Thank you, MESSENGER.
Mission controllers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., confirmed today [30 April 2015] that NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the surface of Mercury, as predicted, at 3:26 p.m. EDT this afternoon (3:34 p.m. ground time).
Mission controllers were able to confirm the end of operations just a few minutes later at 3:40 p.m., when no signal was detected by the Deep Space Network (DSN) station in Goldstone, California, at the time the spacecraft would have emerged from behind the planet had MESSENGER not impacted the surface. This conclusion was independently confirmed by the DSN’s Radio Science team, who were simultaneously looking for the signal from MESSENGER from their posts in California.
MESSENGER was launched on August 3, 2004, and it began orbiting Mercury on March 18, 2011. The spacecraft completed its primary science objectives by March 2012. Because MESSENGER’s initial discoveries raised important new questions and the payload remained healthy, the mission was extended twice, allowing the spacecraft to make observations from extraordinarily low altitudes and capture images and information about the planet in unprecedented detail.
Last month — during a final short extension of the mission referred to as XM2′– the team embarked on a hover campaign that allowed the spacecraft at its closest approach to operate within a narrow band of altitudes, 5 to 35 kilometers above the planet’s surface. On April 28, the team successfully executed the last of seven orbit-correction maneuvers (the last four of which were conducted entirely with helium pressurant after the remaining liquid hydrazine had been depleted), which kept MESSENGER aloft for the additional month, sufficiently long for the spacecraft’s instruments to collect critical information that could shed light on Mercury’s crustal magnetic anomalies and ice-filled polar craters, among other features.
With no way to increase its altitude, MESSENGER was finally unable to resist the perturbations to its orbit by the Sun’s gravitational pull, and it slammed into Mercury’s surface at around 8,750 miles per hour, creating a new crater up to 52 feet wide.
“Today we bid a fond farewell to one of the most resilient and accomplished spacecraft ever to have explored our neighboring planets,” said Sean Solomon, MESSENGER’s Principal Investigator and Director of Columbia University’s Lamont-Doherty Earth Observatory. “Our craft set a record for planetary flybys, spent more than four years in orbit about the planet closest to the Sun, and survived both punishing heat and extreme doses of radiation. Among its other achievements, MESSENGER determined Mercury’s surface composition, revealed its geological history, discovered that its internal magnetic field is offset from the planet’s center, taught us about Mercury’s unusual internal structure, followed the chemical inventory of its exosphere with season and time of day, discovered novel aspects of its extraordinarily active magnetosphere, and verified that its polar deposits are dominantly water ice. A resourceful and committed team of engineers, mission operators, scientists, and managers can be extremely proud that the MESSENGER mission has surpassed all expectations and delivered a stunningly long list of discoveries that have changed our views not only of one of Earth’s sibling planets but of the entire inner solar system.”
When it comes to the question of what NASA can do, the MESSENGER mission is every bit as exemplary as Voyager or the Martian rovers. MESSENGER mapped the entire surface of Mercury; there is even a Google Earth version.
This is still a wonderful show; much work remains:
Although the MESSENGER flight mission has now officially ended, the science data collected by MESSENGER are archived in NASA’s Planetary Data System, where they are preserved and remain accessible for future use by the scientific community for years and even decades to come. The Science Team will continue to use these data to pose and answer questions about Mercury’s formation and evolution and the planet’s place in our Solar System through the end of the MESSENGER project in May 2016.
And they even managed to have some fun along the way.
Something goes here about a government agency doing its job. I don’t know, I would be remiss without it. But, yeah. This is pretty damn awesome.
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Image note: Top―Detail of Mercury global mosaic, one result of MESSENGER’s mission. Via Johns Hopkins University, 8 March 2013. Right―Final mission statistics for MESSENGER, which crashed into Mercury on 30 April 2015 SCET; image via MESSENGER mission page at Johns Hopkins University.
Johns Hopkins University. “NASA Completes MESSENGER Mission with Expected Impact on Mercury’s Surface”. 30 April 2015.
—————. “Global Mosaics of Mercury”. 2013.
—————. “Three Easy Steps to Explore Mercury in Google Earth”. (n.d.)
—————. “Five New Crater Names for Mercury”. 29 April 2015.
Jet Propulsion Laboratory. “Voyager: The Interstellar Mission”. (n.d.)
—————. “Mars Exploration Rovers”. (n.d.)
This Is 