Mars' wet past has researchers baffled

Mars was, in its ancient days, a wet place, at least at times. It is believed that lakes existed on the planet, and that water flowed in various places. How that was possible, though, has researchers baffled, at least according to NASA. As it turns out, ancient Mars wasn't as hot as it is today, and according to current estimations, it seems ancient Mars would have been too cold for the water to be in a liquid state. Even the possibility of warmth from greenhouse gases is problematic.

During the part of Mars' history when water was present, the sun was estimated to be about a third less warm, and thusly the environment was colder. It is thought that carbon dioxide in the Martian atmosphere may have caused a sort of global warming effect, causing the temperatures to rise, but it is estimated the amount of gases in the atmosphere weren't high enough to provide sufficient heat.

One created model has successfully demonstrated a way Mars could have been warm enough to have liquid water, but it involves molecular hydrogen in the atmosphere as well as carbon dioxide. That itself is controversial, though, according to NASA, which says there's no clear way that such hydrogen could have been created and then sustained at the time.

Yet another possibility is put forward, with researchers speculating that maybe the planet's ancient lakes were covered with a layer of ice, with liquid water existing beneath that ice. There is no observable evidence that this was the case, however, and so researchers are left searching for the missing clues that could shed light on what actually happened.