Give Now

A Moment of Science

The Disappearing Atmosphere

As of three point eight billion years ago, Mars had already lost much of its atmosphere.

An image of the Juventae Chasma, a box canyon on Mars. The canyon has different channels in it that some theorize were caused by different water sources. More about this image can be read at

Spacecraft have found evidence that there used to be bodies of liquid water on Mars billions of years ago; ponds, rivers, and maybe even oceans.


Liquid water isn’t stable on Mars. Most would freeze into ice because the average surface temperature is about eighty degrees Fahrenheit below zero.

Temperatures in the equatorial regions sometimes do rise above freezing, but even then, ice would generally turn directly into vapor because Mars’s atmosphere is a hundred times thinner than Earth’s.

Scientists think that Mars’s atmosphere was once thicker. A thicker atmosphere would have trapped more of the sun’s heat, and allowed water to remain liquid on a warmer Mars.

Where Did The Air Go?

NASA launched a spacecraft called MAVEN to orbit Mars and study how its atmosphere interacts with solar radiation. Researchers found that, even today, the Martian atmosphere is gradually being stripped away by a wind of charged particles from the sun.

About sixty-five percent of the gas argon that was ever present in the atmosphere has vanished.

Since argon is chemically inert (a general, basic definition of chemically inert means that it’s an element that rarely has chemical reactions), it can’t have been taken from the atmosphere by chemistry at the Martian surface, and must have been lost to space.

Mars is less massive than Earth, so its gravity is weaker. But that’s not the only reason why its losing its atmosphere.

Magnetic Fields

The main difference is Earth is protected by a strong magnetic field, but Mars’s field is much weaker. As of three point eight billion years ago, Mars had already lost much of its atmosphere.

Since primitive Earth had similar conditions and had, by then, given rise to life, it’s possible that Mars did, too. But if that did happen, the theoretical life on Mars had a much harder surviving because of Mars’ environment.

Sources And Further Reading:

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science