2001 Mars Odyssey

What is Mars Odyssey?

Mars Odyssey, officially 2001 Mars Odyssey, is a NASA orbiterOrbiterAn orbiter circles Mars without landing, studying the planet from above — and many also relay rover data back to Earth.More in the glossary that maps Mars from 385 to 450 km (239 to 280 mi) up and relays rover data to Earth.[1][12] It launched on a Delta II rocket from Cape Canaveral, Florida, on Apr 7, 2001. It fired its main engine to enter orbit on Oct 24, 2001 (UTC), the evening of Oct 23 in California.[1][3] It then spent three months dipping into the top of the atmosphere to shrink its orbit, a technique called aerobraking, and sent its first science data on Feb 19, 2002.[2][8]

Its main job was to map what Mars is made of. It was the first spacecraft to make a global map of the chemical elements and minerals on the surface.[1] JPL leads the mission, Lockheed Martin built the spacecraft and helps fly it, and Arizona State University built and runs its camera.[9]

NASA figures as of the dates shown. Mb is megabits. The lap and distance totals have grown since NASA published them.[1][10][16][9][2][12][11]

How long has Odyssey been at Mars?

Since Oct 24, 2001: almost 25 years, longer than any other spacecraft.[1][2] NASA says Odyssey holds the record for the longest continually active mission in orbit around a planet other than Earth.[1] It became the longest-serving spacecraft at Mars on Dec 15, 2010 (US time), when it began its 3,340th day in orbit. That beat NASA’s Mars Global Surveyor, which orbited Mars from 1997 to 2006.[4]

That was never the plan. “Odyssey was designed for a four-year mission,” project scientist Jeffrey Plaut said in 2016.[8] Its prime science mission ran from February 2002 to August 2004, and NASA has extended it again and again since.[1][6] In November 2012 it switched to a backup set of equipment, including its main computer, that had not been used since launch.[17] A 2025 NASA review panel, looking at a proposed tenth extended mission through fiscal year 2028, called the health of its hardware “particularly impressive given the age (almost 24 years) of the spacecraft.”[11]

What has Mars Odyssey found?

Water ice hidden just under the surface across large areas of Mars, plus the first global map of what the surface is made of.[5][1]

• 01Buried ice. On May 28, 2002, NASA announced that Odyssey’s gamma ray spectrometer had found hydrogen, read as water ice, in the top meter (3 ft) of soil around the south pole: enough to fill Lake Michigan twice, NASA said. In the lower layer the ground is more than half ice by volume.[5] NASA’s Phoenix landerLanderA lander touches down on Mars and works from one spot, unlike a rover, which drives.More in the glossary confirmed the ice in 2008.[4]
• 02What Mars is made of. Its infrared maps showed that a mineral called olivine is widespread. Water turns olivine into other minerals, so NASA read this as a sign that the environment there has been quite dry.[6]
• 03Radiation risk for astronauts. Its MARIE instrument, the first experiment sent to Mars to prepare for human missions, found radiation from solar flares and cosmic rays two to three times higher around Mars than around Earth. A solar flare knocked MARIE out in October 2003.[4][6]
• 04More than a million pictures. Its camera, THEMIS, sees in visible and infrared light.[13] Infrared shows how fast the ground warms and cools, which tells rock from sand and dust, and NASA has used THEMIS maps to choose landing sites, including Perseverance’s.[2][7] A 2025 NASA review called it the only infrared camera orbiting Mars.[11]
• 05The horizon, as an astronaut would see it. Since 2023 the team has turned the spacecraft 90 degrees so THEMIS looks at the horizon, showing layers of dust and ice clouds. It caught Olympus Mons this way on Mar 11, 2024, and the volcano Arsia Mons poking above morning clouds on May 2, 2025.[9][14]
• 06Mars’s moons. THEMIS has also photographed Phobos and Deimos, measuring how their surfaces heat and cool, a clue to what they are made of.[7][14]

How does Odyssey relay data from the rovers?

It picks up data from landers and rovers on a UHF radio as it passes overhead, then sends it to Earth on its X-band radio.[1] Odyssey made this routine. More than 90% of the data NASA received from the Spirit and Opportunity rovers came through Odyssey, and it handled most of the data from Phoenix.[8][4] By 2021 it had supported more than 18,000 relay sessions.[7]

Today it is one of four orbiters in NASA and ESA’s Mars Relay Network.[12] Its orbit passes over the ground at about 6 a.m. and 6 p.m. local mean solar timeLocal mean solar timeLocal mean solar time is the clock a rover team works by: the average time of day at the rover’s spot, ignoring the Sun’s seasonal drift.More in the glossary, which is convenient for scheduling passes over the rovers. A 2025 NASA review found it had recently handled 14% of Perseverance’s relay sessions and 13% of Curiosity’s.[11] NASA puts its average at 170.4 megabits a day through 2025 and 107.3 megabits a day from February to May 2026.[12] After MAVEN went silent in December 2025, NASA arranged extra passes from Odyssey and the other orbiters still working.[18] Our Mars Reconnaissance Orbiter page compares all the relay orbiters.

How long will Odyssey’s fuel last?

NASA hasn’t given an end date. Fuel is one limit; money is another. NASA’s mission page lists Odyssey as active, “2001 - ongoing.”[1] NASA’s budget request for fiscal year 2026 proposed ending Odyssey’s funding, but Congress funded it for that year, The Planetary Society reported.[19][20] The 2027 request again slates it for cancellation, the society says.[21] In 2025 a NASA review panel put its usable propellant at about 3.2 kg (7 lb), with an uncertainty of 2 kg (4.4 lb) either way. The proposed extended mission through fiscal year 2028 needs 1.3 kg (2.9 lb), if no safe-mode events or other problems use extra.[11]

Odyssey has no fuel gauge. Engineers estimate what is left by heating its two tanks and timing how fast they warm, because a nearly empty tank heats faster. Day to day it uses little: solar panels power it, reaction wheels point it, and short thruster bursts get rid of momentum that builds up in the wheels.[10]

In 2021 this gave a scare. Measurements suggested only about 5 kg (11 lb) was left, then 2.8 kg (6 lb) in January 2022, which would have run out in less than a year. Engineers found that heaters on a fuel line were warming the tanks faster than expected, making them look emptier. In 2023 NASA said about 4 kg (9 lb) remained, enough for a few more years.[10]

A hardware failure could use up the margin sooner. One of Odyssey’s reaction wheels has failed and it has no spare. If another fails, the team plans to steer with thrusters, which would burn fuel faster, as would a safe-mode event.[11]

Why is it called 2001 Mars Odyssey?

It is a tribute to Arthur C. Clarke and his novel “2001: A Space Odyssey.” The year it launched and arrived, 2001, played into the choice, and Clarke endorsed the name before launch.[8][7] The mission also carried NASA’s hopes after two Mars missions launched in 1999 failed. All six NASA missions sent to Mars after it had succeeded too, JPL noted in 2016.[8]

Mission timeline

1. Apr 7, 2001Launches on a Delta II rocket from Cape Canaveral.[1]
2. Oct 24, 2001Enters orbit around Mars (UTC; Oct 23 in US time), then aerobrakes for three months.[1][3][8]
3. Feb 19, 2002Sends its first science data.[2]
4. May 28, 2002NASA announces water ice just under the surface.[5]
5. October 2003A solar flare knocks out its radiation instrument, MARIE.[6]
6. August 2004Completes its prime mission and begins the first of many extensions.[1][6]
7. May 25, 2008Phoenix lands in the far north. Odyssey relays most of its data, and Phoenix confirms the buried ice.[4]
8. Dec 15, 2010Becomes the longest-serving spacecraft at Mars (US time).[4]
9. November 2012Switches to backup equipment, unused since launch.[17]
10. Mar 11, 2024Photographs Olympus Mons on the horizon.[9]
11. Jun 30, 2024Due to complete its 100,000th orbit, NASA said.[9]
12. Apr 7, 2026Marks 25 years since launch. The team celebrates at JPL on Apr 15.[15]

Sources

1. NASA Science — Mars OdysseyPrimary · checked Oct 6, 2026
2. NASA Science — Odyssey Celebrates 25 YearsPrimary · checked Oct 6, 2026
3. NASA JPL — Mars Odyssey Mission Status (Oct 23, 2001)Primary · checked Oct 6, 2026
4. NASA JPL — NASA’s Odyssey Spacecraft Sets Exploration Record on MarsPrimary · checked Oct 6, 2026
5. NASA JPL — Odyssey Finds Water Ice in Abundance Under Mars’ SurfacePrimary · checked Oct 6, 2026
6. NASA JPL — Mars Odyssey Begins Overtime After Successful MissionPrimary · checked Oct 6, 2026
7. NASA — NASA’s Odyssey Orbiter Marks 20 Historic Years of Mapping MarsPrimary · checked Oct 6, 2026
8. NASA JPL — Mars Longevity Champion Launched 15 Years AgoPrimary · checked Oct 6, 2026
9. NASA — NASA’s Mars Odyssey Captures Huge Volcano, Nears 100,000 OrbitsPrimary · checked Oct 6, 2026
10. NASA — Engineers Keep an Eye on Fuel Supply of NASA’s Oldest Mars OrbiterPrimary · checked Oct 6, 2026
11. NASA Planetary Science Division — 2025 Planetary Mission Senior Review: Final ReportPrimary · checked Oct 6, 2026
12. NASA Science — Mars Relay NetworkPrimary · checked Oct 6, 2026
13. NASA Science — Mars Odyssey Science InstrumentsPrimary · checked Oct 6, 2026
14. NASA — NASA Mars Orbiter Captures Volcano Peeking Above Morning Cloud TopsPrimary · checked Oct 6, 2026
15. NASA Science (Photojournal) — Odyssey Team Celebrates on a Global Map of MarsPrimary · checked Oct 6, 2026
16. NASA JPL — NASA Moves Longest-Serving Mars Spacecraft for New ObservationsPrimary · checked Oct 6, 2026
17. NASA JPL — Long-Lived Orbiter Resumes Work With Fresh EquipmentPrimary · checked Oct 6, 2026
18. NASA Science — NASA Continues MAVEN Spacecraft Recontact EffortsPrimary · checked Oct 6, 2026
19. NASA — FY 2026 President’s Budget Request Summary (technical supplement)Primary · checked Oct 6, 2026
20. The Planetary Society — You just saved NASA’s budgetSecondary · checked Oct 6, 2026
21. The Planetary Society — The FY 2027 NASA budget requestSecondary · checked Oct 6, 2026