How best to bring back to Earth the ultimate in candy store samples from Mars is receiving top attention at the Seventh International Conference on Mars. That gathering of some 500 leading Mars experts from around our world is being held here at CalTech in Pasadena, California.

On Tuesday there was a heart-to-heart long-distance phone hookup between meeting attendees and Alan Stern, NASA’s Associate Administrator for the Science Mission Directorate at space agency headquarters in Washington, D.C.

Stern said that pulling off a multi-billion dollar robotic Mars sample return (MSR) effort will require “focus and discipline” to find the cash within the agency. He said that he’s personally looking at the 2018-2020 time period for MSR activities. Moreover, to help dredge up the money there’s need to skip at least one Mars mission opportunity somewhere in the next decade.

Other ideas are on the table too, Stern said, including a relook at the NASA Discovery and New Frontiers programs to help get MSR underway. That view produced audible sounds as conference participants began to squirm in their seats.

Stern is also backing use of the Mars Science Laboratory to practice caching Mars specimens. That huge and high-priced rover is now under development at the Jet Propulsion Laboratory, headed for liftoff in 2009. Adding a sample caching device to that rover so late in the game is a nail-bitter in some quarters.

But Stern said such an initiative would be a plus. For one, it would help build the foundation of support for future Mars sample return activities, not only in scientific and public circles, but also in Congress and the Office of Management and Budget.

“I think there’s something concrete about putting your stake in the ground,” Stern advised.

Meanwhile, a small tiger team at NASA’s Ames Research Center has already sketched out a small, hockey puck-like device to be installed on Mars Science Laboratory. It’s billed as a “secondary payload” for caching bits and pieces of Mars gathered by the powerful, long-lasting robot during its mission. The final study results from the Ames team on the caching hardware are due by the end of July, early August.