HiRISE images of Phobos!, "images available NOW". Options

[elakdawalla]

You're right that Stickney is about equidistant between the leading apex and the sub-Mars apex, but the splat trials to the sub-Mars side. Here's a version of the image, rotated so that north is upright. It's an almost perfectly equatorial view of the sub-Mars hemisphere (just a hair more to the north than equatorial). Remember, everybody, that nearly all Mars missions are in pretty low-altitude, circular orbits, much lower altitude than Phobos orbits, so they can see only as much of Phobos as we can see of our own Moon: the sub-Mars hemisphere. I've been debating starting to call this the "nearside" of Phobos to help bring home that point, but I'm not sure if that will be any less confusing than "sub-Mars hemisphere." Of the orbiters at Mars since Viking, only Mars Express has an elliptical orbit that allows it to see other parts of Phobos.

I actually like this version better, think I'll make it this way on the Society web pages...

--Emily

[edstrick]

"I actually like this version better, think I'll make it this way on the Society web pages"

In that orientation, it matches our "expected illumination" orientation. Our brains are somewhat wired, at least by lifetime experience if not evolution, to expect illumination from "above". That's why faces lit from below are creepy-horrorshow feeling, in part.

A trick for viewing images where topography looks inverted and craters are bumps and valleys are ridges is to 1.) orient the image so the real illlumination comes from "above" in the viewer's orientation. Even physically matching real illumination (from a desk light or something) to the on-page (or on screen) illumination can sometimes help force the brain to counter-invert the image back to it's proper craters-are-craters perception.

[ElkGroveDan]

A trick for viewing images where topography looks inverted and craters are bumps and valleys are ridges is to ....

If you have a desk lamp move it so that your ambient lighting is coming from the same direction as the light source in the image. Opening or closing curtains, or turning on or off ceiling lights often helps.

[marswiggle]

This might help to counter any inverted topography. After some trial and error, I managed to produce, imo, an almost professional-looking crossed-eye stereo image of Phobos (reduced image quality though). I didn't get working anaglyphs perhaps due to light colour.

I first resized the nearer and bigger of the original HiRISE images, which is the left-eye (ie. right side) image, to 87 %, rotated the l/r images 108 and 112 degrees respectively, the resulting stereo pair shrunk to approximately 31 %. Extra white spaces filled with black.

It's rather an exaggerated stereo effect... beware eye strain!

Attached thumbnail(s)

 

[ngunn]

I managed to produce, imo, almost professional-looking crossed-eye stereo image of Phobos

Brilliant! I should have joined the original round of applause for the HIRISE team but didn't - what images!! - but seeing this I could no longer remain silent.

Now what's really wanted there is simultaneous 'zoomify' on the two images so you could roam the surface with moving crops of small areas. Then you could get the images the right distance apart for a non-exaggerated effect. I'm sure this could be illustrated with ordinary non-movable crops of, say, the near rim of Stickney. Maybe worth trying as you've already done all the work registering the images.

[tedstryk]

Wouldn't "Mars-facing hemisphere" be clear enough?

[ElkGroveDan]

Maybe Pink Floyd should record an album called The Dark Side of Phobos

[4th rock from th...]

Here's a "real color" attempt at the Phobos image, using only the Red and Green-Blue channels and gamma adjustment.

[tedstryk]

That is nice, although the color variations still seem a bit strong.

[Bill Harris]

I've been debating starting to call this the "nearside" of Phobos to help bring home that point, but I'm not sure if that will be any less confusing than "sub-Mars hemisphere."

"Nearside" works. It is a very familiar concept with our own Moon, and is an economy of words. May not be as good with other tidally-locked moons, but for the Martian satellites and HiRISE it's about the only view we'll have.

--Bill

[jasedm]

Fantastic images - well worth waiting for!!
From my 'wild theory' bag:
This view of phobos and the colouration makes it look ablated, with material having streamed back from the stickney area.
Could it be possible that Phobos dipped into a historically denser Mars atmosphere during capture of the moon (the general consensus I think is that the moons are asteroidal in origin)?
Has aerocapture been suggested as a possibility for the position of the little moon?

Edit: Have just read Emily's blog which has a section relating to Phobos' grooves - very informative, and a lot more convincing........

[marsbug]

These images are great, and they've made me look at phobos as being more of a place in its own right, rather than 'one of the rocks orbiting mars'.

[ngunn]

This view of phobos and the colouration makes it look ablated, with material having streamed back from the stickney area.
Could it be possible that Phobos dipped into a historically denser Mars atmosphere during capture of the moon (the general consensus I think is that the moons are asteroidal in origin)?
Has aerocapture been suggested as a possibility for the position of the little moon?

Emily's blog which has a section relating to Phobos' grooves - very informative

I can't shake off the visual imression that Phobos is a flying lump of wind-eroded sandstone with almost parallel 'beds' running right through it - even though I know that's nonsense!

[ilbasso]

My first impression of the false-color close-up with Stickney on the image's right side, was the Planet Killer from Star Trek "The Doomsday Machine".

"It's got a maw that could swallow a dozen starships!"

[Phil Stooke]

I have never been satisfied with the various explanations for grooves - they obviously don't radiate from Stickney, but Peter Thomas showed that years ago from 3D mapping in Viking images (Mars Express data not required for that interpretation). I think the Mars ejecta hypothesis is too contrived, though I might accept it for a small subset of crater-chain structures superimposed on the regular groove pattern.

I have argued elsewhere that the regular groove pattern is the surface expression of jointing in the interior, possibly produced by relaxation of compressive stresses when Phobos was impact-excavated out of a larger parent body. By this hypothesis, Deimos was from a shallower, less compressed part of its parent, if they are genetically related.

Nevertheless, the new pics are fab.

Phil