Which NASA spacecraft became the first to orbit Mercury?

NASA’s MESSENGER spacecraft became the first spacecraft to orbit Mercury.

MESSENGER entered Mercury orbit on 18 March 2011 after a journey of more than six years. It used repeated flybys of Earth, Venus, and Mercury to reduce its speed relative to the planet and conserve propellant.

The spacecraft mapped Mercury’s surface, measured its magnetic field, studied its thin exosphere, and investigated the planet’s unusually large iron core. Its observations showed that permanently shadowed polar craters contain water ice.

Mariner 10 is the common mix-up because it was the first spacecraft to visit Mercury and the first to use a gravity assist. However, Mariner 10 only performed flybys. MESSENGER was the first mission to remain in orbit and conduct a sustained survey.