Home Plate Speculations, Get it in now, before we know the truth! |
Home Plate Speculations, Get it in now, before we know the truth! |
Jan 25 2006, 04:10 PM
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#1
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Down in the Front Page Stories board, Phillip asked what all of us UMSF types think Home Plate might be made of and how it was formed. He actually wants Jim Bell's speculations, but asked for UMSF's speculations, as well.
Since we're getting close to getting there, it's time for any of your uninformed speculations out there to be recorded for all posterity... I posted the following in that thread, but it really belongs here, so I'm reposting it here and inviting discussion. I figure that a lot of us don't bother to read the boards we don't stay actively involved with, so for all of you, this is new. Otherwise, I apologize for the repetitiion! Look at the vertically-exaggerated image posted here. Home Plate seems very obviously, in this stretched image, to be the remnant of an impact crater. There are several impact crater remnants in the inner basin, here. Each seems to have been formed in a surface that was a good many meters higher than the present surface -- those missing several meters have been deflated from this terrain, by some process, leaving the shocked "pedestal" remnants of the deeper cratering forms. Remember, when you make an impact crater, you don't just affect the surface. The disruption caused by the cratering event goes well under the surface, consisting of impact melt (if the impact is energetic enough) and shocked, brecciated rocks. The crater remnants we're seeing on the surface look like the brecciated and shocked rocks that were originally created in a bowl-shaped lining beneath this cluster of impact craters. I can see traces of at least five different craters within the inner basin, here. (The ridge of rock Spirit is passing right now is, in fact, a small crater remnant.) As for Home Plate, it sits within the largest and most well-defined of these crater remnants. Maybe such layers were exhumed in *all* of the craters here, and have since been completely eroded away -- but that doesn't seem right. We have traces of several craters, and in only one of them do we see any trace of this lighter-colored material. I'd have to think that either the impact target composition was different where the Home Plate impact occurred -- which seems a little unlikely when you consider some of these impacts are only a few tens of meters apart -- or that some other substance was deposited in Home Plate crater that wasn't deposited in the other craters. (Or that has been completely deflated from the other craters, if it ever existed there.) So, logic *seems* to point towards post-cratering material deposition accounting for the light-rock ring. Personally, I think it could have been water deposition. Home Plate could have been a puddle that was filled and dried thousands of times (maybe with an internal artesian spring) that resulted in aqueous transport and deposition. Or, it could have just been a good wind trap and it trapped a lot of light-colored dust. Hard to say. I'm not only interested in the light-rock ring's composition, I'm getting very curious about the erosion process that deflated the original surface. Could aeolian erosion have deflated *that* much surface, even over a few billion years? Do we need to postulate aqueous erosion, or even glacial erosion? Maybe the specific composition and erosion patterns we see on the light-rock ring will help us puzzle that out. -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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Feb 1 2006, 02:12 AM
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#76
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Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
QUOTE (tty @ Jan 31 2006, 03:37 PM) It might well have been, but that is completely irrelevant to whether Gusev has been filled with mud or not. Any water in the impactor is instantly turned into (very) superheated steam on impact and most of it is dispersed at hypersonic speed. Any mud in the crater would be due to either (1) melting of permafrost by the impact, (2) groundwater, (3) discharge from the Ma'adim valley or (4) rain. tty I appreciate your comments since they are good ones! This topic is becoming very interesting since nobody are VERY sure about the origin of HP. Rodolfo |
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Guest_Richard Trigaux_* |
Feb 1 2006, 08:48 AM
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#77
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Guests |
What do you think, you all, that Homeplate is a fosilized cricket ground? or a former Commonwealth colony? Please tell it aloud, not by allusion!
It is since permitted, so long that we don't know what Homeplate really is... a french petanque ground. PRRRT Hahahaha By the way, this is only a friendly joke, I have nothing against english people. I live in a little integrated town, with all kind of people, French, English, and we have no racial problems |
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Feb 1 2006, 07:38 PM
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#78
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Senior Member Group: Members Posts: 1229 Joined: 24-December 05 From: The blue one in between the yellow and red ones. Member No.: 618 |
QUOTE (Richard Trigaux @ Jan 31 2006, 10:48 PM) What do you think, you all, that Homeplate is a fosilized cricket ground? or a former Commonwealth colony? Please tell it aloud, not by allusion! It is since permitted, so long that we don't know what Homeplate really is... a french petanque ground. hehehehehe.....my lips are sealed... O.K. Reeshard, I assume this is your final official guess for the HP Sweepstakes: "a petanque ground" (whatever in God's green earth that might be) By the way, I've heard a rumor that the Grand Prize is a trip for two to France . Not bad, eh? -------------------- My Grandpa goes to Mars every day and all I get are these lousy T-shirts!
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Feb 1 2006, 09:28 PM
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#79
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Senior Member Group: Members Posts: 2998 Joined: 30-October 04 Member No.: 105 |
This is wild... I was reviewing recent imagery, and saw a rind (exfoliation?) in one of the Spirit images. Near the lower side.
--Bill -------------------- |
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Feb 2 2006, 06:30 AM
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#80
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Senior Member Group: Members Posts: 2228 Joined: 1-December 04 From: Marble Falls, Texas, USA Member No.: 116 |
OMG! That whole thing went right over my head. Thank goodness "/english humour" was posted with a leading slash. Otherwise my head might not be here today to enjoy the aftermath. I'll never cease to be amazed by the interplay of languages here.
-------------------- ...Tom
I'm not a Space Fan, I'm a Space Exploration Enthusiast. |
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Feb 2 2006, 10:34 AM
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#81
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Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
QUOTE (Bill Harris @ Feb 1 2006, 10:28 PM) This is wild... I was reviewing recent imagery, and saw a rind (exfoliation?) in one of the Spirit images. Near the lower side. --Bill Bill: Oh, for a brush... Bob Shaw -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Feb 2 2006, 04:58 PM
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#82
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Senior Member Group: Members Posts: 1887 Joined: 20-November 04 From: Iowa Member No.: 110 |
The of edge Homeplate is visible. Speculations anyone?
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Feb 2 2006, 05:53 PM
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#83
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Member Group: Members Posts: 320 Joined: 19-June 04 Member No.: 85 |
Well, it looks too rough textured to be, say, a lacustrine sediment. In my opinion, the majority of the exposure has a volcanic appearance to it. But there is some hint of layering, so maybe there's a volcanic ash airfall component to the unit.
-------------------- |
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Guest_Richard Trigaux_* |
Feb 2 2006, 06:39 PM
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#84
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Guests |
QUOTE (alan @ Feb 2 2006, 04:58 PM) hmmmmm... it looks like anything else here. Maybe it's just a volcanic ash layer. Pity, I think everybody expected something more exotic. But wait for analysis of rock. Maybe also this image is not in the same wavelength than the orbital image, so it appears here the same colour than other rocks, when on orbital images it appears white. |
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Feb 2 2006, 10:26 PM
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#85
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Member Group: Members Posts: 866 Joined: 15-March 05 From: Santa Cruz, CA Member No.: 196 |
yup, that picture uses the "R1" 739nm filter, so the white doesnt show up.
Here's the unfiltered navcam image of the same area, the above R1 image is the area right below and to the left of the white mound, and shows the same isolated rock at its left side (topmost large rock), and you can see how white the dust pan above it is in the unfiltered image but the layer in question doesnt show up as white, so i dont think that line of strata is really part of the white part of the homeplate, its probably an older layer below it. Are we actually seeing into the bowels of homeplate or are we looking up onto its slope? (i dont have my anaglyphs) In any event you can compare the unfiltered white chalky mound to the same "R1" filter's lifeless rendition of it. |
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Feb 2 2006, 11:32 PM
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#86
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Senior Member Group: Members Posts: 2488 Joined: 17-April 05 From: Glasgow, Scotland, UK Member No.: 239 |
As ever, the closer we get to something the less we see the structures and only the surface rocks!
Try these images for orientation - we're looking *up* one of the slopes in the Pancam image above. There's bedding, there's textural changes, there's also much more of a cohesive feel now to the whole area, right from HP through Baby Mound and up to Pitcher's Mound. We really need to get a bit closer, and see some outcrops... ...the good news is, sandtraps excepted, it all looks as though it could be driven over! Bob Shaw -------------------- Remember: Time Flies like the wind - but Fruit Flies like bananas!
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Feb 3 2006, 12:03 AM
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#87
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Member Group: Members Posts: 311 Joined: 31-August 05 From: Florida & Texas, USA Member No.: 482 |
QUOTE (aldo12xu @ Feb 2 2006, 11:53 AM) Well, it looks too rough textured to be, say, a lacustrine sediment. In my opinion, the majority of the exposure has a volcanic appearance to it. But there is some hint of layering, so maybe there's a volcanic ash airfall component to the unit. The ashfall layer is very likely, but it's still strange that it's so contained in a restricted area. There are outcrops that may be the same unit on Ramon, but maybe the ash has been modified. Just one crackpot idea before reality clonks me on the head (again): since it almost resembled an exhumed crater and a layer of ash, maybe it's a little of both? Perhaps something like a small comet fragment hit a layer of sultate-rich ash. The ice and energy from the comet was just enough to fuse it into a wind-resistant layer that we now see? I guess 100m will take a few more Sols to reach, but I'm already holding my breath. |
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Feb 3 2006, 03:32 AM
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#88
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Senior Member Group: Members Posts: 1229 Joined: 24-December 05 From: The blue one in between the yellow and red ones. Member No.: 618 |
Dam' How can something look so prominent from orbit, and so underwhelming close up? The guys over in the yellow forum don't even see it; they're looking off in the wrong direction.
Where's our big white Plate? Big Black Rock Redux There is a white layer - not very thick - 10cm? Hey Dilo, Caro, How thick is the white layer and the whole structure? -------------------- My Grandpa goes to Mars every day and all I get are these lousy T-shirts!
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Feb 3 2006, 04:48 AM
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#89
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Senior Member Group: Members Posts: 2998 Joined: 30-October 04 Member No.: 105 |
There is a simple explanation for the lack of tonal contrasts in these initial Homeplate Pancam images: They are taken with L7 and R1, which are at 430 microns (UV-ish). I'd expect a reddish feature like Homeplate to look a bit bland.
I'd suspect that a proper L257 or L456 will look better. --Bill -------------------- |
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Feb 3 2006, 04:49 AM
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#90
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Guys -- if you compare the pancam image in which alan declares that the edge of Home Plate is visible, to the navcam locator image linked by atomoid, you'll see that the white ring structure is not at all visible in the pancam image.
The flat sand patch with the bent rock that points to the left is identifiable in both images. When you then compare the two images, you see that the entire field of view of the pancam image lies below the visible portion of Home Plate's white ring. We're looking up the outer slope of the "inner rim" around the white ring. This inner rim obscures the white ring from Spirit's present vantage point. So, there's your answer -- the white ring isn't visible in the frame! -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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