Mariner 10 made it past Mercury on March 29, 1974, the first of three passes. (The other two were on Sept. 21, 1974, and March 16, 1975.) Mariner 10 took this photo of the southwest region of Mercury.

NASA’s Mariner 10 became the first space probe to fly by Mercury on March 29, 1974. It was launched on November 3, 1973, approximately two years after Mariner 9 and was the last spacecraft in the ...

Mariner 10 flew by Mercury again on Sept. 21, 1974, this time on the sunlit side, at a whopping distance of almost 30,000 miles, or the equivalent of about six round-trip flights between New York ...

This mission was for the exploration of the planets Venus and Mercury. Credit: NASA. Mariner 10 launched atop an Atlas-Centaur rocket from Cape Canaveral’s Pad 36B at 12:45 a.m. EST on Nov. 3, 1973.

Image of Mercury captured by NASA's Mariner 10 spacecraft, the first probe to visit Mercury. (Image credit: NASA/JPL/USGS) Even though Mercury is the closest planet to the sun, its surface can ...

MESSENGER was only the second probe to venture to Mercury, and it came three decades after Mariner 10 completed a whistle-stop tour and three close-range flybys between 1974 and 1975.

Mariner 10 showed that Venus had at best a weak magnetic field, and the ionosphere interacted with the solar wind to form a bow shock. At Mercury, it confirmed that Mercury had no atmosphere and a ...

Based on my research, which include image composites of two flyby views of Mercury from the MESSENGER spacecraft, I conclude that Mercury has not cooled and shrunken as much as previously thought.

MESSENGER was the first spacecraft to orbit Mercury and the second spacecraft to study it up close after NASA's Mariner 10 flew by the planet in the 1970s. MESSENGER spent four years orbiting Mercury.