28. "Big Joe" Boulder

Many of the prominent rocks and features at the Viking landing sites were given colloquial names like “Sponge Rock” in slide #25. This large (2-m) boulder is known as “Big Joe.” The morphology of the drifts is not the only line of evidence that aeolian erosion has occurred; note that there is drift material atop Big Joe. There is no reasonable way to deposit fine-grained sediment on top of a boulder where aerodynamic stress is high; therefore, the material is a remnant from when Big Joe was once buried. Another important item can be seen in this slide: There is a slump in the drift material immediately in front of and to the right of center of Big Joe. The slump was not present when Viking 1 landed and is proof that modification of the surface is currently active. The Viking 1 lander would not have survived a landing atop Big Joe.

Frame numbers 11I075/697 (high resolution) and 11H016/556 (color triplet).

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