Space Radiation

The following essays are written by and are  solely the opinion of E.G. Stassinopoulos.  Civil discussion and thoughtful comments are invited and welcomed. 

There You Are, Steven Hawking

Space Potatoes are Not Ready for Consumption Just Yet

The  Mars  Conundrum

Opinions and suggestions have been recently expressed by scientific leaders such as Stephen Hawking promoting the colonization of other planets in other solar systems, and by Dr. Hawking and Elon Musk encouraging Homo sapiens to become a multi-planet species over the next millennium.  The goal would be to save the human race from possible extinction from a cataclysmic event on Earth.

In a letter to the ‘Washington Post’ on June 16, 2016, Dex Torrike-Barton, Senior Director of Communications for Space-X, declared that “…. At the same time, we should not slow down our effort to reach Mars. Humanity’s long term progress depends on becoming a multi-planet species”.

According to Micky Woolf in San Francisco, CA, September 20, 2016, Elon Musk stated that “…. There are only two fundamental paths for humanity : 1. We stay on Earth forever and then there will be an inevitable extinction event, and 2. The alternative is to become a space-faring civilization and a multi-planet species.”

Stephen Hawking gave a speech at Oxford University in England on November 18, 2016, in which he stated : “….By that time we should have spread out into space and to other stars, so a disaster on Earth would not mean the end of the human race.”

Multi-planet Species

Though an understandable and appealing goal, the question of whether Earthlings can ever become a multi-planet species is important to realistically explore. Because of the adoption of artificial intelligence, the ravages of climate change, and the threat of nuclear terrorism, Stephen Hawking forecast the end of humanity within the next 1000 years unless humans were able to successfully find and colonize another planet. Otherwise, remaining on Earth any longer could put humanity at great risk of encountering another mass extinction. Hawking believes that the Earth’s cataclysmic end might be hastened by mankind, which will continue to devour the planet’s  resources at overwhelming rates. For a disaster on Earth not to mean the end of the human race, Hawking advocates that humans move beyond Earth to other planets and solar systems.

Hawking did not explicitly mention Mars as the ‘other planet’ that humans should colonize, but it is the only planet in our solar system possibly suitable for human settlement. The study and exploration of Mars has already begun via orbiting satellites and rovers on its surface. There are plans afoot for future missions with astronauts, although the challenges of long-distance human travel and radiation exposure remain obstacles. Mars, even if successfully colonized, however, would not be immune to the disasters that threaten Earth with human extinction, e. g. asteroid impacts, climate change, etc.

Unfortunately, human travel beyond Mars, or perhaps through the asteroid belt to Jupiter’s moon Io, is impossible with current technology. Hawking should be aware that human travel to other ‘solar systems’ would require more than evolving human technology, but requires a change in physical laws and our relationship to them. The nearest star in our galaxy, Alpha Centauri, is 4 light years away. That is, 4 years away at the speed of light: 300,000 km/second. At the speed of 15,278 km/hr that ‘raced’ the CURIOSITY rover to Mars, the trip to  Alpha Centauri would take 282,752 years. Technology limited to the scope of science fiction, such as ion drives and matter-antimatter, that could increase propulsion a hundred times to 1,527,800 km/hr, would still require colonists to brave 2,827 years traveling in space. Captain Kirk and Commander Spock guiding us through wormholes with warp drive speed is an appealing fantasy, but we it is unlikely we will ever live long enough and prosper enough to make that fiction a reality.

It took life billions of years to evolve on Earth as a unique phenomenon in our solar system, as far as we know. If in the billions of galaxies, with the trillions of stars and planets, and with head-starts on Earth of over ten billion light years, there exists no scientific evidence that intelligent biological systems have become multi-planet species before us, not even in our own small Milky Way galaxy.  Therefore, it is not likely that we will successfully colonize any planet outside of our solar system.  It follows that humanity would be condemned to stagnation and deprived of progress, because we could never realistically become a multi-planet species.

To even colonize a planet within our solar system is questionably achievable, and at best, will be a one way street for the astronaut immigrants. Humans, a prime evolutionary product on Earth, could, theoretically, be transplanted and survive on Mars, which is apparently the best suitable planet available for human colonization. However, that planet is significantly smaller than Earth, and has only 1/3rd the gravity of our home planet and about only 10% of the Earth’s mass. The descendants of the colonizers would probably not be able ever to return to Earth, having been conceived, born, and raised in that low intensity gravity, to which they will have become fully and irreversibly adapted. These proposals also ignore the likelihood that a cataclysmic event could also occur on Mars or within our entire solar system, e.g. our Sun's nova.

This admirable “blue-sky” goal of saving the human species does not undermine the scientific value in a reasonable, well-planned, and carefully executed manned explorative mission to Mars.  However, the unpleasant, dangerous, and harmful conditions that a human would face on the journey to and settlement on Mars, either for a short exploratory mission or for a permanent colonization, are significant barriers to successful colonization.

As compared to Earth, Mars is an unhealthy and inhospitable place. It is a dead, cold, barren planet which harbors: (a) no breathable atmosphere, (b) no liquid water, (c) no resources of food, (d) toxic soil, not suitable or food production, (e)  freezing temperatures (Ed Regis [1]).  Mars has an average surface temperature of -60 degrees C, but its environment can reach temperatures as low as -120 degrees C for extended periods of time. Mars’ tenuous, un-breathable atmosphere is mostly composed of carbon dioxide (96 %), with a density of only 6 g/cm squared.  Earth’s atmospheric density is 1033 g/cm squared, which is equivalent to 3.83 meters of regolith (12.56 ft), and constitutes the second most effective shield against solar and galactic cosmic ray radiation.  (Earth's first level of protection from such radiation is our magnetic field, which deflects these charged heavy ion particles in a process referred to as the ‘rigidity’ concept (momentum over charge).

Mars has no magnetic field, and does not provide significant magnetospheric or atmospheric protection against cosmic radiation.  Any habitat on the planet, above ground or below the surface, has to provide adequate shielding of at least 12 ft of regolith. Ideally, a permanent habitat should be at 25 ft underground or deeper. If such a shielded habitat is not available for temporary visitors or permanent settlers, the unfortunate humans will have accumulated a surface radiation dose of approximate 1 Sievert in about 1.5 years, during the minimum phase of the solar cycle; and in about 4 years during the solar maximum phase.  This exposure is in addition to the significant radiation dose the travelers will have received on the journey to Mars, depending on the actual length of the trip and the phase of the solar cycle; estimates based on measurements from the RAD instrument on the CURIOSITY rover during its journey to Mars (1.84 mSievert/day) and on Mars (0.64 mSievert/day).  

For permanent settlers, the problem is even more serious, because they are exposed over a lifetime to these conditions.  Colonists would have to limit their presence on the unshielded surface to only a few hours per day outside their shielded habitat.   Additionally, the standard concept of a solar cycle’s length is 11 years, on average. In reality, solar cycles can vary from <9 to >13 years. The incident radiation levels also vary with (a) perihelion or aphelion position of Mars’ orbit, (b) the location on Mars’ surface, and (c) elevation.

The Journey

The tedious business of getting to Mars involves many discomforts, annoyances, difficulties, and even dangers and threats, such as: (a) a grueling, extended nightmare for the crew, living for months in a small, closed, packed spacecraft the size of an SUV, (b) tears, sweat, urine, and perhaps even solid waste, will need to be collected and recycled, (c) crew members will be floating around sideways, upside down, and at other nauseating angles (Ed Regis [1]).  Simple functions will become complex, such as:  (e) male crew members shaving, (f) female crew members taking care of monthly menstruation cycles, (g) both genders brushing their teeth, (h) bathing, washing, cleaning themselves, (i) and laundering their clothes, etc.

In addition to the health and hygiene concerns, there will be: (a) persistent mechanical noises and vibrations, (b) sleep disturbances in the confined common space, (c) unbearable tedium, (d) trance states, (e) depression, (f) monotonous repetition of meals, clothing, routines, conversations, (g) emotional and psychological stress, exponentially magnified by being restricted to a tiny, hermetically sealed pressure cooker capsule hurtling through space (Ed Regis [1]) with no escape possible, and (h) significant  boredom.

Despite these constraints, the crew must oversee cutting edge technology which is continuously at risk of failures or accidents from : (a) equipment failure, (b) computer malfunction, (c) power interruptions, (d) software glitches (Ed Regis [1]), and most importantly (e)  human error. These events demonstrate just how much preparation still needs to be done to get humanity to Mars. Schiaparelli, Beagle-2, and even the Challenger and Columbia disasters, and show how difficult and dangerous space travel can be [2,3].

  • Failures: (1) A one-second sensor failure doomed the ESA’s Schiaparelli LANDER. The ESA states that the Inertial Measurement Unit (IMU) sensor ran one second longer than expected, which caused the lander to break too early and crash into Mars. This event underscores the dangers of space travel and the remarkable level of precision that will b e needed in order for humans to successfully colonize Mars [2]. (2) The British microsatellites STRV 1c & 1d, launched on November 16, 2000, failed two weeks later and were declared lost [4].

  • Accidents: In 2003, Britain piggybacked its Beagle-2 Mars probe on ESA’S ‘Mars Express Orbiter’. Unfortunately, after parking with the orbiter to get to the Martian surface, the Beagle-2 was never heard from again [3].


A major concern on a journey to Mars, whether the voyage is for a temporary scientific research expedition or to colonize the planet permanently, is the health of the biological organisms being transported (including the astronauts).  All of the Earth’s biological systems evolved in a gravitational field of a specific value.  If we assume a field of 1G on Earth, humans may be able to colonize other planets with equal or lower gravity.  But, Homo sapiens cannot survive on a planet with significantly greater gravity. A consequence of colonizing a planet with substantially lower gravity, such as Mars (about 1/3rd G), however, is that the descendants of the colonists, conceived and raised in Mars’ low gravity field, will never be able to visit or return to Earth, because they would not survive the 3-times greater gravity. These progeny would therefore evolve separately from their Earth cousins.

The original colonists would suffer, unavoidably, from several types of health problems as well, including zero-gravity effects from the long duration space journey, and low-gravity effects after settlement.  These problems include:

  • Vision impairment
  • Bone loss
  • Mass-losing muscle atrophy
  • Shrinking spines
  • Cardiovascular alterations
  • Immunological function impairment
  • Dental susceptibility to cavities
  • Mental health challenges
  • Digestive and pulmonary system impairment
  • Space fungus
  • Radiation exposure to cosmic rays and solar protons
  • Red blood cells reduction (space anemia)

“Russian cosmonaut Mikhail Kornienko and NASA astronaut Scott Kelly, on landing in Kazakhstan, could barely breathe: after a year of weightlessness, their lungs and chests were weak and once they landed, they could barely walk. The ground crew carried them from the capsule, for fear they might stumble and break a bone.” [5] : These serious effects were suffered despite the ISS having been supplied with exercising equipment designed for use in a zero gravity environment for two hours a day. The corresponding health status of crews to Mars, after a long 6-8 month journey, would be much worse.

“In an experiment that charted the changes in the quadrupeds of rats flown in space, more than a third (1/3) of the total muscle bulk was lost within 9 days”. [6]: In other words, colonization will be a one-way street, and unlikely to salvage the human species in its current form. 

If successfully colonized, Mars may be more vulnerable to catastrophic events than Earth, and, if Earth serves as an example, may quickly be overpopulated, or depleted of its limited natural resources.

Additional items of concern include:

  • Solar proton events (flares and coronal mass ejections)
  • Galactic and solar cosmic rays
  • X-ray and gamma-ray inundation from cosmological events
  • The toxic Martian soil (Perchlorate)
  • Intense, long-lasting global dust storms

Toxic soil:

"Test made the unexpected discovery that the Martian soil in the vicinity of the VIKING lander is highly reactive chemically, favoring rapid destruction of organic matter".[7]  This toxicity is likely to make the surface unsuitable for farming.

"Toxic Martian dust will undoubtedly be brought into the habitat on instruments, spacesuits, and through any gaps or openings, and would inadvertently be inhaled in small amounts by astronauts." [7]  Contamination risk may be unavoidable or require implementation of elaborate prevention measures.

Static Electricity:

"On Mars, there is no natural grounding mechanism (no surface water).  As a result, astronauts may develope huge differences in electrical charges relative to their equipment.  This might produce an arc between the astronaut's space suit and equipment, causing potential damage to sensitive instruments or the space suit." [7]

Dust storms:

Mars global dust storms are unpredictable. Their top speed can reach up to 97 km/hour. For the first two months of the MARINER 9 spacecraft's flight in Mars orbit, the most severe Martian dust storm ever recorded obscured Mars' surface features [8].  In 2007, two Martian rovers, SPIRIT and OPPORTUNITY, had to be placed in "survival mode" during a global dust storm that lasted for weeks, contaminating everything that was exposed. [9]  Such long lasting intense storms block the solar light. Dust would go everywhere --- inside the habitat, all over the suits, and into machinery.  It would be essential to find out if this dust would also be toxic, as is the Martian regolith. In sum, (a) global storms throw enough dust into the atmosphere to reduce sunlight reaching the surface, (b) can consume the entire planet, altering atmospheric conditions, and (c) are unpredictable.

Growth of Plants/Food

An issue frequently arising in plans and proposals to colonize Mars is the potential of raising food locally, as imagined in the popular science fiction movie ‘The Martian’. An effort to explore this possibility through an experiment was initiated by the ‘International Potato Center’ [10], in an attempt to grow a crop of tubers in an environment with simulated Martian atmospheric conditions.  The Center announced that “Preliminary results are positive”. The experiment involved a sealed cube-sat container that was rigged with pumps, water hoses, LED lights, and instruments to emulate Mars-like temperatures, night-and-day cycles, gases, and air pressures.

However, when compared to the actual Mars conditions expected, there are several major differences in this experiment:  (a) the impact of low gravity on the plants (1/3rd of Earth’s), (b) the toxic soil of the planet (Perchlorate), (c) the total absence of liquid water on the surface, (d) the average -60 degree C temperatures, (e) the continuous, unshielded exposure to cosmic ray radiation, and (f) the total absence  of a magnetic field.  It is most likely that these conditions would adversely affect the growth, or even the survival, of these plants.

A further set of questions regarding this particular experiment need to be answered before final valid conclusions can be reached about its applicability to a Mars expedition.  These include (a) how accurately the gases in the test mimicked the composition of the Martian atmosphere  (~96% CO2, ~2% Argon, ~1.9% Nitrogen, and ~0.1%  Oxygen), (b) how accurate the air pressure was in the container matching the Martian environment (about 6% of the Earth’s), (c) how closely the LED lights approximated the Martian sunlight; i.e. the wavelength of visible, ultraviolet, infrared lights, and (d) how well did the experiment maintain within the Cube-Sat the sub-freezing average temperature of -60 degrees C.

A study by a team at MIT, which researched food for 4 persons for a Mars-One mission to the planet, found that the most economical  way to provide it was to supply it from Earth, rather than growing it locally [11]. Of course, it can be argued that plants have been grown experimentally in space in the past on the ISS.   In contrast, however, to the Mars environment, these plants had the advantage of: (a)  a ‘normal’ atmosphere, in terms of composition and pressure, (b) a benign, mild, steady temperature, (c) non-toxic soil, (d) plenty of water, (e) exposure to adequate (constant ?) light, and (f) relative protection from solar and galactic radiation. The plants were only challenged by zero gravity vs the low gravity of Mars, and a reduced magnetic field value. It would not be surprising that, just as humans suffer from zero or low gravity, so would most biological systems that evolved on Earth, including plants.

Plans & Costs

Elon Musk has repeatedly said that “…The human race must learn how to live on planets other than Earth, as an insurance against a planet-wrecking disaster.”. What is new and surprising is Musk’s statement that “To get there (to Mars) will mean building a spaceship that can keep occupants alive for a journey that will last for months, and a rocket that can sent it on its way. ….”, to which he added : “…. The spaceship would be 495 meters long with room for around 100 persons …”.

A half-kilometer long spacecraft with 100 people on board, and loaded with most items needed to keep them alive, safe, and healthy for such a long many-months trip, would need an enormous rocket that is not likely to be available for decades in the future, if ever. Even a partial assembly of such a machine in near-Earth space would be difficult to build and enormously expensive.

A significant study conducted by the MIT research team, relating to a modest attempt of MARS-ONE to send only 4 persons to Mars [11] indicated that new technologies will be needed to keep humans alive, and that at least 15 Falkon-Heavy rockets would be required to provide initial supplies, before arrival on Mars, at a cost of 4.5 billion dollars, i.e. 23% of NASA's annual budget.  This hefty price tag would grow with any additional crews or supplies, and may be considered unaffordable. 



The only planet that can be potentially colonized in our solar system in the foreseeable future is Mars. But colonization of the Red Planet would not only be questionable, but futile. Questionable because a similar or identical catastrophic event such as an asteroid impact or inundation from cosmological radiation that might cause the extinction of the human race on Earth, could also happen on Mars.   Futile because, after 1 or 2 generations of progeny are raised in the low gravity of the planet (1/3rd of Earth’s), the human species as we know it will be adapting in differing and discrete evolutionary paths. Martian “humans” may be different in size, physically weaker and more vulnerable in terms of health, and possibly even cognitively impaired, on account of the lifelong exposure to cosmic radiation.  They will be adapting to the physical conditions of the colony planet, unable to safely return to Earth, with its 3-times greater gravity, or to colonize heavier gravity planets in our or other solar systems.

Multi-Planet  Species

There is no scientific evidence that, despite the passage of billions of light-years in trillions of galaxies, other biological civilizations have become multi-planet systems.  We have yet to identify biological civilizations or even life beyond Earth.  Therefore, the concept of Earthlings becoming a multi-planet species, colonizing Mars, and eventually traveling to other planets or solar systems for the ultimate purpose  of surviving extinction, is not only an illusion, but also an impossibility.   At this time, it is impossible for any humans to travel to other solar systems, even to the closest star in our Milky Way galaxy, Alpha Centauri, 4 light years away; and, were it possible, such colonization would significantly change who and what humans are.


It is most unlikely that the descendants of colonists from Earth will be able to successfully and sustainably terraform their new home. In the particular case of Mars, it is pure fantasy, considering the many unsurmountable problems described.  For example, a) an artificial  magnetic field will have to be generated to provide an adequate magnetospheric shield analogous to Earth’s for primary protection against cosmic radiation, (b) a breathable, oxygen based atmosphere will need to be created (current: 96% CO2), (c) the atmospheric density would have to be increased sufficiently to serve as a secondary shield for protection against cosmic radiation, similar to Earth’s, (d) the average subfreezing temperature of -60 degrees C will have to be raised to Earth-like levels, (e) free flowing surface water would need to be produced on the desert-dry surface of the Mars (lakes, rivers, seas),  (f) the toxic soil of the planet would have to be de-contaminated to allow plant growth, (g) the enormous global dust storms, contaminating all in their paths, blocking  sun-light, and infecting the atmosphere with toxic dust, would have to be globally controlled; and (h) the low gravity effects on biological systems would have to be addressed. A terraforming effort of this magnitude would probably require centuries to be accomplished--at a literally astronomical cost. Would Mars colonists  be able to handle such challenges, or even to survive long enough to accomplish successful terraforming? Terraforming is, and will remain for a long time, if not forever, a fantasy, a dream, a mirage for science-fiction books and media.

There is nothing in our arsenal of science, biology, technology, or knowledge, that allows or can support this fantasy, beyond the limited, restricted, initial and simultaneously terminal one-way move to another suitable, nearby planet. It is not very encouraging to think that the future of mankind has to depend on such a questionable, unrealistic adventure. Even if we were to somehow conquer the challenges and make our way into space, we would still be vulnerable from threats to our species. Infections by lethal organisms, susceptibility to natural disasters or predators, cataclysmic asteroids impact, etc., could still be likely. But most importantly, our greatest danger would come from ourselves. The human traits that have led us to the brink of nuclear war, and are contributing to the potential need for finding another planetary home, will accompany us as we travel to another planet. If we cannot address the factors within us that have led us to attack each other and destroy our beautiful home, we will be fated to repeat our behaviors and create a ‘scorched Mars’ and beyond.

Dreamers need not lose hope, however.  Despite the enormous difficulties identified in the process of extraterrestrial travel and colonization, scientific advances and innovations may be able to minimize or mitigate some of the challenges, risks, and dangers that make multi-planet settlements impossible today.  We should continue to explore our solar system, and should definitely continue our research related to our Red Planet neighbor.  With more cost-efficient, safe, and rapid modes of transportation, perhaps waves of colonists from Earth could arrive on Mars repeatedly over centuries in the future, to help and guide a native population to build a new home and avoid the extinction envisioned by our prophets such as Hawking and Musk.  Or, better yet, the future may be brighter than expected, and Earth can take on the mantle of the vital "home town" planet that harbors the ancestors of a new multi-planet humanity.

E. G. Stassinopoulos                                                                                                               Astrophysicist                                                                                                                                  4/3/2017


1.  Regis, E  "Let's Not Move to Mars"  Retrieved from April 2017

2.  Gallego, J  "Plan to Colonize Mars?  A One-Second Sensor Failure Doomed the ESA's Mars Lander" Retrieved from  April 2017

3.  Wall, "UK's Beagle 2 Mars Probe Nearly Aced 2003 Landing, Study Suggests"  Retrieved from  April 2017

4.  Avery, K  "A scientific study of the problems of digital engineering for space flight systems, with a view to their practical solution."  Retrieved from  April 2017

5.  Achenbach, J  'Mars: Inside the High-Risk, High-Stakes Race to the Red Planet"  Retrieved from  April 2017

6. Fong, K  "The Strange, Deadly Effects Mars Would Have on Your Body"  Retrieved from  April 2017

7. US Congress and the US Office of Technology Assessment "Exploring the Moon and Mars--Choices for the Nation"  Chapter 5 Scientific Exploration of Mars  Retrieved from  April 2017

8. Cain, F  "Dust Storm Threatens the Martian Rovers" Retrieved from  April 2017

9.  Chu, J  "MIT Evaluation of Mars-One Mission"  MIT News Office, October 14, 2014

10.  Lanatta, M  "Indicators show potatoes can grow on Mars"  Retrieved from March 2017