Associated Press
PASADENA, California: Soaring over Jupiter’s poles, a Nasa spacecraft arrived at the solar system’s largest planet on a mission to peek behind the cloud tops.
The final leg of the five-year voyage ended on Monday when the solar-powered Juno spacecraft fired its main rocket engine and gracefully slipped into orbit around Jupiter.
Mission controllers celebrated when Juno sent back radio signals confirming it reached its destination.
“We’re there. We’re in orbit. We conquered Jupiter,” Juno chief scientist Scott Bolton said during a post-mission briefing.
In the weeks leading up to the encounter, Juno snapped pictures of the giant planet and its four inner moons dancing around it.
Scientists were surprised to see Jupiter’s second-largest moon, Callisto, appearing dimmer than expected.
The spacecraft’s camera and other instruments were switched off for arrival, so there weren’t any pictures at that key moment. Scientists have promised close-up views of the planet when Juno skims the cloud tops during the 20-month, $1.1 billion (R163bn) mission managed by Nasa’s Jet Propulsion Laboratory.
The fifth rock from the sun and the heftiest planet in the solar system, Jupiter is what’s known as a gas giant – a ball of hydrogen and helium – unlike rocky Earth and Mars.
With its billowy clouds and colourful stripes, Jupiter is an extreme world that likely formed first, shortly after the sun. Unlocking its history may hold clues to understanding how Earth and the rest of the solar system developed.
Juno’s mission: To peer through Jupiter’s cloud-socked atmosphere and map the interior from a unique vantage point above the poles.
Among the lingering questions: How much water exists? Is there a solid core? Why are Jupiter’s southern and northern lights the brightest in the solar system?
“What Juno’s about is looking beneath that surface,” said Bolton, of the Southwest Research Institute in Texas. “We’ve got to go down and look at what’s inside, see how it’s built, how deep these features go, learn about its real secrets.”
The trek to Jupiter, spanning nearly five years and 2.8 billion kilometres, took Juno on a tour of the inner solar system, followed by a swing past Earth that catapulted it beyond the asteroid belt between Mars and Jupiter.
Along the way, Juno became the first spacecraft to cruise that far out powered by the sun. A trio of massive solar wings sticks out from Juno like blades from a windmill, generating 500 watts of power to run its nine instruments.
Juno meets its demise in 2018 when it deliberately dives into Jupiter’s atmosphere and disintegrates – a sacrifice to prevent it crashing into the planet’s habitable moons.