The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission was a NASA robotic spacecraft that orbited the planet Mercury. MESSENGER was the first mission designed to orbit Mercury and provide detailed, comprehensive observations of the planet’s surface, atmosphere, and magnetic field.
Launched on August 3, 2004, MESSENGER performed a series of flybys of Earth, Venus, and Mercury to gradually adjust its trajectory and eventually enter orbit around Mercury. It entered orbit around Mercury on March 17, 2011, and conducted scientific observations for more than four years. 
During its mission, MESSENGER provided a wealth of data, including high-resolution images of Mercury’s surface, information about its geological features, and insights into its magnetic field and exosphere. The spacecraft helped scientists better understand the planet’s composition, history, and the processes that shaped its surface.
MESSENGER’s mission came to an end on April 30, 2015, when the spacecraft deliberately crashed onto the surface of Mercury after running out of propellant. The impact provided additional scientific data and marked the conclusion of a highly successful mission that significantly expanded our knowledge of the innermost planet in our solar system.
See our Mercury space t-shirt if you are a fan of Mercury!