting mainly of molecular nitrogen and methane. Titan
also has an ionosphere due to the photoionization of the neutrals by solar
extreme ultraviolet photons or due to ionization by energetic electrons
associated with Saturn's magnetosphere. Complex photochemistry takes place in
the upper atmosphere and ionosphere due to the presence of methane in the
atmosphere and the existence of energy inputs such as solar ultraviolet
radiation and energetic external plasma.
The current view is that Titan does not have a significant intrinsic
magnetic field; hence, the external plasma impinges directly on Titan's upper
atmosphere and ionosphere. The atmosphere and ionosphere of Titan act together
to create an obstacle to the flow of Saturn's magnetospheric plasma that is
incident on that satellite. Usually, Titan is located inside Saturn's
magnetosphere and the external plasma is the magnetospheric plasma; but
occasionally solar wind conditions will be such that Titan will be outside the
magnetopause and Titan will interact with the solar wind.
Most of our early knowledge about Titan and its magnetospheric interaction derived from data gathered
by the Voyager 1 spacecraft when it encountered Titan on November 12, 1980.
Titan was located within the Saturnian magnetosphere on this occasion. Voyager
approached to within a radial distance of 6900 km from Titan, and downstream
of the satellite with respect to the motion of the magnetospheric plasma.
On July 1, 2004 the Cassini Orbiter successfully entered orbit around Saturn, passing within about
30,000 km of its
surface and passing through the ring plane outside the main rings. During this "Saturn Orbit Insertion" (SOI) event
many instruments measured the properties of the rings of Saturn. The Orbiter first encountered Titan on October 26,
2004, when it approached within 1200 km of the surface. The Huygens probe separated from the Orbiter in December 2004
and parachuted to the surface in January 2005, and while doing so taking measurements and sending images back to
Earth (via a link through the Orbiter). The Orbiter, which has an extensive set of field and particle instruments, has
since encountered Titan several more times. The Space Physics group at KU is participating in this mission with a team
member on the Ion and Neutral Mass Spectrometer (INMS) and a co-investigator on the Magnetosphere Imaging Instrument
(MIMI).
During SOI as the spacecraft flew over Saturn's A-ring, the INMS measured oxygen ions which indicated the existence
of a tenuous ring atmosphere. During the October 2004 encounter with Titan, the INMS made the first in situ
measurements of the neutral atmosphere of this satellite, and during the April 2005 "T5" encounter the INMS observed a
rich and complicated ion composition in Titan's atmosphere.
The Space Physics group at the University of Kansas has undertaken a number
of studies of the upper atmosphere and ionosphere of Titan and its interaction
with Saturn's magnetosphere. This website includes a number of papers and
preprints on these topics.
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See our Cassini website for more information and publications.
Return to Space Physics and Plasma Astrophysics Home Page.
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Tizby Hunt-Ward tizby@ku.edu |