I think the starfish pattern comes from the threading on the airbags.

They're not perfectly round 'bags'... if you look at any test shots of them, they're shaped more like a five-sided bag. When they hit the surface, these lines would have been imprinted into the planet's surface.

Although its hard to say owing to the absence of any scale, is this 1cm square or 1km?

I say its a print of of one of the balloons that protected the craft when it bounced, like the mark of a ball on the ground, the lines may be the seams of the balloon.

Those are imprints in the soil from the lander's airbags. The soil in that area is taking such good "impressions" from objects pressing down on them that you are seeing the seams and joins from the airbags laid out in the soil.

The behavior of this "soil" is looking more and more like it is at least slightly moist... I'm beginning to strongly suspect that the brine explanation may account for a lot of what we've seen so far on Mars: The reports of dark liquid stains in a variety of overhead shots, the "magic carpet" behavior, the soil surrounding Opportunity... heck, there are even frames showing what looks like recent flows with evaporation and salt-like mineral residue left behind coloring the rocks.

Let's hope that the investigators aren't "wedded" to some exotic electrostatic process, and that they at least allow for the possibility of liquid brine in the area.

It certainly is very interesting. I imagine if some sort of natural (or man made!) disaster occured on Earth which caused all of the large bodies of water to evaporate, then you would be left with a mineral rich sludge.
Where would the water have gone though? Is it possible for it to have evaporated into space somehow?
Could a very large impact cause this to happen perhaps...

I read somewhere that Mars has evidence of a huge impact on one side of it, and the other is smoother.

So that is a good point.....

Well, actually, if I remember right, the "smoother" part is where the impact happened. If you take the great rift (which is actually a split in the crust due to a huge bulge) and draw a straight line at a slant through the planet (slanting toward the north pole), you get to the impact site. It just kind of tried shove everything through the other side.