Well, the artifacts we've seen so far from those cameras have conformed to either the rectangular geometry--black monolith rectangles, silicon chip wafers, etc.--or they've been the white bird-dropping streaks caused by overloading CCD sensor cells to the point where the charge spills down several rows when the sensor's read out.

We've seen streaks at non-perpendicular angles in long-exposure images that were almost certainly caused by cosmic rays. It might be something like that, in this case a particularly energetic particle since the exposure time was normally fast. That's the most likely explanation in the glitch/electronic anomaly category.

Tom came up with an explanation in the real-object category, which makes two with a perfectly ordinary cause. Another: Maybe a nearby meteor impact and it's a bit of ejecta. Another far-fetched possibility, admittedly. None of the conjecturs have a really high probability. That's what makes it an amusing little game, eh?