The unusual channels ASTRONOMERS know that Mars was once wet. There is plenty of evidence for that, from dried-up river valleys to the presence of chemicals that need water to form. Modern Mars, though, is a freezing desert. In the 4.5 billion years since the planet came into existence, a sizeable chunk of its water has boiled away into space, another chunk is thought to have seeped deep into its interior, and what little remains on or near the surface has frozen solid. That is depressing for th...
The unusual channels ASTRONOMERS know that Mars was once wet. There is plenty of evidence for that, from dried-up river valleys to the presence of chemicals that need water to form. Modern Mars, though, is a freezing desert. In the 4.5 billion years since the planet came into existence, a sizeable chunk of its water has boiled away into space, another chunk is thought to have seeped deep into its interior, and what little remains on or near the surface has frozen solid. That is depressing for th...
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