How Mars Would Alter Human Anatomy

Ethan Wong

December 27th, 2024

How would a human born on Mars have altered anatomy? We have all seen images of concept aliens–they’re often ridiculous. But what would humans look like after living under the Martian conditions for hundreds and thousands of years? 

This article will explore some of the different factors humans would encounter when transitioning from a life on Earth to one on the red planet: gravity, atmosphere, radiation, dust and soil, eyes, sound, and temperature. Some changes could allow for evolutionary changes in human anatomy. Others would not. However, this article assumes the following parameters: humans will be without adequate technology or clothing to experience the same conditions as Earth, yet still meet the necessary parameters to ensure survival. This additionally indicates that food scarcity will not become a factor. 

Weaker Gravity:

Gravity is fundamental to our biological evolution; internal organs and structure have had to develop themselves to sustain Earth’s gravitational force. When humans enter space and experience microgravity, bones become less dense because they aren’t required to maintain as much gravitational force as on the surface of Earth. Muscles can also become weaker due to weaker gravity. This is why astronauts continuously exercise (often varied exercises meant specifically to deal with such biological changes). 

Mariam Kramer from Scientific American highlights that “past studies have shown that when the spine is not exposed to the pull of Earth's gravity, the vertebra can expand and relax, allowing astronauts to actually grow taller.” On Mars, with a lower gravitational force, it might certainly be possible to be taller, especially as humans evolve on the red planet; however, this would then be accompanied by reduced muscle potential and weaker bones overall.

But humans might not achieve this stereotypical configuration (as mentioned all across the internet) after living on Mars–nor even become taller than humans on Earth. According to evolutionary biologist Scott Solomon via Astronomy.com, while biological changes can occur due to Mars’s altered gravity, “these body types might [actually] pose certain hazards during childbirth–weakened skeletons could fracture people’s pelvises while giving birth. So, natural selection may actually favor shorter people with denser bones.” Solomon brings up an amazing point, yet another question then arises: would human reproductive biology eventually adapt, and therefore allow the successful birth of these “weakened skeletons?” I’m certainly not the person to answer (or attempt to answer) this question. And obviously, a guaranteed truth must originate from the experience.

Intense Radiation (due to thinner atmospheric protection and absence of magnetic shield): 

In space, it is difficult to protect astronauts from all of the additional radiation they are exposed to. The main danger with radiation is an increased probability of cancer and degenerative diseases; particle radiation can damage cells and DNA after penetrating the human skin if no protection is equipped. 

In 2015, NASA conducted a research study with identical twins–Scott Kelly and Mark Kelly–to understand potential genetic alterations caused in a microgravity environment. Radiation was believed to be one of the main causes related to an altered gene expression in Scott Kelly’s body. From “The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight,” some results showcased how “a distinct subset of genes did not return to preflight levels within 6 months of return to Earth (811 genes across different cell types), including genes related to immune function and DNA repair, representing candidate genes that may be altered for an extended period of time as a result of long-term spaceflight exposure.”

Due to a thin Martian atmosphere, humans would lack adequate protection from radiation. On Mars, similar “DNA repair” genes could aid damaged DNA with intense radiation conditions; yet, these changes would instead be fully and permanently integrated, as humans would likely never leave Mars once they arrived. From Scott Kelly’s results, it's evident that DNA alterations will probably be present as humans experience, as well as evolve, on the red planet. And while humans are currently thankful to melanin for shielding UV rays, increased radiation exposure might lead humans born on Mars, Martians, to develop stronger pigmentation techniques to protect themselves. This is often where people point to the idea of Martians having darker skin complexion (or even a different color entirely).

However, physicist Marco Durante states “we don’t understand space radiation very well and the long-lasting effects are unknown.” Again, the impacts of radiation on humans on Mars will only be confirmed when humans step foot on Mars. 

Change in Atmosphere (mainly made of carbon dioxide, and also has different pressure): 

One of the most commonly known challenges humans will face on Mars is the atmospheric composition–over 95% carbon dioxide (CO2). And while technology can combat this issue, in my opinion, evolution will not permit humans the ability to breathe and live on CO2.

But CO2 in the atmosphere is actually one of the least-deadly parameters that need to be taken into account when considering the Martian atmosphere’s influence on the human body. Earth’s atmospheric pressure keeps our blood stable inside our bodies, as it prevents fluids like blood inside our bodies from boiling and turning into a gaseous state. But while the Earth has an atmospheric pressure of 101.3 kPa, Mars’s atmospheric pressure is 0.6 kPa. As you can see where this is going, being under such low pressure would cause your blood to boil. As stated by NASA Ames’s scientist Pascal Lee, the extremely low atmospheric pressure on the red planet would mirror “popping a can of Coke, you would fizz to death” within seconds. 

Dust and Soil Toxicity Hazard:

While the atmosphere is dangerous, it can also create more dangerous environments for future astronauts and civilizations. Martian soil and subsurface ice are plagued with perchlorate, which is a deadly chemical to human health. According to a book, “Dust in the Atmosphere of Mars and its Impact on Human Exploration” by Joel S. Levine, Daniel Winterhalter, and Russell L. Kerschmann, they note that “some ingestion of perchlorates would seem to be an extremely likely scenario. Goiter…As well as swelling in the thyroid, it can also be responsible for fatigue, weight gain…brain damage and death.” Aside from regular inhalation of these toxic conditions, Mars frequently experiences high winds and dust storms, which does not bode well for humans given these circumstances. 

If humans are capable of surviving and reproducing on Mars, evolution might adapt various parts of the body to combat this issue: a stronger thyroid, for instance, or maybe an altered respiratory system and more external bodily defenses to dust and soil inhalation.

Eyes (due to atmosphere):

In space, astronauts commonly experience Spaceflight Associated Neuro-Ocular Syndrome (SANS) with swelling in the head and inflammation with the eyes. According to Ross Either, a proposed ingredient to these symptoms in microgravity could be from increased cranial pressure. The causes and effects of this are still being researched. However, humans on Mars would also notice dimmer sunlight and increased radiation; through evolution, humans might adapt to these two specific factors such as increased eye protection, as well as larger eyes for the decreased sunlight (although that might not be the case).

Sound (behaves differently due to atmosphere):

Humans born on Mars, Martians, might develop better hearing due to the way sound is impacted by Mars’s atmosphere (from the physics equations, speed of sound is directly proportional to the square root of temperature, and inversely proportional to square root of pressure). The speed of sound and loudness both decrease on the red planet because of a colder environment and less-dense atmosphere. In simple terms, you would need to shout louder for someone to hear you the same on Mars, as if they shouted regularly on Earth.

Temperature Changes (much colder at night):

Compared to Earth, humans will experience drastically colder temperatures on Mars, especially during the night. However, this condition is easily manageable compared to the others listed above if technology was available. In the long run, however, I believe humans would struggle (to death) to continue reproducing under such cold temperatures without proper warming.

Yet, for the sake of this article, let’s assume humans did survive and reproduce under these conditions. According to “How Ancient Humans Came to Cope with the Cold,” by Laura Buck and Kyoko Yamaguchi, they noted that a “fossilized hominin shin bone from Boxgrove is robust compared to living humans, suggesting it belonged to a tall, stocky hominin. Larger bodies with relatively short libs reduce heat loss by minimizing surface area.” So on Mars, humans might develop similar features, and probably insulation through fat as well. However, with a proper diet, clothing, and other factors, survival in the cold without such biological changes is possible. Granted, Mars would reach much colder temperatures than the Arctic. 

Ultimately, Mars will present countless challenges to humans. And even if the horrific use of animals to test the influence of Mars becomes a method to ensure human safety, there’s no definitive truth until it happens. My prediction: by the time multi-planetary tourism becomes a reality, humans visiting Mars will not recognize those living there.