Van Allen radiation belt "Impact on space travel"

http://en.wikipedia.org/wiki/Van_Allen_radiation_belt

Solar cells, integrated circuits, and sensors can be damaged by radiation. Geomagnetic storms occasionally damage electronic components on spacecraft. Miniaturization and digitization of electronics and logic circuits have made satellites more vulnerable to radiation, as incoming ions may be as large as the circuit's charge. Electronics on satellites must be hardened against radiation to operate reliably. The Hubble Space Telescope, among other satellites, often has its sensors turned off when passing through regions of intense radiation.[citation needed]

Missions beyond low earth orbit leave the protection of the geomagnetic field, and transit the Van Allen belts. Thus they may need to be shielded against exposure to cosmic rays, Van Allen radiation, or solar flares.
An astronaut shielded by 3 mm of aluminium in an elliptic orbit passing through the radiation belt will receive about 2,500 rem (25 Sv) per year.[6]

Van Allen radiation belt

http://en.wikipedia.org/wiki/Van_Allen_radiation_belt

The Van Allen radiation belt is a torus of energetic charged particles (plasma) around Earth, held in place by Earth's magnetic field. Earth's geomagnetic field is not uniformly distributed around its surface. On the sun side, it is compressed because of the solar wind and on the other side, it is elongated to around three earth radii. This creates a cavity called the Chapman Ferraro Cavity, in which the Van Allen radiation belts reside. The Van Allen belts are closely related to the polar aurora where particles strike the upper atmosphere and fluoresce.
The possibility of trapped charged particles had previously been investigated by Kristian Birkeland, Carl Størmer, and Nicholas Christofilos[1] prior to the Space Age. The existence of the belt was confirmed by the Explorer 1 and Explorer 3 missions in early 1958, under Dr. James Van Allen at the University of Iowa. The trapped radiation was first mapped out by Sputnik 3, Explorer 4, Pioneer 3 and Luna 1.
Energetic electrons form two distinct radiation belts, while protons essentially form a single belt.
In addition to protons and electrons, the belts contain lesser amounts of other nuclei, such as alpha particles.
The term Van Allen belts refers specifically to the radiation belts surrounding Earth; however, similar radiation belts have been discovered around other planets. The Sun does not support long-term radiation belts. The Earth's atmosphere limits the belts' particles to regions above 200–1,000 km,[2] while the belts do not extend past 7 Earth radii RE.[2] The belts are confined to an area which extends about 65°[2] from the celestial equator.
An upcoming NASA mission, Radiation Belt Storm Probes will go further and gain scientific understanding (to the point of predictability) of how populations of relativistic electrons and ions in space form or change in response to changes in solar activity and the solar wind.
Several NASA Institute for Advanced Concepts–funded studies are exploring whether it might be possible to use magnetic scoops to collect the antimatter that occurs naturally in the Van Allen belts of Earth, and ultimately, the belts of gas giants like Jupiter, hopefully at a lower cost per gram than laboratory production of antimatter.[3]

Hypothesis of rainfall

Lately has appeared another explanation to which they give the name of ' Hypothesis of rainfall ' according to which, the energy liberated during the formation of our planet warmed part of the material, forming a warm and dense atmosphere, especially composed by steams of metal and oxides. These were spreading about the planet and, on having cooled, precipitated the particles of dust that, once condensed, gave origin to the only satellite of the Earth.