NASA orbits Mercury for first time with Messenger probe


For the first time in human history, an Earth-made vehicle has successfully entered the orbit of Mercury, the closest planet to our sun.

NASA’s Messenger spacecraft entered Mercury’s orbit at about 9:15pm EST on Thursday after a 30-minute rocket blast pushed the unmanned probe into the planet’s gravitational pull, the Los Angeles Times reports. Announcement of Messenger’s orbit entry was met with jubilation from the mission control room at Johns Hopkins University in Laurel, Maryland.

About 40 minutes after confirmation of Messenger’s entry into Mercury’s orbit, mission lead engineer Eric Finnegan declared that the team had pulled off the unprecedented with near-perfect accuracy. “We hit the trajectory to within half a sigma, for my engineer friends in the crowd,” Finnegan tells the LA Times. “It was right on the money.”

Messenger, which originally launched in 2004, will photograph Mercury from its close proximity, and send those images back to NASA for analysis. This will help to better discover the planet’s composition, magnetic fields, atmosphere and other details.

In the 6.5 years the probe has been in space, Messenger — which stands for “MErcury Surface, Space ENvironment, GEochemistry and Ranging” — has traveled a total of about 4.9 billion miles, during which it completed 15 orbits of the sun. It has reached near-record speeds of about 140,000 mph.

While the craft only measures 4.7-feet-tall by 6.1-feet-wide by 4.2-feet-deep, it weighed approximately 2,420 pounds when it launched. About 55 percent of that weight — 1,320 pounds — was fuel. Messenger’s dry weight is only about 1,100 pounds. (For more interesting facts about Messenger, click here.)

Mercury is located about 39 million miles from the sun — about three times closer than Earth, which orbits at about 93 million miles from the center of our solar system.

Watch a brief animated simulation that shows Messenger’s entry into Mercury’s orbit:

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