Mars Global Surveyor
Mars Orbiter Camera
Mars Orbiter Camera (MOC) High Resolution Images
Small Volcano In Tempe Terra
Mars Global Surveyor Mars Orbiter Camera Release: MOC2-64a, -64b, -64c, -64d
Mars Global Surveyor Mars Orbiter Camera Image ID: 588261451.50704
149 KByte GIF image
(A) Tempe-Mareotis Fossae, Tempe Terra, Mars. White box indicates
the location of Viking image subframe 627a28, shown in (B),
below. MOC image 50704 is located near the center of this box (see
below). The fossae are the linear troughs that are seen
running approximately diagonal across the scene from upper right
toward lower left. The fossae are a series of horsts and
graben formed by faulting of the upper martian crust. Graben are
the down-dropped trough floors, horsts are the uplifted, relatively
flat areas between the troughs. Horst and graben terrain forms by
spreading (extension) of the planet's crust. The Tempe and
Mareotis Fossae troughs are radial to the Tharsis "bulge"--a huge
uplifted region on Mars that contains many volcanoes and fault
systems. The major Tharsis Montes volcanoes--Arsia Mons, Pavonis
Mons, and Ascraeus Mons--lie along the same trend as the
Tempe-Mareotis Fossae. The base map is a U.S. Geological Survey
photomosaic of Viking Orbiter images with a scale of 64 pixels per
degree of longitude. Most of the mosaic images are illuminated from
the right. North is up.
339 KByte GIF image
(B) Local context of MOC image 50704 in the Tempe-Mareotis Fossae
region. This is a portion of Viking 1 Orbiter image 627a28, taken in
1978. The white box indicates the location of the MOC image--taken 20
years later--shown in (C), below. The white box is centered on
a small volcano that has a linear summit depression--a caldera.
The linear caldera is only 2 kilometers (1.2 miles) long. The Viking
image is presented here as a mercator projection with a scale of 1100
pixels per degree of longitude. Illumination is from the left; north
is up. The linear caldera is located at 36.2°N, 85.1°W, in
the martian western hemisphere.
386 KByte GIF image
(C) MOC image 50704 subframe, presented at 50% of its original
size. The spatial resolution of the 50%-size image is approximately
8 meters (26 feet) per pixel. The linear depression--the summit caldera
of the volcano--is 2 kilometers (1.2 miles) long. The regularly-spaced
lineations in the troughs in the lower third of the image are drifts
of windblown material. Sun illumination is from the left. North is up.
226 KByte GIF image
(D) Full-resolution view of volcanic linear vent (caldera), as seen
in MOC image 50704. The caldera is 2 kilometers (1.2 miles) long.
The spatial resolution of this image is approximately 4 meters
(13 feet) per pixel. The regularly-spaced ridges hidden in the shadow
on the caldera floor are drifts of windblown material.
Illumination is from the left. North is up.
You may need to adjust the images for the gamma of your monitor to
insure proper viewing.
Note: This MOC image is made available
in order to share with the public the excitement of new
discoveries being made via the Mars Global Surveyor spacecraft.
The image may be reproduced only if the
image is credited to "Malin Space Science Systems/NASA".
Release of this image does not constitute a release of
scientific data. The image and its caption should not be
referenced in the scientific literature. Full data releases
to the scientific community are scheduled by the Mars Global
Surveyor Project and NASA Planetary Data System. Typically, data
will be released after a 6 month calibration and validation period.
Click Here for more information on MGS data release and
Mars is famous for its giant volcanoes, such as
Elysium Mons--observed by Mars Global Surveyor in July 1998--and
Olympus Mons--3 times the height of Mt. Everest and as big as the
U.S. state of Arizona.
However, not all martian
volcanoes are large. One of Mars Global Surveyor's most recent
pictures, indeed, highlights one of Mars' tiniest volcanoes--a small
"shield" volcano with a 2 kilometer- (1.2 mile-) long depression
at its summit.
The small volcano is located in the Tempe-Mareotis Fossae region of
Tempe Terra. Centered at 36.2°N, 85.1°W, this is one of
many small volcanoes on Mars. The Mars Global Surveyor MOC image
presented here is the first close-up view of one of these small
This volcano is similar in both shape and size to many of the small
basalt shield volcanoes found on the Snake River Plain in southern
Idaho, U.S.A. Other similar volcanic vents are found in Hawaii and
Iceland. Basalt is the dark, iron- and magnesium-rich silicate rock
found in places like the Snake River Plain, Hawaii, and Iceland.
Basalt is also common on the floor of Earth's oceans and on the flat
plains of the Moon known as maria.
The volcano seen in this MOC image does not show many of the features
generally found around volcanoes of this size on Earth. Instead of
the lava flows and leveed channels found on Earth, we see only a faint
pattern of subtle, somewhat sinuous ridges and troughs that are radial
to the long, elliptical summit depression (or caldera). This
pattern gives the surface of the volcano and its surroundings quite a
rough appearance. Much of the appearance of this "sandpaper-like"
texture appears to be unrelated to the volcano, but is instead an
expression of the eroded regolith--"soil"--that covers the old
lava flows. The MOC image suggests that a person hiking around on
this small martian volcano would find the walk pretty difficult
(especially in a spacesuit).
But what an exciting and fascinating walk that would be. Not only
would one be able to look, and even hike down, into the 150 m (460
foot) deep caldera, but one could also inspect the spectacular,
regularly-spaced ridges seen on the floors of nearby troughs
(e.g., in the lower 1/3 of the MOC image in (C)). These
ridges are formed by wind and are probably composed of a mixture of
sand and granules--perhaps reworked cinders from ancient volcanic
eruptions in the region. Some windblown ridges can also be seen in
the shadows on the floor of the volcano's linear caldera.
The MOC image was taken at 6:57 a.m. (PDT) on August 22, 1998, during
the 506th orbit of Mars Global Surveyor as the spacecraft was nearing
its 507th periapsis (closest point to the planet during the
orbit). The local time (on Mars) was late in the afternoon--the Sun
was only 10° above the horizon--equivalent to about 5:20 p.m.
Malin Space Science Systems and the California Institute of
Technology built the MOC using spare hardware from the Mars Observer
mission. MSSS operates the camera from its facilities in San Diego,
CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA
and Denver, CO.
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