QUOTE (sattrackpro @ Feb 23 2006, 04:36 PM)
Most tektites are pretty irregular in shape, and normally quite rough... concretions are produced by deposition from aqueous solution in rock - so I'm not inclined to believe we are seeing either.
Below is a snip of one image enlarged, with green arrows pointing to what may be tiny spherules, and some red arrows pointing to cavities with possible spherule content and a couple of other round-ish objects.
Does anyone else think these are spherules? Or, is what we're seeing a trick of lighting and high magnification...
I have to say that the light, irregular - rather flocculant
-looking aggregations - are just that. Aggregations of the light dust which has been otherwise removed from the underlying sandstone by the IDD brush. The aggregations may have been partly produced
by the brushing action, picked up by the brush itself, and then fell back onto the rock in more or less random locations. I believe they are entirely superficial to the rock, and could be removed by a puff of compressed gas (which BTW I have often wished MER had the capability to deliver - some of that clinging dust is very distracting.). The appearance of this sandstone seems no different to my nonprofessional
eye than that of the piece of float brushed and MIed, down at the base of the section:http://marsrovers.jpl.nasa.gov/gallery/all...A0P2936M2M1.JPG
Allowing for the difference in magnification, I see an identical sandstone, with dark, partly worn clasts plus a few light flocculent dust aggregations scattered across it. (Prof. Tim, If you see differences with your highly-trained eyes
, I would be eager
for another lecture!)
This does confirm that the original float examined was
representative of the upper unit of HP, and so this revisit to the edge has scientific justification. But I agree there is no reason to postulate tektites or concretions in this MI. Those pearl-like
large spheres down below, however, may be more provocative, and it's a pity there was no time to take MIs of them.