[Moonman62]

Mars owes its dry and dusty appearance to its wispy atmosphere, less than 1 percent of the thickness of the Earth's. But it wasn't always that way: The Red Planet formerly had a much thicker atmosphere that probably allowed for liquid water on the surface, an atmosphere that was depleted when the planet's magnetic field faded away.

[chuckles]

So Popular Mechanics is the new paradigm of all knowledge?

These are just theories. Nothing wrong with theories, but there are just as many that say other things.