[meteorite-list] Martian Cave Entrance Detail

From: Chris Peterson <clp_at_meteoritecentral.com>
Date: Wed, 13 Jun 2007 22:35:46 -0600
Message-ID: <006001c7ae3d$7f9e7e40$2721500a_at_bellatrix>

> 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" <sterling_k_webb at sbcglobal.net>
To: "Kevin Forbes" <vk3ukf at hotmail.com>;
<meteorite-list at meteoritecentral.com>
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
Received on Thu 14 Jun 2007 12:35:46 AM PDT