posted on Jun, 8 2009 @ 11:04 AM
reply to post by contemplator
They are simply spots on the camera lenses.
Those are two consecutive shots -- they are two shots taken at the exact same time by the two
cameras that make up the rover's "Navcam".
There are two cameras in order to get stereoscopic (i.e., "3D") images. The two cameras act as a "Left Eye" and a "Right Eye".
Those spots have been on Spirit's Navcam lenses since it landed on Mars.
Here is an image (showing both the left and right cameras) taken the day before the image in the OP. This is from Sol 1907; the OP was from 1908:
And here is and image from sol 680 (a few years ago) taken showing simultaneous left and right images from the Navcam
You could actually go all the way back to Sol 1 and see that the spot on the left "eye" was there then, too.