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NASA Facts
NASA's Mars Global Surveyor, the first in a
series of spacecraft destined to explore the red planet,
began its primary mapping mission in March 1999.
Mars Global Surveyor is a global mapping mis-
sion, carrying a suite of science instruments designed
to study the entire Martian surface, atmosphere and
interior. Measurements are be col-
lected from a low-altitude, nearly
polar orbit 378 kilometers (234
miles) above the Martian surface
over the course of one complete
Martian year, the equivalent of
nearly two Earth years.
The mission is providing a
new, global portrait of how Mars
looks today. The new outlook is
helping planetary scientists to bet-
ter understand the history of Mars'
evolution, and is providing clues
about the planet's interior and sur-
face evolution. With this informa-
tion, we will have a better under-
standing of the history of all of the
inner planets of the solar system,
including our home planet, Earth.
Mars Global Surveyor contin-
ues NASA's long exploration of
the red planet, which began more
than 30 years ago with the
Mariner 4 spacecraft that produced the first pictures
of the planet's cratered surface. Following the suc-
cessful landing of the Mars Pathfinder lander and
rover on July 4, 1997, Mars Global Surveyor was the
first in a multi-year series of missions called the Mars
Surveyor program that could lead to eventual human
expeditions to the red planet.
Mission Overview
Mars Global Surveyor was launched at 12:00:49
p.m. Eastern Standard Time on November 7, 1996,
atop a three-stage Delta II launch
vehicle from launch pad 17A at Cape
Canaveral Air Station, FL. The third-
stage Star 48B solid rocket later pro-
pelled the spacecraft out of Earth
orbit and on its way to Mars.
Once on course for the cruise to
Mars, the spacecraft deployed its two
solar panels to begin generating solar
power. One of the solar panels did
not fully deploy and is tilted about
20 degrees from its intended posi-
tion. The low-gain antenna was used
for initial spacecraft communica-
tions, until the spacecraft was far
enough away from Earth in early
January 1997 to begin using its 1.5-
meter-diameter (5-foot) high-gain
antenna.
Mars Global Surveyor's six sci-
ence instruments the thermal
emission spectrometer, laser altime-
ter, magnetometer/electron reflec-
tometer, ultra-stable oscillator, camera and radio relay
system were calibrated during the cruise to Mars.
Three trajectory correction maneuvers were per-
formed to fine-tune the spacecraft's flight path.
Mars Global Surveyor
NASA Facts
National Aeronautics and
Space Administration
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
Signs of water erosion and debris flow are
seen in this high resolution view of gullies
eroded into the wall of a meteor impact
crater in Noachis Terra on Mars, taken by
NASA's Mars Global Surveyor. The start of the primary mapping mission was
delayed by about a year due to a structural problem
with the spacecraft's solar panel that required the
flight team to take a more cautious approach to aero-
braking to ensure that the weakened panel was not
overstressed.
During the aerobraking technique, the spacecraft
uses frictional drag as it skims through the planet's
thin upper atmosphere to alter the shape of its orbit
around the planet. First tested in the final days of the
Magellan mission at Venus in 1994, the technique is
an innovative way of changing the spacecraft's orbit
while carrying less onboard fuel.
When Global Surveyor arrived at Mars in
September 1997, it initially entered a looping, ellipti-
cal orbit around the planet that has been gradually cir-
cularized through aerobraking. Its winged solar panels
which feature a Kapton flap at the tip of each wing
for added drag supply most of the surface area that
slowed the spacecraft by a total of more than 1,200
meters per second (about 2,700 miles per hour) during
the entire aerobraking phase. Since the start of aero-
braking, Surveyor's orbit around Mars has shrunk from
an initial elliptical orbit of 45 hours to the now nearly
circular orbit taking less than two hours to complete.
Science Highlights
Mars Global Surveyor is examining the entire
planet from the ionosphere, an envelope of
charged particles surrounding Mars, down through the
atmosphere to the surface and deep into Mars' interi-
or. Scientists are gleaning valuable new information
on daily and seasonal weather patterns, geological
features and the migration of water vapor from hemi-
sphere to hemisphere over a complete Martian year.
Among major science findings from the mission
so far are:
q
In what could turn out to be a landmark discov-
ery in the history of Mars exploration, imaging scien-
tists have seen gullies and debris flow features that
suggest there may be current sources of liquid water,
similar to an aquifer, at or near the surface of the
planet. Features that appear to be gullies that were
formed by flowing water have been identified, along
with deposits of dirt and rocks transported by these
flows. The scenes of the surface of Mars are reminis-
cent of features left behind after flash flood in the
deserts of the southwestern United States, and scien-
tists are trying to determine mechanisms that would
account for such features on rainless Mars.
2
Mars Orbiter
Laser Altimeter
Mars Orbiter
Camera
Thermal Emission
Spectrometer
Celestial Sensor
Assembly
Mars Relay
Electron Reflectometer
Mars Horizon Sensor
Magnetometer
Attitude Control Thruster
(1 set on each corner of spacecraft)
High-Gain
Antenna
High-Gain
Antenna Gimbals
Propellant
Tank
Solar Panel
Solar Panel
Solar Panel
Solar Panel
Drag
Flap
Drag
Flap
Magnetometer q
The planet's magnetic field is not globally gen-
erated in the planet's core, but is localized in particu-
lar areas of the crust. Multiple magnetic anomalies
were detected at various points on the planet's sur-
face, indicating that magma solidified as it came up
through the crust and cooled very early in Mars' evo-
lution.
q
Mars' very localized magnetic field also creates
a new paradigm for the way in which it interacts with
the solar wind, one not found with other planets.
While Earth, Jupiter and other planets have large
magnetospheres, and planets like Venus have strong
ionospheres, Mars' small, localized magnetic fields
are likely to produce a much more complicated inter-
action as these fields move with the planet's rotation.
q
New temperature data and closeup images of
the Martian moon Phobos show its surface is com-
posed of powdery material at least 1 meter (3 feet)
thick, caused by millions of years of meteoroid
impacts. Measurements of the day and night sides of
Phobos show extreme temperature variations on the
sunlit and dark sides of the moon. Highs were mea-
sured by the spacecrafts thermal emission spectrome-
ter at -4 degrees Celsius (25 degrees Fahrenheit) and
lows registered at -112 Celsius (-170 degrees
Fahrenheit).
q
New mineralogical and topographic evidence
suggest that Mars had abundant water and thermal
activity in its early history is emerging from data
gleaned by NASA's Mars Global Surveyor spacecraft.
Data from the thermal emission spectrometer indicate
the first clear evidence of an ancient hydrothermal
system. The finding implies that water was stable at
or near the surface and that a thicker atmosphere
existed in Mars' early history.
q
Measurements by the thermal emission spec-
trometer also show an accumulation of the mineral
hematite, well-crystallized grains of ferric (iron)
oxide that typically originate from thermal activity
and standing bodies of water. This deposit is localized
near the Martian equator, in an area approximately
500 kilometers (300 miles) in diameter. (Fine-grained
hematite, with tiny particles no larger than specks of
dust, generally forms by the weathering of iron-bear-
ing minerals during oxidation, or rusting, which can
occur in an atmosphere at low temperatures.) The
material has been previously detected on Mars in
more dispersed concentrations and is widely thought
to be an important component of the materials that
give Mars its red color. The presence of a singular
deposit of hematite was intriguing to scientists
because it typically forms by crystal growth from hot,
iron-rich fluids.
q
Data from the spacecrafts laser altimeter have
given scientists their first 3-D views of Mars' north
polar ice cap. Initial profiles show an often striking
surface topology of canyons and spiral troughs in the
water and carbon dioxide ice that can reach depths as
great as 3,600 feet below the surface. Many of the
larger and deeper troughs display a staircase structure,
which may ultimately be correlated with seasonal lay-
ering of ice and dust observed by NASA's Viking
mission orbiters in the late 1970s.
q
Data from the altimeter have also shown that
large areas of the ice cap are extremely smooth, with
elevations that vary only a few feet over many miles.
At 86.3 degrees north, the highest latitude yet sam-
pled, the cap achieves an elevation of 2 to 2.5 kilome-
ters (6,600 to 7,900 feet, or 1.25 to 1.5 mile) over the
surrounding terrain. The laser measurements are accu-
rate to approximately 30 centimeter