Ok, so this is most likely an image artifact, or if not, a chance capture of a small meteor, right?

Just out of curiosity, I saved the jpg and produced a negative image, using a common graphics application.
When I zoomed in on the “streak”, it gave me a little start, because there is another object (image artifact, meteor, thing) which appears to line up quite nicely with the apparent trajectory of the streak. It appears as a round object about as wide as the streak at it’s broadest point.
Using the negative image, project a line along the “path” of the streak from upper left to lower right. The second object (image artifact, meteor, thing) is about 15 or 16 “streak lengths” along that line.

Would be pretty cool if Spirit just happened to photo a Mars meteor as it passed and began to break up.
OTOH, guess it’s more likely to be image related noise.