B.) Please note that in the unprocessed photo of the
"hole," there is clearly a whitish "stain" or discoloration
of the terrain that is plume-shaped and that extends
away from the "hole." Hot CO2 or H2O vapors might
have produced the plume, but I think a sulfurous gas
more likely (as frequently seen in Earthly volcanoes).
I'm not at all certain that's the case. Certainly, if you look at a
lower resolution image that's the impression. Look closely, however, and
you'll see that the area above the hole is actually a different texture-
apparently sand dunes on a ~10m scale, quite different from the
surrounding area. My guess is that these are the product of a complex
wind flow around the hole. I don't see anything to suggest that a plume
from the hole is responsible (and it seems likely that the ever shifting
sands would have long ago covered up a true material plume, since it's
presumed that Mars has been volcanically inactive for a very long time).
I have my doubts that the processed image is showing anything other than
noise. The HiRISE team, working with ~14-bit data, couldn't stretch it
enough to pull out anything above the noise floor (a parameter I'm sure
they are familiar with). I certainly wouldn't expect that real details
would be present in the much lower dynamic range JPEG2000 image. But
even if there is some faint detail, there would be nothing surprising
about it. The hole is probably an opening onto a lava tube, so it's
likely the floor is not more than a few hundred meters down. Even at the
low (38°) Sun angle, it's possible that enough light is making it down
to allow for a tiny signal to be recorded.
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
----- Original Message -----
From: "Sterling K. Webb" <[EMAIL PROTECTED]>
To: "Kevin Forbes" <[EMAIL PROTECTED]>;
<[email protected]>
Sent: Wednesday, June 13, 2007 10:02 PM
Subject: Re: [meteorite-list] Martian Cave Entrance Detail
Hi, Kevin, List
When I looked at your processed image and mentally
subtracted the stitchlines and the periodic noise, what I
saw was vague dark arcs nested inside each other toward
a darker center. So I took your image and fiddled with it
in the manner you described (luminance, contrast). Your
processed image definely has a darker center. As you stretch
the contrast, the center darkens more than the rest and so
on, for a bigger and bigger dark center.
Now, if this was a vast cavern under the surface and the
hole was a "skylight" break-through, even if the "floor" was
thousands of feet down, the center under the skylight would
be faintly brigher than the edges, brightest at the center,
the opposite of this.
IF (that was a big "if") the center is darkest and the circle
near the center is next darkest and so on, it can only be
interpreted as our looking down a very deep, relatively
straight tunnel or pipe. Why would Mars have a vertical
tunnel miles deep?
A.) This feature is located on the slopes of a big volcano.
Volcanoes frequently have side vents, vent pipes, lava
tubes, a variety of geological "plumbing" extending from
them that release volcanic gasses.
B.) Please note that in the unprocessed photo of the
"hole," there is clearly a whitish "stain" or discoloration
of the terrain that is plume-shaped and that extends
away from the "hole." Hot CO2 or H2O vapors might
have produced the plume, but I think a sulfurous gas
more likely (as frequently seen in Earthly volcanoes).
Is there infrared spectroscopy available on this small
scale? It would be worthwhile to identify the substance because
we could then estimate long it would persist on the surface
and correspondingly get an idea how recent the activity that
deposited it was.
Sterling K. Webb
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