Close-ups of the contrail gap area

I made these two short videos during UA935 flight LHR-LAX on December 6 2011. They are taken from a seat 39A window at the rear of Boeing 777, the first video when approaching Greenland and the second one after crossing the Canada-US border in Minnesota. 

In the first video, condensation of water vapour from the engine exhaust is clearly visible probably due to colder air outside. Also, it is illuminated by the sun and stands out agains the cloud background:  
 

In the second video, condensation is less apparent but is still visible: