U.S. to launch Mars probe in search for clues of life

By Irene Klotz

CAPE CANAVERAL, Florida (Reuters) - A NASA probe that will analyze Mars for water and other chemicals needed for life is on track for launch aboard an unmanned Delta rocket on Saturday, NASA officials said on Thursday.

The Phoenix spacecraft, which will take nine months to reach Mars, is designed to land in the planet's northern polar region and dig into the frozen soil for samples to analyze. Launch is targeted for 5:26 a.m. (10:26 a.m. British time) on Saturday from Cape Canaveral Air Force Station in Florida.

"The launch team is ready," NASA launch director Chuck Dovale said in a news conference at the Kennedy Space Center on Thursday.

Rain storms have plagued launch preparations but there was an 80 percent chance of good weather for Saturday, said Air Force meteorologist Joel Tumbiolo.

Any delays could affect NASA's plans to launch the space shuttle Endeavour on Tuesday on a construction mission to the International Space Station.

Earth and Mars will be aligned for Phoenix's launch only until August 24. After that, the planets with take another 26 months to get back into a favourable position.

The mission's primary goal is to ascertain if Mars is, or ever was, suited for life to develop. Previous Mars probes, including the two rovers Spirit and Opportunity, have found geologic and chemical evidence of past water, but did not have the tools for in-depth analysis.

Instead of roaming the planet's surface, Phoenix will zero in on a target zone and scrutinize the terrain on a molecular level. Scientists are particularly interested if organic molecules are present.