Click on image for larger version
East Mareotis Tholus is a small volcano in Tempe Terra, Mars. This area is
on the northeast edge of the Tharsis bulge that was built up by many large
and small volcanoes.
One of the many questions we hope to address with HiRISE is the relative
roles of the giant shield volcanoes (such as Olympus Mons) and smaller
volcanic features (such as East Mareotis Tholus).
The anaglyph covers 4.4x6.9 km (2.7x4.9 miles) and the topography can be
viewed using red-blue glasses. The elongated pit at the summit of the
volcano is where the lava issued forth. The large circular hole just to
the SW of the vent is an impact crater. The gouges in the ground to the SE
of the volcano are tectonic fissures (called graben) that are now filled
with sand dunes. The area is covered with large amounts of wind-blown
dust, so it is not surprising that lava flows and other smaller volcanic
features are not visible.
However, the smooth shape of the volcano, and the lack of lava layers
exposed in the impact crater, allow for the possibility that this volcano
is composed largely of ash, rather than lava flows.
Observation Geometry
Image PSP_001760_2160 was taken by the High Resolution Imaging Science
Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter
spacecraft on 11-Dec-2006. The complete image is centered at 35.9 degrees
latitude, 274.9 degrees East longitude. The range to the target site was
312.2 km (195.1 miles). At this distance the image scale is 62.5 cm/pixel
(with 2 x 2 binning) so objects ~187 cm across are resolved. The image
shown here has been map-projected to 50 cm/pixel and north is up. The
image was taken at a local Mars time of 03:36 PM and the scene is
illuminated from the west with a solar incidence angle of 54 degrees, thus
the sun was about 36 degrees above the horizon. At a solar longitude of
148.8 degrees, the season on Mars is Northern Summer.
NASA's Jet Propulsion Laboratory, a division of the California Institute
of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for
NASA's Science Mission Directorate, Washington. Lockheed Martin Space
Systems, Denver, is the prime contractor for the project and built the
spacecraft. The High Resolution Imaging Science Experiment is operated by
the University of Arizona, Tucson, and the instrument was built by Ball
Aerospace and Technology Corp., Boulder, Colo.
