NASA's Odyssey orbiter marks 20 historicyears of mapping Mars8 April 2021, by Andrew Good

A sea of dark dunes, sculpted by the wind into long lines,surrounds the northern polar cap covering an area as bigas Texas in this false-color image from NASA's MarsOdyssey, the longest-working Mars spacecraft in history.Credit: NASA/JPL-Caltech/ASU

NASA's 2001 Mars Odyssey spacecraft launched20 years ago on April 7, making it the oldestspacecraft still working at the Red Planet. Theorbiter, which takes its name from Arthur C.Clarke's classic sci-fi novel "2001: A SpaceOdyssey" (Clarke blessed its use before launch),

was sent to map the composition of the Martiansurface, providing a window to the past soscientists could piece together how the planetevolved.

But it's done far more than that, uncovering trovesof water ice, serving as a crucial communicationslink for other spacecraft, and helping to pave theway not just for safer landings but also futureastronauts.

Here's a partial list of Odyssey's manyaccomplishments.

Mapping Martian ice

Odyssey's two decades of data have been a boonfor researchers working to determine where waterice is locked up on the planet. Understanding thewater cycle on Mars—a planet that was once muchwetter, like Earth—offers insights into the way it haschanged over time: How does water move aroundthe planet today? Does the tilt of the planet affectwhere ice is stable? Odyssey's discoveries havehelped chip away at those questions.

"Before Odyssey, we didn't know where this waterwas stored on the planet," said Project ScientistJeffrey Plaut of NASA's Jet Propulsion Laboratoryin Southern California, which leads the Odysseymission. "We detected it for the first time from orbitand later confirmed it was there using the Phoenixlander."

Stores of water ice are also needed to helpastronauts survive on Mars and to provide fuel fortheir spacecraft. (In fact, astronauts were the focusof an instrument aboard Odyssey that measuredhow much space radiation they would have tocontend with before it stopped working in 2003.)The orbiter finds the water ice using its gamma-rayspectrometer (GRS) detector, which has proven tobe a capable hunter of near-surface hydrogen—aproxy for water ice. The GRS measures the amount

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of different elements on the Martian surface andalso serves as a node in NASA's interplanetarygamma-ray burst (GRB) detection network, whichidentifies source locations of GRB's for follow-upastronomical observations.

What Mars is made of

Look at almost any mapping study of the Martiansurface, and it probably includes Odyssey data. Formany years, the most complete global maps ofMars were made using Odyssey's infrared camera,called the Thermal Emission Imaging System, orTHEMIS. The camera measures the surfacetemperature day and night, allowing scientists todetermine what physical materials, such as rock,sand, or dust, exist. Its data reveals the presence ofthese materials based on how they heat up or cooldown over the course of a Martian day.

The net effect of two decades' worth of all thatmapping? Scientists haven't just used the data tomap valley networks and craters, they've also beenable to spot sandstone, iron-rich rocks, salts, andmore—findings that help lend deeper insight to Mars'story. "It's hard to overstate how the THEMIS globalmap has filled gaps in our knowledge," said LauraKerber of JPL, Odyssey's deputy project scientist.

If a meteorite breaks in two shortly before hitting theground, the typical bowl shape of a single impact craterbecomes doubled. This image is from NASA's MarsOdyssey, one of an 'All Star' set. Credit: NASA/JPL-Caltech/ASU

Safer landings

THEMIS has sent back more than 1 million imagessince it began circling Mars. The images and mapsit's produced highlight the presence of hazards,such as topographic features and boulders, butthey also help ensure the safety of futureastronauts by showing the location of resourcessuch as water ice. This aids the Mars sciencecommunity and NASA in deciding where to sendlanders and rovers—including the Perseverance

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rover, which touched down on Feb. 18, 2021.

Routine calls home

From early on, Odyssey has served as a long-distance call center for NASA's rovers and landers,sending their data back to Earth as part of the MarsRelay Network. The idea of Mars relay goes backto the 1970's, when the two Viking landers sentscience data and images through an orbiter back toEarth. An orbiter can carry radios or antennascapable of sending back more data than a surfacespacecraft. But Odyssey made the process routinewhen it began conveying data to and from NASA'sSpirit and Opportunity rovers.

"When the twin rovers landed, the success ofrelaying data using UHF frequency was agamechanger," said Chris Potts of JPL, Odyssey'smission manager.

Each day, the rovers could go somewhere new andsend fresh images back to Earth. Through a relaylike Odyssey, scientists got more data sooner,while the public got more Mars images to beexcited over. Odyssey has supported over 18,000relay sessions. These days, it shares thecommunications task with NASA's MarsReconnaissance Orbiter and MAVEN, along withthe ESA (European Space Agency) Trace GasOrbiter.

Candy-Colored moons

Odyssey has done such a thorough job of studyingthe Martian surface that scientists have startedturning its THEMIS camera to capture unique viewsof Mars' moons Phobos and Deimos. As with theMartian surface, studying each moon'sthermophysics helps scientists determine theproperties of materials on their surfaces. Suchinformation can offer glimpses into their past: It'sunclear whether the moons are captured asteroidsor chunks of Mars, blasted off the surface by anancient impact.

Future missions, like the Japanese Space Agency'sMartian Moons eXploration (MMX) spacecraft, willseek to land on these moons. In the distant future,missions might even create bases on them for

astronauts. And if they do, they'll rely on data froman orbiter that began its odyssey at the start of themillennium.

THEMIS was built and is operated by Arizona StateUniversity in Tempe. Odyssey's Gamma RaySpectrometer was provided by the University ofArizona, Tucson, Los Alamos National Laboratory,and the Russian Space Research Institute. Theprime contractor for the Odyssey project, LockheedMartin Space in Denver, developed and built theorbiter. Mission operations are conducted jointlyfrom Lockheed Martin and from JPL, a division ofCaltech in Pasadena.

Provided by Jet Propulsion Laboratory

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APA citation: NASA's Odyssey orbiter marks 20 historic years of mapping Mars (2021, April 8) retrieved6 February 2022 from https://phys.org/news/2021-04-nasa-odyssey-orbiter-historic-years.html

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