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How did Jupiter form? Juno hopes to find out

The first planet to form around the sun was greedy, sucking up more than twice of what was left for its sister planets, including Earth, to share.
Image: Juno
An artist's conception shows the solar-powered Juno probe in orbit around Jupiter. Juno is due for launch next week, with arrival at the giant planet scheduled for 2016.NASA
/ Source: Discovery Channel

The first planet to form around the sun was greedy, sucking up more than twice of what was left for its sister planets, including Earth, to share.

Scientists believe giant Jupiter then used its great girth to slingshot other bodies around the solar system, though it may have started off in a different locale than where it resides today, roughly 400 million miles from Earth.

Figuring out where — and how — Jupiter formed would refine knowledge about the birth of planets and how some — like Earth, and possibly others in other solar systems — ended up being in the right place at the right time for life.

"What we're after is discovering the recipe for how to make planets," planetary scientist Scott Bolton, with the Southwest Research Institute at San Antonio, Texas, told Discovery News.

To that end, United Launch Alliance, a commercial launch services firm owned by Boeing and Lockheed Martin, next week plans to send NASA's Juno spacecraft on its way to Jupiter. Scientists hope the five-year journey ends with the spinning, solar-powered probe orbiting over Jupiter's poles and passing as close as 3,100 miles above its cloud tops.

From that vantage point, Juno's eight science instruments can determine how much water is in Jupiter, a key measurement needed to determine where the planet formed.

"Possibly the single most important measurement Juno is going to make is going to be the global water content of Jupiter," Juno project scientist Steve Levin, with NASA's Jet Propulsion Laboratory in Pasadena, Calif., told Discovery News.

If the planet formed roughly where it exists today, scientists expect Jupiter would be about nine times richer in water than the sun. If Jupiter formed farther out in the solar system where it's colder, the amount of water might be around three times solar levels. Other models predict Jupiter has about the same abundance of water as the sun.

Juno also will map Jupiter's gravity to look for signs of a solid core, as well as map its magnetic mazes.

For pure spectacle, Juno has a camera, which is no doubt poised to capture fantastic pictures of Jupiter's ultraviolet aurora.

Juno is not the first probe to go to Jupiter, but it will be operating in unexplored terrain. Of eight previous visiting spacecraft, only the Galileo atmospheric probe got closer than where Juno is headed and that mission lasted just 58 minutes before Jupiter's heat and pressure destroyed the spacecraft.

After a year, the planet's harsh radioactive environment will cripple Juno too, despite a strong and elaborate titanium shield. Juno's last maneuver will be a suicidal dive into the planet's atmosphere to avoid possible contamination of Jupiter's potentially life-bearing moons.

Juno was hoisted on top of an Atlas 5 rocket at Cape Canaveral, Fla., on Wednesday, in preparation for launch at 11:34 a.m. ET on Aug. 5.

An earlier version of this report misstated how long the Galileo atmospheric descent probe survived.