Sample return is a long-term scientific objective of the international Mars-exploration effort., Our seismic and ground-penetrating-radar experiments will provide unique 3D images of the fine-scale subsurface structure in the first 10s of meters of the Martian surface. Our package will add an additional surface-reference site, providing invaluable new information on the geological composition of Mars. This precursor investigation will enable future mission planners to employ appropriate drilling technology to gather subsurface samples for return for analysis on Earth. It will also enable Canada to develop further our space technology and to take a leading role in these missions as they are conceived during the next decade.