Rosetta - Post Separation Ops at Comet 67P C-G, November 14, 2014 - Options

[Gladstoner]

I would guess the pit is a low profile feature that produces shadows only when sunlight is at a very low angle. Otherwise, the lack of albedo differences in the smooth material renders it invisible otherwise.

Of course, the very recent formation of a collapse pit would be pretty cool....

[Phil Stooke]

I don't think the lighting is sufficiently different for the pit to not show up in the earlier image. What you describe is always a possibility in this type of comparison, but I don't think it applies here.

Phil

[nprev]

If it's all real, and it sure looks like it is, this will set some significant constraints on the life expectancy of comets in the inner Solar System. Could be a huge mission finding.

Well spotted, Phil!!!

[Phil Stooke]

I spotted the second example, but it was the Rosetta blog:

http://blogs.esa.int/rosetta/2014/12/11/co...tch-9-december/

which drew attention to the first one. I just illustrated that first one.

Phil

[Gladstoner]

If the pits did form very recently, then the smoothing process must have been recent as well.

[jmknapp]

Might the marks be the result of some fragment landing back on the comet after being wafted up by some outgassing activity elsewhere?

[Gerald]

Non-linear brightness stretched (about quadratic) and 8-fold saturation enhanced version of the official OSIRIS color image:


Brightness-stretching gets the grey value nearer to 50%, nonlinearity avoids more-than-necessary numerical instability near full saturation.

My first out-of-the-hip impression has been, that some of the color could be structural.

[eliBonora]

We have tried to pull out more color from the OSIRIS image, not because it 's what the human eye could see but because it's interesting to highlight the differences. Of course we can exasperate more and more but we have preferred to maintain a balance with a pleasant look.



Here's also a curious gif created with the three RGB channels splitted:
https://www.flickr.com/photos/lunexit/15820377179/sizes/o/

[Phil Stooke]

"Might the marks be the result of some fragment landing back on the comet after being wafted up by some outgassing activity elsewhere? "

That's exactly what I would expect for these specific changes.

Phil

[jmknapp]

Request to the comet gods: puff Philae out of its hole so it lands elsewhere, in the sun and upright of course.

[wildespace]

Great to finally see the comet in colour! The original OSIRIS composite has greenish cast (common to raw images, it seems, judging by the Mastcam and MAHLI raw images), so I've used "Auto color" in Photoshop to normalise the colours, and then decreased levels to reflect its dark albedo. This also brought out some colours, without the need for enhancing saturation manually:



The neck region seems definitely lighter and somewhat bluer, perhaps it's the un-darkened material being exposed by the comet's activity?

There is interesting golden-red colouration at the bottom of the larger lobe.

[Explorer1]

Request to the comet gods: puff Philae out of its hole so it lands elsewhere, in the sun and upright of course.

Or just sublimate and crumble the overhang above it while we're in the wishful thinking stage....

[neo56]

NavCam mosaic of 9 December:

[Gerald]

The original OSIRIS composite has greenish cast (common to raw images, it seems, judging by the Mastcam and MAHLI raw images), ...

OSIRIS used different color filters for the same CCD, not a Bayer pattern like MSL Mastcam or MAHLI (although Mastcam can also use color filters). So it's more a matter of how the OSIRIS team calibrated colors.

From this Rosetta blog:

A more detailed first analysis nevertheless reveals that the comet reflects red light slightly more efficiently than other wavelengths. This is a well-known phenomenon observed at many other small bodies in the Solar System and is due to the small size of the surface grains. That does not, however, mean that the comet would look red to the human eye. Natural sunlight peaks in the green part of the spectrum and the response of the human eye is similarly matched. Thus, overall, the comet would look rather grey to the human eye, as seen here.

[surbiton]

The neck region seems definitely lighter and somewhat bluer, perhaps it's the un-darkened material being exposed by the comet's activity?

Could it be the interior "ice" exposed ?