New research suggests that regions of the Martian surface could be made habitable with a material -- silica aerogel -- that mimics Earth's atmospheric greenhouse effect. Through modeling and experiments, the researchers show that a 2- to 3-centimeter-thick shield of silica aerogel could transmit enough visible light for photosynthesis, block hazardous ultraviolet radiation, and raise temperatures underneath permanently above the melting point of water, all without the need for any internal heat source.