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Mars 7



Mars 4, 5, 6, and 7 comprised an associated group of Soviet spacecraft launched towards Mars in July and August of 1973. The Mars 4, 6, and 7 missions all had major problems stemming from faulty transistors. (The 2T312 transistors, as a cost-saving measure, used aluminum instead of gold-plated contacts, which dramatically increased degradation.) The Mars 7 interplanetary station was intended to be a Mars lander. It consisted of a flyby bus and a descent module. The descent module was designed to enter the martian atmosphere and make in-situ studies of the atmosphere and surface, but a malfunction on board caused the lander to miss the planet.

Mission Profile

Mars 7 successfully lifted off into an intermediate Earth orbit on a Proton SL-12/D-1-e booster and then launched into a Mars transfer trajectory. Total fueled launch mass of the lander and bus was 3260 kg. After one course correction burn on 16 August 1973, it reached Mars on 9 March 1974. Due to a problem in the operation of one of the onboard systems (attitude control or retro-rockets) the landing probe separated prematurely (4 hours before encounter) and missed the planet by 1300 km. The early separation was probably due to the computer chip error which resulted in degradation of the systems during the trip to Mars. The intended landing site was 50 S, 28 W and landed mass would have been 635 kg. The lander and bus continued on into heliocentric orbits.

Scientific Instrumentation

The Mars 7 Descent Module carried a panoramic telephotometer to image the martian surface around the lander, atmospheric temperature, pressure, density, and wind sensors, an accelerometer to measure atmospheric density during the descent, a mass spectrometer to estimate atmospheric composition, a radio altimeter, an activation analysis experiment to study soil composition, and mechanical properties soil sensors. The flyby module contained a telephotometer to image Mars, a Lyman alpha sensor to search for hydrogen in the upper atmosphere, a magnetometer, an ion trap and narrow angle electrostatic plasma sensor to study the solar wind and its interaction with Mars, solar cosmic ray sensors, micrometeorite sensors, and a French-supplied solar radiometer to measure solar long-wavelength radio emissions. It was also equipped to perform a radio occultation experiment to profile the atmosphere and ionosphere.

Spacecraft image above for illustrative purposes - not necessarily in the public domain.

Alternate Names

  • 06776
  • M-73 No.51P
  • Mars7

Facts in Brief

Launch Date: 1973-08-09
Launch Vehicle: Proton Booster Plus Upper Stage and Escape Stages
Launch Site: Tyuratam (Baikonur Cosmodrome), U.S.S.R
Mass: 1200 kg

Funding Agency

  • Unknown (U.S.S.R)


  • Planetary Science
  • Space Physics

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Mr. Artem IvankovGeneral ContactLavochkin

Selected References

  • Shelton, W., Soviet space exploration - the first decade, Arthur Barker Ltd., Unnumbered, London, England, 1969.
  • Harvey, B., The new Russian space programme from competition to collaboration, John Wiley and Sons, Chichester, England, 1996.
  • Perminov, V. G., The difficult road to Mars - A brief history of Mars exploration in the Soviet Union, NASA, No. 15, Wash, DC, July 1999.

Image of Mars 6/7 Image of Mars 6 and 7 from Perminov, "The Difficult Road to Mars", NASA, 1999

Other Mars flights in the 1973 launch opportunity series

Mars 4
Mars 5
Mars 6

Chronology of Mars Exploration
The Difficult Road to Mars - Online Book, 1999 (PDF file)
Mars Page

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