This Week in Space – March 16, 1975 – Mariner 10 Probe Bids Farewell to Mercury

This Week in Space – March 16, 1975 – Mariner 10 Probe Bids Farewell to Mercury

This Week in Space – March 16, 1975 – Mariner 10 Probe Bids Farewell to Mercury

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By Wes O’Donnell
Managing Editor of In MilitaryInCyberDefense and In Space News.

NASA space probe Mariner 10 was launched on November 3, 1973, to perform reconnaissance of Venus and Mercury.

Mariner 10 was the last spacecraft in the Mariner program and the two planned spacecraft Mariner 11 and 12 were later allocated to the Voyager program and redesignated as Voyager 1 and Voyager 2.

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About the Mission

Mariner 10 was the first mission to employ gravity assist, (using the gravity of a planet to alter a spacecraft’s speed and trajectory to fly by its target planet) and was the first spacecraft to visit Mercury.

Loaded with a suite of scientific instruments, Mariner 10’s payload included:

– Imaging system
– Electrostatic analyzer
– Electron spectrometer
– Triaxial fluxgate magnetometer
– Extreme ultraviolet spectrometer
– Infrared radiometer

An illustration showing Mariner 10’s instruments. Courtesy NASA/JPL

According to NASA, “Mariner 10 data revealed a surprising magnetic field and a metallic core comprising about 80 percent of Mercury’s mass.”

After a brief visit to Venus, Mariner 10 performed three flybys of Mercury; the final flyby occurring this week in 1975.

The spacecraft ran out of its nitrogen fuel on March 24, 1975. Scientists turned off its transmitters, and communication with Earth ceased. Mariner 10 continues to orbit the sun, but solar radiation has likely turned the probe into a scorched husk.

Mariner 10 imaged the Earth and Moon shortly after launch. Courtesy NASA/JPL

Mercury as photographed by Mariner 10. Six hours after closest approach. Courtesy NASA/JPL