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MESUR, the Mars Environmental SURvey was a NASA program designed to explore the planet Mars in preparation for human follow-up missions of the Space Exploration Initiative. The only mission of the program that was completed was MESUR Pathfinder.


MESUR was a planned set of 16 surface missions on Mars that would also set up a planetary network across Mars and work in conjunction with Mars Observer.[1] The original plan was proposed by NASA Ames,[2] but it would eventually include ideas from the competing JPL proposal. It was envisioned as a low-cost method of surveying Mars, with risk tolerance, since a loss of a spacecraft was not fatal to the program, because of multiple relatively cheap space probes.

MESUR Pathfinder would be the "pathfinder" mission for the MESUR program. MESUR regular missions would start landing in 1999. The multi-year MESUR would have 16 more landers, landing in the projected period of 1999-2003,[3] and lasting 10 years.[4] Launches would start in 1996.[5] Several of the landers would carry Sojourner-class rovers.[6] The entire program was projected at a cost of $1 billion US, with per annum spending restricted to $150 million US, starting in FY1994. They were planned to be low-cost missions to Mars, instead of multibillion-dollar missions.[7]

The rovers and landers would have instruments and cameras to examine surface rocks, search for water, perform seismography, and observe meteorology. The seismology experiments would help determine the internal structure of Mars.

After Pathfinder, in 1999, four landers would be launched in a single rocket. At the next launch window in 2001, four more landers would again launch in on a single rocket. Finally in 2003, the last eight landers would launch on two rockets.[8]

On 26 June 1992, NASA unveiled the prototype for Mars Sojourner, Rocky IV, on the 25th anniversary of the first US lunar lander.[3]

After the loss of Mars Observer, the MESUR program was shelved, and Pathfinder became part of the NASA Discovery Program.[9]


MESUR Pathfinder[edit]

The MESUR Pathfinder[10] was launched on December 4, 1996 by NASA aboard a Delta II. After a 7-month voyage it landed on Ares Vallis, in a region called Chryse Planitia on Mars, on 4 July 1997. During its voyage the spacecraft had to accomplish four flight adjustments on 10 January, 3 February, 6 May and 25 June. The lander opened, exposing the rover called Sojourner that would go on to execute many experiments on the Martian surface.

Although the mission was programmed to last a week to a month, it eventually lasted for almost three months. The final contact with the Pathfinder was at 10:23 UTC on September 27, 1997. Although the mission planners tried to restore contact during the following five months, the successful mission was terminated on March 10, 1998. After the landing, the Mars Pathfinder was renamed the Sagan Memorial Station in honor of the famous astronomer and planetologist Carl Sagan. The mission had exceeded its goals in the first month.


  1. ^ Robert C. Cowen (5 July 199). "Launch Window Nears for Mars Observer". Christian Science Monitor. Retrieved 11 March 2023.
  2. ^ Eric Schine (9 September 1991). "The Lilliptians Who May Conquer Mars". Businessweek. Archived from the original on 24 May 2011.
  3. ^ a b David S.F. Portree (13 October 2012). "Measuring Mars: the MESUR Network Mission (1991)". Wired. Retrieved 11 March 2023.
  4. ^ John Noble Wilford (22 September 1992). "After 17 Years, NASA Prepares for a Return Trip to Mars". New York Times. Retrieved 11 March 2023.
  5. ^ Joseph Bauman (16 September 1993). "Small Instruments Cut Cost of Mars Exploration". Deseret News. Retrieved 11 March 2023.
  6. ^ Dennis Romboy (7 June 1995). "Firms's X-Ray Windows Blast Off for Mars in '96". Deseret News. Retrieved 11 March 2023.
  7. ^ John Noble Wilford (8 September 1992). "NASA Plans an Economy Flight to the Solar System's Last Stop". New York Times. Retrieved 11 March 2023.
  8. ^ John Noble Wilford (12 May 1992). "SCIENCE WATCH: NASA Seeks to Send 16 Landers to Mars". New York Times. Retrieved 11 March 2023.
  9. ^ Ben Evans (4 December 2016). "Six Wheels on Martian Regolith: 20 Years Since NASA's Pathfinder Mission Launched to the Red Planet". America Space. Retrieved 11 March 2023.
  10. ^ Kathy Sawyer (13 November 1993). "One Way or Another, the Space Agency Will Hitch a Ride to Mars". The Washington Post. Retrieved 11 March 2023.