Home Plate Summary Options

[Bob Shaw]

If it were a software engineer (s)he would have said:
"Turn it off, and everyone get out of the car then get back in and it should work fine..."

How many software engineers does it take to change a lightbulb?

None - it's a hardware issue.


How many Microsoft Certified Professionals does it take to change a lightbulb?

None - DarkNess ™ is the new industry standard


How many Systems Analysts does it take to change a lightbulb?

Do you really need that lighbulb?


Bob Shaw

[Holder of the Tw...]

Hey but... What happens if the bats ARE COMING BACK???

Now you know the REAL reason they're so anxious to get Spirit off of there!

[dvandorn]

Any explanation for the rock to the right of spirit's solar panels?
http://marsrovers.jpl.nasa.gov/gallery/all...5P2274L2M1.HTML
It almost looks like someone used a trowel to smooth part of it.

Looks more like someone troweled a thin layer of concrete over a rougher surface. In panel-like sections. One panel, for whatever reason, has resisted erosion, but adjacent panels have been flaked off, revealing the pebbly surface below.

Man -- this stuff does look a lot like concrete, doesn't it? A naturally-occurring concrete, of course... which is sort of what sandstone is, I suppose.

-the other Doug

[neb]

Looks more like someone troweled a thin layer of concrete over a rougher surface. In panel-like sections. One panel, for whatever reason, has resisted erosion, but adjacent panels have been flaked off, revealing the pebbly surface below.

Man -- this stuff does look a lot like concrete, doesn't it? A naturally-occurring concrete, of course... which is sort of what sandstone is, I suppose.

-the other Doug

That is a tough one, all I can say is it looks out of place and is not part of the bedded sequence. Also how how about the cylinderical feature imbedded in the top rock.

[Guest_Richard Trigaux_*]

My hypothesis as what homeplate would be evaporites (Jarosite, Meridiani style) seems not to hold in front of close explorations.

My best guess now is for fall of volcanic cinder, away from a vent. Arguments:
-don't show erosion forms of the jarosite
-fine laminations crossing each other like in volcanic falls
-darker round grains into a finer white cement (could be cinder hail)

By the way such a formation perhaps needed more atmosphere than now (all the scoriaced lava blocks we see, where the holes are much larger than on Earth, are hinting for a thin atmosphere even in early Mars history). Perhaps the diametre of cinder hails could give an atmospheric density.

But the problem now is why they are not publishing the analysis results? Certainly not to "censor" them, but to reserve them for a thorough publishing of an unexpected or difficult result.

Basalt cinder would not be unexpected, there is basalt everywhere. So there is no reason that they delay the publishing of such a discovery. So my better guess is for an unusual lava, like the trachyte family or komatiites.

Komatiites, on Earth, result from the direct fusion of mantellic rocks, and they come at 1600°C in violent eruptions. They were common in ancient times, but very rare in more recent times. On Mars, we can expect they happened in early history, when the crust was still forming (assuming the mantle was liquid and very hot from accretion heat).

Trachytes, on Earth, result from a complete differentiation of lavas, the last step. Their magma chambers give rocks in the granite family. So they are elaborated continental rocks, hinting for the presence of cratons (continents building blocks, formed of granites) and of plate tectonics.


Discovering trachytes on Mars would be really a sensational event, an evidence the planet once had some plate tectonics like on earth.

[edstrick]

Note that a lot of team members (and other planetary geosci-geeks) are prepping for presentation at the Lunar and Planetary Conference. This is one of the annual "biggies" for planetary geology researchers.

[Guest_paulanderson_*]

My hypothesis as what homeplate would be evaporites (Jarosite, Meridiani style) seems not to hold in front of close explorations.

My best guess now is for fall of volcanic cinder, away from a vent. Arguments:
-don't show erosion forms of the jarosite
-fine laminations crossing each other like in volcanic falls
-darker round grains into a finer white cement (could be cinder hail)

Yes, as noted in one or two of the othe HP threads, this is what the MER team is thinking now, that HP is the eroded remnants of a tuff cone or maar:

http://www.planetary.org/news/2006/0228_Ma...ate_Spirit.html

See this geology page also for illustrated earthly analogies (courtesy Kye Goodwin):

http://members.iinet.net.au/~boxer/WesternDistrict.htm

Even the volcanic bombs and cross bedding look quite similar to the HP images. What then about PM I wonder? Another tuff cone / maar? Scoria cone? If indeed an eroded volcanic cone, this also implies there was a groundwater table present, if we can go by an earthly analogy. Perhaps the "smaller concretions" seen and theorized about at HP are lapilli, as also mentioned on the geology page linked to?

I thought for a long time that HP and PM might be volcanically related, and wasn't convinced (and still not) that HP was simply a deposit left in an ordinary, eroded crater as some had suggested. I think either HP itself is a tuff cone / maar or a deposit left within a larger tuff cone / maar crater (there's some debate as to just what the MER team is referring to).

[CosmicRocker]

Thanks especially for that last link, Paul. After looking at those examples and doing some related Googling, I think I can better understand what the Team may be thinking.

[Bob Shaw]

Yes, as noted in one or two of the othe HP threads, this is what the MER team is thinking now, that HP is the eroded remnants of a tuff cone or maar:

http://www.planetary.org/news/2006/0228_Ma...ate_Spirit.html

See this geology page also for illustrated earthly analogies (courtesy Kye Goodwin):

http://members.iinet.net.au/~boxer/WesternDistrict.htm

Even the volcanic bombs and cross bedding look quite similar to the HP images. What then about PM I wonder? Another tuff cone / maar? Scoria cone? If indeed an eroded volcanic cone, this also implies there was a groundwater table present, if we can go by an earthly analogy. Perhaps the "smaller concretions" seen and theorized about at HP are lapilli, as also mentioned on the geology page linked to?

I thought for a long time that HP and PM might be volcanically related, and wasn't convinced (and still not) that HP was simply a deposit left in an ordinary, eroded crater as some had suggested. I think either HP itself is a tuff cone / maar or a deposit left within a larger tuff cone / maar crater (there's some debate as to just what the MER team is referring to).

Paul:

Regarding the Australian Maars etc, the bedding is, indeed *very* similar to that which we see at HP, right down to the smallest bedding details - but the *scale* of the structures is so different! I suppose that if we can identify more elements of a volcanic complex in the area then it'll be more credible. One other possibility, I think, might be localised pseudovulcanism as a result of an impact, with the effects of groundwater penetration allowing water alteration and enhancing the (temporary) violence of the events.

Bob Shaw

[Guest_Richard Trigaux_*]

Paul:

Regarding the Australian Maars etc, the bedding is, indeed *very* similar to that which we see at HP, right down to the smallest bedding details - but the *scale* of the structures is so different! I suppose that if we can identify more elements of a volcanic complex in the area then it'll be more credible. One other possibility, I think, might be localised pseudovulcanism as a result of an impact, with the effects of groundwater penetration allowing water alteration and enhancing the (temporary) violence of the events.

Bob Shaw

Bob, In Auvergne in France I have seen cinder laminations which closely look like Homeplate, scale and all. So there is no problem in the identification.

[Guest_RGClark_*]

Yes, as noted in one or two of the othe HP threads, this is what the MER team is thinking now, that HP is the eroded remnants of a tuff cone or maar:

http://www.planetary.org/news/2006/0228_Ma...ate_Spirit.html

See this geology page also for illustrated earthly analogies (courtesy Kye Goodwin):

http://members.iinet.net.au/~boxer/WesternDistrict.htm

Even the volcanic bombs and cross bedding look quite similar to the HP images. What then about PM I wonder? Another tuff cone / maar? Scoria cone? If indeed an eroded volcanic cone, this also implies there was a groundwater table present, if we can go by an earthly analogy. Perhaps the "smaller concretions" seen and theorized about at HP are lapilli, as also mentioned on the geology page linked to?

I thought for a long time that HP and PM might be volcanically related, and wasn't convinced (and still not) that HP was simply a deposit left in an ordinary, eroded crater as some had suggested. I think either HP itself is a tuff cone / maar or a deposit left within a larger tuff cone / maar crater (there's some debate as to just what the MER team is referring to).

Thanks for the links. What might be key is the "bomb sag" features given on the volcanic features in Western District of Victoria page:

Volcanic bomb sag in tuffs at the Lake Purdiguluc maar.


Volcanic bomb sags in tuffs at the Tower Hill maar complex.


On the HYDROVOLCANIC ERUPTIONS page is also given an example of a bomb sag:

Bomb sag.



There was a discussion on Uplink.space.com about some Spirit images that might show a bomb sag, referred to as a "drop stone" on that forum:

Uncalibrated color image at Home Plate.


Taken from these Pancam images:

Panoramic Camera :: Sol 751.
http://marsrovers.jpl.nasa.gov/gallery/all/spirit_p751.html




Bob Clark

[Guest_Richard Trigaux_*]

That Homeplate would be volcanic is very likely.


But my point was rather on the COMPOSITION: if it was just another variety of basalt, they would have published it immediately, as they did for all the other rocks. The fact that they did not (yet) published the analysis results hints that they found something SPECIAL about this composition: unusual, unexpected, or unexplainable. So among possible candidates, volcanic or not volcanic:

-trachytic cinders (Usually such cinder are trachytic, but we also find some basaltic cinders)
-komatiites
-carbonatite (can form thin cinders which harden like concrete)
-limestone. In this case, there is a strong evidence of an ocean, not just a temporary one, but a long standing ocean, hot enough for limestone formation (not under an ice cap).
-limestone cementing round grains which could be fossils. If this is the case, I understand that they want some more checking before publishing!
-other

Please note also that maars form when there is a lava emerging through a watertable or water stream. But they don't do cinders, rather special kind of irregular bombs.
But komatiites, which erupt very violently, can also form maar-like holes.

[Guest_paulanderson_*]

Regarding the Australian Maars etc, the bedding is, indeed *very* similar to that which we see at HP, right down to the smallest bedding details - but the *scale* of the structures is so different! I suppose that if we can identify more elements of a volcanic complex in the area then it'll be more credible. One other possibility, I think, might be localised pseudovulcanism as a result of an impact, with the effects of groundwater penetration allowing water alteration and enhancing the (temporary) violence of the events.

Good point about the scaling. In a previous post in "Home, Sweet Home," sattrackpro had pointed out that HP seems to be surrounded in its immediate environs by the "frothy boulders" which, as he mentioned, seemed to imply a possible direct volcanic connection to HP and maybe PM as well. I'm just keeping in mind also that the MER team has the initial analysis results in hand, which we (or most of here anyway?) haven't been privy to yet. The impact idea is possible of course, I'm just not sure we always need to associate impacts with almost everything we see on Mars (I just think there is sometimes a general over-tendency to do that, since we've learned that Mars is much more geologically diverse than used to be thought in the 60s - 80s for example). But as mentioned elsewhere, this will all sort itself out I'm sure.

[vikingmars]

Well...
(i) to please all the Forum contributors ;
(ii) to thank its Administrators for all the work they are doing for us in keeping alive this wonderful tool of exchange ;
(iii) to honour the 2 discoverers of the Home Plate feature (Dr. Nathalie Cabrol and Dr. Edmond Grin at NASA/AMES + their student in Paris Gilles Dawidowicz who helped them map the Gusev crater and identify features inside),
here is the sol 758 fully calibrated mosaic (reduced 50% in size to fit in the Forum)
PLUS the same image as desktop wallpaper for you to enjoy !

1st desktop wallpaper

(2nd desktop wallpaper)

Attached thumbnail(s)

 

[Bob Shaw]

Well...
(i) to please all the Forum contributors ;
(ii) to thank its Administrators for all the work they are doing for us in keeping alive this wonderful tool of exchange ;
(iii) to honour the 2 discoverers of the Home Plate feature (Dr. Nathalie Cabrol and Dr. Edmond Grin at NASA/AMES + their student in Paris Gilles Dawidowicz who helped them map the Gusev crater and identify features inside),
here is the sol 758 fully calibrated mosaic (reduced 50% in size to fit in the Forum)
PLUS the same image as desktop wallpaper for you to enjoy !

1st desktop wallpaper

(2nd desktop wallpaper)

I think I got a new desktop! Thanks!

Bob Shaw