Juno Arrives at Jupiter

A NASA spacecraft has arrived at the solar system's largest planet after a picture-perfect orbital insertion.

NASA's Juno space probe ended a five-year, 1.7-billion mile trek to Jupiter on Monday, nailing a do-or-die braking burn to shave its speed and settle into orbit around the largest planet in the solar system.

Confirmation of Juno's safe arrival came at 11:53 p.m. EDT when flight controllers reported an expected shift in tones coming from the probe, a live NASA TV broadcast showed.

"A big sigh of relief," said mission commentator Gay Yee Hill, at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Had the 35-minute burn of Juno's main engine failed, the spacecraft would have sailed past Jupiter, ending the mission before it began. Only one other spacecraft, NASA's Galileo probe, has orbited Jupiter.

Juno, named for the mythical Roman goddess who was the wife and sister of Zeus and who had the power to see through clouds, is designed to answer some key questions left over from Galileo's eight-year study of the Jovian system.

Topping scientists' wish list is knowing how much water Jupiter contains, information that they can feed into computer simulations to calculate how and where the planet formed.

"If Jupiter formed really far from the sun and drifted inward you'll get a different amount of water than if it formed where it is now," said Juno project scientist Steven Levin, at NASA's Jet Propulsion Laboratory.

Jupiter orbits about five times farther away from the sun than Earth.

"If it formed, as we think is likely, from icy planetesimals -- large chunks of ice that collided together -- and made a giant planet, then you'll get a different amount of water than if it formed some other way, such as directly condensing from the same material that made the sun," Levin said.

As the largest planet, Jupiter influenced the rest of the solar system's formation, including the location of Earth and its suitability for life.

"By studying Jupiter you're going to get on piece of the puzzle, not necessarily how life formed but maybe how the ingredients that made up life eventually got spread around in the early solar system and got to us," said Juno lead scientist Scott Bolton, with the Southwest Research Institute in San Antonio, Texas.

To collect its data, Juno will spend 20 months flying as close as 3,000 miles form the tops of Jupiter's clouds, a position that leaves it vulnerable to the planet's massive radiation.

The spacecraft's electronics are protected inside a radiation-resistant titanium vault, but NASA expects to end the mission after 37 orbits, each of which will last 14 days.

Read more at Discovery News