Mercury's Atmosphere
Written by Fraser Cain
A High-resolution Look over Mercury's Northern Horizon. Credit: MESSENGER team
When you look at an image of Mercury, it looks like a dry, airless world. But you might be surprised to know that Mercury does have an atmosphere. Not the kind of atmosphere that we have here on Earth, or even the thin atmosphere that surrounds Mars. But Mercury's atmosphere is currently being studied by scientists, and the newly arrived MESSENGER spacecraft.
Mercury's original atmosphere dissipated shortly after the planet formed 4.6 billion years ago with the rest of the Solar System. This was because of Mercury's lower gravity, and because it's so close to the Sun and receives the constant buffeting from its solar wind. Its current atmosphere is almost negligible.
But Mercury does have a tenuous atmosphere made up of hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor. Astronomers think this current atmosphere is constantly being replenished by a variety of sources: particles of the Sun's solar wind, volcanic outgassing, radioactive decay of elements on Mercury's surface and the dust and debris kicked up by micrometeorites constantly buffeting its surface. Without these sources of replenishment, Mercury's atmosphere would be carried away by the the solar wind relatively quickly.
In 2008, NASA's MESSENGER spacecraft discovered water vapor in Mercury's atmosphere. It's thought that this water is created when hydrogen and oxygen atoms meet in the atmosphere.
We have written many articles about Mercury's atmosphere for Universe Today. Here's an article about how magnetic tornadoes might regenerate Mercury's atmosphere, and here's an article about the climate of Mercury.
If you'd like more information on Mercury, check out NASA's World Book on Mercury, with an entry on the planet's atmosphere. You can also learn more at NASA's Solar System Exploration Guide.
We have also recorded an entire episode of Astronomy Cast all about atmospheres. Listen here, Episode 151: Atmospheres.
Filed under: Astronomy
Tags: Mercury, planet mercury, Solar System
