Exoplanet.. The sky over Argentina looked like it was melting upward. After a violent storm passed, rare mammatus clouds hung beneath the anvil like rows of heavy, frozen pouches. They form when pockets of ice and moisture sink through drier air, dragging the cloud base into those distinctive, bulbous sags. The result is one of nature’s strangest ceilings: a storm’s leftover architecture, briefly sculpted in ice and hanging over the plains before it dissolves. By Top-Marionberry-