Here is a link to the official picture:
http://www.nasa.gov/sites/default/files/styles/full_width_feature/public/images/296636main_1241_full_full.jpg
Here is the Picture:

When they first released this picture, they had no idea about the digital photo manipulating software that would be available to the public in the 2000s.
ANYONE CAN DO THIS:

Open the picture in Photoshop or Gimp (free) and adjust the Levels.
You can clearly see a box around the "Earth" because it was cut and pasted in.
Here is a picture of an eclipsed Moon and some planets:
http://astrobulletin.amnh.org/var/ezflow_site/storage/images/media/amnh/images/our-research/hayden-planetarium2/blog-images/moon-venus-and-jupiter-in-conjunction/1892911-1-eng-US/moon-venus-and-jupiter-in-conjunction.jpg

I chose this picture for comparison because the moon is not as bright.
This is what it looks like when not edited with a pasted in moon/earth:

Discuss.
There we go, fixed it.
Now I will respond.
Those artifacts you see are from the jpg image compression. I have another image of a bunch of televisions from Wikimedia Commons that is also a jpg:

I use paint.net, so I downloaded gimp to try and 'replicate' these results like you did.
Results with the TV Wall:

I
did lower the quality of the jpg (meaning it's more compressed) before hand, but that was only to 'replicate' what iWitness was seeing.
Then I went with a much higher quality version of what iWitness used as the first image, which can be found
here. Results:

Nothing from what iWitness saw previously. That's proof it's jpg artifacts, not NASA themselves. The image he used was surely meant for viewing on a webpage, and was more compressed to allow for faster loading to accomodate for people with slower internet.