50 years ago, the first probe to visit Mercury launched

Off to Mercury with a cold glance — Science News, November 10, 1973

Mercury ho! Mariner 10 is on its way. Venus ho, too. Launched at 12:45 a.m. (EST) on Nov. 3, Mariner should pass within 3,330 miles of Venus on Feb. 5. It will then become the first spacecraft to use a technique … of letting the gravitational field of one planet bend its course around toward a second objective. That’s Mercury, of course, where it will arrive less than two months later.

Update

Mariner 10 arrived on schedule, becoming the first probe to visit Mercury and map a portion of its cratered, moonlike terrain. The gravity assist that Mariner used to reach its destination is now a trusted way to get around the solar system (SN: 7/12/15; SN: 7/5/18). NASA’s MESSENGER spacecraft used gravity assists from Mercury, Venus and Earth to reach an orbit around Mercury in 2011, where the probe mapped the rest of the planet’s surface, uncovered evidence of past volcanism and spotted signs of water ice and organic compounds (SN: 11/29/11; SN: 3/22/12; SN: 11/30/12).

Today, the international BepiColombo mission is using gravitational assists from Mercury — following one from Earth and two from Venus — to steer itself into eventual orbit around the planet (SN: 1/15/21). Beginning in 2025, BepiColombo will investigate Mercury’s innards and magnetic field.