NASA has a mystery to be resolved: Can we send people to Mars, or not? It is a question of radiation. We know the amount of radiation that are out there, waiting for us between Earth and Mars, but we are not sure of how it will affect human body.
The NASA astronauts have been in space, occasionally, for 45 years. Except for a couple of quick trips to the moon, never have stayed away from the Earth over a long period of time. The deep space is filled with protons caused by solar flares, gamma rays coming from black holes newborns and cosmic rays from stellar explosions. A long journey to Mars, without major planets in the vicinity act as reflectors that radiation shields, will be a new adventure.
NASA measured the danger of radiation in units of carcinogenic risk. A healthy 40-year-old American, non-smoker, has a probability (huge) 20% eventually die as a result of cancer. That if it stays on Earth. If travel to Mars, the risk would increase. The question is how much?
According to a study in 2001 on people exposed to large doses of radiation - P. E. Survivors of the atomic bomb in Hiroshima, and ironically, cancer patients who have undergone radiation therapy - the risk inherent in a manned mission to Mars that run 1. 000 days, would fall between 1% and 19%. The answer most likely 3.4%, but the margin of error is very wide. Oddly, it is even worse for women. Because of breasts and ovaries, the risk to female astronauts is almost double that of their male counterparts.
The researchers who conducted the study assumed that the spacecraft to Mars would be constructed primarily of aluminum, as the capsule of Apollo. The "skin" of the spacecraft would absorb almost half the radiation impactase against her.
If the percentage of the additional risk is only a bit more ... Will be just fine. We could build a spaceship using aluminum and head to Mars. Aluminum is the material favorite in the construction of vessels due to their lightness and strength, and the long experience that, for decades, engineers have their management in the aerospace industry. But if 19% of our astronaut 40-odd years would face a risk of death due to cancer of 20% plus 19%, ie 39% after their return to Earth. That is not acceptable. The margin of error is large, for good reason. Radiation from space is a unique blend of gamma rays, high-energy protons and cosmic rays. The atomic explosions and bursts of cancer treatments, which is what many studies are based, are not a reliable substitute for radiation "real".
The greatest threat to astronauts going to Mars are the galactic cosmic rays. These rays, are composed of particles accelerated to nearly the speed of light coming from distant supernova explosions. The most dangerous are the ionized. A wave of these rays pass through the shell of the vessel and skin of humans as a tiny gun bullets, breaking the strands of DNA molecules, damaging genes and killing cells.
Astronauts have very rarely been exposed to a full dose of these rays of deep space. Consider the International Space Station (ISS): it orbits only 400 km. On the Earth's surface. The body of our planet, seeming large, intercepts only one-third of cosmic rays before they reach the ISS. Another third is deflected by the Earth's magnetosphere. The astronauts of the space shuttle receive similar reductions.
The Project Apollo astronauts who traveled to the moon absorbed higher doses - about 3 times that of the ISS - but only for a few days during their journey from the Earth to the moon. On his way to the moon, Apollo crews reported seeing flashes of cosmic rays in their retinas, and now, many years later, some of them have developed cataracts. On the other hand do not seem to have suffered too much. But astronauts traveling to Mars will be "out there" for a year or more. We can not estimate yet, reliably, which cosmic rays we will see when we exposed them for so long.
Find Out is the mission of the new Space Radiation Laboratory at NASA (NSRL), located in the premises of the Brookhaven National Laboratory, located in New York, the Department of Energy of the United States. UU, which was inaugurated in October 2003. The NSRL there particle accelerators that can simulate cosmic rays. Researchers expose mammalian cells and tissues to particle beams, and then inspect the damage. The goal is to reduce the uncertainty in the risk estimates to only a small percentage for the year 2015.
Once we know the risk, NASA can decide what kind of spaceship has to be built. It is possible that ordinary building materials, such as aluminium, are not good enough. What manufacture a plastic ship?
Plastics are rich in hydrogen, an element that does a great job as absorbing cosmic rays. For example, polyethylene, the same material which makes the garbage bags, absorbs 20% more cosmic rays that aluminium. Some form of reinforced polyethylene, developed by the Marshall Space Flight Center, is 10 times stronger than aluminum, and lighter. This could become the chosen material for the construction of the spacecraft, if we can produce enough cheap.
If the plastic is not good enough, then it might require the presence of pure hydrogen. Litro a litre liquid hydrogen blocks cosmic rays 2, 5 times better than aluminum. Some advanced designs of spacecraft need big tanks of liquid hydrogen as fuel, so that we could protect the crew from radiation by wrapping the living with the tanks.
Can we go to Mars? Perhaps yes, but first we must resolve the issue of the level of radiation that can support our body, and what kind of spaceship we need to build.
