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When you take a look at Mars, you probably wouldn't think that it looks like a very nice place to live: it's dry, it's dusty, and there's practically no atmosphere.

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But some scientists think that Mars may have once looked like a much nicer place to live,

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with a thicker atmosphere, cloudy skies, and possibly even liquid water flowing over the surface.

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So how do you go from something like this...to something like this?

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NASA's MAVEN spacecraft will give us a clearer idea of how Mars lost its atmosphere, and scientists think that several processes have had an impact.

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One of these processes is called Sputtering, where atoms are knocked away from the atmosphere due to impacts from energetic particles.

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In our solar system, the Sun constantly emits high-energy photons.

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When one of these photons enters the atmosphere of a planet, it can crash into a molecule, knocking loose an electron and turning it into an ion. 

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Ions by themselves don't do much, but when a magnetic field is nearby they'll spin around the field.

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Conveniently, the Sun generates a giant magnetic field that is carried by the solar wind.

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As the magnetic field sweeps past the planet, some ions will get carried away.

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Other ions, depending on where they form, won't get carried away but will hit the top of the atmosphere.

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These ions can then crash into other molecules and fling atoms everywhere, like a cue ball in a game of pool.

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Some of these atoms can be knocked, or sputtered, into space, causing atmospheric loss,

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and over billions of years this could have caused quite a bit of change,

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especially since the solar wind may have been more intense early in our solar system's history.

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Scientists think that all of this may have caused Mars to gradually transform

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from what may have been a very nice place to live, into the dry, dusty world we know today,

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and MAVEN will study this process and tell us how it really works.

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[ music, satellite beeping ]