Final answer:
The presence of shifting dunes on Mars is evidence of wind activity on the planet. Martian winds are capable of redistributing surface material and forming dunes, and the photographs of these dunes indicate active wind-driven processes. So the correcct option is g.
Step-by-step explanation:
The shifting dunes on Mars demonstrate the presence of winds on the planet. These winds play a crucial role in redistributing surface material. As described, much of the material stripped from Martian canyons has been deposited into extensive dune fields, primarily at high latitudes.
Mars experiences various wind-related phenomena, such as dust devils, which are responsible for creating patterns on the surface by moving dust and sand. These dust devils and windstorms have enough power to move sand and create dunes, which change shape and position over time. The passage of Martian winds over loose sediments can also result in cross-bedded sandstone formations, as have been interpreted from images taken by the Curiosity rover in Gale Crater, indicating past interactions with liquid water.
In summary, Mars' winds are integral to the planet's surface dynamics, creating and shifting the dunes observed in high-resolution photographs. These winds are an essential factor in understanding the Martian climate, surface erosion, and geological history.