* Astronomy

Mars 4

• Launch date/time:
  • Mars 4: July 21, 1973 at 19:30:59 UTC
• On-orbit mass:
  • Dry: 2270 kg
  • Fully-fuelled: 3440 kg

The Mars 4 orbiter reached Mars on February 10, 1974. Due to a flaw in the computer chip which resulted in degradation of the chip during the voyage to Mars, the retro-rockets designed to slow the craft into Mars orbit did not fire , and Mars 4 flew by the planet at a range of 2200 km. It returned one swath of pictures and some radio occultation data which constituted the first detection of the nightside ionosphere on Mars. It continued to return interplanetary data from solar orbit after the flyby.