Geology Reference
In-Depth Information
Figure 9.5. A diagram showing the inferred surface processes and cycle of methane and other components on Titan; methane can exist in gas,
liquid, and solid forms. Thus, cryovolcanism and gradation in the form of wind,
fluvial, lacustrine, and possibly glacial processes can occur,
along with impacts and tectonic deformation, as portrayed here before the discoveries from the Cassini mission (from Lunine,
1990
).
sand-like ice grains. Images show the surface littered with
pebbles and cobbles composed of ice, and their rounded
appearance suggests erosion by some
fluid (
Fig. 9.6
).
Radar and infrared images from Cassini and the
remarkable success of the Huygens probe amply con
rm
the speculation on Titan
At 80 km in diameter, Sinlap crater is larger than Ksa
but lacks a central peak. It does, however, also have
extensive ejecta deposits with an inner, radar-dark band
and an outer brighter zone, which might be comparable to
the
craters seen on Mars. If this is the case,
the impact might have melted crustal ice to produce fluid,
slurry-like ejecta.
The largest con
rmed impact structure is the 440 km in
diameter Menrva, found in the northern mid-latitudes.
This basin consists of two rings, both of which are com-
posed of rugged, elevated mountains (
Fig. 9.8
). Relatively
smooth (radar-dark) plains are found between the rings,
and there are suggestions of ejecta deposits beyond the
outermost ring. In addition to the handful of other known
impact craters on Titan, dozens of features of possible
impact origin are seen but are not imaged in sufficient
detail for con
rmation.
The interior of Titan is likely to be partly differentiated.
As reviewed by Sotin et al.(
2009
), Titan is modeled to
have a silicate core, overlain by a zone of high-pressure
“
ejecta
ow
”
s geology and provide evidence
for impact cratering, gradation, tectonism, and possibly
cryovolcanic processes, some of which are active today, as
reviewed by Ralf Jaumann et al.(
2009a
).
Relatively few con
rmed impact structures have been
identified in images of sufficient resolution for detection.
This paucity indicates the relative youth of Titan
'
s surface.
Ksa crater (
Fig. 9.7
) in the equatorial region is about
29 km in diameter and has a radar-bright inner wall and
a distinct raised rim. The radar-bright central peak is
surrounded by radar-dark terrain, suggesting smooth
deposits. Ejecta extends as far as 40 km and has hints of
radial striations. The ejecta deposits are encroached on by
dunes on the west and are slightly eroded by a channel on
the east.
'
