This summer marks the 50th anniversary since Neil Armstrong and Buzz Aldrin became the first humans to set their feet on the surface of the Moon. This has triggered a plethora of questions about our future on the Moon, including the question of whether we are going to plant a human colony on the Moon, whether there will be lunar cities and, if so, when? Published by CityLab, the aforementioned article explains a range of issues, and I was honored to be quoted alongside other futurists, such as Andy Weir, author of The Martian, and a newer novel, Artemis. The novel Artemis shares the name with NASA’s new Artemis Program to return humans to the Moon, this time with both female and male astronauts. As with Project Apollo, the reference is right out of Greek mythology. Artemis, who was associated with the Moon, was the twin sister of Apollo, who was associated with the Sun. Thus, the new program has a name that not only is more appropriate for the Moon, but also is feminine –even if Artemis was, let’s say, not a very friendly goddess.
Project Artemis, along with talk from private companies such as SpaceX, about upcoming colonies on the Moon and Mars, raises the question of whether we are ready yet. It’s a question that must move to center stage, since colonization of a new environment is a bigger step than building a scientific base, like the bases that exist in Antarctica. A lunar colony means a city and schools. A colony means children. A colony means people getting pregnant and having babies. And that means that we need to know if pregnancy will even work in the lunar environment, where the gravitational pull is only about 17 percent of what it is on the surface of Earth. Knowing whether pregnancy will be safe on the Moon, in turn will affect our assessment of the possibility of human pregnancy on Mars, where gravity at the surface is about 38 percent than of Earth.
To be sure, there is a range of health issues connected with human exploration of space environments. Exposure to space radiation is potentially dangerous, an issue that could impact human fertility and the chances of congenital malformation, as well as the risk of cancer and other diseases. But on the Moon and Mars, colonists would live in underground environments, such as in lava tubes, caves, or craters with excellent shielding against galactic cosmic radiation and solar particle events (storms of radiation from the Sun). So, actually, the biggest physical health question is the gravity question.
Based on research using various laboratory animals, including fruit flies, frogs, quails, and rodents in low Earth orbit (LEO) flights, we have learned that the gravitational vector –the direction and strength of gravity– is a vital influence prior to pregnancy, during development in eggs or the uterus (depending on the animal), and prior to implantation of the blastocyst into the endometrium of the uterus in mammals. Because we have not been doing research on the Moon for nearly the last half-century, we could produce lunar gravity only by carrying centrifuges into LEO, but we have had only very limited, very small centrifuges, so we only know about the effects of weightlessness, not the events of fractional gravity, meaning gravity that is a certain fraction of what it is on Earth.
Moreover, based on the weightlessness research, there is reason to worry that that implantation and pregnancy may not be flawless in a lunar colony. We know, for instance, that gravity has a strong influence on gene expression, which in turn affects embryological development, including of very specific phenomena. One notable example is the vestibular system in the inner ear. Developing in weightlessness in laboratory animal embryos, this system develops in a way that is most useful for registering head movements in weightlessness, without causing nausea. How, then, would the system function on Earth in a child who was born in weightlessness who goes to visit Earth, or in a child who visits Earth who was born on the Moon? We simply do not know the answer. There also is evidence from research in LEO of problems with the development of heart muscle cells that develop in weightlessness. Finally, there is evidence of possible reduced sperm counts and the ability of sperm to fertilize ova.
Would the Moon’s 17 percent of Earth gravity be enough for fertilization and pregnancy to proceed normally in human colonists? To find out, scientists will need to conduct research for many years in a situation similar to an Antarctic base, where people rotate in and out for a few weeks or months but do not actually start families there are colonize the place, until we know.
Several scenarios are possible. Human reproduction might work normally in lunar gravity. On the other hand, there might be reduced human fertility, but then lunar colonists could compensate by having children when they are younger, say around 18 or 20 years of age, before beginning their higher education. In such a case, grandparents and the lunar community as a whole would step in to help raise children while young parents are in college and graduate school.
There is still another possibility, namely that there is a high rate of birth defects, or that fertility is greatly reduced to the point that reproduction is not viable. In such cases, colonists may consider genetic modification of embryos, and perhaps use of artificial wombs, rather than canceling the colonization project altogether.