Editing Proton (section)

== Human exposure ==
{{Main|Effect of spaceflight on the human body}}
{{See also|Proton therapy}}

The [[Apollo Lunar Surface Experiments Package]]s (ALSEP) determined that more than 95% of the particles in the [[solar wind]] are electrons and protons, in approximately equal numbers.<ref name="LPI2009" /><ref name="BNL2007" />

{{Blockquote|Because the Solar Wind [[Spectrometer]] made continuous measurements, it was possible to measure how the [[Earth's magnetic field]] affects arriving solar wind particles. For about two-thirds of each orbit, the [[Moon]] is outside of the Earth's magnetic field. At these times, a typical proton density was 10 to 20 per cubic centimeter, with most protons having velocities between 400 and 650 kilometers per second. For about five days of each month, the Moon is inside the Earth's geomagnetic tail, and typically no solar wind particles were detectable. For the remainder of each lunar orbit, the Moon is in a transitional region known as the [[magnetosheath]], where the Earth's magnetic field affects the solar wind, but does not completely exclude it. In this region, the particle flux is reduced, with typical proton velocities of 250 to 450 kilometers per second. During the lunar night, the spectrometer was shielded from the solar wind by the Moon and no solar wind particles were measured.<ref name="LPI2009" />}}

Protons also have extrasolar origin from galactic [[cosmic ray]]s, where they make up about 90% of the total particle flux. These protons often have higher energy than solar wind protons, and their intensity is far more uniform and less variable than protons coming from the Sun, the production of which is heavily affected by [[solar proton event]]s such as [[coronal mass ejection]]s.

Research has been performed on the dose-rate effects of protons, as typically found in [[Human spaceflight|space travel]], on human health.<ref name="BNL2007" /><ref name="Shukitt-Hale" /> To be more specific, there are hopes to identify what specific chromosomes are damaged, and to define the damage, during [[cancer]] development from proton exposure.<ref name="BNL2007" /> Another study looks into determining "the effects of exposure to proton irradiation on neurochemical and behavioral endpoints, including [[dopaminergic]] functioning, [[amphetamine]]-induced conditioned taste aversion learning, and spatial learning and memory as measured by the [[Morris water maze]].<ref name="Shukitt-Hale" /> Electrical charging of a spacecraft due to interplanetary proton bombardment has also been proposed for study.<ref name="Green2006" /> There are many more studies that pertain to space travel, including [[galactic cosmic rays]] and their [[Health threat from cosmic rays|possible health effects]], and [[solar proton event]] exposure.

The [[STS-65#Mission parameters|American Biostack and Soviet Biorack]] space travel experiments have demonstrated the severity of molecular damage induced by heavy ions<!-- is it relevant to protons, indeed? --> on [[microorganism]]s including [[Artemia]] cysts.<ref name="Planel2004" />