An illustration of the Mars Express mission -- the orbiter and Beagle 2 lander. Credit: Astrium

An unprecedented international scientific assault on Earth's cosmic neighbor will be launched in June as four spacecraft are fired to Mars, beginning next week with Europe's first mission to the Red Planet.

With the opportunity to dispatch space probes to Mars once every 26 months, when the planets are suitably aligned, this window sees the Mars Express orbiter and compact lander, called Beagle 2, leading the charge with a planned June 2 launch. NASA's twin Mars Exploration Rovers will follow on June 8 and 25.

An artist's concept of Mars Express atop the Fregat stage. Credit: ESA

Liftoff of the Mars Express spacecraft aboard a venerable Russian Soyuz booster with a Fregat upper stage is set for Monday at 1745 GMT (1:45 p.m. EDT) from the Baikonur Cosmodrome in Kazakhstan.

The Soyuz rocket's three core stages will fire before releasing the Fregat upper stage and Mars Express just under 9 minutes into flight. Separation of Mars Express from the launcher is expected following two Fregat burns about 90 minutes after liftoff.

During its 7-month cruise to the Red Planet, the 2,500-pound Mars Express will undergo a maximum of three course correction maneuvers as required. An initial round of instrument checkout is expected about a month after launch, with another testing period set for late this year prior to Mars arrival, Mars Express project manager Rudolf Schmidt said.

With a June 2 launch date, the Mars Express orbiter will eject the tiny British Beagle 2 lander on December 19.

The Beagle 2 lander package separates from Mars Express orbiter. Credit: ESA

Touchdown on the Martian surface will occur in the early morning hours of December 25, European time. (See full story on Beagle 2.)

Mars Express will begin the process of orbit injection close to the same time, Schmidt told Spaceflight Now.

As the first European spacecraft to visit a planet, Mars Express leads the way for missions in the pipeline for the coming years to Venus and Mercury.

"Mars Express is leading the way into the solar system for Europe," said Professor David Southwood, director of ESA's science program. "This is an important mission because Mars is much like Earth's brother planet, who turned out to be quite different. We have to try to understand why it's so different."

One of the major goals of the Mars Express orbiter is to search for water and moisture embedded within the planet's surface. Such sub-surface water concentrations could exist in the forms of aquifers, pools, rivers, or permafrost, scientists say.

Essential for life, water on the Red Planet is known to be stored in polar ice caps, but evidence gathered by previous missions suggests water existed in abundance almost 4 billion years ago early in the planet's history.

But a so far unexplainable something happened since then that made most of the water disappear. The air pressure rapidly decreased, making liquid water on the surface impossible to form. However, scientists believe it is still possible for water to be present up to a few kilometers below the surface, where temperatures and pressures are more likely to harbor its existence.

Mars Express in orbit around the Red Planet. Credit: NASA

Radar sounding instruments will attempt to create a sub-surface map down to a few kilometers deep. Others will examine processes that could have allowed the water on early Mars to escape the planet.

Mars Express also carries with it a high resolution camera that will image the entire surface of the Red Planet. Spectrometers will also determine mineral compositions on the surface and study the make-up of the Martian atmosphere.

The orbiter has a baseline mission lasting about two years, but it is expected that it will operate in some capacity until at least 2007 to help relay communications between Earth and other spacecraft at Mars.