[meteorite-list] Martian Cave Entrance Detail ADDITIONAL

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Thu, 14 Jun 2007 16:04:59 -0500
Message-ID: <017f01c7aec7$ac771a00$c3e08c46_at_ATARIENGINE>

Hi, All,

    Since it would seem likely to be a lava tube
rather than a Earth-conventional cavern, the
comparison should be to lava tubes on Earth.
The largest (longest) is Kazumura Cave in Hawai'i:
http://www.caverbob.com/lava.htm

    It's 65.5 kilometers long (40.70 miles) at a
depth of 1101.5 meters (3614 feet). The next
three longest lava tubes on Earth are also on
Hawai'i; there are nine known to a length of
more than 10 kilometers.

    The world's deepest vertical pit is at Vrtoglavica,
Slovenia and is 603 meters (1816 feet) straight down.
That could be a mile deep in Mars' gravity. The largest
single chamber in a cave on Earth is 162,700 m2 (600 x
415 x 100 meters). Also would be bigger on Mars.

    There are lots of lava channels on the surface of
Mars. Channels are lava tubes that have collapsed.
Flowing lava always cools on top, forming a solid
"roof" over the molten stream which drains and leaves
the tube behind. Here are Surveyor images:
http://www.highmars.org/niac/motubes.html

    Martian lava tubes on the surface are even bigger
than the scaling of the gravity would suggest:
http://www.astrobio.net/news/article1304.html
    "...on Mars they're hundreds of kilometers long.
And the diameters are equally great. On the average
they're 3 to 10 times the size of the average diameter
on Earth. They are truly enormous." (The gravity ratio
squared is about 6.9.)

    Using such caves on Mars as protective habitats
for human explorers is an old idea:
http://www.marssociety.org/portal/TMS_Library/Clifford_1997/view
It was also proposed for the Moon, back when we
thought the Moon had volcanoes.


Sterling K. Webb
--------------------------------------------------------------
------ Original Message -----
From: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
To: <Meteorite-list at meteoritecentral.com>
Cc: "Kevin Forbes" <vk3ukf at hotmail.com>; "mark ford" <markf at ssl.gb.com>
Sent: Thursday, June 14, 2007 1:59 PM
Subject: Re: [meteorite-list] Martian Cave Entrance Detail


Hi, Mark, List

    Well, since your processing pulled out
exactly what I thought I saw, only in greater
detail, I naturally think you did a great job!
Seriously, there are artifacts: the two "stitch
lines" show up just as they did in Kevin's
processed image, and of course, contours
re-enforce the suggestion of depth.
    Still, center-darkness is clearly THERE.
Sunlight is coming from just below the
left horizontal axis of the photo, yet near
the illuminated (right) side of the "hole"
is another very dark area which ,since it
is adjacent to the illuminated rim, must be
very far below it.
    The World Cave Database:
http://www-sop.inria.fr/agos-sophia/sis/DB/world.bydepth.html
says the deepest cave on Earth is over
2000 meters! Don't even ask about the
longest cave on Earth, which stretches
for 580 KILOMETERS under the Earth
(Mammoth).
    Apart from the possibility of caves too
deep to have an access to the surface, the
chief limit on cave depth is gravity. Mars
could have much deeper caves than the
Earth does (it has mountains three times
higher). Would you believe a five-kilometer-
deep hole?
    There's a great future exploration!


Sterling K. Webb
------------------------------------------------------
----- Original Message -----
From: "mark ford" <markf at ssl.gb.com>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>;
<Meteorite-list at meteoritecentral.com>
Sent: Thursday, June 14, 2007 4:25 AM
Subject: RE: [meteorite-list] Martian Cave Entrance Detail


Hi,

I have had a go at reprocessing the Martian cave detail, see
http://www.freewebs.com/fordmeteorites/martiancaveentrance.htm

There is certainly something there that is more than noise (well not normal
random thermal noise anyway)

Looks like a dark spot in the centre which is probably where the light fades
out as it goes down futher.

Wow - It's a big hole!


Mark



-----Original Message-----
From: meteorite-list-bounces at meteoritecentral.com
[mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Sterling
K. Webb
Sent: 14 June 2007 07:02
To: Chris Peterson; meteorite-list at meteoritecentral.com
Subject: Re: [meteorite-list] Martian Cave Entrance Detail

Chris, List,

> it's presumed that Mars has been volcanically
> inactive for a very long time...

    Presumptions were Born To Be Tested. Which
is not to say that you (and it) are wrong, by any means,
but since we are presumably going to poking about
these curious apertures (instrumentally at least), it
could be done if there's a multiband instrument
suitable (I don't know).

    As for the albedo shift, I think it's real. I'm looking
at it at the scale of 25 cm per pixel. As for the dunes,
I see several light dunes that run right out of the bright
and continue without a break into the darker area --
where they are dark, the same dunes. They may be more
eroded and rounded over so that their shadows are not
as pronounced but even so the peak of the dunes in
the light area are noticeably brighter than any other
feature in the photo except for the illuminated rim of
the "hole." It could be very light frost from water
vapor coming from the hole, or a dusting of sulfur,
or a chemical alteration of the soil, or ground that
was trampled by the boots of a crowd of spelunking
Martians... well, no, not that.

    The most annoying thing about Mars (going to bitch
about a planet, now?) is that you see something interesting
but what you don't know, can't know, really want to know,
is did this happen yesterday, 10 years ago, a century, a
millennium, a million years, a billion?

    Don't know what you meant by "a very long time," but:
http://www.universetoday.com/am/publish/mars_volcanoes_active.html
    "The timeline proposed from studying the complex
Olympus Mons caldera suggests there have been lava
flows from intense volcanic activity within the past 2
million years."

    A puff of steam isn't that intense.


Sterling K. Webb
------------------------------------------------------------------------------
----- Original Message -----
From: "Chris Peterson" <clp at alumni.caltech.edu>
To: <meteorite-list at meteoritecentral.com>
Sent: Wednesday, June 13, 2007 11:35 PM
Subject: Re: [meteorite-list] Martian Cave Entrance Detail


> 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

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Received on Thu 14 Jun 2007 05:04:59 PM PDT