Thursday Reader: NASA’s Mercury Messenger Says Goodbye

NASA's Mercury MESSENGER Probe

NASA’s Mercury MESSENGER Probe

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 smash into the surface at more than 8,750 miles per hour (3.91 kilometers per second). The impact will add a new crater to the planet’s scarred face that engineers estimate will be as wide as 52 feet (16 meters).

The end is likely to come at about 3:30 p.m. EDT on April 30, 2015.

Unmasking the Secrets of Mercury Scientists have worked to learn more about the minerals and surface processes on Mercury using instruments on the MESSENGER spacecraft to diligently collect single tracks of spectral surface measurements since entering Mercury orbit on March 17, 2011. The track coverage is now extensive enough that the spectral properties of both broad terrains and small, distinct features such as pyroclastic vents and fresh craters can be studied. 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. MESSENGER's highly successful orbital mission is about to come to an end, as the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury near the end of April 2015. Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Unmasking the Secrets of Mercury
Scientists have worked to learn more about the minerals and surface processes on Mercury using instruments on the MESSENGER spacecraft to diligently collect single tracks of spectral surface measurements since entering Mercury orbit on March 17, 2011. The track coverage is now extensive enough that the spectral properties of both broad terrains and small, distinct features such as pyroclastic vents and fresh craters can be studied.
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. MESSENGER’s highly successful orbital mission is about to come to an end, as the spacecraft runs out of propellant and the force of solar gravity causes it to impact the surface of Mercury near the end of April 2015.
Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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.

Mercury is not the garden spot of the solar system. It’s a small, airless sphere, only slightly larger than Earth’s moon, with stark and foreboding landscapes. Daytime temperatures can reach about 800 degrees Fahrenheit (430 degrees Celsius) and drop to -290 degrees Fahrenheit (-180 degrees Celsius) at night.

But MESSENGER brought to light the intricacies of an intriguing world. The mission discovered a surface rich in diverse chemistry, including volatiles. It sensed a bizarrely offset magnetic field. It photographed strange “hollows” where material seems to have boiled away into space under the scorching sun. It mapped vast volcanic deposits, found that the entire planet has shrunk by as much as 7 kilometers in radius, and, of all things, uncovered deposits of water ice in the depths of polar craters where the sun never shines.

When MESSENGER disappears behind Mercury’s horizon for the last time, no spacecraft will scan its strange surface until the European Space Agency’s BepiColombo mission arrives in the 2020s. But for many years to come, planetary explorers will be pouring over the gigabytes of information that MESSENGER sent home.

On the Web: 

Messenger Mission Pages

Mercury Messenger

Journey’s End: Follow along with MESSENGER during its final orbits, and count down its top discoveries and engineering breakthroughs.

Facts About the First World: Pay a virtual visit to Mercury and see some of the best images of this odd and intriguing world.

The Trailblazer: Meet Mariner 10, the first spacecraft to explore Mercury.

Crash

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