Mars Odyssey Finds Large Water Concentrations

Mars Global Surveyor
Artist impression of NASA’s Mars Odyssey. Credit: NASA

The first results from the Mars Odyssey are in, and they reveal that the Southern Hemisphere of the Red Planet has a lot of water ice just below the surface.

"The signal that we’ve been getting – loud and clear – is that there’s a lot of ice on Mars," says William Boynton of the University of Arizona. Boynton is the Principle Investigator for the Gamma Ray Spectrometer Suite on the Mars Odyssey. "Once we turned on the instrument, some of the signals were much stronger than we expected, and it really just blew us away."

The ice signals from Mars extend from the South Pole to -60 degrees latitude. Mars may have just as much ice in the Northern Hemisphere, but at the moment the Odyssey cannot see through the large amount of CO2 frost that currently covers that region. The scientists expect that once the seasons change, this cap of CO2 ice will dissipate and the Odyssey will be able to determine if the Northern Hemisphere also has a lot of water ice.

The scientists know that the water is ice rather than liquid, because the temperatures on Mars are well below freezing. The average temperature of Mars is -63 C (-81 F) and the instruments of Odyssey indicate the coldest temperature in the Southern Hemisphere right now is -101 C (-150 F).

"It’s just too darn cold for it to be liquid water," says Boynton.

The evidence for water ice comes from the gamma ray spectrometer and two neutron detectors that make up the Gamma Ray Spectrometer Suite. All three instruments indicate large amounts of hydrogen in the Martian Southern Hemisphere.

"We designed these instruments to reveal the past and present existence of water on Mars," says Steven Saunders, Odyssey Project Scientist from the Jet Propulsion Laboratory. "Water is vital to life, water has changed the face of Mars in the past, and water is necessary for the future exploration of Mars."

The instruments onboard Odyssey will do more than just detect the presence of water, however. The Thermal Emission Imaging System (THEMIS) will map the temperature variations of the Red Planet. Because different minerals absorb different amounts of heat, THEMIS will enable the scientists to determine the planet’s mineralogy.

"How the different geologic terrains on Mars warm up in the sunlight and cool off at night will reveal a lot about the rocks and soils on Mars," says Saunders.

Mars Clouds
Clouds over Mars as seen by the Viking mission. Credit: Viking Project, USGS, JPL

THEMIS has 10 filters that provide color infrared images of the surface of Mars. These color infrared images will reveal compositional differences in the elemental chemistry of the surface of Mars.

"A major objective of the THEMIS investigation is to map the entire surface, look for compositional variations, and in particular look for the most interesting and exciting minerals – minerals that may have been formed in water," says Philip Christensen of Arizona Statue University, the Principle Investigator for the Camera System. "Those will act as beacons of the places we want to go and study Mars in detail with future Rovers, Landers and sample return."

THEMIS is actually two cameras in one – one for visible images, the other for thermal infrared. The thermal infrared camera works like night vision goggles, allowing pictures to be captured in the dark.

"One of the things I was really struck by when we first saw these images is the amazing clarity and crispness," says Christensen. "Most of us think of night vision goggles as being grainy and blurry. We have created a scientific instrument that has a resolution and a quality that is truly going to allow us to peer into the dark recesses of Mars."

The THEMIS images show remarkable landscape variability, with a diversity of landforms, structures, and textures.

"The differences in the distribution of rocks on the surface will tell us a great deal about the physical fate of Mars," says Christensen.

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The wide angle view of the martian north polar cap was acquired on March 13, 1999, during early northern summer. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north polar cap is roughly 1100 kilometers (680 miles) across.Credit: NASA/JPL/Malin Space Science Systems

At night, when sun-warmed areas cool down, THEMIS will look for anomalous hot spots. Such hot spots could indicate volcanic activity on Mars. If Mars does have volcanic activity, it may also have hot spring activity – where water, heat and minerals could provide an abode for life.

Roger Gibbs, Odyssey Deputy Project Manager at JPL, says that in addition to the Odyssey science data, the orbiter will support other Mars programs like the Mars Exploration Rover, the Beagle mission, Mars Express, and the Mars Reconnaissance Orbiter. Odyssey also will provide landing site characterization for future Mars Landers.

"Today we have a very well operating spacecraft," says Gibbs. "The main consumable, propellant, is ample for both our prime mission and a good healthy extended mission beyond that."

What’s Next?

"We’re really looking forward to following this with time," says Boynton. "We’ll probably be having a lot more sleepless nights just watching as these data come in."

The boom of the Gamma Ray Spectrometer will be extended in the next few months. Currently, the instrument is reading background signals coming from the spacecraft as well as some signals coming from Mars. Once the boom is deployed, other signals from Mars will come in more clearly.

"For some elements, like hydrogen, it’s not going to make too much difference in the quality of the data, because we already know we’ve got a whopping signal coming from Mars, so what’s coming from the spacecraft is not too important," says Boynton. "There are going to be other elements, like aluminum, where right now probably most of the signal we were getting is coming from the spacecraft. For an element like that, it’s going to be a very significant enhancement once we extend the boom."

"Our Odyssey is just begun," says Saunders. "We expect to map and monitor Mars for at least two Mars years. What we show today – although it’s new and exciting – is only a glimpse of what is to come."


Related Web Pages

Mars Odyssey
European Space Agency
Exiting the Martian Ice Age?
Jet Propulsion Laboratory
Malin Space Systems
Mars Global Surveyor
Arizona State THEMIS
Mars 2001 Odyssey