On a separate note, this is good news for future colonists, regardless of presence of water for them to use. The “fines”, or very small material (dust), is a big problem on the moon, since it is rough and sharp edged, and so small it gets into all the joints of equipment and into fabric, causing bearings to stick. We found that out on the moon landings. If it gets transported into the living space (on equipment and suits thru the airlock most likely) it might cause a problem in people’s lungs, like asbestos does, if you breath it for months. The reason the fines on the moon are so sharp-edged is that there’s no erosion there, just rocks getting blasted apart by occasional meteorites. Seeing this picture with rounded gravel (clasts, they call it, learn a new word every day), shows that erosion has a long history on Mars, and the fines shouldn’t be such a problem there. In fact, the longevity of the rovers so far is another good indication of that. So far, Mars is looking like a much better place to colonize than the moon, except that it’s so far away…