Mercury Flyby 1 Options

[belleraphon1]

Thanks nprev!

But Stu is the true jewel..... beautiful, sir!

Yes, it appears Mars had an intrinsic magnetic field early on..... and some of the remnant frgaments are fairly strong!

As for Venus... hmmmmm..... the lack of a field cannot be soley due to slow planetary rotation, Mercury's rotation is long as well..... Venus I would also love to dive into...... does she have one thick lithosperic plate over a stagnant mantle and core?
Or are there other complications................ ???

All just so fascinating..... I was born when planets were basically just dots in the sky, litttle known.... and now I can virtually partipate in roving worlds....

Craig

[Gladstoner]

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[Juramike]

The spider grabens seem to radiate from a dark albedo feature that is offset from the crater.

Nice illustration and observation!

[Phil Stooke]

The spider fracture pattern looks to me like what I would expect from a dome-like uplift - either related to isostatic compensation in the old basin, or later intrusions.

But I'm particularly interested in this feature on the SW edge of Caloris:



a diffuse halo nothing like crater rays or ejecta. The multispectral images show it has a non-impact-like composition, as well. And it has an irregular depression in the middle. To me, it looks like a volcanic plume deposit of some kind.

Phil

[nprev]

Nice find, Phil! That is indeed intriguing. Additionally, the thing looks like it's sitting on some sort of darker flow itself, or at least there seems to be a sharp boundary (a scarp?) to the right of the feature.

Can't wait for the orbital phase...bet we find a lot of things like this!

[Gladstoner]

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[Gladstoner]

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[Bill Harris]

The spider fracture pattern looks to me like what I would expect from a dome-like uplift - either related to isostatic compensation in the old basin, or later intrusions.

Bingo. The radial graben are clearly extensional features. The impacting asteroid excavated the basin, and the mobile, plastic mantle overlying the fluid iron core made an isostatic adjustment. I'll suspect that altimetry will show that Caloris isn't a basin...

It'll be interesting to see what the Skinakas Basin has to offer, as well as the Weird Terrain at the antipode of Caloris, etc.

--Bill

[Nirgal]

Based on all the superb color reproductions posted here by tedstryk, ugordan, Vikingmars and others
I tried my own (hand-)colorized interpretation of one of the Mercury recent fly-over-limb images...
:-)

[Stu]

Browsing the Planetary Photojournal yesterday, looking for a pic to use in a talk, I found a Magellan image that looked naggingly familiar... then it came to me...



Venus image info: http://photojournal.jpl.nasa.gov/catalog/PIA00150

Not suggesting anything, just pointing out a similarity, that's all... Does make you think tho, especially with the speculation here about Caloris actually being Mercury's Tharsis...

Edit: Also interesting: Navka

[pgrindrod]

stu, i think it could be a very valid similarity! i’ve hunted through some of my own images and found a couple more features on venus that look similar.



there are about 160 on venus, and over half of these have a raised central summit region, showing that uplift might be playing a part in their formation. in fact, you can have some fun inflating a balloon in a box full of flour (sand would probably be better) to show how uplift can cause radial fractures.



but back to mercury…i don’t know how differently magma bodies (if they are the cause) behave inside mercury, but i wasn’t expecting this kind of feature (i was more hopeful for titan, but that doesn’t seem to have borne out). very exciting stuff though. the topography of the area will be very interesting i imagine.

pete

[Juramike]

(i was more hopeful for titan, but that doesn't seem to have borne out).

Actually, I've been wondering if Sotra Facula on Titan might be a Nova - something like Ganesa Macula that bulged up, cracked in a goofy way, then oozed out a ways from the center. The T25 RADAR Swath image (PIA09182) shows bright "cracks" (cliff faces?), but doesnt' quite show the RADAR darker fracture depths you'd expect on a Nova. (Could these be infilled due to Titans erosion and dune sands and harder to see at this RADAR resoultion?)

If it indeed is a Titan version of a Nova, it's fracture pattern seems more random when compared to Venus and Mercury's regular star-crack pattern. Perhaps the goofy fracture pattern on Titan is due to it's different crustal materials?



(Alternatively, the radar bright features might be the steep edges of cryovolcanic flow boundaries.)

((This feature is right at the edge of the T28 Swath and there might be subtle hopeful hints of associated darker cracks, but it's of lower resolution.))

-Mike

[tasp]

I suspect a similarity to the "Tiger Scratches" on Iapetus. In that example however, the compressional effect is offset along the flight vector of the impactor into the Iapetan equivalent of mantle. We do not see a 'spider' pattern, in that case, just the released compressional effects of the impacting body under and away from the rim.

Hate to harp about this, but we really do need a good close up set of observations of the Tiger Scratches. Neglecting everything else on Iapetus, the Tiger Scratches themselves, in view of this new Mercury finding, strongly merit additional study.


Amazing feature on Mercury, and one we can learn more about by studyoing additional examples. It is an intersting probe of deep material properties.

[ngunn]

A query - would subsidence produce a similar pattern as doming upward? Both involve extension of the surface. When molten metal cools from the outside in you tend to get dimple formation and tensional cracking in the middle. I'm thinking large 'ball' of molten rock following the Caloris impact, again cooling and shrinking from the outside inward. The last bit to solidify can't fill the available volume, hence subsidence and tensional cracking.

[Gladstoner]

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