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Last Updated: Thursday, 1 March 2007, 08:24 GMT
Probe spies moon's volcanic plume
Io  Image: Nasa, JHUAPL, Southwest Research Institute
The plume is seen as an umbrella-shaped feature in the long exposure image to the right

Nasa's New Horizons spacecraft has sent back images of a huge volcanic eruption on Jupiter's moon Io.

A massive dust plume, estimated to be 150 miles (240km) high, can be seen erupting from Io's Tvashtar volcano.

On Wednesday, the US probe flew by Jupiter, using the planet's gravity to boost its speed, reducing the travel time to its ultimate target of Pluto.

New Horizons also took photos of the icy moons Europa and Ganymede in the run-up to its encounter with Jupiter.

Turning its cameras to the giant planet itself, the spacecraft captured an image of Jupiter's little red spot, a nascent storm south of the famous great red spot.

Volcanic fallout

New Horizons made its closest approach to Jupiter at 0543 GMT (1243 EST) on Wednesday, passing within 2.3 million km (1.4 million miles) of the planet.

Jupiter's red spot, Image: Nasa, JHUAPL, Southwest Research Institute
Red Jr is a swirling storm in Jupiter's atmosphere
The gravity "kick" will accelerate the probe's speed by 14,000kmph (9,000mph).

The probe will carry out more than 700 observations of the Jupiter system by June, in a dry run for its planned rendezvous with Pluto and its moons in 2015.

The pictures of Io provide the best glimpse yet of Tvashtar, one of the most active volcanoes on Io. The volcano can be seen in the "11 o'clock" position in the images. It is surrounded by a dark patch the size of Texas consisting of the fallout from the eruption.

The probe's observations of icy moons like Europa and Ganymede will allow scientists to map their surface features and composition.

Subsurface ocean

Europa is an attractive target; planetary scientists consider it one of the best places in the Solar System to find extraterrestrial life forms.

Europa, Image: Nasa, JHUAPL, Southwest Research Institute
Europa is a promising target in the search for extraterrestrial life
Beneath its outer shell of ice, the moon is thought to host an ocean of water warmed by heat from the interior.

The little red spot, or Red Jr, is a swirling storm that formed from three smaller features between 1998 and 2000.

Its larger counterpart, the great red spot, is Jupiter's most famous feature. It has been in existence for at least 130 years.

After an eight year cruise across, New Horizons will conduct a five-month study of Pluto and its three moons in 2015, characterising their geology, structure and composition.

Animated images of the Nasa mission

Nasa probe makes flyby of Jupiter
28 Feb 07 |  Science/Nature
New Horizons targets Jupiter kick
19 Jan 07 |  Science/Nature
Pluto loses status as a planet
24 Aug 06 |  Science/Nature
Pluto probe launches from Florida
20 Jan 06 |  Science/Nature
Mission guide: New Horizons
19 Jan 06 |  Science/Nature
The girl who named a planet
13 Jan 06 |  Science/Nature

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