Russia's space agency Roscosmos has confirmed it is willing to help Europe explore Mars, putting the ExoMars project back on track after NASA pulled out.
Head of Roscosmos Vladimir Popovkin met Jean-Jacques Dordain, Director General of the European Space Agency (ESA) on Friday to discuss combining forces.
The two men signed a memorandum of understanding which will be followed by a formal agreement in November after further discussions on funding the missions.
The deal comes as a huge relief to European space scientists who have spent years working on ExoMars. One of the UK's leading experts, Professor John Zarnecki, of the Open University, told Sen: "It looks like the cavalry has come riding over the horizon to save us, but this time they are dressed in Russian uniforms.
"There will be a lot of scientists in universities and research institutes throughout Europe who will be very relieved to hear this news. Otherwise it seemed that several years work preparing instruments for this mission was going to go down the drain."
Popovkin’s spokeswoman Anna Vedishcheva said: "The sides consider this project feasible and promising. They are to sign the deal by year-end."
Participation by the eastern power was also approved last week by the space council of the Russian Academy of Sciences.
Their agreement comes after preliminary talks at an Ariane 5 launch at Kourou, French Guiana last month, as reported previously by Sen. It follows NASA's decision to pull out as a partner in February as a result of swingeing cuts to the US space budget. This removed $2 billion of funding from the joint project.
Two missions are planned under the ExoMars banner. ESA is due to take the lead in 2016 with an orbiting satellite that will study methane and trace gases in the martian atmosphere, and an Entry, Descent and Landing Demonstrator Module (EDM) that would hopefully become Europe's first craft to touch down successfully on Mars.
Two years later, NASA was to have taken charge with a mission that would carry two rovers, one from the US and the other from ESA, to land at the same spot on Mars. Astrium's UK division has been carrying extensive tests developing prototypes for Europe's rover.
As well as a stereoscopic camera acting as the rover's eyes, the rover's experiments will include Life Marker Chip, developed by Professor Mark Sims at the UK's University of Leicester, that has been compared to a pregnancy test. It will study samples of Martian soil drilled from beneath the surface for molecules associated with life, such as amino acids.
Russia had already been indicating late last year that it would like to get involved with ExoMars before it suffered the disastrous loss of its own probe Phobos-Grunt which was meant to bring back a sample of a martian moon but which failed to escape Earth orbit.
Now it wants to fill the void left by NASA and to supply Proton rockets to launch the ExoMars missions plus other equipment in return for sharing the scientific data gained from them.
ESA has allocated a one billion euro budget for its share of spending on ExoMars. Funds for Russia's contribution are expected to come partly from insurance payouts for the loss of Phobos-Grunt.
A NASA rover, Mars Science Laboratory, or Curiosity, is currently en route to Mars and is due to land on August 6.