The Messenger spacecraft orbiting Mercury has crashed into the planet on April 30, ending a mission which started in 2004. Before the robotic explorer met is demise, however, the vehicle returned one last image from just above the surface of this nearly-arid world.
The Messenger mission marked just the second time the inner-most planet of the solar system was visited by a spacecraft from Earth. It was also the first observatory ever to orbit Mercury, entering its path on March 18, 2011. The vehicle was expected to last just one year after arriving at its target destination, but returned scientific data four times longer than expected.
The final image recorded by the spacecraft was of the floor of Jokai Crater, which stretches 58 miles from one side to another. Soon after the image was recorded, the spacecraft impacted just north of Shakespeare Basin.
Seven science instruments flew aboard the Messenger spacecraft, and data recorded during the mission revealed a wide range of new information about the smallest planet in the solar system. This includes discovery of a powerful magnetic field offset from the center of the planet, and the presence of water ice in perpetually-dark craters near the poles of Mercury.
"As the first spacecraft ever to orbit Mercury, Messenger revolutionized our understanding of the solar system's innermost planet, as well as accomplished technological firsts that made the mission possible," NASA officials wrote in a statement accompanying the image.
The resolution in the photo is approximately 7 feet per pixel, and the image itself represents an area around six-tenths of a mile from side to side.
As part of remembering the historic Messenger program, mission leaders have released the last image side-by-side with the first photograph of Mercury ever taken by the vehicle from orbit, on March 29, 2011.
"In total, Messenger acquired and returned to Earth more than 277,000 images from orbit about Mercury," Johns Hopkins University Applied Physic Laboratory reported.
Messenger made history one last time on April 30, 2015, becoming the first space vehicle from Earth ever to collide with Mercury. It struck the planet surface when it ran out of fuel to adjust its orbit to keep it from stiking the surface.
The spacecraft was controlled through pairs of 25-megahertz (MHz) main processors, with 10-MHz fault protection RAD6000 processors. These chips were protected from the high-radiation conditions of space. Although exceptionally slow by the standards of home electronics, the technology was the best available that could withstand the harsh radiation faced by any spacecraft orbiting Mercury. The observatory ran on a total of just 450 watts of electricity.
After a seven-year journey to Mercury, and four years of groundbreaking science, the Messenger program is now over. The spacecraft just had one thing left to show us, and one more mark left to make on the history books, as well as the planet itself.
