Looks to me like a cloud.. Looks to me like a cloud of evaporating rocket fuels expanding, probably from the station or pod's orientation thrusters or docking mechanisms

Or maybe some kind of upper atmosphere cloud, but perspective is skewed on such pictures, hard to tell if it's a little 1 inch long puff in front of the window or a comet larger than the sun type of long distance view. (Remember that comet? it was all blue hued wasnt it?)