Science & Environment

Juno probe makes close pass of Jupiter

Jupiter Image copyright NASA/JPL-Caltech/SwRI/MSSS
Image caption Juno captured this view of Jupiter from a distance of 700,000km

A probe flown by the US space agency Nasa has made its first close approach to the planet Jupiter since going into orbit in July.

Juno was commanded to pass just 4,200km above the cloud tops of the gas giant on Saturday.

No previous spacecraft has got so close to the world during the main phase of its mission.

Juno had all its instruments - and its camera - switched on and primed for the encounter.

Nasa expects to be in a position to release some images from the approach in the next few days. They will be the highest resolution pictures ever obtained of Jupiter's clouds.

The moment of closest approach occurred at 13:44 GMT.

At that time, Juno would have been moving at 208,000km/h with respect to the planet, sweeping from north to south over the multi-banded atmosphere.

Image copyright NASA/JPL/Space Science Institute
Image caption Various probes have taken images of Jupiter, but Juno's will be the highest resolution yet

The probe became gravitationally bound to Jupiter on 5 July after a five-year, 2.8-billion-km journey from Earth.

Executing a carefully choreographed engine burn, the spacecraft put itself in a large ellipse around the world that takes some 53 days to traverse.

"[On 5 July] we turned all our instruments off to focus on the rocket burn to get Juno into orbit around Jupiter," explained principal investigator Scott Bolton.

"Since then, we have checked Juno from stem to stern and back again. We still have more testing to do, but we are confident that everything is working great, so for this upcoming flyby Juno's eyes and ears, our science instruments, will all be open.

"This is our first opportunity to really take a close-up look at the king of our Solar System and begin to figure out how he works," the Southwest Research Institute scientist said in a Nasa statement prior to the flyby.

Image copyright AP
Image caption Juno arrived at Jupiter on 5 July (GMT)

Juno's quest is to probe the secrets of the Solar System by explaining the origin and evolution of its biggest planet.

The spacecraft's remote sensing instruments will look down into the giant's many layers and measure their composition, temperature, motion and other properties.

We should finally discover whether Jupiter has a solid core or if its gas merely compresses to an ever denser state all the way to the centre.

We will also gain new insights on the famous Great Red Spot - the colossal storm that has raged on Jupiter for hundreds of years. Juno will tell us how deep its roots go.

Controllers will send the probe on another 53-day orbit before firing the probe's engine once again on 19 October to tighten the circuit to just 14 days.

The configuration will then be held until February 2018 when the spacecraft will be commanded to make a destructive dive into Jupiter’s atmosphere.

  • Jupiter is 11 times wider than Earth and 300 times more massive
  • It takes 12 Earth years to orbit the Sun; a 'day' is 10 hours long
  • In composition it resembles a star; it's mostly hydrogen and helium
  • Under pressure, the hydrogen becomes an electrically conducting fluid
  • This 'metallic hydrogen' is likely the source of the magnetic field
  • Most of the visible cloud tops contain ammonia and hydrogen sulphide
  • Jupiter's 'stripes' are created by strong east-west winds
  • The Great Red Spot is a giant storm vortex twice as wide as Earth

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

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