Because of the eccentricity the equatorial regions share the southern hemisphere's seasons, approximately. Presumably this would still be true if we were at 2 degrees north (taking seasons as being defined by insolation rather than in the strict astronomical/geometrical sense.) Does anybody know the northerly latitude at which the effects balance out - the 'weather equator' so to speak?

Thanks, marsophile. That's pretty much what I was talking about. We were talking about slope components at that point.

Here's a crude mosaic of the today's navcams where I circled two possible veins.
Click to view attachment

Yes, and if you'll look to the left of the upper "light vein" you'll see a dark (shadowed??) "fin" as well as similarly-trending lineations in the fractured light-toned area.

--Bill

This article from MSSS goes into a lot of detail and has a really nice visual that shows the variation in insolation by latitude over a martian year, I've added some quidelines (with southern seasons) here to make it easier to see approximate latitudes and time of the year.

Click to view attachment

This shows peak insolation at noon not total insolation, the article discusses a lot of the secondary effects (such as atmospheric pressure) which also shows how dominant the eccentricity is for Martian Climate. I don't have an index for the colours used but solar insolation above the atmosphere at LS 270 is ~ 650W/m^2 and at LS 90 it is about 545W/m^2.

My reading of this is that to counteract the effects of eccentricity you would appear to have to go quite far north of the tropics before you would have a Northern location that actually tracked "Northern" seasons in any meaningful way. The deviation of maximimum\minimum insolation levels from the solstices is very apparent here, especially as you reach tropical latitudes.

There are other things to factor in - most notably dust levels. There is a clear trend there for both MER locations, and I guess across all of the planet at least between the tropics, that tracks the SH seasonal changes: dustier in late SH spring\summer, clearer in SH winter.

Sol 2761 anaglyphs

trimmed long quote -mod

Near the tropics (where Opportunity is) this diagram covers the primary effect quite well. For northern and southern latitudes, where length of daylight effects begin to predominate, the diagram would have to be modified significantly.

Steve M

We account for both, of course. The difference is, we can control tilt (insofar as we can find geography with good tilts!). The orbit eccentricity is a fixed constraint, something we can't change.

-m

The ideal spot for Oppy would be a half pipe running North/South with a slight Northern tilt. Then in the morning she could climb the left wall and tilt East, and in the evening move a few feet to the right wall and tilt West. A fully sun tracking rover with her panels always facing the sun

Exactly! Basking lizard-style!

An excellent diagram, even if it maps only one relevant parameter. Assuming that factor dominates between the tropics I'd say the 'weather equator' runs close to 20N. 25N is greenest at LS 270, 15N is greenest around LS 90.

So: land a probe at 20N to avoid seasonal blues!

As SteveM pointed out this really only maps out one parameter and a better map would show total insolation not just the peak value. One other point that should be mapped at the same time would be average Tau and its effect on direct and indirect sunlight - while NH winters are less severe they are also dustier.

A hypothetical MER at (say) 14 deg N would have less severe winters (with more potential noon sunlight at least) than Spirit but it would happen when Tau was generally quite high so there would almost certainly be less incident energy, possibly a lot less. One further complication of this is that higher Tau decreases direct sunlight but increases diffuse sunlight so Southerly facing Winter Haven's and lilly pads would be a lot less effective. I suspect that the net effect would be that deep winter survive-ability would be much more of a challenge.

Great minds think alike

OK I promise to stop this OT discussion soon! but your latest post leaves me confused. Which winters would be a problem at 14N, northern winters or southern ones? You seem to refer to both as winter?? Taking tau, daylength, everything into consideration what's your best estimate for the latitude on Mars that receives 'even seasons' insolation-wise? (That's what I mean by the 'weather equator'.)

And here is a vertical perspective panorama of the onlap area on Sol-2761, showing the light-toned "vein" and the razorback and lineations on the exposed bedrock.

--Bill

I'm really excited to learn that these "veins" are being targeted. When we first saw them I predicted they would be an excellent target when Oppy first arrived at CY. It was a serious letdown for me when they drove right past the suckers. I can't wait to learn more about them.

I see the light-toned "vein", but am not sure what you mean by "razorback". I remember seeing thin blades sticking up at certain joints years back, but dont see that here. Any interest in the dark-toned (black) short "vein"?

Thanks

Whoops, nix that. Looking closer, that feature was a chance alignment of rock fragments. I guess you'd call it an occipital illusion-- it wasn't there...

--Bill

There were some pancam sequences on 2759 that were intended for superres views of Endeavour, but also caught gusts of wind blowing through the big crater. Here's the best example, 8 frames over a period of about 7 and a half minutes:
Click to view attachment
Let's hope we get a good strong gust over CY!

Here's an update after the new pics. This is 5 frames showing an especially nice gust blowing across:
Click to view attachment

Very nice! And here's a super-res shot of the dunes from this set of images. 11 images enlarged and registered.

Phil

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re: fredk's series: Winds of Opportunity!

And another composite looking across at the far side of Endeavour. There's a lot of detail over there just waiting for a really clear day.

Phil

Click to view attachment

The light-toned "vein" is of interest. Oppy is doing positioning Pancams, is flexing her IDD and the spot now has a name: Homestake.

This is a preliminary L721 Pancam view from Sol-2763. Homestake is apparently composed of some form of hydrated Iron (III) oxide (which suggests low-temp hydrothermal) and the surrounding rock has a hematitic signature, which suggests an impact breccia. Note that there are some basaltic fragmants on the surface, presumably as cast ejecta from nearby impacts. I don't see anything suggesting Blueberries, but we could use some foreground quarter Pancams of the surface we're travelling on.

--Bill

EDIT:
And here are better Pancam views (L257 and R721) of the new IDD target Homestake:

http://i142.photobucket.com/albums/r91/wil...70L2M3--res.jpg

http://i142.photobucket.com/albums/r91/wil...70R7M1--res.jpg

Indiana Squyers thinks so...

The name suggests they expect to strike paydirt at Homestake Mine.

SteveM

Indy really should have peeked at that 80 Sols ago.



And there are many other interesting features at this onlap area that Oppy will revisit.

--Bill

"Homestake"...

Click to view attachment

my3D stereo pair of "Homestake", sol 2763

Completed 360x90 Navcam panorama for sols 2761-2762:

left - right - anaglyph

This one is centered on east since that provides a more encompassing view of Cape York. I'm figuring anyone who wants to (Phil) can rotate it 90 degrees if needed.

Just to wrap up for me today, here's a 90 degree wide view facing northeast, showing Oppy's position on sol 2763 (looking at "Homestake").

Gorgeous!

Thank you. It takes some work (about an hour in this case) to manually de-vignette and brightness-adjust everything, plus feed it to PTGui, etc.

Very nice! And here it is in circular form. Looking at it, I would make a small edit to Tesheiner's map - the last drive (the last part of it anyway) was right along the boundary, not at an angle to it.

Phil

Click to view attachment

Took mhoward's stereo pair of Homestake to make this "super gif," for what its worth. Some color was lost in the gif compression.

Click to view attachment

Here's one of the MIs of Homestake on today's batch. I guess we will be here for a little while.

Click to view attachment

Yes!! And as an added bonus, we finally get a close-up look at the rock fragments we've seen.

Let me work up a context/location from the color images that we got yesterday.
...........EDIT: I couldn't quite place the MIs on the context Pancam-- couldn't find enough reference points. Maybe later today.

I added "crisper" Pancam images to my post from yesterday:
http://www.unmannedspaceflight.com/index.p...st&p=179756


--Bill

Here are the first few fragments of the MI pan of Homestake with a bit of tweaking . . .

EDIT: Had a bit more time -- upgraded image stitching

Spectacular!

-m

That's really good work, Dan, nice one.

Very interesting!!

There appears to be some banding along the length of the vein. Would this indicate some kind of periodic deposition as the vein grew?

There won't be clearer Pancams for a couple of days and I wasn't able to match up specific features between the MIs and Pancams, but based on a TLAR anaylsis of the FHazcam images, this may be the likely location of the current MIs and the IDD work.

This should be mineralogically interesting. An R721-yellow is typically a hydrated Iron III oxide-hydroxide, but this is a lemon-yellowish, so who knows. And note the ruby-red zones along the feature. What are they? What is the nature of the county rock surrounding the fracture fill? A gajillion questions, no?

--Bill

Fresh off the aether-- a cropped L257 showing the location of the IDD spot. It is on the left, next to the IDD arm joint.

And yesterday's (Sol-2764) quick-and-dirty MI stitch.


EDIT-- and for the cross-eyed mineralologists, an R521 (sorry, no deep-IR R7 was down yet).


--Bill

Right on the money. We're going to do some Pancam 13Fs before we leave; perhaps some background APXS or APXS-Argon measurements to subtract out the extraneous stuff that isn't Homestake itself.

Maybe the Pancam 13F from 2765 is down by now... I'm sure they plan on doing more over the weekend.

-m

EDIT:


Here's to hoping for a dust cleaning event... that deck is getting dusty.

-m

Those current P2572 Pancams are so much better. They'll keep us giddy for a while.

--Bill

Anaglyph and my3D stereo pairs of Homestake, sol 2765. This one took a lot of monkeying around but was worth it.

Sol 2765 Homestake micro image anaglyph and my3D stereo pair. This one works really well in the my3D.

I overlaid Bill's colors on the base MI image and came up with these rough composites. The L257 has a desaturated section on the left where the IDD arm joint was intruding into the color image.

My take on Homestake in 3D...

Click to view attachment

...and a colour view, too...

Click to view attachment

...and again, great work Dan

wow! That looks