Nasa to send probe in search of water on Mars

MIAMI - NASA prepared an unmanned spacecraft for launch to Mars on Wednesday on a quest to learn whether Earth's neighbouring planet had water long enough to nurture life.

Previous Mars missions have shown that water once flowed across the planet's surface. Scientists hope data from the Mars Reconnaissance Orbiter will tell them where and for how long Mars had water, whether it ever had life and whether it could support a human outpost.

The 2-ton orbiter is scheduled for launch on Wednesday from the Cape Canaveral Air Force Station between 7.54am and 9.39am EDT (11.54pm Wed and 1.39am Thurs NZT). Weather conditions were favourable, with only a 20 per cent chance that isolated showers would cause a delay, Air Force weather officer Clay Flinn said.

The 6.5m spacecraft will ride aloft on a Lockheed Martin Atlas V rocket and is scheduled to reach Mars in March 2006. Using the friction of the planet's upper atmosphere as a brake, it will slowly dip into a low orbit about 300km above the surface of Mars, NASA said.

Beginning in November 2006, the Mars orbiter will use an array of scientific instruments to zoom in for close-up photos of the Martian surface, analyze mineral deposits, search for subsurface water and shorelines of ancient seas, trace dust and water distribution in the atmosphere and monitor the planet's weather through a full cycle of Martian seasons.

Previous Mars probes have literally only scratched the surface, project manager Richard Zurek told journalists during a teleconference.

The Mars Reconnaissance Orbiter's spectrometer and subsurface radar could give a better indication what lies beneath and whether the ice found on the planet's surface is a thin layer or the tip of an iceberg that could provide a source of drinking water for a potential human mission.

One of the spacecraft's telescopic cameras is the largest ever flown on a planetary mission and can spot rocks and other potential obstacles the width of a desk. It will scout safe landing sites for the next series of robot explorers, NASA said.

"We expect to use this spacecraft's eyes in the sky in coming years as our primary tools to identify and evaluate the best places for future missions to land," said Douglas McCuiston, Mars exploration programme director.

The orbiter carries some of the most sophisticated instruments ever sent into space and NASA expects the mission to provide more information than all previous Mars missions combined.

Its antenna and solar-powered telecommunications system will send data back to Earth at up to 3.5 megabits per second, fast enough to fill a CD-ROM in about three minutes. The spacecraft can send up to 10 times as much data per minute as any previous Mars craft, NASA said.

"We're going to start opening up the firehose," said project manager Jim Graf. "We are going to be awash in data which will enable us to better understand the planet as a whole." The orbiter's telecommunications systems will also act as a relay station for other spacecraft, including the Spirit and Opportunity rovers already on Mars and robotic rovers that are still to be launched.

The Mars orbiter is expected to complete its two-year science mission in December 2008 and then operate as a communications support relay through the end of 2010. It has enough fuel to extend the mission until about 2014, Graf said.

- REUTERS