Colonising other planets is the next grand step for humanity, one that might come to define it in the millennia to come. But distant planets still remain far out of our reach, even if we could somehow travel at the speed of light. With such constraints, the most plausible candidate for planetary colonisation and exploration is our neighbour Mars, which is 54.6 million kilometres at its closest and around 225 million km on average. That is nearly 1.5 times the mean distance of the Earth from the Sun or 1.5 AU.
But before we can colonise Mars, we would need to study it and explore it, which can take years if not decades. But according to a recent study, each mission should only last a maximum of four years in order to protect astronauts from harmful radiation.
Radiation in Space
While it is commonly thought that outer space is empty of all matter, that is not necessarily true. Space is filled with gasses, dust, charged particles from celestial bodies, light, cosmic rays, gravity, electric and magnetic fields, and neutrinos, and radiation.
These elements are usually filtered out by the Earth’s magnetic field and the atmosphere, not causing any harm to those on the surface below. But out in space, radiation can quickly prove to be very dangerous.
“Space radiation is different from the kinds of radiation we experience here on Earth. Space radiation is comprised of atoms in which electrons have been stripped away as the atom accelerated in interstellar space to speeds approaching the speed of light -- eventually, only the nucleus of the atom remains,” explains NASA.
“Space radiation is made up of three kinds of radiation: Particles trapped in the Earth’s magnetic field; particles shot into space during solar flares (solar particle events); and galactic cosmic rays, which are high-energy protons and heavy ions from outside our solar system. All of these kinds of space radiation represent ionising radiation,” NASA adds.
Astronauts are exposed to over 50 to 2,000 Milli-Sievert (mSv) of ionising radiation while on six-month long missions on the International Space Station (ISS). Over 100 mSv is known to cause a higher risk of cancer. First responders of the Chernobyl Nuclear Plant fire were exposed to 700-13,400 mSv, leading to acute radiation sickness in many. Radiation can increase the risk of various cancers, cause cellular defects, radiation burns, organ failures and can lead to death as well.
Why is radiation a risk on Mars and not Earth?
Unlike Earth, Mars has essentially no magnetic field and a very thin atmosphere that does very little to block radiation from reaching down onto the surface. Since the radiation is also in the form of ionising radiation -- which can easily penetrate various objects -- the amount of protection for astronauts on the surface is very little to minimal.
It is not just humans who can get exposed to radiation, but various equipment can also break down as a result and carry the radiation back home, further exposing the astronauts and others in the process.
Scientists from the University of California, Los Angeles (UCLA), who are behind the research, estimated that the safest time for a Mars mission would be during a solar maximum when the Sun enters an intense period of activity over its cycle. “The most dangerous and energetic particles from distant galaxies are deflected by the enhanced solar activity,” explained the study.
The study also highlighted that astronauts should only stay for a period of four years on Mars, in order to not be exposed to dangerously high levels of radiation, even if they go during the safest possible time. They would also need special protective material.
What this means for future missions
The study comes at a time when the NASA and Chinese Space Agency are both racing towards sending a manned mission to Mars. Both the agencies are in the process of developing the necessary protective gear and equipment needed to survive on Mars.
China has already announced that it would be sending astronauts to Mars by 2033, while NASA has not set a date. Besides the government missions, there is Elon Musk and his famed dream of colonising Mars via his private SpaceX venture.
Considering that it will take none months to just reach Mars, any mission on Mars would have to be of significant length in order to be worth its while. But the study is not a dampener on future Mars missions.
“This study shows that while space radiation imposes strict limitations on how heavy the spacecraft can be and the time of launch -- and it presents technological difficulties for human missions to Mars -- such a mission is viable,” said Yuri Shprits, UCLA research geophysicist and co-writer of the study.
(Edited by : Shoma Bhattacharjee)
First Published: IST