Excellent article from Spaceflight Now describing the multiple missions being collaboratively planned by the United States and Europe to discover and excavate samples from the surface of Mars, launch them in to Mars orbit, rendevouz with a return orbiter, fly them back to Earth and land them safely on Earth's surface.
Mars sample return mission could begin in 2018
July 20, 2010
The costly mission would blast off on an Atlas 5 rocket in 2018 and land two rovers on Mars with a single "sky crane" descent system...
The European Space Agency's ExoMars rover and a $2 billion NASA Mars Astrobiology Explorer-Cacher mission are the leading candidates for the tandem project.
Planners haven't decided on a schedule for the sample's return to Earth, and it's possible the the precious soil could wait for up to six years -- or even longer -- before NASA and ESA can afford to send a mission to bring it back.
One sample return option involves launching the caching mission in 2018, skipping a launch opportunity in 2020, then sending the an orbiter to Mars in 2022 that would ferry the cargo back to Earth, according to McCuistion.
Another mission could fly in 2024 to fetch the samples from the 2018 landing site and launch the cache into orbit around Mars, where it would dock with the return orbiter and begin the journey home.
"When we write the history, that decision taken by the council will be seen as the turning point," Southwood said in a July 8 interview. "That will be the point at which the Europeans said the future Mars program is together with the United States."