May 23, 2007, HiRISE release |
May 23, 2007, HiRISE release |
May 25 2007, 05:05 PM
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#61
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Wait a minute, ustrax...are you sure that's not actually their home?
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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May 25 2007, 05:22 PM
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#62
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Member Group: Members Posts: 242 Joined: 17-February 04 From: Ohio, USA Member No.: 34 |
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? |
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May 26 2007, 11:30 AM
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#63
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Member Group: Members Posts: 111 Joined: 14-March 05 From: Vastitas Borealis Member No.: 193 |
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.) |
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May 26 2007, 02:01 PM
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#64
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Member Group: Members Posts: 242 Joined: 17-February 04 From: Ohio, USA Member No.: 34 |
Thanks.
I should do more than look at the pictures. |
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May 26 2007, 06:31 PM
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#65
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Member Group: Members Posts: 688 Joined: 20-April 05 From: Sweden Member No.: 273 |
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? |
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May 27 2007, 09:48 AM
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#66
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
What's causing that lighter area to the top of the hole?
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? -------------------- |
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May 27 2007, 10:08 AM
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#67
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
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 -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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May 27 2007, 10:21 AM
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#68
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
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! 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... And talking about smaller holes... anyone taken a closer look at these dark spots? 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... -------------------- |
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May 27 2007, 11:38 AM
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#69
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Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
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 |
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May 27 2007, 03:13 PM
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#70
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
... 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... 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 -------------------- |
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May 27 2007, 03:58 PM
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#71
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
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!
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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May 27 2007, 05:30 PM
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#72
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Member Group: Members Posts: 688 Joined: 20-April 05 From: Sweden Member No.: 273 |
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May 28 2007, 03:12 PM
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#73
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Junior Member Group: Members Posts: 94 Joined: 22-March 06 Member No.: 722 |
That. Is. Incredible.
Interesting, how this one image has completely usurped the others in the press release. 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. -------------------- Mayor: Er, Master Betty, what is the Evil Council's plan?
Master Betty: Nyah. Haha. It is EVIL, it is so EVIL. It is a bad, bad plan, which will hurt many... people... who are good. I think it's great that it's so bad. -Kung Pow: Enter the Fist |
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May 28 2007, 05:22 PM
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#74
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Member Group: Members Posts: 428 Joined: 21-August 06 From: Northern Virginia Member No.: 1062 |
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.
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Guest_Oersted_* |
May 30 2007, 10:55 AM
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#75
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Guests |
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! 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/ |
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