Nasa spacecraft reaches orbit around Mars

PASADENA, California - A US$450 million Nasa spacecraft achieved orbit around Mars today, successfully completing a make-or-break manoeuvre in its two-year mission to scour the red planet for evidence of life and landing spots for future astronauts.

Mission controllers at Nasa's Jet Propulsion Laboratory in Pasadena erupted in loud cheers when the Mars Reconnaissance Orbiter signaled it had dropped into a perfect orbit around a planet that has defeated most of the probes sent there.

"We are in orbit around Mars," a Nasa commentator announced amid jubilation in the control room this morning NZ time.

The spacecraft, which left Earth in August on its 490 million kilometre journey, will spend the next six months using the drag of Mars' atmosphere to reel itself in from an elongated 35-hour loop to a nearly circular two-hour orbit.

It will then begin its primary scientific mission.

To ease into orbit around Mars, the ship was required to turn its main thrusters forward and fire them for 27 minutes, effectively slamming on the brakes while cruising at more than 17,000km/h.

The orbit insertion burn began on schedule and about an hour later the ship, which lost contact with Nasa when it went behind Mars, regained contact with Earth and signaled that it was on course.

If the spacecraft had failed to achieve orbit it would have flown past Mars and off into space -- a fate that befell a probe Japan sent in 1998.

Japanese mission controllers managed to gain control of the Nozomi orbiter and send it back toward Mars, but it was damaged by solar flares and ultimately lost.

The most advanced spacecraft ever sent to another planet, Nasa's orbiter is designed to spend two years searching for signs of life on Mars and scouting possible landing spots for astronauts. It is equipped to send back 10 times as much data as all previous probes put together.

But missions to Mars have proven notoriously difficult, with two of the last four attempts by Nasa to put a spacecraft in orbit around the planet ending in failure. Only about one-third of humanity's probes to Mars have succeeded.

"Mars is just for some reason harder to get a mission to than other places in the solar system," lead mission planner Rob Lock said. "I might even use the word 'unluckier' because there's nothing intrinsically more difficult than other planets."

The Mars Reconnaissance Orbiter program was expected to cost a total of about US$720 million, including US$450 million for the spacecraft and its on-board instruments, US$90 million for the launch and US$180 million for mission operations, science processing and support.

- REUTERS