The pictures of Jupiter's moon Io were taken by the spacecraft Galileo during its flyby of 10 October and show a spectacular lava flow.

Scientists at Nasa's Jet Propulsion Laboratory (JPL) in Pasadena said the image of Io was 50 times better than the previous best pictures, taken in 1979 by the Voyager spacecraft.

"Visible in the image are new lava flows from the volcanic centre named Pillan. This area erupts lava which is hotter than any known eruption on Earth for billions of years," said JPL spokeswoman Jane Platt.

Scientists are now studying the lava flow to determine the characteristics of the volcanic eruption. They are looking forward to more images and data due to be sent back to Earth over the coming weeks.

Closest approach

An earlier Galileo image shows the area displayed in the new image

To take the images, Galileo came within 671 kilometres (417 miles) on the closest approach yet to the Jovian moon.

It had to pass through a region of intense radiation from Jupiter's radiation belts. Even a fraction of this dose of radiation would kill a human being and it can hamper performance of spacecraft like Galileo.

Galileo's original mission was to spend two years studying Jupiter, its moons and magnetic environment. That mission ended in December 1997 but has been followed by a two-year extended mission set to end in January 2000.

Galileo is scheduled to get closer still to Io next month, when it is scheduled to fly-by at an altitude of 300 km (186 miles).