Interesting. Thanks Phil.

Am I right in thinking that the crater just north of the D in Scandia is the big one on the map Emily posted above?

btw, does that crater have a name?

James

Yes to the first, and Heimdall Crater to the second (see the labeled version of PIA09946)

From the MarsPhoenix twitter feed:
"The team is considering a maneuver to nudge my flight path toward a landing spot on Mars 18 kilometers to the NW of where I'm headed now."

I'm wondering if this maneuver is rock-hazard related, or maybe they're just aiming for a more central position in the valley. Topography and Terrain of Phoenix Target Area shows that, as of now, even the 1-sigma ellipse crosses over from the "Lowland Bright" unit onto the ejecta from Heimdall.

First this:

And then this:

So there is a net shift 5 kilometers to the NW from the original position? I guess
they had second thoughts about the "increased safety" of the initial move.

Unless it means "I'm 18 km off course... they are going to push me back towards the place I need to be". The statement is ambiguous.

Phil

That makes sense, Phil. I don't think they'd be changing the intended landing zone this late into the approach.

The NASA Phoenix Site has a few sentences more information:



I think this confirms that the landing trajectory is nudged back towards the intended x marks the spot.

Tim Parker is a god.
http://www.planetary.org/blog/article/00001431/

--Emily

Brilliant stuff - I was hoping something like the MSSS 25 and 10m/pixel MER ellipse imagery would make it out in time..

Combined with this : http://hirise.lpl.arizona.edu/HiBlog/?p=180 : we should be able to identify which image to look in when the time comes!

Doug

Do you know if a chart showing actual landing places as compared to the center of the targeted elipses exits for all US landing?

MPF, MERA and MERB are the only succesfull direct entry landings - attached, ellipses with X marks the spot on each. They're not to scale. The lesson is - they've all been VERY close to the centre line - but changes up and down range are quite significant.

...And then MERB just rolled out of its landing ellipse, far away from the center line. Amazing really

I already pointed this out to Emily - the two maps she links to above have grids with different labels - compare the longitude labels with the locations of individual hills or craters. You will see that one has to be wrong, probably the colored map. Because the ellipses were plotted relative to grid labels they appear offset among the topographic features, but in fact they shouldn't be.


Phil

Hi Phil:

I made the MPF map that's shown. Back in the old days with Canvas 5.0, I believe. One version of that map had a glaring error - I think the 20 degree lat line was labeled at the 19.5 degree line.

Also, that map was made pre landing, with the nav update ellipses and the X added within a day or two of landing - before we realized that the control net was off by about 6 kilometers (0.1 degrees or more).

Sadly, the multi-layer version of that file was on a hard drive that crashed a few years ago. I thought I had a backup copy, but I've never found it.

-Tim.

I'll fix the colored map tomorrow (will move the longitude labels to match). I wonder why it's off by that half-degree. Can't believe I didn't notice the offset in the surface features.

--Emily

Now all we need is a few new placenames...

That prominent hill to the south of the ellipse center looks like the most likely feature - IF any - to show over the horizon.

Phil

An anaglyph from the newest landing ellipse centerline, about 9 kilometers down (ESE) from the centerpoint. The new center line cuts the frame in half, from upper left to lower right (not shown). The image is half of the normal HiRISE resolution and its width is approximately 550 m. I don't think there's significant exaggeration compared to a realistic elevation model, very little at best.

Images used:
PSP_002249_2485 (left eye)
PSP_002328_2485 (right eye)

No mountains visible, but the surface is far from featureless!
Enjoy.

This is the best I can do with one of Randy's DEM's. To be honest, I could save myself a lot of render time and not use the full resolution of the DEM itself, and just pre-displace a 100 x 100 poly plane.

Doug

who cares about the surface anyway? I'm very curious to see if the subsurface will be more interesting than the surface. I would think it is

I like that!

Can I ask - on the USGS geological map, what's the meaning of that funny meandering line of dashes that cuts more or less through the centre of the landing ellipse?

I agree...

If I think that ACC Memorial Station would be a fitting name for Phoenix's landing site, as we're going to the North Pole I would, somehow, like to see a reference to:

EDITED: forget what was written here before...

-Peary, Henson and the Inuits (does anybody know Inuit words?)

Edited again: Got one!:

Tunnga-sugitsi

It stands for "you are welcome here"
A nice way of making Phoenix feel at home...

Rui,

"Tunnga-sugitsi"

Sounds a bit too much like "Tunguska" for my liking and we all know what happened there........

http://en.wikipedia.org/wiki/Tunguska_event


Brian

Didn't think of that...

Here's a list of words we can play with...

I like particularly "aimerpok" which stands for "visiting and expecting food"

You'd think I'd get paid better if that were the case! Well, I do get to do fun stuff, I suppose...


I didn't complete my update of the map until late evening last night, and the frustrating thing about going from a graphics program like Canvas to some raster image format for the plotter is that I had to reduce the resolution of the HiRISE images tremendously to keep the file size down (and get home before too late!). I built the Canvas map with 4 meter/pixel versions of the HiRISE images, but by the time I rastered the file, the result was more like 8 meters/pixel. That's still probably sufficient for triangulation to horizon features. And once we know which HiRISE image(s) the lander resides in, matching to local rocks and bumps (hah!) at full resolution will be possible (and immediately "obsolete" the map!).

-Tim.

Phil:

I'm optimistic for two reasons:

Number A: Some of the massifs to either side of the trajectory are over 100 meters tall. If Phoenix lands within 20 or 30 kilometers of these, I think they should be visible (remember that Far Knob in MPF was over 35 kilometers away, though it was something like 450 meters tall, IIRC).

Letter 2: Phoenix's camera has on order 4 times the resolution of the IMP, making Number A easier.

But we'll see!

-Tim.

I had long suspected that you were Tim Parker, it's nice to finally have evidence in that direction.

Number A and Letter 2... an Archie Bunker fan perhaps?

"A, he's unemployed, and 2, he don't woik!"

Phil

As long as we don't have Meathead Mountain on the distant horizon...

He's a Junior Member by post count, but Doug made a Senior Member group just for him and of which he is the only member.

Crop from latest HiRISE landing ellipse image... looks like frost was lingering as recently as May 2nd...

Click to view attachment

.. and here, too...

Click to view attachment

Reckless predictions corner:
1 .the montony of a mostly flat horizon will be balanced by a lot of small-scale relief, of the order of a metre or two, that will be clearly visible all around the lander.
2. the lander will come to rest with a significant tilt (more than ten degrees.)

Now I can relax until Monday morning, knowing that th e universe will have to allow a successful EDL, in order to prove me wrong

It would be cool indeed if Phoenix lands in a patch of surface frost.

Cooler still if the trench uncovers multiple layers of ice...

Well, I've been wandering around the latest HiRISE Phoenix landing site image, and I've found some very interesting (well, I think they are anyway!) features that suggest it's at least possible we might see some decent surface relief... A couple of these images have me really puzzled, to be honest, because the lighting conditions are very confusing. So I'm not sure if they're real features, casting shadows, or some strange kind of lens flare effect. Anyway, take a look experts, and see what you make of these...

Click to view attachment

What's that then?

Click to view attachment

... and that? A quite high ridge with frost on the top?

But this is making me scratch my head in a not-too-good way...

Click to view attachment

That looks like either a steep-sided trench, or a very narrow, steep ridge, depending on how I look at it. What do you think? Either way, landing on that would give Phoenix's pix a tilting horizon, wouldn't it..?

Feel free to ignore, I'm just killing time before making tea...

some of those spots seem over-exposed, hence the confusing lighting conditions perhaps? little ice mounts? cool in any case if visible from phoenix!

Yeah, I thought "over-exposed" too when I saw them, but that raises the question of WHAT is being over-exposed... what is so much brighter there that it made HiRISE squint? The more I look at it the more I think the feature in that 3rd image is the side of a trench rather than a ridge... what happened there? A collapse of some kind?

I've also noticed LOTS of small dark spots dotted over the image, like little drops of ink. They're puzzling, too...

Edit: just been looking at #3 again... now I'm seeing a ridge... I give up! Anyone got any ideas?

To me, in this image it looks like the polygonal terrain is organized at three different levels.

• The regular polygons.
• A meso-polygon cluster of 5-7 polygons with a slightly larger border.
• A meta-polygon cluster of a huge set of meso-clusters with really impressive borders.

The really big "cracks" in the image above would be the borders between the meta-polygon clusters. But they shouldn't be cracks, they are little cute rock walls (a garden gnome would look right at home here).

The borders should be little walls of rock that has been shoved to the edges of the frozen soil due to mutliple freeze-thaw cycles. They should have uniform relief and thickness along the border that might be dependent on the pattern scale.

Regular polygon border should be X high and wide,
Meso-cluster borders should be higher and much wider
Meta-cluster borders should be even higher and even much more wider.


It would be just so beyond cool if all three types of pattern borders were visible from the Phoenix landing site.

-Mike

Here is a freely available reference:

Mangold et al. JGR 109 (2004) E08001. Spatial relationships between patterned ground and ground ice detected by the Neutron Spectrometer on Mars. doi: 10.1029/2004JE002235.

(Figure 1a shows the sorted stone polygons)

-Mike

Picture one : Backshell and parachute
Picture two : heatshield
Picture three : Phoenix landing site
Where have you been since Phoenix landing?

Bingo! Found an even better freely available reference for polygonal terrain near the Mars Phoenix site (apologies if it's been linked before):

Haltigin et al LPS 39 (2008) Abstract 2475. "Comparative Morphometric Analysis of Polygonal Terrain at Potential Mars Phoenix Landing Sites."

The cracks are troughs bound by two shoulder-like ridges. As the terrain "sets up" the troughs widen and the ridges get bigger.



And another freely-available abstract describes Devon Island as an Earth analog for the Phoenix site, (with a caution that some of the polygonal terrain studied on Devon Island could be quite blocky with relief up to 1.5 m)

Desportes et al LPS 38 (2007) Abstract 2341. "Periglacial Polygon Fields on Devon Island, High Arctic, as Possible Analogs for High-Latitude Polygonal Terrain on Mars: Implications for Phoenix."

[OK, now I'm getting a little more worried...]

-Mike

I hadn't seen that specific paper before, but had found some other papers talking about horizontal and vertical relief on Devon Island - it must be a poster-child for polygonal frost heave. So, as someone else said, even if EDL goes perfectly, disaster could strike at the very last moment. Ah well, it'll keep things interesting on Sunday. Reminds me of a nice bit in a recent post on the Phoenix blog:

(emphasis mine). Understatement or what? The intestinal fortitude required to watch 5-10 years' worth on one's career possibly going "foom!" is more than I can imagine...

** Phoenix lands in: 2 days, 12:37:02 **

Okay, these features are definitely trenches or ditches of some kind...

Click to view attachment

Really don't want a leg coming down in something like that now, do we..?

... and a second candidate for the "Places Best Avoided" list...

Click to view attachment

Definitely, Stu!

However, I sure wouldn't mind if we came down within a few meters of one of these. Shooting from the hip, here, those look one hell of a lot like fresh fractures that have permitted sublimation & recrystallization of H2O...perhaps evidence of VERY extensive subsurface ice?

Quit showing those interesting features! You'll get the "Phoenix should have wheels" people started up all over again!

As far as "Phoenix has wings" occurs, I don't mind too much !

This is one of my favourite crops so far, and I think it shows that Doug's winning entry in Rui's art competition is probably very prescient... A few rocks, here and there, some vertical relief, here and there... maybe some low ridges, shallow trenches...

Click to view attachment

Can't help thinking the HiRISE team is cheating and actually photographing rhino hide with a close-up lens...

I can't avoid to think, looking at that image, that this is a tricky ground...tricky tricky...