Earth

Does Earth’s atmosphere lose molecules to space?

The answer is yes – Earth’s atmosphere does lose some of its atmosphere to space. But our atmosphere won’t disappear completely in the near future, because most of it is bound to the Earth by the force of gravity – the same force that keeps us anchored to Earth.

Molecules in our atmosphere are constantly moving, spurred on by energizing sunlight, and some move quickly enough to escape the grip of Earth’s gravity. The escape velocity for planet Earth is a little over 11 kilometers per second – about 25 thousand miles an hour. If Earth were much less massive – say, as massive as Mars – gravity’s grip would be weaker. That’s one reason why Mars lost most of its original atmosphere. Here on Earth, not all particles are equally likely to escape. Light ones, like hydrogen and helium, typically move faster than heavier ones, like oxygen and nitrogen. That’s why light molecules are rare in our atmosphere – in contrast to their abundance in the universe at large.

Visit EarthSky Tonight for easy-to-use night sky charts and info. Updated daily.

Posted 
January 25, 2010
 in 
Earth

Like what you read?
Subscribe and receive daily news delivered to your inbox.

Your email address will only be used for EarthSky content. Privacy Policy
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.

More from 

Editors of EarthSky

View All