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Gray
QUOTE (ustrax @ May 24 2007, 09:36 AM) *
Note: I know that it has already a name but Cernunnos, the Celtic God of Fertility, Life, Wealth and the Underworld sounded just perfect for the occasion...



Perhaps we could we could use the name 'Cernunnos' for the underground chamber(s) for which there may be more than one entrance.
Stu
Maybe one day...

Click to view attachment

ohmy.gif
tuvas
MRO flight rules limit the off-NADIR pointing to 30 degrees. But that's only 24 degrees difference, it might allow one to see the bottom of the cave. It would almost certainly allow seeing the wall of the cave. Still, this is turning to be a highly unusual feature.

Oh, SHARAD might be able to find the depth of the cave, I'm just guessing though.

Also, you might be interested in knowing that the HiRISE team talked about the cave in a HiOPs meeting last Monday, we were joking that MSL should repel down into the cave, and then we thought, well, it can already repel, skycrane... Hmmm...
ustrax
Regarding the "work" I've done with the image, Alfred McEwen told me that it may be "scattered light", "the camera optics are excellent but not perfect."
But, might I add, the closest to perfection I have ever seen... rolleyes.gif
ngunn
Thinking about the possible pattern of illumination in the cavern made me think again of that wonderful Pantheon photo. The patch of sunlight in this case might be falling on a horizontal floor, but more likely somewhere part way up one sloping side of the tunnel, thus preferentially illuminating the opposite side with scattered light. I have a sketch of the geometry which could produce the apparent slight grading in interior illumination that may be showing on that image, but unfortunately no easy way of posting it here.
ngunn
QUOTE (Juramike @ May 23 2007, 11:06 PM) *
Ouch!

Am I the only one that didn't immediately see the pun??
GROAAAAAAAN! wacko.gif


Actually you saw it before me, so - it was all in the eye of the beholder! (Maybe a case of the pot calling the kettle black? How appropriate.)

By the way I'm going to be incommunicado for a few days - probably just as well.
ustrax
I've made a new animation focusing on the top-right quadrant.
Noise? Scattered light?
I just love the way the appearing features, layers-like, matching so nicely with the rim, seem to belong there... rolleyes.gif
tedstryk
Perhaps they could rotate the spacecraft to compensate for motion, allowing longer exposure times (same principle as CPROTO with MOC, but using the reduced speed at which the surface goes by for longer exposure time per line instead of higher resolution. Would be difficult, but worth trying once if at all possible.
marswiggle
I had a quick look in the MOC Gallery for similar features around the Arsia flanks and happened to find these. The first one is clearly Dena, from here. The second one is from here (lower right of the narrow angle img), and AFAIK it has not been referred previously. Both images are full size crops from the gif files, so I think the sizes are ~about~ proportional. The second one certainly could be an artefact, but it is very similar to the other ones anyway. A thorough search in the MOC imagery could reveal more.
Click to view attachment Click to view attachment
ustrax
QUOTE (marswiggle @ May 25 2007, 04:23 PM) *
I had a quick look in the MOC Gallery for similar features around the Arsia flanks and happened to find these.


They may not know yet what happened to their loved one but let's have some respect by Bwwn family's privacy... wink.gif
nprev
Wait a minute, ustrax...are you sure that's not actually their home? tongue.gif
Gray
Marswiggle,

The image of Dena that you posted has much better resolution and lighting than the image published in the Cushing, et al. paper (http://www.lpi.usra.edu/meetings/lpsc2007/pdf/1371.pdf).

Are we actually seeing the bottom of the pit in that one?
marswiggle
While I don't know, let them answer, in that very report:
QUOTE
However, a fortunate
MOC observation of Dena at ~2 p.m. (R0800159)
actually does show an illuminated floor, allowing us to
tightly constrain the depth using a 1-D photoclinometry
routine. This routine returns a depth of ~130 m for
the illuminated floor, while the minimum depth estimated
from the THEMIS observation is only ~80 m.
Because THEMIS IR observes at 100-m resolution,
cavern skylights with diameters much smaller
than that are probably not thermally distinguishable
from regular temperature variations on the surface

(The last paragraph also explains why the possible new skylight in S0901483 has not been observed with THEMIS, it evidently and perceivably being less than 100 m in diameter.)
Gray
Thanks.
I should do more than look at the pictures. sad.gif
tty
130 meters deep, that is really something for a lava tube. I've tried to find out what the maximum diameter of lava tubes on Earth is and the largest figures I have found is about 40 meters. However I remember seeing a considerably larger collapsed tube on Iceland so very likely it is the high gravity that limits the diameter.
When it comes to lengths, tubes here on Earth can extend many kilometers. Interestingly the longest seem to be on Hawaii (sensu stricto) which of course is the largest shield volcano complex on Earth, so on Mars' vastly larger shield volcanos tubes might very well be hundreds of kilometers long!

A tube 200 km long and 200 meter in diameter, how about that for an underground habitat?
Stu
What's causing that lighter area to the top of the hole?

Click to view attachment

Is wind coming up out of the hole? If so, that could suggest caverns linked by a tunnel network around here, maybe?

Does anyone else think the ground in this lighter area looks more rippled (duned?) than the other terrain?
dvandorn
Actually, Stu, I think the lightened area looks roughly the same in terms of the extent of duning as the rest of the surrounding terrain. It looks more to me like the lightened area has seen more deposition than the surrounding terrain -- the underlying lava-flow surface is more muted and softened in the lightened area.

I think what's happening here is that the prevailing winds are coming from the bottom of the image. As they pass over the hole, the air sinks a bit, and winds strike the rim of the hole along the top arc (all directions -- top, bottom, etc. -- relate to the orientation of your posted image). So the top arc of the rim is being eroded a little more rapidly than the rest of the rim, and the erosion product (basaltic dust, most likely) has been deposited on the ground beyond the top rim arc.

It's also at least somewhat possible that winds are entering the hole, swirling around, eroding the interior of the lava tube, and blowing dust out from the cavern and onto the ground above the top rim arc. I just don't think that Martian winds are powerful enough to reach into such a deep hole and scoop dust out of it, but I could be wrong. At any rate, it's impossible to model airflow into and out of that hole without having a decent idea of the size and shape of the empty lava tube, and we really have no way of determining that...

-the other Doug
Stu
QUOTE (dvandorn @ May 27 2007, 11:08 AM) *
Actually, Stu, I think the lightened area looks roughly the same in terms of the extent of duning as the rest of the surrounding terrain. It looks more to me like the lightened area has seen more deposition than the surrounding terrain -- the underlying lava-flow surface is more muted and softened in the lightened area.


Ok, just me then! wink.gif

I did think first about airflow over the crater being responsible for the change in brightness, but I can't help wondering if there are other - smaller, so as yet unseen - holes in this area and they're all linked together... would that allow winds to be generated within a tunnel network leading to a higher-than-usual speed for winds coming up out of a hole like this? Please, no-one cuff me around the ear for asking that if it's impossible or stoopid, I'm just thinking aloud... smile.gif

And talking about smaller holes... anyone taken a closer look at these dark spots?

Click to view attachment

No sign of lighter "streaks" above them, so maybe I'm just seeing holes that ain't there... or maybe they are holes that just aren't big enough to generate much airflow...

As I said, just thinking aloud...
djellison
I doubt it's wind through the lava tube itself. Think of a crater - that can have a dust tail of some sort and there's no network to do that. I imagine it's just a function of prevailing wind and topography. Wind blowing over a lage flat area suddently finding a big hole is going to get chucked up a bit - you might even find that the area under the hole is at a slight negative pressure relative to the surrounding area because of it.

Another thought - given that this tube is beginning to collapse at this one obvious site and potentially many others, it's quite likely that the tube itself isn't much of a tube anymore and more like a range of adjacant chambers. Who knows...I can't imagine we will for a few decades.

Doug
Stu
QUOTE (djellison @ May 27 2007, 12:38 PM) *
... it's quite likely that the tube itself isn't much of a tube anymore and more like a range of adjacant chambers. Who knows...I can't imagine we will for a few decades.


True... but fun to imagine... smile.gif

HOLE TRUTH

Look at that beckoning circle of black.
Darker than a dying shark’s eye,
a hole cut out of Mars’ ancient hide
revealing – nothing. Nothing At All.
No light falls on the far-below floor;
this is not a doorway but a pit
and deep inside it secrets lie in wait.
No world beneath is glimpsed
through this perfectly-punched puncture
in the planet’s brittle crust; just
more black, more emptiness,
a lack of everything is all we see
beneath this round-rimmed void.

It’s as if one of Sax’s laser beams
screamed from the salmon sky
and bored into Barsoom right here,
cauterising the wounded, light-seared
land… but more likely a giant’s hand of a meteor
smashed through the stone to the underworld
below, where no sol-light has ever shone
and millennia of darkness have passed
in cold, silt-softened silence.
Once lava, scarlet as Sauron’s eye ran
under here in smoking smears; for years
red and orange rocky vomit belched
through countless corridors of heat-and light-
baked stone yet this one alone has been revealed,
its shielding ceiling stabbed through by
who knows what. All we know is that all
are cold now, weaving and meandering
beneath these badlands like dust-clogged
arteries running through a mummy’s corpse.

If I stood shaking on its crumbling ledge,
daring to gaze o’er the edge of this abyss,
what blissful wonders would I see?
With my torch beam slicing through the gloom
would I swoon at the sight of stalactites
jabbing down like serpents teeth
from the ground beneath my feet?
Or on the shadowed floor far far below
would my sweeping light ray show
a carpet of pastel-paint hued life?
Enough streaks and plumes of green and blue
to make some cry “I KNEW it!”
Or would a Balrog’s fetid breath blow
over me before I felt its flaming whip
grip my ankle and drag me to my doom..?

© Stuart Atkinson 2007
nprev
Chilling yet fascinating, Stu...really captures the ominous feel/excitement of what it might be like to stand near the edge of one of these things...well done! smile.gif
tty
QUOTE (Stu @ May 27 2007, 12:21 PM) *
And talking about smaller holes... anyone taken a closer look at these dark spots?


I think the two elongated black spots with white rims in the 11 o'clock position from the big hole look like better candidates.
J.J.
That. Is. Incredible.

Interesting, how this one image has completely usurped the others in the press release. biggrin.gif It's interesting to speculate on what's it's like inside...I wonder if the floor has a thick coating of dust from (perhaps) eons of storms. Any way you slice it's, it's a beautiful image.

P.S.--Groovy poem.
tuvas
It's interesting, not since the Victoria crater picture has a HiRISE picture gathered so much interest as this one. And that's the only one that I know of that has surpassed the interest in this picture of any one image we have taken. Kind of funny how that works out sometimes.
Oersted
QUOTE (ngunn @ May 25 2007, 11:01 AM) *
Thinking about the possible pattern of illumination in the cavern made me think again of that wonderful Pantheon photo.


Good one thinking of my photo, I didn't even do that, but yes, there are definitely similarities in the spatial lay-out!



QUOTE (ngunn @ May 25 2007, 11:01 AM) *
The patch of sunlight in this case might be falling on a horizontal floor, but more likely somewhere part way up one sloping side of the tunnel, thus preferentially illuminating the opposite side with scattered light. I have a sketch of the geometry which could produce the apparent slight grading in interior illumination that may be showing on that image, but unfortunately no easy way of posting it here.


Something like this?



My "Pantheon - Earth and Moon-page":
http://www.dalsgaard.eu/Pantheon/
bdunford
I don't know if this is news to anyone, but FWIW, after a similar amount of interest about this image on my site, I asked the MRO team for some more info, and received this reply from Nathan Bridges on the HiRISE team, via Suzanne Smrekar:

"1. Yes, HiRISE is planning to image this again. We can't do much about the Sun angle because MRO's orbit is close to 3:00 P.M. and we are near the equator. Seasonal variations mostly affect the solar azimuth at this latitude, not the angle above the surface. However, we can change the angle that MRO looks at the target. So, for our 2nd observation, we will do a large roll to the east in the hopes of seeing the west-facing wall.

2. The two prevailing hypotheses is that this feature is either a deep collapse pit or a "skylight" ( opening) into an ancient lava tube. The location is between Pavonis and Arsia Mons, two large shield volcanoes, so a volcanic origin is appealing."
Juramike
QUOTE (djellison @ May 27 2007, 07:38 AM) *
...I imagine it's just a function of prevailing wind and topography. Wind blowing over a lage flat area suddently finding a big hole is going to get chucked up a bit - you might even find that the area under the hole is at a slight negative pressure relative to the surrounding area because of it.



What would it sound like next to the hole? Would it whistle in the wind?

How fast would the wind have to go past the hole to get any sound at all?

(High frequency or low frequency? How would it compare to a similar setup on Earth? Is the frequency dependant on the absolute depth and inner structure?)

Any wild guesses?

-Mike
ngunn
QUOTE (Oersted @ May 30 2007, 11:55 AM) *
Good one thinking of my photo, I didn't even do that, but yes, there are definitely similarities in the spatial lay-out!


Yes, and thanks for the additional image. The only difference between this and my sketched geometry is that I have replaced the spherical internal shape of the Pantheon with a horizontal cylinder representing the inferred lava tube. The internal illumination pattern then depends on the azimuth difference between the illumination direction and the cylinder axis, as well as the sun's altitude.
AlexBlackwell
Are There Giant Caves on Mars?
Planetary Radio
Monday, June 18, 2007
ustrax
Wow! They were able to actually get the bottom of a pit out of the dark! smile.gif
http://www.universetoday.com/2009/03/19/hi...ars/#more-27497

Nothing new here...done it two years ago... laugh.gif
http://www.unmannedspaceflight.com/index.p...ost&p=90761
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