In the second decade of the 21st century, NASA plans additional science orbiters, rovers, and landers. One proposal is for a Mars Sample Return mission that would use robotic systems and a Mars ascent rocket to collect and send samples of martian rocks, soils, and atmosphere to Earth for detailed chemical and physical analysis. Researchers on Earth could measure chemical and physical characteristics much more precisely than they could by remote control. On Earth, they would have the flexibility to make changes as needed for intricate sample preparation, instrumentation, and analysis if they encountered unexpected results. In addition, for decades to come, the collected Mars rocks could yield new discoveries as future generations of researchers apply new technologies in studying them.