A SPACE probe designed to look for signs of life in the oceans that once covered Mars will be unveiled by Nasa scientists this week.

The Phoenix Mars Lander will be sent to the icy wastelands near the red planet’s north polar ice cap. It will be launched next month and is expected to reach the planet in May.

When the probe lands its task will be to dig deep into the soil, scoop out chunks of ice and analyse them for signs of past or present life forms.

The landing site has been chosen as the most likely point to find buried ice that once formed part of the planet’s oceans.

“The arctic plains are the right place for the next step in Mars exploration and this is the right time to go there,” said Leslie Tamppari, Phoenix project scientist at Nasa’s Jet Propulsion Laboratory. “We expect to touch Martian ice for the first time.”

Mars is now a cold desert planet with the thinnest of atmospheres and no water on the surface. However, previous missions have shown that there are large amounts of ice below the planet’s crust in the northern arctic plains.

Data from previous missions suggest that billions of years ago water flowed through canyons and formed large shallow seas. Some of these may have still been in existence 100,000 years ago.

The search for water is more than scientific. Nasa’s long-term goal is to send a human to Mars and a manned mission would be easier if the crew was guaranteed a source of water on arrival.

The Phoenix probe is one of the largest that Nasa has sent to Mars and will require descent thrusters to control the landing. A Nasa spokesman said that the probe would use a high-definition camera to gather geological data on the area around the landing site as the craft descended.

Many of the scientific instruments for Phoenix were built or designed for the 2001 Mars Surveyor Lander, which was mothballed, and the ill-fated Mars Polar Lander in 1999, which is though to have crashed on landing.

“This site wouldn’t be my first choice as a place for looking for life,” said Colin Pillinger, professor of planetary sciences at the Open University, who oversaw Britain’s ill-fated Beagle mission that was lost on the red planet in 2003.

“The temperature is going to be very low in a permanent polar region, which reduces the chances of finding [signs of] life. If you were a microbiologist you wouldn’t be keen to send a probe to the Martian north pole but it is new and that makes it exciting.”

Nasa is also this week due to launch its Dawn probe, which will penetrate deep into the asteroid belt that lies between Mars and Jupiter. It will investigate two of the largest asteroids, thought to be part of the “rubble” left over from the formation of the solar system 4.5 billion years ago.

Scientists think these may have been potential planets in the making that were never given the opportunity to grow.

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