The robotic spacecraft MESSENGER has run out of fuel. With no way to make major adjustments to its orbit around the planet Mercury, the probe will add a new crater to the planet’s scarred face. The end is likely to come at about 3:30 p.m. EDT on April 30, 2015.
None of this is a surprise to MESSENGER’s handlers on Earth, who have managed a highly successful mission during a flight of nearly 11 years. The intrepid MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft was launched on August 3, 2004. It embarked on an odyssey of nearly seven years and more than eight billion kilometers that included 15 trips around the sun, along with several gravity-induced speed boost flybys of Earth, Venus, and Mercury itself. It finally slipped into orbit around Mercury on March 18, 2011, the first mission to ever do so.
The mission plan called for MESSENGER to spend one Earth year at Mercury, but when early findings raised new questions, NASA granted two mission extensions for a total of three additional years. Mission engineers also found ways to save fuel, such as maneuvering the spacecraft with a technique called solar sailing, which allowed an extra month of operations in orbit.
The only previous expedition to see the planet up close was Mariner 10 in the 1970s. It provided valuable scouting reports, but since it only flew by, it left large gaps in the images of Mercury’s surface. MESSENGER not only filled in those blank places on the map, its suite of powerful instruments delved deep into the small world’s many mysteries.