Geoscience Reference
In-Depth Information
Table 12.1
Major dune fields on Mars
and modification of dune fields within craters on Mars (see
Fenton et al. 2003, 2005; Fenton 2006a).
Kaiser crater (46.6 S, 19.1 E). Kaiser crater is 210 km in
diameter and is located in the southern cratered highlands to
the west of Proctor crater. The dune field present on the
crater floor was imaged late in the mission of Viking Orbiter
2 (Fig.
12.15
), showing dune crests that are likely trans-
verse to the winds that transported the sand into the crater.
Much later, the Mars Orbiter Camera (MOC) on the Mars
Global Surveyor spacecraft provided higher-resolution
images of individual barchan sand dunes near the main dune
field (Fig.
12.16
), probably the result of sand that has
escaped from the margin of the main dune field. The Hi-
RISE camera obtained a stereo image pair from which very
detailed elevation information is obtained for an individual
dune in the Kaiser crater (Fig.
12.17
). This dune showed
avalanche features on its slip face in MOC image R06-
00380, so HiRISE stereo data were collected to investigate
the relief associated with avalanche modification of dune
slip faces on Mars, in an effort to assess what mechanisms
may have produced the avalanching of the sand.
Lyot crater (50.8 N, 28.8 E). Lyot crater is 240 km in
diameter, located in the northern lowland plains of Vastitas
Borealis. Lyot has the largest crater dune field found within
the northern lowland plains of Mars. The Lyot dune field
has been monitored regularly by orbiting cameras (e.g.,
THEMIS VIS image 6044, 9/10/12) to see whether there
are distinguishable variations in how dunes in the northern
hemisphere change with time, as compared to the more
numerous dune fields in the southern hemisphere, but so far
the dunes in Lyot do not display unique characteristics.
Herschel basin (4.5 S, 130.0 E). Herschel is a 300 km-
diameter impact basin in the equatorial portion of the cra-
tered southern highlands. MOC images of the dune field in
Herschel showed a 'grooved' texture that was interpreted to
suggest that the sand was moderately indurated and subject
to erosion aeolian scour (see Fig. 42 of Malin and Edgett
2001). However, recently the Herschel dune field has shown
1 m of movement between two HiRISE images taken on
March 3, 2007 and 1 December, 2010, and the grooved
appearance is resolved to be a confluence of aeolian ripples
on the dune surface (Fig.
12.17
), so that induration of the
sand is no longer required. This is merely one example of
several locations where HiRISE repeat imaging is now
documenting the planet-wide movement of sand under
current climatic conditions (e.g., Bridges et al. 2012b).
Rabe crater (43.6 S, 34.8 E). Rabe crater is 108 km in
diameter, and is located in the southern cratered highlands
in what used to be called the Hellespontes region, the same
general area where both Proctor and Kaiser craters are
located. Monitoring of the Rabe dune field using MGS/MO
data was unable to document any observable dune move-
ment, leading to an estimate for the local sand migration
Name
Location
Width (km)
Abalos Undae
78.5 N, 272.5 E
440
Hyperboreae Undae
80.0 N, 310.5 E
460
Olympia Undae
81.2 N, 178.5 E
1500
Siton Undae
75.6 N, 297.3 E
220
Aspledon Undae
73.1 N, 309.7 E
220
The IAU Gazetteer of Planetary Nomenclature lists the term
'undae' to indicate 'a field of dunes', and the NPE includes
the only five locations on Mars that have been approved so
far to become named dune fields on Mars (Table
12.1
).
The largest polar dune field has received considerable
attention because compositional data from the Compact
Reconnaissance Imaging Spectrometer for Mars (CRISM)
instrument (see
Sect. 18.5
;
Fig.
18.13
) revealed that gyp-
sum is a significant component of the Olympia Undae polar
sands (Fishbaugh et al. 2007; Horgan et al. 2009). Imaging
from the High Resolution Imaging Science Experiment
(HiRISE) camera allows the dune sands to be traced back to
eroded exposures of a thick bed within the basal component
of the polar layered deposits, which would indicate that the
origin of polar sand likely preceded the emplacement of the
thick sequence of polar layered deposits (Fishbaugh and
Head 2005). The NPE sand deposits can now be placed in
context with other bedrock materials exposed throughout
the north polar region (Tanaka and Fortezzo 2012), but this
provides no additional insight into where the sand may have
originated prior to its involvement in the deposition of the
polar layered deposits. The dune morphology has been
studied by Tsoar et al. (1979) and more recently subjected
to a quantitative pattern analysis by Ewing et al. (2010). The
high latitude of these dunes makes them particularly
prominent sites for the frosting and defrosting processes that
occur around winter (e.g., Hansen et al. 2011).
Proctor crater (48.0 S, 29.5 E). Proctor crater is 150 km in
diameter, located in the southern cratered highlands to the
west of the giant Hellas impact basin. The dune field on the
floor of this crater was the first to be identified on Mars from
Mariner 9 images (Fig.
12.2
); the field covers an area
approximately 35 by 65 km in area, and the dune field has
been targeted often by subsequent orbiters. The resolution of
the Mariner 9 image is not sufficient to allow potential long-
term movement of the dunes to be detected; comparison of a
higher-resolution image (Fig.
12.5
) obtained in 1999 by the
Mars Orbiter Camera (MOC) on the Mars Global Surveyor
spacecraft to the Mariner 9 image showed that any movement
must have been less than the size of a Mariner pixel
(62 m/pixel) during the 14 Mars years (28 Earth years) that
elapsed between the two images. On-going study of the
Proctor dune field, notably with the HiRISE camera (e.g.,
Fig.
12.6
) has yielded many insights into the emplacement
Search WWH ::
Custom Search