By Jonathan Amos
BBC News science reporter
Europe has confirmed its intention to try again to land on Mars, to search for evidence of past or present life.
The ability to drill under the surface is a "must have"
The European Space Agency mission, which would include a roving robot, would leave Earth in June 2011 and arrive at the Red Planet in June 2013.
The 500-million-euro mobile laboratory would "sniff" the air for signs of biology and listen to the ground for evidence of Marsquakes.
Esa's last landing attempt, Beagle 2, went missing without a trace in 2003.
Top scientists and officials from the space agency (Esa) met this week to assess the best landing options. The workshop's ideas were presented to the media in London, UK, on Friday.
They still require a great deal of further detail and the agency's member states will also have to sign off the mission. Ministers will have their say when the Esa Council meets in December.
But the commitment is clear. "We know we're going, we want to go and the intention is to go - but there are an awful lot of steps between now and then and they will be critical," explained Dr Mark Sims, of Leicester University, UK, who is helping to pull together the mission, which comes under Esa's Aurora programme.
EUROPE'S MISSION TO MARS
To leave Kourou, French Guiana, spaceport in 2011
Will launch on Russian-built Soyuz-Fregat vehicle
Planetary positions account for long journey time
Landing date will avoid worst of duststorm season
US may be asked to provide orbital relay of data
Could also provide entry, descent and landing expertise
Would employ parachutes, airbags and retro-rockets
The likely final mission will emerge and evolve from concepts that are already on the table and have been debated for some time.
One is ExoMars - a large rover that flies with a relay orbiter. An ExoMars-lite version would use orbiters already at Mars to send home its data.
And then there is BeagleNet, a twin lander design with smaller rovers, which delivers improved versions of the instruments that flew with Beagle 2.
Although the final architecture of the mission will not become clear for several months, there are certain "must haves" scientists have said should be built in to any lander - and these go to technologies that Europe feels will complement any instrumentation the Americans plan to send on their future rovers. The must haves include:
- a drill or "mole", such as the one designed for Beagle 2, that could go under the oxidised surface of Mars to find water and help investigate the subsurface geochemistry
- "life-marker" experiments that would analyse the soil, rocks and gases in the atmosphere for signs of biological activity. Life traces would have specific chemical "signatures"
- a seismometer to detect Marsquakes and other geological activity.
No one has got as far as identifying landing sites yet, but they could include the locations shown by Europe's Mars Express orbiter to have local "hot spots" of methane in the atmosphere.
One such location is the planet's near-equatorial Elysium region, which also appears to have a huge, frozen sea just beneath the Martian surface.
The site has been proposed as an excellent place to start looking for life.
As a known by-product of biochemistry, methane could indicate the presence of microbial organisms - it could also just be an outcome of volcanism.
"You have to eliminate the possible solutions," said Professor Colin Pillinger, the chief scientist on the illfated Beagle 2 mission.
A joint sample-return mission will not happen before 2016
"We have seen hints of recent lava flows, but if you go to Mars and you can't recognise any geological activity that solution has a problem," he told the BBC News website. "If you can't find a geological signal, don't propose a geological answer."
Aurora envisages not only a roving mission to Mars in the near future, but a sample-return mission, too. Scientists want to bring rocks back from the Red Planet to study in labs on Earth.
But the scale of such a mission, probably costing billions of euros, means it will almost certainly be a joint effort with the US, much like the successful Cassini-Huygens double spacecraft sent to Saturn.
Sample-return means not only getting to the planet, finding and storing suitable rocks, but then blasting them off the surface of Mars in a secure container that can be returned safely to Earth free from contamination.
"It is such a big undertaking and in its present concept, it is American-led - the same as Cassini," said Bruno Gardini, the Esa Aurora programme manager.
"The question is what can Europe contribute? This could be a rover that goes to fetch the samples. This could be the European component and ExoMars gives us that tremendous possibility."
The UK is expected to have a major input into the new landing mission. British scientists and industrialists were the lead partners in the Beagle 2 probe.
Although this mission never achieved its final objectives, scientists and engineers on the project felt they built up considerable expertise in the process and would like another go.
The Particle Physics and Astronomy Research Council (PParc), the major funding body in the UK for this area of science, plans to put aside considerable sums of money over the next few years to give British researchers a leading role in Aurora.
"From the studies that have been conducted, UK industry has participated in developing a number of the leading technologies and that puts us in a good position for the follow-on phases," Mark Roe, from EADS-Astrium, the prime contractor on Beagle 2, told BBC News.
The final mission design should take the best of the BeagleNet concept