Mariner 10 - End of Mission

End of Mission

With its maneuvering gas just about exhausted, Mariner 10 started another orbit of the Sun. Engineering tests were continued until March 24, 1975, when final depletion of the nitrogen supply was signaled by the onset of an un-programmed pitch turn. Commands were sent immediately to the spacecraft to turn off its transmitter, and radio signals to Earth ceased.

Mariner 10 is still orbiting the Sun, although its electronics have probably been damaged by the Sun's radiation. Dave Williams of NASA's National Space Science Data Center said in 2005: "Mariner 10 has not been tracked or spotted from Earth since it stopped transmitting. We can only assume it's still orbiting, but the only way it would not be orbiting would be if it had been hit by an asteroid or gravitationally perturbed by a close encounter with a large body. The odds of that happening are extremely small, so it is assumed to still be in orbit."