Eye of wpsa


How come some of the images released look like sand pictures?

The 'official' image doing the rounds of TV news programs is currently this:

News image 6th April

...(as of 6th April, CNN and BBC). Now this to me looks nothing like the level of 'height' detail that's available from another officially released NASA image:

NASA image

...but it's fairly easy to produce an image like the current 'News' version, simply by inverting the better positive image above to produce a pair like this:

NASA image pos NASA image neg

...and then adding them as 2 separate channels in PhotoShop, and selecting 'Overlay' as the method by which to calculate the result:

Average image

This is a perfectly valid image analysis technique - it just depends what you're looking for. The result, however, subdues the impression of height in favour of bringing out certain fine details.

Here's the official 'News' image alongside my constructed 'average' of the contrast stretched pos. and neg. images...

News image 6th April Average image

... a world away from what can be seen from either the original pos. image, or its negative version:

NASA image pos

One final question - how could the 'sand picture' version, if a true representation of the surface topology, produce the length of shadow on the original Viking images? It just isn't high enough for the Sun angle to work.

This is what you get if you rotate the good positive image in 3D:

3D rotation of positive image

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