A series of vertical 'vapour trails' can been seen emanating from the base of a crater in this image.
The same vapour trails in close up. Note how they can clearly be seen originating from round fissures on the floor of the cave. The white trail on the right appears to have the double contrail appearance of a jet-engined plane here on earth. A close inspection of this trail-head seems to indicate (double click the image) there is indeed something within the twin trails. So what is the cause of these clear trails on Mars?