Solved cryptogram

The air on Mars is so thin that liquid water at the surface would boil away rather than pool.

Astronomy Facts, sourced to NASA.

Or go to the puzzle’s own page first.

What it means

Boiling happens when the pressure pushing down on a liquid drops below its vapor pressure, and on Mars the atmosphere is under a hundredth of Earth's. Water there tends to go straight from ice to vapor without a liquid stage. That does not mean Mars is dry. There is a great deal of ice at the poles and under the surface, and the landscape is carved with channels cut by water long ago.

The claim comes from NASA.

Nearby in the collection

The facts either side of this one.

About as hard as this one

Scored closest to it by the model behind our guide to solving cryptograms.

Every Astronomy Facts cryptogram · All fact collections