We've discussed this guy before, but now he has a new argument.

Enjoy!

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Everything I need to know I learned through Googling.

Chasing pixels again... :roll:

Hmm, I was following this over at GLP and I must admit the guy does seem to have a point, at least on the face of it.

I copied the pictures off the NASA site he linked to, loaded them into a photoshop document as two layers, and they are taken from exactly the same place but in one the sky is replaced by rock. Does anyone know what's going on? :-?

Hmm.... he goes from claiming to not be pushing a conspiracy theory in his first paragraph to stating that NASA is covering up evidence of an active geyser on the surfice by editing pictures on their website, and that the person responsible is putting secret messages in the edited portion of the picture for whatever reason (guilt and/or vanity). (Hmm... my crazy-o-meter is getting a reading...)

Once again, the conspiracy folks fail at a key realization. If there was something in the pictures that NASA didn't want us to see, the easiest and most foolproof approach would be to simply not post them in the first place, rather than paying some guy to do a crappy PS job after the fact.

If only our conspiracy theorist had put as much effort into actually emailing NASA to ask what's what as he did into detailed photo analysis of zoomed JPEGs, I think we'd have an answer already.

The sky isn't replaced by rocks, the rocks have been replaced by electron overflow on the CCD.

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I think um3k is dead on, this is overflow (those pixels aren't sky, they are just maxed out at 255 brightness) from overexposure.

Notice that all the images the webpage references, in their raw form, are ESF files (143097697"ESF"3221P2595L7M1). That means they are subframes of a full 1024x1024 image. They've been using this mode more often now that the power situitation is getting worse, since this will require less time and bandwidth to uplink (and very often, the subframe contains only the parts they are interested in anyway) Here's what I'm thinking is going on.

The rovers are commanded to take a subframe image of a feature on the rock wall, and the subframe is at the bottom of the real 1024x1024 image. They point the camera at the wall so the center of the subframe lines up with their target. The sky now resides inside the bins that will not 'be counted' for the subframe.
The autoexposure algorithms onboard MER work like this :
they wait for a certain % of the image subframe to reach brightness X. Unfortunetly, in the time it takes for those CCD bins in the subframe to reach their requested brightness, the brightness of the bins outside the subframe that contain sky become saturated, and beyond. As the image keeps exposing, long after the sky portions of the fullframe have saturated, those saturated pixels begin to bleed down into the bins below them. The amount of bleed will correspond to the length of the exposure, which fits perfectly with what we're seeing on his webpage. The rocks within Endurance crater are brightest in L2 and least bright in L7, which means to get to the requested brightness, L2 images need to expose for much shorter times than L7's. The L2's show the bleeding effect, but to a very small degree. The L7's show a very large amount of bleed (almost 1/8 of the image), as they have been exposed much, much longer. The amount of bleed increases between L2 and L7 accordingly.

In this respect, I'm surprised that the rover planners continue to do this though. I think (and could be fully and totally wrong about this) they can subframe an image any way they like, and it would make much more sense to have your subframe be the top of the ccd (so you don't have sky in the rest of the frame). This would prevent the effect from happening, as you would have less bright features in the rest of the image that isn't in the subframe, thus preventing them from becoming grossly overexposed, and bleeding.

Thank you, slinted! Your description makes perfect sense, and explains the question I was about to ask. I knew it was some sort of data wash out, but was wondering what could be causing it. Bleed over from an area not in the exposure frame but in the camera field of view is an excellent explanation, and matches well with the larger wash out on the longer exposed images.

I actually put a little page together on this subject. I hope that slinted won't mind my quoting his post.

I had a little play as well as using slinted explaination of the CCD bleeding, my objective to show that had NASA been attempting to edit the images as claimed, that with the mulitple shots of the area, they could very easily have created set of "unedited" images, just as I have.

Here's my final colour image. It's made from all three images (L4, L5 and L7.) See if you can tell that it has been altered.

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