by MarkBour » Thu Oct 01, 2015 7:09 pm
Although not shown in the depiction in today's APOD, the actual images I saw in the first link in the caption, all have a common characteristic. They show a top-of-hill rocky region, then a smooth sandy sloped region below it. In these, the RSLs form growing down in the sand.
I am reminded first of all of being at the beach and how water can move through the sand. These RSLs may be just in the sand, right up at its surface, but not really exposed on top of it. They could be darkening the sand simply by their presence in it. As they evaporate away, the sand will return to its light color, and the sand isn't actually moving in the process. However, evaporation from within will cause the sand there to depress.
Meanwhile, back to the large rocks. I would not be surprised if these rocks are sitting on top of subsurface liquid sources, perhaps some of significant volume (I guess probably water). The rocks may act as "heating stones" in RSL season. They absorb and retain enough heat that they are warming the area below them, and the resulting melt is being more or less squished out of the sides by their weight.
So, those were my wild speculations for today. Sooner or later one of them ought to turn out correct!
Less speculative, I think is the idea that in some places we should expect to find water underground on Mars. I think the next robotic craft sent to Mars perhaps ought to be a portable drilling rig. Pick a few likely spots and try going down 100 feet, if necessary. Actually, I'm thinking that NASA will become interested in drilling deeper on lots of Solar system bodies. But for Mars, there is a practical benefit in this -- feasibilty of a water well, because they're looking toward manned missions to the place.
Although not shown in the depiction in today's APOD, the actual images I saw in the first link in the caption, all have a common characteristic. They show a top-of-hill rocky region, then a smooth sandy sloped region below it. In these, the RSLs form growing down in the sand.
I am reminded first of all of being at the beach and how water can move through the sand. These RSLs may be just in the sand, right up at its surface, but not really exposed on top of it. They could be darkening the sand simply by their presence in it. As they evaporate away, the sand will return to its light color, and the sand isn't actually moving in the process. However, evaporation from within will cause the sand there to depress.
Meanwhile, back to the large rocks. I would not be surprised if these rocks are sitting on top of subsurface liquid sources, perhaps some of significant volume (I guess probably water). The rocks may act as "heating stones" in RSL season. They absorb and retain enough heat that they are warming the area below them, and the resulting melt is being more or less squished out of the sides by their weight.
So, those were my wild speculations for today. Sooner or later one of them ought to turn out correct!
Less speculative, I think is the idea that in some places we should expect to find water underground on Mars. I think the next robotic craft sent to Mars perhaps ought to be a portable drilling rig. Pick a few likely spots and try going down 100 feet, if necessary. Actually, I'm thinking that NASA will become interested in drilling deeper on lots of Solar system bodies. But for Mars, there is a practical benefit in this -- feasibilty of a water well, because they're looking toward manned missions to the place.