Good morning, Rallypoint, and welcome to the June 8th edition of Astronomy Picture of the Day (APOD): "Ship Tracks over the Pacific Ocean." No, those aren't aircraft contrails in this NASA satellite image. They are ship tracks. A ship track is an aerosol (a suspension of particles/liquid in air or another gas) that forms as water vapor condenses around exhaust from the engines of ships. This 2009 image was taken in the northeast Pacific Ocean south of Alaska.