SHARON SHANKS | The Cosmos Mars Odyssey mission will try, try again

The 2001 Mars Odyssey mission is due to arrive at Mars on Tuesday, and you can bet the rent that the hundreds of people involved in the project are hoping the third time's a charm.
After all, this is the first mission to the red planet since the loss of the Mars Climate Orbiter and the Mars Polar Lander.
It's time for something to go right.
The Odyssey spacecraft will officially arrive at Mars at 10:30 p.m. Tuesday. That's when it will fire its engines in a braking maneuver and begin slowing.
The rest of the slowing will be accomplished by aerobreaking -- the same slowing method used by the Mars Global Surveyor.
Aerobreaking uses the friction of Mars' atmosphere to gradually slow down. It will take 76 days to arrive to its optimal orbit, but the trade-off is the craft has to carry less fuel to use for braking.
Once it reaches the right height, the craft will use a variety of instruments to look at Mars' surface and try to figure out what it's made of. What kind of minerals? How much hydrogen? What geological processes led to the type of surface that Mars has today? What kind of radiation is present, and how harmful is it to humans?
Three instruments will be doing all the work.
THEMIS -- the Thermal Emission Imaging System -- will look at minerals in the soil. To do this, it will use something akin to night vision goggles or thermal imaging cameras used by fire departments to find "hot spots" in walls.
Thermal (heat) images give off infrared radiation when exposed to sunlight. Each element has its own distinct thermal "fingerprint," which allows scientists at a distance to tell what kinds of minerals are present.
The Mars Global Surveyor now at Mars has a similar thermal emission spectrometer on board, but the Odyssey THEMIS instrument improves the resolution dramatically.
The MGS instrument indicated where to look; now THEMIS will study those areas in detail.
Quest for water: The gamma ray spectrometer, meanwhile, will be sniffing out hydrogen in a quest for water. Hydrogen is half the familiar recipe for water (two parts hydrogen, one part oxygen).
The GRS will take advantage of a process taking place continually on the Martian surface: bombardment by radiation from space.
The GRS will be able to tell what kind and how much elements are present by the amount of energy released through the cosmic ray bombardment.
We don't worry about cosmic radiation here on Earth because our planet's thick atmosphere acts like a shield and stops the radiation before it can hit the surface.
The GRS will be able to measure the amount of hydrogen in about the upper meter of soil and, by association, estimate the amount of water present. It also can detect sodium, potassium and chlorine, usual leftovers in the ground where bodies of water once existed, and will be able to measure the thickness of Mars' icy polar caps.
Charged particles: The third instrument is MARIE, the Mars Radiation Environment Experiment, which will measure the amount of energetic charged particles present from Mars orbit.
It is especially interested in the amount of radiation from solar flares, powerful explosions from the surface of the sun that blast fast-moving, high-energy particles into space.
The exploration of Mars has been as pockmarked with failures as the surface of the planet is pockmarked with impact craters.
Starting in the early 1960s the U.S.S.R. launched five probes to Mars, all of which failed. The first successfully flyby came in 1964 by the U.S. Mariner 4, and Mariners 6 and 7 also gave us a few images throughout the decade of the1960s.
Mariner 8 failed during launch in 1971, and the same year the Russian Kosmos was able to make it only to Earth orbit.
The first really successful mission to Mars was Mariner 9 in 1971, which orbited for nearly a year and returned more than 7,000 photographs.
More Russian failures followed (Mars 4-7), and then the twin U.S. Vikings arrived in 1976 to perform the first successful landings.
Russia didn't give up, however, and sent Phobos 1 and 2 in 1988 (both were lost en route to Mars).
U.S. mission: The next U.S. mission to Mars was the Mars Observer in 1992, which also failed just before Mars arrival.
The Mars Global Surveyor arrived in 1996, the first successful mission in 20 years, and is still diligently orbiting Mars in its science mapping mission.
Russia's Mars 96, an orbiter and lander, was destroyed when its launch vehicle failed, but Mars Pathfinder made it successfully to Mars in 1997 and conducted a wildly successful mission until the lander's batteries finally failed.
The MGS was supposed to act as a relay station for data from the surface from the U.S. Mars Polar Lander, which was lost in its landing attempt early in 1999.
Just one month earlier, the U.S. Mars Climate Orbiter was lost when it attempted to enter orbit.
Heads Up for November: The annual Leonid Meteor Shower should peak the evening of Nov. 17 and morning of Nov. 18. Look toward the constellation of Leo, which will be rising in the east around midnight.
For more on Mars exploration, check out the Jet Propulsion Laboratory's Web sit at Mars.jpl.nasa.gov. For information on the Leonids, go to www-space.arc.nasa.gov/~leonid/.