Complex sentence: Following two mission extensions, the "MESSENGER" mission ended on April 30,2015, after the spacecraft used the last of its maneuvering propellant and suffered orbital decay, ultimately impacting onto the surface of Mercury.
Split into simpler sentences: Following two mission extensions, the "MESSENGER" spacecraft used the last of its maneuvering propellant and began to suffer orbital decay in early 2015. The mission ended on April 30,2015, when the probe impacted onto the surface of Mercury.