A newfound reservoir of dry ice on Mars suggests that the planet’s surface has been wetter in the relatively recent past, though not necessarily warmer than it is today.
The new study adds to evidence that Mars once had a carbon dioxide atmosphere thick enough to keep liquid water on the surface from evaporating. It’s unclear whether the planet would have been hospitable for life, however, because temperatures on Mars may actually have been slightly colder during times when the atmosphere had a greater amount of carbon dioxide.
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