Good question! The sand moves on its own! Think of it as the planet being covered by glaciers, but instead of ice, it’s sand! That’s the rumbling sound you hear. Visually you’d see the surface moving as one giant slow wave, and the collectibles can be seen through the surface.
(The graphics are like a grid that covers the surface, that you can see through, but instead of grid lines, there are points at the corners of each cell. It’s very simplistic, but complemented with gradients of warm Mars-like colors: rusty reds and oranges, blending into to lighter pinks, yellows, or blues depending on the time of day.)
Anyway, you can stand over them, or come back later, to collect them. They are stationary. And with the Attractors upgrade, it has the ability to pull items out from the sand directly into your Cargo Racks.