A feast for astronomers

Press, 27 January 1986, Page 10

A feast for astronomers

NZPA-Reuter Pasadena, California The Voyager 2 spacecraft’s first close-up photographs of two of the larger moons of Uranus yesterday astounded scientists with clear views of river-like canyons, jagged craters and other features they never expected to see. After announcing earlier that Voyager’s cameras had detected a fifteenth moon and tenth ring orbiting the' planet, scientists finally began receiving the pictures, from nearly 3.2 billion kilometres away, which they had eagerly awaited for more than a day. High-resolution photographs of the Uranian moons, Miranda and Ariel, taken on Saturday as Voyager made its closest approach to the gaseous planet before speeding off towards Neptune, gave scientists more than they had hoped for as they sought to learn inner

secrets of the strange Uranian system. Hundreds more pictures of the rings and planet itself will pour into the Jet Propulsion Laboratory. "What we’re seeing is quite unexpected,” said the astronomer and author, Carl Sagan, one of the original members of the Voyager project, after watching the play-back of nine pictures of Miranda. “It shows the continuing surprise and mystery of the universe.”

Garry Hunt, an English meteorologist, who like Dr Sagan, is a member of the team digesting a wealth of images for the National Aeronautics and Space Administration, pointed out a deep wedge cut out of the side of Miranda and said, "It takes your breath away. We must be looking at the side of a grooved valley.” “I’m totally surprised by what I’m seeing ... the geologists are going to have a field day. Once more, Uranus has held

back its mysteries to the last minute,” said Dr Hunt, who is from the Imperial College, in London.

The one-tonne spacecraft recorded a treasure trove of pictures and other data about the moons, rings and planet on Saturday as it drew to within 80,000 km of the cloud-topped surface of Uranus.

But only yesterday could the nuclearpowered craft start beaming back at the speed of light the information scientists needed to learn more about the planet than had been known in the 205 years since it was discovered.

It takes three hours for Voyager’s weak radio signal to transmit the photographs and data from 10 other instruments to huge dish antennae in California, Australia, and Spain.

Dr Hunt and Robert Strom, from the University of Arizona, said the topographies of Miranda

and Ariel were astounding. Impact craters had been expected, but the valleys, rifts and other signs of some kind of internal heating source were not.

Most scientists expected fairly featureless surfaces on the grey-brown satellites because of the incredible coldness of the Uranian atmosphere. Dr Strom said that the two moons had features that apparently did not occur in the three largest moons — Umbriel, Titania and Oberon.

Of Miranda, Dr Strom said, “This is going to be one of the more interesting bodies in the solar system.” Before Voyager’s mission, which began more than eight years ago and took the spacecraft past Jupiter and Saturn, and now on to Neptune, very little was known about the composition or origin of the satellites, rings or I planet.