For nearly 50 years, our civilization has been attempting to send
spacecraft to Mars. By the beginning of the 21st century, only 10
missions out of 33 tries had been a complete success. Journey with us
down the rocky road of Mars exploration.
Mars Exploration Rovers
Spirit: June 10, 2003
Opportunity: July 7, 2003
The Mars
Exploration Rover mission (MER) renews a NASA tradition of launching
twin vehicles to the Red Planet. The tradition began in 1964 with
Mariner 3 and 4, and
continued with Mariner 6 and
7, Mariner 8 and 9,
and Viking 1 and 2. Now,
more than 25 years later, America is again sending twin spacecraft to
the surface of Mars. NASA has returned to this strategy to double the
mission’s science return and, at the same time, increase the odds
of mission success.
Spirit and Opportunity are large, powerful rovers that will land on opposite
sides of Mars this January. Both landing sites are located near the
equator of the planet in order for the solar-powered vehicles to capture
as much sun as possible. Spirit lands in
Gusev
Crater on the evening of January 3 (EST). Gusev Crater is a region
that may have once been the site of a former lake. A large valley,
probably the site of an ancient river, extends from the Gusev impact
basin. Opportunity lands at
Meridiani
Planum just past midnight on January 25 (EST). This region is a
smooth plain that contains deposits of gray crystalline hematite –
a mineral that often forms where liquid water has been present.
The Mars Rovers carry everything they need for energy, communication, and
science. Unlike Pathfinder which had a lander that contained the bulk
of the science and communication equipment, the landers for the Mars
Exploration Rovers are shells – vehicles to get the rovers to the
surface of Mars. Once the rovers are off their landers, they are free
to roam the Red Planet in any direction that the MER team deems fit.
They will each be able to travel tens of yards per day as they search
for evidence of ancient water.
Spirit and Opportunity will examine Martian rocks, soils, and atmosphere with a
sophisticated set of science instruments called the Athena Science
Payload. On the mast of each rover is a
Pancam camera, which is a
high resolution color stereo camera; and a
Miniature Thermal Emission
Spectrometer (Mini-TES), which is an infrared spectrometer that can
determine the composition of rocks and soils from a distance. On each
rover’s arm is a
Microscopic Imager for
close-up views of rocks and soils; an
Alpha Particle X-Ray
Spectrometer (APXS) and
Mössbauer Spectrometer
for measuring the composition of rocks and soils in detail; and a
Rock Abrasion Tool (RAT) for
grinding the outer coatings of rocks to expose fresh surfaces for study.
The Mars Exploration Rovers will use the Athena Science Payload to read the
geologic history that is preserved in the rocks at each landing site.
They will use Pancam and Mini-TES to scan their surroundings for
interesting science targets. When a target is chosen, each rover will
be commanded to drive to the target and deploy the instruments on its
arm for further study. It may take several sols for a rover to inspect
just one rock target.
To maximize the accuracy of science data, each science instrument has a
calibration target onboard the rover to use as reference point. The
most unusual calibration target on the rover belongs to Pancam. It was
built in the shape of a sundial. The
MarsDial sits on the rear solar panel
and will be used by Pancam to correct brightness and color in Mars
images.
While the rovers do their work, another science experiment is passively
collecting information. Three sets of
magnet arrays will
collect airborne dust for analysis by the science instruments. Some of
the dust on Mars is very magnetic. The patterns of accumulation on
these magnets of varying strength can reveal clues about the content of
the dust grains and, in turn, about the planet’s geologic history.
Communication with Earth is
limited to once per day. This means that each rover must travel the
surface of Mars unsupervised. They will use their
hazard avoidance
software to safely move around boulders and over rocks in their path.
Hazcams (Hazard-Identification Cameras) are positioned under the solar
panel deck at the front and rear of the rover’s warm electronics
box to provide a wide-angle view of the terrain. Navigation software
analyzes the images to identify obstacles. Each sol, as the rovers
strive to complete a daily set of instructions from Earth, they will be
on their own to carefully creep through a rugged landscape.
Spirit and Opportunity will only work during daylight hours. Each has a large
solar panel deck that can produce, at the beginning of the mission,
nearly 900 watt-hours of energy per sol and repeatedly recharge two
batteries inside the body of the rover. As dust builds up on the solar
panels, power output will be reduced. Eventually, the dust will become
so thick that the rovers will not be able to recharge their batteries
and will cease to function.
The primary mission for each Mars Exploration Rover is 90 sols.
Mars Express: June 2, 2003
The Beagle has a PAW, the PAW has a Mole and their objective is to
search for evidence of life in martian soil. It’s all part of the
European Space Agency’s first mission to Mars.
The
Mars
Express orbiter and the
Beagle 2
lander were launched from Baikonur Cosmodrome, a facility steeped in
Russian space history, on June 2, 2003. The location of the launch was
fitting since Mars Express inherited many of its science goals from
Russia’s failed Mars 96 mission. Mars 96 consisted of an orbiter and
two small landers that were to probe the surface, interior, and
atmosphere of Mars. Mars Express consists of an orbiter and one small
lander that will examine the planet’s geology, structure, and atmosphere
to search for water and signs of life.
The Mars Express orbiter carries seven science instruments – a high
resolution stereoscopic camera
(HRSC),
a visible and near-infrared spectrometer for mapping minerals (OMEGA),
an infrared spectrometer to measure water vapor in the martian
atmosphere (PFS), an ultraviolet atmospheric spectrometer (SPICAM),
particle sensors to learn how the solar wind interacts with the martian
atmosphere
(ASPERA),
subsurface radar and altimeter to map the distribution of water ice in
the planet’s crust
(MARSIS), and a
radio science experiment that will use radio waves to study the surface
and atmosphere of Mars (MaRS).
The Beagle 2 lander is a British-led project named for the HMS Beagle –
the ship that Charles Darwin used to explore the Earth in 1831. The
small lander weighs only 60 kg (about 132 lbs) and is mounted on the
orbiter for its journey to Mars. Packed inside the Beagle 2 is a suite
of instruments and a laboratory designed to search for evidence of past
or present microbes in the martian soil. The science package includes a
robotic arm called PAW (Payload Adjustable Workbench) which carries a
microscope, two cameras, two spectrometers, and a flashlight for night
work. The workbench also contains a corer/grinder and the “Mole” – a
robotic instrument that can crawl across flat surfaces and burrow into
soil to collect samples.
The Mars Express mission will arrive at Mars this December. The Beagle
2 lander will be released from the orbiter on Dec. 19 and coast for five
days before it enters the martian atmosphere. A parachute will slow its
descent, and airbags will cushion its landing. The landing site,
Isidis Planitia, is a large, flat, low lying impact basin near the
planet’s equator. On Christmas Day, the same day that Mars Express is
scheduled to enter orbit around Mars, Beagle 2 is scheduled to land.
After the Beagle 2 is on the surface of Mars, its top will open and
solar panels will unfold. The antenna will be deployed and the robotic
arm released. Panoramic images will be taken as well as images of the
soil and rocks surrounding the lander. When a rock target is chosen,
the PAW’s grinder will be used to expose a fresh rock surface for study
by the microscope and spectrometers. A sample of the rock may be
collected with the corer and delivered to the lander’s laboratory with
the PAW. When the Mole is deployed, it remains attached to the PAW by a
power cable which retracts after the instrument has gathered its soil
sample. Then the PAW delivers the sample to laboratory ovens for
heating. A mass spectrometer will be used to search for signs of life.
The Beagle 2 lander is expected to operate for about 180 sols on the
martian surface. The Mars Express orbiter mission will continue for one
martian year (687 days).
2001 Mars Odyssey: Apr. 7, 2001
“2001: A Space Odyssey” is a book and film from the 1960s that many
science fiction fans still enjoy. When it came time to name to the
first spacecraft to travel to Mars in the 21st century, the word
“Odyssey” seemed like a natural.
Mars Odyssey was the first American mission to Mars following the loss
of Mars Climate Orbiter and Mars Polar Lander. It was important that it
be a success. When Odyssey reached Mars, a critical event was facing
the spacecraft – an event that triggered the loss of the Mars Climate
Orbiter – orbit insertion. On Oct. 23, 2001, Odyssey fired its main
engine to slow its speed. As planned, it disappeared behind the planet
and was out of contact for 20 minutes. Those 20 minutes felt like hours
to Odyssey scientists and engineers. When the spacecraft emerged from
behind Mars, its radio signal was greeted with cheers and a collective
sigh of relief. Odyssey had safely achieved Mars orbit insertion.
Mars Odyssey carries three science experiments. They are designed to
study the planet’s climate and geologic history, search for shallow
subsurface ice, create global maps of elements and minerals, and analyze
radiation levels to determine harmful effects on future human explorers.
The spacecraft took its first look at Mars on Oct. 30, 2001. It was a
thermal infrared image of the planet’s southern hemisphere taken as part
of the calibration and testing of the
Thermal Emission
Imaging System (THEMIS).
THEMIS collects information in both infrared and visible wavelengths. It
is studying the minerals on the martian surface, especially those
minerals that are formed in water. In the infrared spectrum, different
minerals show up as different colors. THEMIS can detect their spectral
fingerprints. A recent infrared discovery showed distinct layers of
rock with very different physical properties. Scientists suggest that
Mars may have weathered a series of past environmental changes fueled by
volcanoes, water, or climate.
THEMIS visible imaging will help scientists determine where water may
have flowed on the surface of Mars. Using images from the visible light
camera, Odyssey scientists posed a theory that the gullies first seen on
Mars in 2000 by the
Mars Global
Surveyor may have been
formed
by melting snow. Prior to Odyssey’s images, the martian gullies
were thought to have been created by underground springs.
More than 15,000 visible images will be taken by THEMIS to aid in the
study of the martian surface, provide views of the Mars Exploration
Rover landing sites, and identify landing sites for future missions.
The Gamma
Ray Spectrometer (GRS) experiment uses a gamma ray spectrometer, a
neutron spectrometer, and a high energy neutron detector (HEND) to probe
the chemical elements in the surface and subsurface of Mars. Each
element has a distinct gamma-ray signature. The GRS experiment looks at
these signatures to get a global view of their distribution and
quantities. Neutrons emitted from Mars are helping scientists determine
the abundance of hydrogen on or just below the martian surface. Hydrogen
often indicates the presence of water or ice.
The GRS suite of instruments started to make important discoveries as
soon as the formal science mapping mission began in February, 2002. It
found significant amounts of hydrogen in the south polar region of Mars
– most likely due to water ice. By May of that year, scientists
concluded that there are
enormous
amounts of water ice just below the surface of Mars.
The Martian
Radiation Environment Experiment (MARIE) is designed to gather
information about the level of radiation it encounters throughout the
entire mission. But three months before Odyssey reached Mars, the
instrument stopped communicating and was shut down. Troubleshooting
efforts traced the source of the problem to memory error in the
instrument’s software. MARIE was revived and is returning information
that suggests humans who travel to Mars would receive more than twice
the dose of radiation that reaches astronauts on the International Space
Station.
Mars Odyssey’s primary science mission will continue through August
2004. It will serve as a communications relay for the Mars Exploration
Rovers arriving at Mars in January, 2004, and will continue to act as a
relay for missions to Mars until October 2005.
Web content editor/writer: Pamela R. Smith
