It looks so lonely there, poor rover.

Just curious about something. After twin crater how much of an elevation change will there be going downhill?
Will the drop in elevation be more then how deep Victoria Crater is? Will the exposed rock still be the
same ones the rover sees now or will they be older as we drop in elevation?

We're going about 50m downhill from here to Santa Maria and perhaps another 50m from there to Endeavour.
Tim Parker (tim53) posted a topographic map somewhere here... edit: got it! http://www.unmannedspaceflight.com/index.p...st&p=155924

I think we can see the twins on this today's pancams.
Click to view attachment
Original: http://qt.exploratorium.edu/mars/opportuni...00P2394L6M1.JPG

Only 300m to go. If we keep the current pace that means some 4-5 driving sols or, in other words, next weekend if we're lucky.
BTW, the 20km mark will be crossed soon.

Or at least one of the twins - they should be about twice as wide as your marker now.

It seems with the last drive we gained a bit height. The two should be about here:

Click to view attachment

The dunes are getting a bit, uh 'choppy-looking'.

Interesting; wonder if we're beginning to see some topographic wind effects on their formation patterns.

I've been thinking the same thing about the dune morphology.

As we approached/ arrived at Concepcion, I noticed that between the usual longitudinal (N-S trending) ripples transverse dunes (ripples) had started to appear. Given a set supply of sand and/or a set wind velocity, the sand will settle into a quasi-stable longitudinal dune configuration. I attributed the appearance of the transverse dunes as a local increase in sand supply as a result of the rubble created by the impact and the weathering at Concepcion.

However, after we left Concepcion I noted that the transverse dunes were still present, clearly "upwind" of any sand created by that impact. As we saw on on the approach and look-back at Concepcion, the crater is on a slight rise. What I am thinking is that the local topographic high has created a small wind shadow with slightly lower wind velocity to the north of Concepcion. Once we passed by Concepcion, the wind velocity increased slightly.

No direct meterological data here, just an observation of how the sand is behaving.

--Bill

Is there a "prevailing" wind as such at Meridiani?

Hopefully you're right, Bill - we could use some stronger winds to clean the arrays a bit.

As far as prevailing winds, they do vary seasonally as the streaks emerging from Victoria crater showed.

Hopefully she will get some array-cleaning winds. A Watt-Hour Zephyr?

One side-observation I've made is noting an accumulation of dust at the top of the Low Gain Antenna starting sometime around Sol 1710, the stopover at Santorini. No idea why a ring of dust would accumulate at this spot, but it ought to serve as an indicator of wind (or lack thereof?). But I digress, I'll open a separate thread on this particular puzzle. Here is a recent Sol 2125 Navcam of the phenom...

http://origin.mars5.jpl.nasa.gov/gallery/a...0P1987L0M1.HTML

--Bill

Are we seeing Twin Craters top left there?

Click to view attachment

Probably not. Seriously, I'm feeling quite lost and disoriented at the moment. About time we found another meteorite to let me get my bearings!

No, that view's to the north. The giveaway is the bit of tracks you can see in the original image.

Stu? Lost?! Physically in Kendal, Cumbria, UK, and mentally on Mars as always surely!

He doesn't use MMB

Ah, ok, thanks Fred. Think I'll just sit here in the back seat, quietly reading my magazine and listening to my MP3 player; someone give me a shout when we get there...

That reminded me...I finally just now installed MMB on my new computer (old one couldn't handle it)...WOW!!!

It's truly remarkable, Mike; thanks!!!

You're welcome. I actually find it a little embarrassing now, since I don't have time to make it as good as it should be, or even maintain it.

MMB? Qu'est-ce que sais?

C'est Midnight Mars Browser.

(...and he's embarrassed by it!!! Would that I could accomplish something even a hundredth as embarrassing by that token... )

Just want to clarify that my lack of MMB is nothing to do with the prog itself! It's just a combination of having a Jurassic era PC that groans in protest if I dare to open Photoshop and Google Earth at the same time, and finding a somewhat perverse enjoyment in manually logging on to Exploratorium every morning when I get up, or when I get back from work later in the day, and having a "yes!!!" moment when I see there are new raws for me to play with. I'm sure I'll download and love MMB when I afford to get a new PC, later this year.

BTW, latest MER-inspired poem here, if anyone wants a look... best to click on "full size" if you want to read it without damaging your eyes...

http://twitpic.com/19zn62

(Text only: http://astropoetry.wordpress.com/2010/03/21/museum-peace )

I'm the same way. MMB is a great program, but there is a certain aesthetic to logging on and manually collecting Rover gems.

--Bill

That's what I do too.

Back to the main topic and our next waypoint, we're 70m closer to them. I think the crater is the dark feature visible on the top left corner of this pancam image: http://qt.exploratorium.edu/mars/opportuni...FPP2397L6M1.JPG. There's another shot to the left of this one but unfortunately it doesn't cover the whole horizon so we're missing the whole picture.

This R1 frame shows more of the twins (plus it's a bit sharper than the L6), upper left:
http://qt.exploratorium.edu/mars/opportuni...FPP2397R1M1.JPG
I wonder when they'll first look recognizably like craters?

They're also faintly visible as a light streak along the midlle-left horizon in this navcam view:
http://qt.exploratorium.edu/mars/opportuni...FPP0705R0M1.JPG

Again lots of duplicate images in the latest exploratorium batch. This time they don't even have the different suffix M7. For example, here's an image that's appeared twice:
http://qt.exploratorium.edu/mars/opportuni...00P0713R0M1.JPG
http://qt.exploratorium.edu/mars/opportuni...00P0713R0M1.JPG

Pretty low activity (actually zero) on this thread on the last 24h, isn't it?
Let's see if it changes after the next images' downlink which should happen in 18h or so. I'm looking forward new pictures from a point 70m (?) closer to those craters. Hopefully, we'll be there before the weekend.

Made from some of today's lower quality pancams...

Click to view attachment

Thanks for that, Stu. The north rim of Endeavour should be on the left side of that mosaic, but it's not visible - that shows how we've gone over a ridge at Concepcion and have dropped down a ways.

Something's there:
http://qt.exploratorium.edu/mars/opportuni...NWP2399R1M1.JPG
If it weren't for the orbital imagery I'd never guess it was a pair of craters...

During the travelling sessions the discussion usually slows down. Especially since the Twins are quite low-relief and featureless from a distance, as Fredk showed.

I notice a few color Pancams and Navcams of ripples and Rover tracks, which makes me think that they've noticed something new afoot. I'm waiting til tomorrow's imagery is downlinked, but if anyone else has ideas they want to show, go ahead.

--Bill

Yep, definitely something there...

Click to view attachment

Couple of days away from Quite A View, I reckon...

I'm pretty much convinced there will be almost nothing but only a few eroded remnants to see.
Get there, take a few pancam shots here and there and

Edit: I was typing the post while you did yours, Stu.
"Couple of days away from Quite A View": Are you talking about the craters or the view that should open to the horizon?

The ground truth will be revealed soon, but before that, let this HiRise anaglyph speak (in 2 x original size). The central ridge between the Twins seems to offer a nice opportunity for some rope-dancing for Opportunity.

P.S. I have included an unusual-looking craterlet or whatever it is at the lower right of this frame.

That's cool -- I definitely had not appreciated how high the inter-crater ridge was before I saw that 3D view. Thanks!

Quite a thought! I make the central isthmus to be around 1.5 metres wide, and it looks like reasonably flat bedrock. The rover wheelbase is around 1.2 metres. Of course, there likely won't be any reason to take that kind of risk, but I suspect any rover driver would salivate at the thought of that kind of precision driving!

I notice there's also a high ridge on the west side of the western crater of the pair. I therefore would guess that both ridges are aeolian, each resulting from the crater to its east (and therefore probably not great footing for Oppy). We'll know pretty soon.

John

The two ridges seem to have a different brightness though, with the west ridge more like the ripples, while the ridge between the craters more resembles the pavement material.

I see that another consecutive driving sol has been planned. Since we're around 200m from the craters that makes for three driving days, including thisol 2191, to get there and in normal conditions that would mean this weekend. But given the limited energy of Opportunity during this season I'm not sure if a "recharging sol" or two will be needed or not. Let's see.

BTW, the odometer is right now at 19970m so the 20km mark will almost certainly be crossed thisol.

Assuming that the impacts were simultaneous, I'd suspect that the central ridge is the result of two reinforcing shock fronts and consists of highly fractured and "bulked" bedrock. Seems though, that it would weather/erode more readily than the usual broken ejecta rubble, but we'll see the story in a few sols.

I just did some reminiscing on the approach to the North Rim of Erebus (Sol620-ish). Now, those were DUNES, and it was a skillful task of navigation that got her through that.

Attached is an annotated 5x-vertical exaggerration of one of today's Pancams of the Twin Craters...

--Bill

Hah! Any really talented rover driver wouldn't stop at just driving between the craters!!!
Click to view attachment

There was a few presentations at LPSC 2010 on recent impacts seen by HiRise on Mars. What was wierd to me was that of the new impacts, about 42% are single craters, while 58% are multiple crater.

[Immediately after impact, many are dark from the airburst shockwave pressure-drop "sucking" the dust into the air. (Interestingly enough, the shockwave compressive wave itself is not enough to lift dust - ca. 5 mPa)]

Twin Craters probably looked similar to Figure 3 in the Ivanov abstract right after impact, except probably excavated much deeper and with an intervening pavement ridge thrust up between the two craters. There was likely an impressive parabolic shockwave stained (cleaned) on the surface.:

Ivanov et al. LPSC 41 (2010) Abstract 2020: www.lpi.usra.edu/meetings/lpsc2010/pdf/2020.pdf

I wonder if the raised pavement will reveal details of the frozen shock front? Who made the bigger splat? Which hit first?

Funny, I have a different challenge for the drivers:

Click to view attachment

the girls (well Oppy at least) get even smarter

http://www.jpl.nasa.gov/news/news.cfm?release=2010-094

very cool stuff

Click to view attachment

Twin Craters will provide a good source of data on the actual rock behavior in a multiple impact scenario. Better, in a way, that it is an older impact with much of the rubble weathered and eroded away so we can examine the rock between the craters.

We are finding that many asteroids are complex rubble piles instead of simple large rocks and I wouldn't be suprised if many meteors turned out to be small rubble piles (agglomerations?). Back when, it was thought that many of the meteors seen in Earth's atmosphere were fragile, friable pieces since they disintegrated so easily, so it might be that they are small rubble piles. This might be the reason for the prevalence of multiple impacts on Mars.

We'll know in a few days.

--Bill

Homer Simpson? George Jetson? I could swear it looked like Elvis was there!

No, I meant the view of the craters themselves; I think it will be aesthetically pleasing, even if it's not that dramatic, if that makes sense. (i.e. there won't be lots of rocks and boulders and ejecta scattered about, a la Concepcion, but the combination of two craters, that ridge between them and the dust inside them will, I think, make for some uniquely 'martian' pictures, especially if we get some 'low angle lighting' views.) We'll just have to wait and see - shouldn't be long now!

Getting there...

Click to view attachment

Click to view attachment

Some more pix: http://roadtoendeavour.wordpress.com/2010/...ching-the-twins

New navigational PanCams this morning. Here is a pan of two R1, exagerrated 3x and contrast-tweaked. Some detail starting to be seen in the West Twin-- fore and aft rim, the East Twin is still behind the Center Ridge and low in the ripples. We need to get some L257 and R721 on the approach, maybe they'll be downlinked this evening (or later this week).

--Bill

Here's the view looking back at the tracks.
Click to view attachment

...I thought that she was getting a bit frisky driving over the ripples. You can almost imagine her being a little WALL_E-like and jumping the crests...

Click to view attachment
http://qt.exploratorium.edu/mars/opportuni...MIP1994L0M1.JPG

--Bill

--Inline image changed by link. Mod.

Oh my, I'm sorry-- I did the "URL" tag first but the image didn't show, so I edited it to the "IMG" tag. Age-related "CRS"...