Human interest in Mars has grown dramatically over the past few decades. In addition to the eight active missions currently taking place on or near the Red Planet, seven more robotic modules, rovers and orbiters will be sent to Mars by the end of the decade. By the 2030s, several space agencies plan to deploy manned missions to the surface.
In addition, there are still quite a few volunteers who are ready to go to Mars one way, and people who advocate making it our second home. All these proposals also draw our attention to the dangers that lie in wait for people on Mars. Besides the cold, dry environment, lack of air, and giant sandstorms, there is also the issue of radiation.
Where does radiation come from on Mars?
Mars does not have a protective magnetosphere like Earth does. Scientists believe that at one time there were convection currents in the core of Mars, creating a dynamo effect that set in motion a planetary magnetic field. But about 4.2 billion years ago - apparently due to a collision with a large object or the rapid cooling of the core - this dynamo effect disappeared.
As a result, over the next 500 million years, the atmosphere of Mars was slowly evaporated by the solar wind. Due to the loss of magnetic field and atmosphere, the surface of Mars is exposed to much higher levels of radiation than Earth. And in addition to constant exposure to cosmic rays and the solar wind, Mars is exposed to lethal doses of sterilizing radiation along with solar flares.
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How did the research go?
In 2001, NASA sent the Mars Odyssey spacecraft to Mars, equipped with a special instrument MARIE (Martian Radiation Experiment), which was supposed to measure the level of radiation around Mars. Since Mars has a rather thin atmosphere, the radiation recorded by Mars Odyssey should have been almost the same as on the surface.
Over 18 months of operation, the Mars Odyssey probe has detected permanent radiation, the level of which is 2.5 times higher than the level at the International Space Station - 22 millirad per day, or 8000 millirad (8 Rad) per year. The spacecraft also recorded two solar proton events in which radiation levels rose to 2,000 millirads per day.
By comparison, people in developed countries are exposed to an average of 0.62 Rad per year. And although research has shown that the human body can withstand a dose of up to 200 rad without any damage, prolonged exposure to Martian-level radiation can lead to all kinds of health problems - acute radiation sickness, increased risk of cancer, genetic damage, and even death.
Therefore, NASA and other space agencies adhere to a strategy of minimum risk when planning missions.
Possible solutions
The first visitors to Mars will definitely have to face increased levels of radiation on the surface. Moreover, any attempt to colonize the Red Planet will also require measures to minimize the impact. Several solutions already exist, both short term and long term.
For example, NASA maintains several satellites that study the sun, the space environment throughout the solar system, and track galactic cosmic rays in the hopes of providing a better understanding of solar and cosmic radiation. Also, the agency is looking for the best options for shielding astronauts and electronics.
In 2014, NASA launched the Reducing Galactic Cosmic Rays Challenge, an intense competition with a prize of $ 12,000 that will reward the best ideas for reducing the effects of galactic cosmic rays on astronauts. After the first competition in April 2014, another one followed in July with a total prize of $ 30,000 for ideas related to active and passive defense.
When it comes to long-term stays and colonization, a few more ideas have surfaced in the past. For example, as suggested by Robert Zubrin and David Baker in the Mars Direct mission plan, dwellings can be built right in the ground, which will be a natural shield from radiation.
It was also proposed to create inflatable modules enclosed in ceramics created using Martian soil. This plan will rely on a 3D printing technique known as “sintering,” where sand is converted into molten material using X-rays.
MarsOne, a non-profit organization that promises to colonize Mars in the next few decades, offers its own option to protect the Martian settlers from radiation. The organization has proposed embedding shielding into the mission's spacecraft, vehicle, and habitation module. In the event of a solar flare, if protection is not enough, they propose to create a dedicated radiation shelter (located in a hollow water tank) inside their Mars Transit Habitat.
But the most drastic mitigation proposal involves restarting the planet's core to restore its magnetosphere. To do this, we need to liquefy the outer core so that it can convect around the inner core again. The planet's proper rotation will begin to create a dynamo effect and a magnetic field will be generated.
According to Sam Factor, a graduate student in the Department of Astronomy at the University of Texas, there are two ways to do this. The first is to detonate a series of thermonuclear warheads near the planet's core, and the second is to send an electric current through the planet, producing a resistance in the core that will heat up.
Scientists from the National Institute of Synthesis Science (NIFS) in Japan conducted a study in 2008 that considered the possibility of creating an artificial magnetic field around the Earth. Finding that the intensity of the magnetic field has dropped by 10% over the past 150 years, they advocated the creation of superconducting rings surrounding the planet, which could compensate for future losses.
With a few changes, such a system could be adapted for Mars. It will create a magnetic field that can help shield the surface from some of the harmful radiation. And if terraformers can create an atmosphere on Mars, such a system will also protect it from the solar wind.
Finally, a 2007 study by researchers at the Institute of Mineralogy and Petrography in Switzerland showed what the core of Mars looks like. Using a diamond chamber, the scientists were able to reproduce the pressure conditions on the iron-sulfur and iron-nickel-sulfur systems that correspond to the center of Mars.
They found that at temperatures of the Martian core (about 1227 degrees Celsius), the inner core would be liquid, but the outer would be slightly solidified. This is very different from the Earth's core, in which solidification of the inner core releases heat, which keeps the outer one molten, thus creating a dynamo effect and a magnetic field.
The absence of a solid inner core on Mars would mean that one day the liquid outer core must have had a different energy source. Somehow this source dried up and the outer core solidified, ending the dynamo effect. However, their study also showed that cooling the planet could lead to solidification of the core in the future, as either iron-rich solids would fall into the center, or iron sulfides would crystallize in the core.
In other words, the core of Mars may one day become solid by heating the outer core and melting it. Combined with the planet's own rotation, this will generate a dynamo effect that will once again trigger the planet's magnetic field. If this is true, then the colonization of Mars and safe living on it will be a matter of time - it will be necessary to wait until the core crystallizes.
There is no other way. At present, radiation on the surface of Mars is quite dangerous. Therefore, any future missions to the planet will take radiation protection and countermeasures into account. And everyone who stays on Mars for a long time will either have to bury themselves deeper in the earth, or protect themselves from the sun and cosmic rays.
But necessity is the mother of invention, isn't it? And since we need to start colonizing other worlds, if we want to survive as a species, we will have to resort to innovative solutions.
ILYA KHEL