NASA celebrates, mourns probe’s end
NASA’s Messenger spacecraft ended its mission to Mercury on Thursday with a smashing grand finale.
The spacecraft wrapped up its four years in orbit by crashing into the tiny planet’s surface about 12:26 p.m. Pacific time, officials said.
“On behalf of MESSENGER, thank you all for your support,” officials said on the mission’s Twitter account. “We will continue to update you on our great discoveries. We will miss it.”
Even though the spacecraft met its end alone, scientists in the mission control room at Johns Hopkins University Applied Physics Laboratory in Maryland said they mourned the passing of the spacecraft, whose observations have significantly altered the understanding of the sun-scorched little planet.
“I think everybody has mixed feelings,” Messenger’s lead scientist, Sean Solomon, director of Columbia University’s Lamont-Doherty Earth Observatory, said in an interview shortly before the crash. “Everybody is proud of the many accomplishments of the Messenger mission. ... At the same time, there’s this impending sense of loss.”
In some ways, it was like losing a family member, said Solomon, who called the spacecraft an “almost animate object that has become very known and dear to us.”
Messenger, launched in August 2004, was the first spacecraft ever to orbit Mercury, the smallest planet in the solar system and the closest to the sun.
Circling a planet so close to its home star is an engineering feat — the spacecraft needed to withstand damaging solar radiation and resist the sun’s powerful gravitational tug. At launch, more than half of the spacecraft’s mass was taken up by fuel.
But with its fuel reserves finally exhausted, Messenger had no other options but to crash, scientists said.
The spacecraft has done stellar work, Solomon said. Among its many discoveries: that even though Mercury sits searingly close to the sun, it holds reserves of water ice and organic matter in permanently shadowed regions at its poles; that a surprising amount of light and volatile elements still remains on the planet; and that the planet has dropped a dress size or two, shrinking nearly 9 miles in diameter over the last 4 billion years or so.
“That speaks to the processes by which the building blocks of the inner planets came together to form the planets we see today,” Solomon said. “Each of the planets had an important chapter to tell us in the history [of the solar system], and the challenge is to make sense of it.”
Mission officials have identified the patch of land that probably holds the spacecraft’s final resting place. Messenger sped toward Mercury at more than 8,700 mph, carving a roughly 52-foot-wide crater into its surface.
Even in death, the spacecraft will generate more scientific data: That crater’s properties, and how its appearance changes over time, can be studied by future missions, Solomon said.
“It would be nice if the end of Messenger were actually the beginning of experiments that told us something about how the surface of Mercury got darker over time,” he added.