October 13, 2004
Your birthday marks the moment a small planet circling a modest star gained another witness to its wonders.
Contrail Clutter over Georgia
Birthday · October 13, 2004
A little universe, just for you
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APOD published October 13, 2004. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Artificial clouds made by humans may become so common they change the Earth's climate. The long thin cloud streaks that dominate the above satellite photograph of Georgia are contrails, cirrus clouds created by airplanes. The exhaust of an airplane engine can create a contrail by saturating the surrounding air with extra moisture. The wings of a plane can similarly create contrails by dropping the temperature and causing small ice-crystals to form. Contrails have become more than an oddity - they may be significantly increasing the cloudiness of Earth, reflecting sunlight back into space by day, and heat radiation back to Earth even at night. The effect on climate is a topic of much research. You can help NASA measure the actual abundance of contrails by participating in a contrail counting exercise that runs over the next two days.