“A lot of this is a coordination problem, and I do believe it could be better coordinated, better integrated over time,” says Bobby Braun of Georgia Institute of Technology, a longtime engineering adviser on NASA's Mars program and the agency's immediate-past chief technologist. “A couple of things that the MPPG team pointed to that I thought were interesting examples of additional ways that the technology programs could be involved [include] even more advancements in entry, descent and landing technology [and] in situ propellant production.”

Braun notes that all the ideas are intriguing, but need further study.

While the science community sees a sample-return mission to Mars as the “Holy Grail” of planetary space exploration, Bolden is not so sure.

“One piece of NASA, and the National Research Council, say the international community is going to figure out how to capture the Holy Grail,” Bolden says. “The question for many of us is what the timing of accomplishing the Holy Grail is. Do you have to do it before you can send humans? Some would say 'Certainly.' But when Neil Armstrong landed on the Moon, we did not have a sample.”