The US space agency (Nasa) has announced plans for yet another mission to land on Mars.
It has selected a proposal for a craft called Phoenix to touch down in the high northern latitudes of the Red Planet to study the water-ice thought to lurk just beneath the surface.
How Phoenix will look on the Martian surface
The lander will dig a trench up to a metre deep in the Martian soil and then deploy a suite of instruments to study the accessible ice, soil and rock. It will also analyse the local atmosphere.
Phoenix, which has a budget cap of $325m, will be a joint endeavour between the University of Arizona, the agency's Jet Propulsion Laboratory in California, and Lockheed Martin Space Systems in Colorado.
The Canadian space agency is supplying metrological instruments.
The craft, which beat off three other design concepts - a Mars plane, an orbiter and a mission to return Martian dust to Earth - will launch in 2007 and land in 2008.
Join the queue
The lander will follow up on the orbiter Mars Odyssey's spectacular discovery of near-surface water-ice over large swathes of the Red Planet.
It will touch down in terrain suspected of harbouring as much as 80% water-ice by volume within 30 centimetres of the surface.
Included in the instrument payload are microscopic imaging systems
capable of examining materials at scales down to 10 nanometres (billionths of a metre), while others will investigate whether organic molecules are contained in ice or soil samples.
Dr Ed Weiler, the associate administrator for space science at Nasa, said Phoenix would "explore the Red Planet in a unique way, and may mark the beginning of a line of innovative, competitively selected and lower-cost missions in the Mars Exploration Program".
Nasa currently has two landing missions in transit to the fourth planet. The Mars Exploration Rovers will touch down in January next year, just after the Europeans arrive with their Mars Express mission in December.
Mars Express is an orbiter with a lander, called Beagle 2, that will be dropped on to the surface on Christmas Day.
Back to life
Nasa commissioned a lander which was built and tested to fly as part of the 2001 Mars Surveyor Program. But the mission was cancelled when the agency's Mars Polar Lander was lost on entry into the Red Planet's atmosphere in 1999.
Since then, the 2001 lander has been in storage. Now it will be renamed Phoenix and updated to carry more advanced instruments.
Phoenix will help scientists better understand the history of water on Mars. It may also find the environment in which microbes are most likely to survive.
Mars Odyssey has shown the way
"The selection of Phoenix completes almost two years of intense competition with other institutions," said Dr Peter Smith, of the University of Arizona Lunar and Planetary Laboratory, who will head the Phoenix mission.
"I am overjoyed that we can now begin the real work that will lead to a successful mission to Mars."
He added: "Even though the northern plains are thought to be too cold now for water to exist as a liquid, periodic variations in the Martian orbit allow a warmer climate to develop every 50,000 years.
"During these periods the ice can melt, dormant organisms could come back to life, (if there are indeed any), and evolution can proceed. Our mission will verify whether the northern plains are indeed a last viable habitat on Mars."