Being on Earth, seeing the blue sky it is hard to believe that terrestrial weather is influenced by space weather. But nothing could be more true. Weather on a terrestrial planet such as the Earth and Mars is restricted to the small gaseous envelope we call the atmosphere. The atmosphere is constantly being bombarded by cosmic radiation and solar wind. But occasionally enormous amounts of mass are erupting from the sun, called coronal mass ejections (CME).

Lucky for terrans only a small amount of these life threathening particles make it to the surface. This is because the Earth has a magnetic field bending off the ionic particles present in the solar wind, CME's and the cosmic radiation. Another radiation blocker is the ozone layer, located high in the upper parts of the atmosphere. It contains the gas ozone [O3] which blocks UV radiation. Mars doesn't have a natural magnetic field anymore and the atmosphere at sealevel is 150 times thinner than on Earth [~6 mbar]. Therefore Martians need to stay sheltered and protected against the sun and cosmic radiation as much as possible.

Travelling beyond Earth means leaving our natural protector. In space: on the Moon, on Mars, in the Asteroid Belt and at all the other ExTerra locations we need artificial protection against radiation. The artificial protection scientist came up with is just plain water. Water has protected life all it's evolutionary history and continues until today.

Protective radiation shelters can be found on all colonized ExTerran worlds. On Mars, for example, most of Areopolis is built underground. After the 2012 Sun Storm event radiation protection standards have been devised for mechanical engineering and architectural designs. The roof of a Mars rover for example needs to have a 10 cm water layer. The 2012 Sun Storm was the highest Solar activity ever measured, lasting one month. Since this event ExTerra infrastructure needs to satisfy very tight post-2012 radiation protection guidelines.