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Mars was once wet, 
but what happened to its water? 

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NASA’s Hubble and MAVEN missions 
are helping solve the mystery.

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Scientists combine the missions’ data 
to measure how atoms escape into space. 

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This helps estimate past escape rates and
understand the planet's water loss over time.

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Sunlight breaks Martian water molecules
into hydrogen and oxygen. 

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The team measured hydrogen and
deuterium, a heavier form of hydrogen. 

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Due to its higher mass, deuterium escapes 
into space more slowly than regular hydrogen.

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As Mars loses water,
the deuterium-to-hydrogen ratio rises. 

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The ratio reveals past water levels…

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…and helps scientists understand what regulates 
the escape of these atoms into space today.

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Mars has a more dynamic annual cycle 
than astronomers previously thought. 

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The atmosphere expands (heats) 
and contracts (cools) rapidly…

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…as the Sun's brightness
annually varies by 40%.

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Hydrogen and deuterium escape 
faster when Mars is near the Sun.

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Studying Mars' water history is key to
understanding our solar system… 

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…as well as Earth-sized planets around other stars. 

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Mars, Earth, and Venus share the same 
habitable zone but have vastly different conditions…

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…making Mars a valuable proxy
for exploring distant worlds.

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