Daniel's correct: it appears the stems are made of the softer matrix. (thanks for the "color" photo.) Hopefully the MI gets a good shot of one of these so we know for sure, but I think they are tiny hoodoos, I do.

Here's a hoodoo I love near Echo Amphitheater near Ghost Ranch in New Mexico. It's located at ~ 36-21.76N 106-31.65W. If you are ever driving by here, do lunch at Echo Amphitheater, the echo is so amazing, like no echo you've ever heard, trust me! If you want to see this hoodoo, go up the drywash just north of the campground. It's a rough trail (trail? ha!). You'll see it up the North side of the canyon. If you want to get to where I took this photo, good luck, damn near broke my neck up on this nasty slope. BTW, that white layer on top of the ridge on the other side of the canyon is gypsum. In the background you can see Ghost Ranch, where Georgia O'Keefe hid out for a while. The rock on top is the size of a small car.

(sorry 'bout the crappy copy, I can't find my negative, and I had to take a photo of a big photo) It's copyrighted, so no reproductions without asking me, okay?

Why does this pertain to the stems on blueberries? The hoodoo forms because the softer stuff under the big rock is protected by the rain. The weathering agent on the Mars rocks is wind, which is coming horizontal to these rocks, therefore the small blueberry hoodoos are inclined towards the wind direction. (which probably changes from time to time). The sand particles are bouncing all around close to the ground during a dust storm, this "saltation" is a very effective erosive tool.

Here's a map if you really wanna go there: topozone.com map

Cool, yeah? The picture was taken on Halloween of 1987, I hope it is still there. Now back to that hard drive transplant.

~jms~