The League of Mars-bound Gentlemen

When National Aeronautics and Space Administration officials announced Dec. 4 that they were postponing a $1.6 billion – soon-to-be $2.2 billion to $2.3 billion – mission to put a VW Bug-sized rover on Mars, the hottest news of the moment was the delay and its contribution to the project's growing cost.

But during the press conference announcing the delay, Ed Weiler, who oversees the agency's space-science efforts, committed news of another sort – one that could have profound implications for the future of robotic space exploration.

Simply put: He and his counterpart at the European Space Agency (ESA), David Southwood, have agreed to rework their individual Mars exploration programs into a single program both agencies will follow.

This isn't just another shot at adding one agency's hardware to the other's spacecraft on a mission-by-mission basis. That can certainly work, as the highly successful Cassini-Huygens mission at Saturn shows.

Instead, ESA might become the lead agency on one Mars mission, NASA on another.  But launches would flow from a commonly agreed set of priorities for each mission, launched on a commonly agreed schedule, and the two agencies would share the costs. Ideas and instrument packages would still be welcome from researchers and space agencies outside this joint effort.

The ultimate goal: To launch a sample-return mission to the red planet (bring Martian dirt home), probably around 2020 or shortly thereafter.

In phone chats with both men, they emphasize that the details still need to be worked out. Teams from each agency are likely to be meeting over the next few months to start organizing for the effort.

Look for signs of progress at the next bilateral meeting the two agencies' science directorates regularly hold, Dr. Weiler says. The next one is scheduled for May in Plymouth, England.

"David and I would like to see significant progress" by then, Weiler says. "We should have a pretty good idea of where we're going, with groups in place and initial meetings having taken place."

So how did this come about?

Turn the clock back to July. The two top officials and their division directors gathered in Annapolis, Md., for their annual conclave.

"There's always a session where Ed and I shoot the breeze between the two of us," says Dr. Southwood, who three days before the meeting took over ESA's Mars-exploration program. "We both are a little bit skeptical about the over-optimism of some of our colleagues" in laying out how much a mission can accomplish and at what price.

In Europe, leaders were gulping at the price of ESA's ExoMars mission, estimated at 1.2 billion Euros ($1.5 billion US).  At the time, the effort faced the prospect of slipping its launch from 2013 to 2016.

In October, ESA announced it would in fact delay the mission to 2016.

This has a familiar ring.

In the United States, the Mars Science Laboratory mission – which NASA has now rescheduled for a 2011 launch, from 2009 – was dipping deeper than expected into the till and was hitting some technical snags.

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