1971 American probe orbits Mars

The American space probe, Mariner 9, has become the first spacecraft to orbit another planet, swinging into its planned trajectory around Mars without a hitch.

An engine burn at 2337 GMT put the craft into an elliptical orbit around the Red Planet set to take it within 800 miles of the surface.

Three previous missions, Mariners 4, 6 and 7, have flown past Mars, but none has gone nearer than 2000 miles.

Mariner 9 is due to circle the planet twice a day for three months, sending back more than 5000 pictures covering 70% of the surface.

Dust storm

It’s hoped it will map the planet’s white polar caps, believed to consist of carbon dioxide, as well as provide vital clues about the possible existence of life.

However, the first photographs, taken on the approach to the planet, have been disappointing.

A vast dust storm which began on 22 September has been sending huge red clouds at high speeds across much of the planet’s surface.

The setback led to a groundbreaking exercise by Nasa scientists, who had to re-program the space probe over millions of miles of space to wait until the dust storm had abated before continuing with its mission.

Geologists hoping for a closer look at the features on Mars are dismayed, but atmospheric scientists are delighted.

Courtesy BBC News

In context

It was another month before the storm died away and scientists saw the first truly clear pictures of the surface of Mars.

They showed a planet of huge seismic activity, with gigantic volcanoes over twice the height of the largest found on Earth, and a grand canyon stretching 3000 miles across its surface – the largest in the solar system.

There were also channels which suggested that water once flowed on Mars.

Mariner 9 orbited the planet for far longer than expected. Its two television cameras returned 7329 photographs before contact ended on 27 October 1972.

The Soviet probe, Mars 2, arrived shortly before Mariner 9 and crashed due to the dust storm. Mars 3 touched down on the surface, but malfunctioned after 20 seconds.

The first successful landing on the Martian surface was carried out by Viking 1 five years later in 1976