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

.. and here, too...

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...



What's that then?



... 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...



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...



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...