Mars, a planet of grossly Earth-like composition with a somewhat lower density and 10-fold lower mass than Earth, is located much closer to the realm of volatile-rich comets and asteroids. The lower density strongly implies a greater degree of oxidation and a higher abundance of volatiles than we have on Earth, fully in keeping with a cooler origin at its place of origin, farther from the Sun. Mars has an atmosphere, polar caps, and widespread geological evidence of the former presence or rivers, glaciers, and even oceans. Yet the atmosphere today is a frigid veil of carbon dioxide, less than 1% of the atmospheric pressure of Earth, so cold that water is found as vast deposits of ice and wisps of water vapor. Liquid water is certainly very rare, and possibly absent, on the surface of Mars today.



Table of Contents


Atmospheric Structure of Mars
Atmospheric Circulation of Mars
Atmospheric Composition of Mars
Photochemical Stability and Atmospheric Escape
Water Photochemistry
Explosive Blow-away
Martian Atmosphere Observations
Photos of Martian Surface