Originally posted by ArMaP
I don't see any reason for them to keep some parts of their shapes intact and some parts broken or eroded (...)
If we consider for a moment that they actually 'were' artifacts, we may also need to ask: how did they get to their current and final location? Were
they buried by layers of sand and rock? Were they under water? For how long? Was there freshwater or saltwater? Currents? What exactly were these
features made of? Was there a subsequent and gradual
uncovering of sand/rock layers over time? Or were they transported to their current
location in a stream of mud and debris originating from the source of the alluvial fan?
I think that the above questions could shed light on why there are some irregular features sticking out of the rocks or why they look partially
damaged.
(...) as an artefact would probably be made from a more consistent material than the (apparently) fragile sedimentary rocks that we can see on
the photos from Mars.
That's what I would assume as well. On the other hand, I don't know just how fragile the sedimentary rocks are. But it seems that rocks of different
consistency are scattered around in that area (see below).
The problem I see with that is for that to happen then the artefacts should behave in the same way as the surrounding rocks, reacting to
erosion in the same way.
For example, if a piece of metal is left on the surface and gets subjected to the same erosion as the surrounding rocks, do you think it will be
affected in the same way?
That's probably the most interesting aspect of it. One tends to think that they should react in the same way to erosion, yes. And the whole
arrangement of rocks in that area does look somewhat uniform, although they seem to have a slightly different coloring than the surrounding rocks. But
when looking at the 'Hugo' feature, erosion obviously can yield different results:
Here's what NASA/JPL wrote about that particular feature:
This knob has a different type of rock on the end of the projection. This rock may vary in composition or the rock grain size may be smaller. The
rock on top of the projection is likely more resistant to wind erosion and protects the underlying rock from being eroded. The shiny surface suggests
that this rock has a fine grain and is relatively hard. Hard, fine-grained rocks can be polished by the wind to form very smooth surfaces
(...)
Link to the official NASA/JPL document (PDF) on 'ventifacts'.
Apart from that, the erosional effects would certainly depend on a number of things. For example, the inclination of the features and their position
in the terrain, the grain size of aeolian particles (when it comes to wind erosion), atmospheric conditions, surrounding vegetation (if any), time
etc.
As far as I'm concerned, I'm still baffled by the amount of geometrical features that is visible in such a small area. And they don't look like square
basaltic rock pillars (like the
Giant's Causeway that resulted from volcanic activities).
To me they look more like coherent frames or beams that had intentionally been formed like that, but who can tell for sure. Ultimately, a lot of
unknowns are involved into this and there's still a plethora of questions to be answered ...
edit on 20-3-2013 by jeep3r because:
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