[X] My Assistant

[aldo12xu]

Don't mean to compete against the Home Sweet Home thread, but I thought I'd put together a summary of the main observations and points discussed so far with regard to Home Plate, especially now that the thread is almost 20 pages long. I wouldn't be surprised that even after we eventually get the spectroscopy data, we'll probably still have a way to go before we get a handle on the origin of Home Plate.

So, anyways, I hope everybody finds the post of some use. The link is on my homepage.

Cheers,
Aldo.

[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.

[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).