The following table is a list ofMarsorbiters, consisting ofspace probes which were launched from Earth and are currently orbitingMars. As of August 2023, there have been 18 spacecraft missions operating in Mars' orbit, 7 of which are currently active.
TheSoviets'Mars program and theUnited States'Mariner program became the two first successful space programs that intended toexploreMars throughorbiters.Mars 2,Mars 3 andMariner 9 were all launched into space in May 1971, and all entered Mars’ orbit that same year. NASA's Mariner 9 reached the planet's orbit first on November 14, narrowly beating the Soviet's spacecraft amid thespace race, and subsequently became the first spacecraft to orbit another planet.[1]
Contact with all eight Mars orbiters launched during the 20th century has been lost. NASA's four spacecraft are conjectured to remain in Mars' orbit. Mariner 9,Viking 1 andViking 2 are expected to lower down into the Martian atmosphere by 2022 and either burn up or crash into the planet's surface.[2]Mars Global Surveyor is expected to crash onto the surface of the planet by 2047. The fate of the Soviet's three Mars program orbiters andPhobos 2 remains unclear, but they are still presumed to be in orbit.[3]
In 1999 theMars Climate Orbiter impacted the Martian atmosphere.
2001 Mars Odyssey was launched April 7, 2001 on aDelta II rocket and currently holds the record for the longest-surviving continually active spacecraft in orbit around a planet other than Earth at 24 years and 26 days.[4]
In 2003, theEuropean Space Agency (ESA) launched their first planetary mission withMars Express to conduct reconnaissance and exploration of Mars from orbit.[5] On 12 August 2005, NASA launchedMars Reconnaissance Orbiter (MRO). As MRO entered orbit in 2006, it joined three other active spacecraft which were in Mars' orbit:Mars Global Surveyor (MGS), Mars Express, and2001 Mars Odyssey; at the time, this set a record for the most operational spacecraft in the immediate vicinity of Mars. MGS has since ceased to function.
On November 5, 2013, theMars Orbiter Mission (Mangalyaan-1) was launched by theIndian Space Research Organisation (ISRO) as a "technology demonstrator" project. Its secondary goal is to analyze the Martian atmosphere and topography. The orbiter reached Mars orbit on September 24, 2014. Through this mission, ISRO became the first space agency to succeed in its first attempt at a Mars orbiter. The mission is the first successful Asian interplanetary mission.[6] Ten days after ISRO's launch, NASA launched their seventh Mars orbiterMAVEN to study theMartian atmosphere. Its goals include determining how the planet'satmosphere andwater, presumed to have once been substantial, were lost over time.[7]
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After achieving orbit, functional or not, Mars orbiters have been predicted to remain in orbit for a certain amount of time.[8]
Besides decaying to Mars, a collision with a moon or other spacecraft is also a possibility.[12] In March 2017,MAVEN had to change its orbit to avoid colliding with Phobos, and with an increasing number of spacecraft at Mars this risk increases.[13] TheMars Global Surveyor is still being tracked, although it is no longer functioning.[14]
| Color legend |
|---|
| Destroyed |
| Loss of contact |
| Operational |
Note that days active category does not necessarily equate to time in orbit, for example Mars Global Surveyor is expected remain in Mars orbit for 50 years after its arrival.[15] The detection of derelict spacecraft in Mars orbit has some interest due to the minute risk of collision with such a spacecraft. One example of this is a proposal to use the Optical Navigation Camera on the Mars Reconnaissance Orbiter to search for small moons, dust rings, and old orbiters.[16]
| Artificial object | Agency | Launch date | Entered orbit | Days active | Image |
|---|---|---|---|---|---|
| Mars 2 |  Lavochkin | 19 May 1971 | 27 November 1971 | 269 days | |
| Mars 3 | Lavochkin | 28 May 1971 | 2 December 1971 | 264 days | |
| Mariner 9 |  NASA | 30 May 1971 | 14 November 1971 | 348 days |  |
| Mars 5 | Lavochkin | 25 July 1973 | 12 February 1974 | 16 days | |
| Viking 1 | NASA | 20 August 1975 | 19 June 1976 | 1,520 days |  |
| Viking 2 | NASA | 9 September 1975 | 7 August 1976 | 717 days | |
| Phobos 2 | Lavochkin | 12 July 1988 | 29 January 1989 | 57 days |  |
| Mars Global Surveyor | NASA | 7 November 1996 | 12 September 1997 | 3,338 days |  |
| 2001 Mars Odyssey | NASA | 7 April 2001 | 24 October 2001 | 8,792 days | |
| Mars Express |  ESA | 2 June 2003 | 25 December 2003 | 8,000 days |  |
| Mars Reconnaissance Orbiter | NASA | 12 August 2005 | 10 March 2006 | 7,194 days |  |
| Mars Orbiter Mission (Mangalyaan) |  ISRO | 5 November 2013 | 24 September 2014 | 2,930 days |  |
| MAVEN | NASA | 18 November 2013 | 22 September 2014 | 4,076 days |  |
| ExoMars Trace Gas Orbiter | ESA Roscosmos | 14 March 2016 | 19 October 2016 | 3,318 days |  |
| Emirates Mars Mission (Hope) |  UAESA | 19 July 2020 | 9 February 2021 | 1,744 days | |
| Tianwen 1 orbiter |  CNSA | 23 July 2020 | 10 February 2021 | 1,743 days | |
| Tianwen 1 Deployable Camera 2 | CNSA | 23 July 2020 | 10 February 2021 (released on 31 December 2021) | <1 day |
It was the first spacecraft to enter orbit around another world. ... [It] continues to orbit Mars to this day, sailing around the planet deaf and dumb in the cold darkness.
It's expected to orbit Mars for at least 50 years before crashing onto the surface of the planet.
It's expected to orbit Mars for at least 50 years before crashing onto the surface of the planet.
It's expected to orbit Mars for at least 50 years before crashing onto the surface of the planet.
It's expected to orbit Mars for at least 50 years before crashing onto the surface of the planet.
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