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Mars's atmosphere is much less dense than the Earth's, it only has about one percent of the density of the Earth's atmosphere.

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However, we're pretty sure that Mars had a much thicker atmosphere in the past,

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because there's such strong evidence for running water on the surface, and to have running water, Mars's atmosphere had to be much thicker.

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Now MAVEN is going to look at how Mars lost its atmosphere, in particular whether it could have lost its atmosphere to space.

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My name is Bob Lin, I'm a professor of physics and I work at the Space Sciences Laboratory of the University of California at Berkeley.

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MAVEN is a Mars Scout mission for NASA, and it's an orbital mission to Mars

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which is designed to study the loss of the atmosphere of Mars.

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For example if there was a large solar eruption, if the solar wind increased in strength,

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we could then look at how the atmosphere gets lost in each of these situations.

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Because Mars is in the solar wind, a lot of the loss comes from these ions and electrons that are escaping,

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and the Particles and Fields package is designed to look at the escape of the charged particles from the atmosphere.

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We have the Solar Wind Ion Analyzer, which measures the incoming solar wind,

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then we have the Solar Wind Electron Analyzer, which measures the incoming solar wind electrons.

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We have the Langmuir Probe and Waves instrument, and that measures solar ultraviolet.

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It also measures low-energy electrons that might be escaping from Mars,

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and furthermore it measures waves that might be accelerating the ions so that they can escape from Mars.

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We then have the STATIC instrument. It will give us the composition of what is escaping, whether it's CO2, or hydrogen, or helium and so forth.

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The Solar Energetic Particle instrument, SEP, measures high-energy particles from the Sun,

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and those particles will hit the atmosphere and cause a lot of damage.

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And finally there's a magnetometer, which will measure the magnetic field in the solar wind and the magnetic field of Mars.

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Mars is the only planet, besides the Earth, where you really have a chance that life might have formed.

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The conditions for life are water, running water, and a reasonably thick atmosphere.

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We have a chance now to see whether that was in fact what Mars had early on,

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and whether the atmosphere was lost by this means, so we think it's an extremely important mission to do.

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[ George Diller ] Five, four, three, two, one.

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Main engine start, ignition, and liftoff of the Atlas V with MAVEN,

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looking for clues about the evolution of Mars through its atmosphere.

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