Cosmic,

How do you get "we do know that it's material that was carried out of the crater" to be ambiguous?!?!

The ambiguity is in the fact that a scientist is saying one thing and an engineer the other

PERHAPS...the answer is that we're ALL right. It's fast winds all right, clearing the lighter dust, and depositing heavier dark sand as well. Consider El-Dorado....where was the dust there....none to be found...just dark sand. You need stronger winds to carry that stuff. But stronger winds will get rid of dust as well.

Just a thought.

Doug

That's not ambiguity, that's Normal Working Practice, surely?

I really don't think we're going to crack this until either Oppy heads into the crater and examines some of the dark material, or she catches sight of a haze of dark dust approaching from out of the crater after a strong wind gust. There just doesn't seem to be enough evidence in the surface pictures taken recently to wrap up this argument one way or t'other. It's going to take a guy or gal walking around Victoria, taking samples and working it out the good old fashioned way.

It might be time to move on, move in, raise your eyes to the sky again and start looking up at some of those outcrops Oppy instead of staring down at the ground beneath your tired wheels...

Stu, I haven't been as pessimistic as that. JPL has access to a lot more data that we, and (perhaps) better arguments. Still, the apparent disagreement between the two is disheartening.

Doug, I (for one) have been pointing out again and again that things may be more complicated that pure Sweep or Deposition. The real question is do we have a dominant mechanism.

Still, I expect we will find out what the Bigwigs are thinking very, very soon.

Not really being pessimistic Fred, just think it's time to stop flogging a dead berry and go see some more of the sights. I'm sure the explanation will emerge eventually, but Oppy is a Mars Exploration Rover, not a Mars Stare At The Ground For Days On End Rover Time to get rollin'; again...

Unless there are some of those endlessly fascinating festoons just lying on the ground...

-the other Doug

Stu: It is ambiguous because he made no specific comments about the timing of events. The dark material could have come out of the crater rather recently, or it may have come out quite some time ago. The former scenario would correspond to the depositional idea as I understand it. The latter scenario would be consistent with the removal idea if the dark material was later covered with light dust that was selectively removed recently.

Ah, I see what you meant now CR, thanks. I thought his statement was pretty unambiguous in that he was saying the dark stuff came from inside the crater, but you're right, the lack of a timeline still leaves the waters muddy.

About time this was sorted once and for all now... Oi! All you MER people reading: will someone PLEASE tell us what's going on?!?! You know, don't you, you're just enjoying watching us tie ourselves up in knots here!

Here's what I meant:
From the latest planetary society update.

Depositionists rejoice!

To quote an Olde English folk song from days of yore...

"Oh it's all gone quiet over there... yes it's all gone quiet over there..."

So if future HiRise passes see the streaks fade, will that make everyone satisfied?

"...even the fruits of victory would be ashes in our mouths."
-John F. Kennedy

"..everything is dust in the wind"
-rock 'supergoup' Kansas

Not so fast.

I don't think it would take too much prodding to get Squyres to say further
that keeping the streaks dust free is essential to keeping them dark.

"The dark material appears to be just sand blown out of the crater," informed Squyres.
It could just as well be sand NOT blown out of the crater, but blown in from somewhere else.
The ESSENTIAL is that, wherever the sand came from, it has been blown free of dust.

"It's dark because the sand on Mars is dark." He says. The dark sand blown
out of Victoria was probably blown into the crater at some previous time. And is
probably not significantly different from sand being blown all about Meridiani all
the time. It is not the fact that much of the sand in the streaks came from the crater
that makes them dark, it's the fact that the streaks are dust free that makes them dark.

Poor Stu, you don't see that Steve Squyres has burst the bubble of all
who imagined some unique dark substance unearthed in Victoria:

"[it's] just sand.... It's dark because the sand on Mars is dark."

The deposition theory always said there was a cycle. Dust blows out forming a dark streak. Seasons change, wind patterns change. Streak fade due to dust deposition. Cycle starts over.

There is no cleaning going on. There is dark sand deposition and light dust deposition. That's it.

I'm satisfied to see the cause of the streaks as two sides of the same coin.
The same wind blowing dust clear of the streaks is also depsiting sand from
the crater. However, the streaks would be dark if no additional sand were
blown onto them from the crater, if only the ubiquitous sands of Merridiani
were present and blown free of dust. Yes, sand from Victoria is deposited
on the streaks. But I still give the bottom line to the sweepers: the
streaks are dark because they are dust free.