The Messenger spacecraft spent more than a decade since launch traveling to, and studying, the inner-most planet, Mercury. Now, that vehicle has reached the end of its life, as fuel needed to maintain an orbit above the tiny planet is exhausted.
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission (Messenger) launched from Earth on Aug. 3, 2004. A highly circuitous flight plan brought the vehicle around the sun 15 times, and also included a pair of flybys of Venus, one trip past Earth, and three visits to Mercury. Messenger finally arrived at its target destination in 2011, following a journey of 4.9 billion miles.
This little spacecraft that could was NASA's second mission to Mercury. The first vehicle to visit the planet, Mariner 10, was launched in 1973, and visited the tiny world twice in 1974 and 1975.
The observatory revealed new secrets about the heavily cratered world, including surface composition. Material coating Mercury was found to be rich in sulfur and sodium, but poor in iron - an unexpected result for astronomers.
Mercury is exceptionally dense when compared with other planets of the inner solar system. Interactions between the interplanetary magnetic field and Mercury results in a complex electromagnetic structure surrounding the planet. The center of this magnetic field was also found to be offset far from the center of the planet.
"The Messenger spacecraft operates in one of the most challenging and demanding space environments in our solar system, and we have met that challenge directly through innovation and hard work, as exemplified by the stunning discoveries and data return achievements. Our only regret is that we have insufficient propellant to operate another 10 years," Andy Calloway from the Johns Hopkins University Applied Physics Laboratory said last year as the spacecraft began to wind down its mission.
In 2012, NASA announced the spacecraft had detected water ice with craters at the poles of Mercury, protected from the Sun.
As fuel supplies ran low, scientists took advantage of declining altitude to study the surface of Mercury up close for the first time in history.
Messenger met its demise on April 30, as the hard-working spacecraft crashed into the planet at a speed of more than 8,700 mph. This impact created a new crater on the planet, estimated to be 50 feet across.
"The Messenger spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the solar system's innermost planet. In the mission's more than four years of orbital operations, Messenger has acquired over 250,000 images and extensive other data sets," NASA officials reported.
A total of seven science instruments were carried aboard Messenger, allowing astronomers to view Mercury like never before, revealing secrets of the mysterious planet.
The Messenger spacecraft may no longer be orbiting Mercury, but the science it produced will last forever.
