Wow, Oppy's next stop ...

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For instance, it has seen fluid flow features in Victoria Crater just south of the equator, where NASA's Opportunity rover is trudging along the rim. The fractures appear to be surrounded by cemented rock on the eastern crater rim and floor.

One of NASA's goals for Opportunity is to get to that side of the crater. If it is able to get close enough, Opportunity might provide some microscopic observations of the rock to confirm whether the rock has been cemented together by fluid.
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- Underground pipes channelled water on Mars

And the MRO image of the potentially targets ...

- PIA09191: Linear Ridges at 'Victoria Crater'

I heard several radio reports today here in the US about MRO finding more evidence of subsurface water...wonder if this is what they've been referring to, haven't seen any actual articles yet.

Try this thread.

(slaps head) Do'h!!! I just now went to the JPL site & there it was. Sorry...long day. Thanks!

Well, heck, we've been discussing those linear features in the east-southeast portion of Victoria's rim ever since the first HiRISE pictures came in.

While it might be interesting to discover some basic faulting that's associated with subsurface water flow, I think there are so many ways in which the local crust could have been gifted with linear faults that assuming the water flow origin is rather premature.

-the other Doug

One obvious mechanism would be that they are artifacts of the Victoria impact itself that may have been altered later by water intrusion. What we've seen of Meridiani thus far seems to indicate a tectonically quiet history, at least at the scales observable by Oppy.

Yes, but this is rather like Occam's Razor. There is no need to bring in extraordinary events here; the areas in Victoria where we see these linear features were originally outside of its rim. The crater has expanded via wall slump so that the walls have expanded *into* linear fault features, which more than likely pre-existed the crater. (In fact, I'd say they'd almost have to -- how many craters have you seen that have created faults tangential to their rims? Impacts more commonly create radial cracking than cracking transverse to the impact surge.)

I'm not saying that these fault features are definitely *not* associated with fluid flows. All I'm saying is that linear faults are fairly common on all of the rocky bodies we've observed (Earth, Moon, Mars and Venus) and in most cases these faults are tectonic in nature. Of the remaining sources of linear faulting that have been observed, only a relatively few are related to fluid flow.

So, if it turns out that Oppy can visit these ridges and they turn out not to show signs of fluid flow formation, that doesn't mean there aren't other locations on Mars where fluid flow faulting has occurred. And, conversely, if fluid flow *is* indicated in Victoria's linear faults, that doesn't mean that every similar set of faults we see on Mars were also formed in the same manner. Linear faults are just too common and have too many different causes for such generalizations to always be valid.

-the other Doug

I agree - personally I'm backing the theory that these are soup pipes. That dragon's not there for nothing!

Andy

I don't think they're saying that the fluid created the faults, only that it exploited them. Both the formation of the faults now revealed in the Victoria hole and their hardening by cementation from ground fluids would have predated the impact event, probably by a long interval. The only connection, as I see it, is that this raises the odds that there could be icy - or watery - layers buried beneath the visible aeolian deposits. I (and others before me) have previously proposed sapping by the fluidisation and partial sublimation of such a layer to account for Victoria's vertical cliffs and scalloped rim.

More pieces to the puzzle. If the faults were caused by the Victoria impact and IF
water flowed through them, that would prove the presence of post Victoria water.

I wouldn't be surprised if they didn't see one or two linear features like these as far back as Mariner 9 and vaguely speculated about volcanic dikes. They almost certainly show up in scattered Viking high resolution images. What we now have is the geologic ground truth supplied by the rovers to give a specific, different interpretation of these features, given our new knowledge of ground water activity and rock alteration history examples from the two rovers.