Cosmic Rays: They are particles, not rays.

By | October 8, 2008


Cosmic rays are energetic particles originating from space that impinge on Earth’s atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, about 9% are helium nuclei (alpha particles) and about 1% are electrons (beta minus particles). The term “ray” is a misnomer, as cosmic particles arrive individually, not in the form of a ray or beam of particles. – wiki

http://xenophilia.com/wp-content/uploads/2008/10/cosmic_ray_supernova-4.jpgCosmic rays are super-charged subatomic particles coming mainly from outside our solar system. Sources include exploding stars, black holes and other characters that dwarf the sun in violence. Unlike solar protons, which are relatively easy to stop with materials such as aluminum or plastic, cosmic rays cannot be completely stopped by any known shielding technology.

Even inside their ships, astronauts are exposed to a slow drizzle of cosmic rays coming right through the hull. The particles penetrate flesh, damaging tissue at the microscopic level. One possible side-effect is broken DNA, which can, over the course of time, cause cancer, cataracts and other maladies.

No one knows all the things cosmic rays might do to humans. “We haven’t been in space long enough,” says Cucinotta.

Except during brief trips to the Moon forty years ago, he explains, astronauts have never been fully exposed to galactic cosmic rays. Close to Earth where the ISS orbits, crews are protected not only by their ship’s hull, but also by Earth’s magnetic field and the gigantic solid body of Earth itself. A 6-month trip to Mars, far from these natural shields, is something new. What are the long-term risks? How much shielding is needed to keep astronauts safe? NASA researchers are grappling with these questions.

One thing is clear. “Reducing exposure is a good thing,” he says.

The sun can help. Every 11 years, solar activity reaches a fever pitch called Solar Max. It last happened in 2000; future episodes are due around 2011 and 2022. During Solar Max, CMEs are produced daily, and the solar wind blows knotty magnetic fields through the inner solar system as a matter of routine. These fields provide a measure of extra protection for trips to the Moon and Mars, dropping cosmic ray fluxes in the biologically dangerous energy range 100 MeV to 1000 MeV by 30% or more. Mission planners of the future might actually schedule long trips through the solar system to coincide, roughly, with Solar Max, thus taking advantage of this decline in cosmic rays.

Maybe solar flares aren’t so bad after all. – nasa

This is interesting. It seem Apollo 16 did get hit by a solar flare.

The Cosmic Ray Detector Experiment was performed on Apollo 16.

It seems no data is available on that, however, because “The experiment shield mechanism failed to retract completely, thus obscuring the field of view of the detector.”

A reduced-scale version of this experiment was also performed on Apollo 17, when it was called the Lunar Surface Cosmic Ray Experiment. These experiments measured particles with energies of 100,000 to 150 million electron volts, much higher than measured by any other experiment during the Apollo program. The particles detected by these experiments originate both in the solar wind and from sources elsewhere in our galaxy. On Apollo 16, particles from a solar flare (an energetic eruption of material away from the surface of the Sun) were also recorded.

These experiments consisted of a set of detector plates made of various glasses and plastics, aluminum and platinum foils, and the minerals mica and feldspar. On Apollo 16, the experiment was mounted outside the lunar module prior to launch and exposed to space a few hours after launch. On Apollo 17, the experiment was carried inside the lunar module and exposed to space after landing on the Moon. On both missions, the experiment was ended during the third moonwalk, for a total detector exposure time of 167 hours on Apollo 16 and 45 hours on Apollo 17. The detector plates were returned to Earth for laboratory analysis. – nasa

http://nobelprize.org/nobel_prizes/physics/laureates/1936/hess.jpgHow and when were cosmic rays discovered? In 1912 a scientist named Viktor Hess carried an instrument called an ionization chamber in a balloon to high altitudes. An ionization chamber is a device that records the passage of charged particles. As Hess made his ascent in the balloon, the ionization chamber recorded fewer particles, up to an altitude of 2,000 meters. The interpretation is that some of this ionization is due to the natural radioactivity of the earth, and its influence decreases with altitude. Above 2,000 meters, however, he recorded more particles, and the increase in particles became even more rapid as his balloon reached its maximum altitude of 5,350 meters. Hess correctly guessed that this increase was due to radiation entering the atmosphere from space. On one occasion he rode the balloon during a solar eclipse, and found no decrease in ionization. From this he concluded that the radiation was coming from somewhere other than the sun. We now know that much of this cosmic radiation originates far outside the solar system. – auger

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