Spreading life to other planets. How can we adapt them to sustain terrestrial biosphere?
The prospect of setting permanent bases on other planets is very exciting, to say the least. However, there is something that is even more interesting – terraforming those planets and setting up permanent colonies on them. In my previous article about the Moon, I have briefly covered the possibility of creating underground colonies on the Moon. Those would provide humongous protection against radiation and meteoroids. However, the next step would be reshaping the planet’s surface in order to make those planets completely habitable for human life. This would go as far as recreating the flora and fauna in a contained space. Which is extremely interesting, since we would bring the terrestrial samples and adapt them to different planets. We would likely see our flora and fauna develop and adapt to a new environment. The process would most certainly involve a considerable effort in adapting the life to the planets where it had barely existed in developed form and reshaping the local environment to sustain it. This would rely upon getting enough water and air to sustain it. As well as adapting to different soil than the one we have here on Earth as well as an artificial environment. The developments achieved in that way would allow us to spread humanity farther to other planets as well as develop some fascinating technologies that would be applicable here on Earth. First, we will take a look at the current characteristics of planets that can be potentially colonized, in order to determine how habitable they are and how they can be made habitable.
Mars has nearly equal day length as we have here on Earth. However, it takes 687 days for Mars to revolve around the sun, compared to our terrestrial 365 days. The axis has 25 degrees tilt which is near 23.5 of that of our Earth. However, its orbit is more elliptical, making seasons last twice as long. The most noticeable difference is that the atmosphere is extremely thin. It is also 95 percent carbon dioxide. With the average atmospheric pressure on Mars being 7.5 millibars, compared to 1,013 millibars on Earth. On top of that, there is harmful radiation that bombards the planet. Due to those factors, Martian weather is vastly different from ours. It is an extremely cold planet with an average temperature around minus -80 degrees Fahrenheit. Temperatures can dip to minus -225 degrees Fahrenheit around the poles. Periods of warmth are very brief – with highs that can reach 70 degrees for a brief time around Noon at the equator in the summer. Rain is non-existent on Mars and the water exists in the polar caps and quite likely in the underground reserves.
Which planets are most suitable?
The polar ice deposits are something that is widely known. However, the underground reservoirs also exist on Mars. The recurring slope linear (RSL) streaks would serve as evidence for that. Previously scientists have estimated that they are caused by transient flows of briny water at, or just beneath, the Martian surface. "We suggest that this may not be true," study co-author Essam Heggy, a research scientist at the University of Southern California (USC) and NASA's Jet Propulsion Laboratory in Pasadena, said in a statement. "We propose an alternative hypothesis that they originate from a deep pressurized groundwater source, which comes to the surface moving upward along ground cracks." The aquifers feeding the RLS lie about 2460 feet (750 meters) underground, according to the new study. Abotalib and Heggy found a spatial correlation between RSL and tectonic and impact-related faults – features that could facilitate the movement of water from deep underground to the surface.
This is very similar to the water movement that we can see here on Earth: "The experience we gained from our research in desert hydrology was the cornerstone in reaching this conclusion," Abotalib said in the same statement. "We have seen the same mechanisms in the North African Sahara and in the Arabian Peninsula, and it helped us explore the same mechanism on Mars. The system shuts down during winter seasons, when the ascending near-surface water freezes within fault pathways, and resumes during summer seasons when brine temperatures rise above the freezing point." On July last, year satellites have also found a large underground lake under the Mars’ South Pole. About 12 miles across, hidden under a mile of ice.
Scientists have offered some evidence for such reservoirs, as well as strong amounts of water on the planet. Hopefully, we will find out more about the water reservoirs on Mars. And once their existence is proven and exact location is found we will be able to proceed to establish the permanent bases. In addition, those can be developed into planetary domes afterward. Potentially, a system of surface domes with enough space to support not only a habitable colony but have a self-contained biosphere. This may be at a more distant point of time. However, the precursors for it, such as sustainable water, oxygen supply, and greenhouses can be established with the first planetary bases.
There are also giant dust storms on Mars that are a considerable hazard. At times, those can last for months, blanketing the entire planet. Turning the sky hazy red. Giant dust devils often kick up the oxidized iron dust that covers Mars’ surface. It is also a permanent part of the atmosphere, with higher amounts of it in the northern fall and winter and lower amounts in northern spring and summer. The dust storms are the largest in the solar system.
At times though it even snows on Mars. With Martian snowflakes, made of carbon dioxide, with very small particles falling down, creating a fog effect. Rather than appearing to fall from the sky, as our terrestrial snow does. The north and south polar regions are both caped in ice with much of it consisting of carbon dioxide, instead of water. “During winter, the temperatures in the polar regions are cold enough for the CO2 in the atmosphere to condense into ice on the surface. The CO2 then sublimates off the ice cap in the spring and summer, returning to the atmosphere,” NASA stated. “In the northern hemisphere, the CO2 ice cap completely vanishes in the summer, a small CO2 covered ice cap survives; this perennial ice cap is offset from the South Pole. This cycling of CO2 into and out of ice on the surface changes the atmospheric mass by tens of percent over the course of a Martian year.”
In regards to the Moon, I would recommend the reader to refer to my previous paper to get a broader understanding of all environmental factors and necessary component of establishing a lunar settlement. However, I will briefly outline the most important environmental factors. First of all, there is a problem with radiation. That is threefold. This includes solar rays, solar winds, and cosmic rays. All of those combined can contribute to a large amount of radiation – 30 rem/year that is well above what an average radiation worker receives (5 rem/year). While the general public norm is as low as 0.5 rem per year. This is coupled with the solar flares that can deliver up to 1000 rem. Those flares thankfully happen only a few days per 11-year cycle. However, the cosmic rays are constant. Therefore, the astronauts are exposed to a constant influx of radiation on the lunar surface. Making it a permanent factor that has to be dealt with.
Another major hazard would be meteoroids that can bombard the lunar surface from time to time. However, it is somewhat easier to deal with. Particularly if we consider shelters and vehicles. There are also considerable temperature fluctuations. From 100 C to -173 C. The Moon also tilts on about 1.54 degrees. That is far less than 23.44 degrees axis of our Earth. Most of the lunar surface is made up of the heavily cratered terrain, rich in mineral – ‘plagioclase feldspar’ and known as the lunar ‘highlands’. The uncompacted pockets of regolith go as deep as 10-20 feet and can be easily dug up in the same place to create lunar shelters in the smallest amount of time.
The smaller portion of the lunar surface consists of basaltic lava flows and is better known as the lunar ‘maria’. It is mainly on the Earth-facing side. This portion is geologically younger and has been cratered far less. The regolith is much shallower here, with only 4 to 5 meters depth. The meteoroids hitting the lunar surface are probably one of the greatest colonization hazards. Those can even form large craters periodically. This would be the greatest potential threat to any lunar colony. There is also a splash from those impacts that can be damaging as well.
Currently, there has been a successful attempt to grow the cotton seeds on China’s Chang’e 4 Moon lander. The mission became the first touch down on the surface of the far side of the Moon in January 2019. Designed to study the lunar surface and geology of the Von Karman crater. Together with the scientific instruments, the lander carried a sealed container with a biosphere experiment. This experiment contained soil and cotton, rapeseed, arabidopsis and potato seeds. This was the first time that biological matter was grown on the Moon. Growing inside a seven-inch tall canister on the lander that supplies the organisms with enough air, water, nutrients, and controlled temperature and humidity, allowing them to grow.
As previously mentioned, one of the main challenges for both habitation and plant growth is the constantly changing temperature of the Moon. Those go as low as -173 (-279.4 Fahrenheit) and as high as +212 (413.6 Fahrenheit) degrees Celsius.
It should be possible to obtain all of the necessary nutrients required for the plant life from the lunar soil. Hydrogen, carbon, and nitrogen will be extractable by heating it. Once the necessary conditions are created, the plants should be able to adapt and grow in the lunar ground.
There are two more options for potential colonization. However, those are farther away and are not in the direct plans of the current space programs. Those are Venus and Titan. First of all, the Venusian year is around 225 Earth-days long. This might seem short, though the time from one sunrise to the next is only about 117 Earth-days long. The atmosphere is 96.5 percent carbon dioxide with 3.5 nitrogen, minor amounts of sulfur dioxide, argon, water carbon monoxide, helium, and neon. The magnetic field is only 0.000015 times that of Earth's field. Venus crust is mostly basalt and is estimated to be six to 12 miles (10 to 20 km).
The Venus’ sky gets covered by clouds every four Earth-days, driven by hurricane-force winds going as fast as 224 mph (360 kph). This super-rotation of the planet’s atmosphere is 60 times faster than the rotation of Venus itself and is one of the Venus’ biggest mysteries. The winds at the planet’s surface are much slower, estimating just a few miles per hour. The Venus Express spacecraft has all found evidence of lightning on the planet. It is unique since it is not associated with clouds of sulfuric acid. Scientists are excited by these electrical discharges because they can break molecules into fragments that can then combine with other fragments in unexpected ways. A long-lived cyclone on Venus that was first observed in 2006 is in constant flux, with elements constantly breaking apart and reforming.
The clouds also carry signs of meteorological events known as gravity waves, created when winds blow over geological features, causing rises and falls in the layers of air. “Unusual stripes in the upper clouds of Venus are dubbed "blue absorbers" or "ultraviolet absorbers" because they strongly absorb light in the blue and ultraviolet wavelengths. These are soaking up a huge amount of energy — nearly half of the total solar energy the planet absorbs. As such, they seem to play a major role in keeping Venus as hellish as it is. Their exact composition remains uncertain; some scientists suggest it could even be life, although many things would need to be ruled out before accepting that conclusion.”
Titan is another interesting prospect for a future settlement and further colonization. It is Saturn’s largest moon, an icy world whose surface is completely obscured by a golden hazy atmosphere. Titan is the second-largest moon in our solar system. Only Jupiter’s moon – Ganymede is larger, by a mere 2 percent. Titan is even larger than Mercury.
It is unique since it is the only moon in the solar system with a dense atmosphere, and it is the only world besides Earth that has standing bodies of liquid, including rivers, lakes, and seas, on its surface. Its atmosphere is primarily nitrogen, plus a small amount of methane. Thus, it is the only other place in the solar system known to have an earthlike cycle. With liquids raining from the sky, flowing across its surface, filling lakes and seas. It is also likely to have a subsurface ocean of water.
Because of its distance from the sun, the sunlight is 100 times fainter than here on Earth. Titan takes 15 days and 22 hours to complete a full orbit of Saturn. While Saturn takes 29 Earth years to orbit the Sun and Saturn’s axis of rotation is tilted like Earth’s, resulting in seasons. However, those seasons last more than seven Earth’s years. The surface of Titan is the most Earthlike from the entire solar system. However, its temperature is so low (-290 degrees Fahrenheit/ -179 degrees Celsius) that the ice plays a role of solid rock. It may have volcanic activity as well. With liquid water “lava” instead of molten rock. Its surface is sculpted by flowing methane and ethane, which carves river channels and fills great lakes with liquid natural gas. With no other places, except for Earth, having that kind of activity. “Vast regions of dark dunes stretch across Titan’s landscape, primarily around the equatorial regions. The "sand" in these dunes is composed of dark hydrocarbon grains thought to look something like coffee grounds. In appearance, the tall, linear dunes are not unlike those seen in the desert of Namibia in Africa.” The surface has no visible craters, just like our Earth, due to the natural activity that erases them.
Titan has a thick atmosphere. Which is about 60 percent greater than on Earth. It extends 10 times higher than Earth’s for nearly 370 miles (600 kilometers) into space, due to its lesser gravity. It composes of 95% nitrogen and 5% methane. “High in Titan’s atmosphere, methane and nitrogen molecules are split apart by the Sun's ultraviolet light and by high-energy particles accelerated in Saturn's magnetic field. The pieces of these molecules recombine to form a variety of organic chemicals (substances that contain carbon and hydrogen), and often include nitrogen, oxygen and other elements important to life on Earth.” Some of the compounds produced by that splitting and recycling create a kind of a smog – thick, orange-colored haze that makes the moon’s surface difficult to view from space. Methane condenses into clouds that occasionally drench the surface in methane storms.
Where all that methane comes from is a mystery. Since the sunlight constantly breaks it down in the atmosphere, there must be some source that constantly replenishes it. With researchers suggesting that it can be belched into atmosphere by cryovolcanism. With volcanoes releasing chilled water instead of molten rock lava.
Mars and Moon. How can we start
First of all, we could say that the initial steps to terraforming both Mars and Moon were done by successfully growing the plants on the international space station, as well as seeds that were sent to the lunar surface on a Chinese mission. This may not seem much, but it proves the possibility of it.
Currently, NASA scientists at the Kennedy Space Center in Florida are collaborating with the University of Arizona to help create sustainable resources for deep space missions. "We're working with a team of scientists, engineers and small businesses at the University of Arizona to develop a closed-loop system," he said. "The approach uses plants to scrub carbon dioxide, while providing food and oxygen." Their prototypes include inflatable, deployable greenhouse to support plant and crop production. The water for it will be taken from the regolith surface and then oxygenated and given nutrient salts that will continuously flow across the root zone of the plants and return to the storage system.
The next step of it would be to use additional lunar greenhouse units for specialized testing to ensure the system will adequately support a crew of astronauts working on either lunar or Martian surface. "We will develop computer models to simulate what we're doing to automatically control the environment and provide a constant level of oxygen," Giacomelli, a professor in the University of Arizona’s Agricultural and Biosystems Engineering Department says.
The developed prototypes are cylindrical – 18 feet long and more than 8 feet in diameter, created by NASA’s partners - Sadler Machine Company. Similarly to all of the surface station units for astronauts, the greenhouse units would likely be buried under surface soil of regolith, thus requiring specialized lighting. "We've been successful in using electric LED (light emitting diode) lighting to grow plants," Dr. Ray Wheeler (lead scientist in Kennedy Advanced Life Support Research) said. "We also have tested hybrids using both natural and artificial lighting." The solar light for it can be captured with light concentrators that track the sun and then convey the light to the chamber using fiber optic bundles.
One of the most interesting greenhouse projects right now is EDEN ISS space greenhouse: “Future, long-term crewed space missions will require locally grown food. EDEN ISS has proven the feasibility of a space greenhouse in the Antarctic and thus demonstrated that this technology could also be used to produce food on the Moon and Mars,” says Hansjörg Dittus, DLR Executive Board Member for Space Research and Technology. “Overall, we have produced 268 kilograms of food in an area of only 12.5 square meters over 9.5 months, including 67 kilograms of cucumbers, 117 kilograms of lettuce and 50 kilograms of tomatoes,” says Zabel. “The taste and smell of fresh vegetables have left a lasting impression on the overwintering crew, and have clearly had a positive effect on the team’s mood over the long period of isolation.”
The company has previously created numerous greenhouse projects in the Antarctic. The information that they have gathered is an outstanding example of how we can also conduct research into other forward-looking issues. The ability to explore regions that are hostile to human life brings us closer to human spaceflight. Not to mention that having a fresh supply of fruit and vegetables is essential for a healthy stay on a lunar or Martian surface.
They prioritize reducing the workload in their greenhouses in order to save the valuable time of the astronauts. They have also successfully applied a remote control technology. “The test run was a complete success. Now, the current AWI overwintering crew is continuing the operation of the greenhouse, with strong support from the control center in Bremen, where we monitor as much as possible from a distance. The procedures developed last year are currently proving their worth in minimizing the crew’s workload and keeping the processes as simple as possible.”
Similar modules can be also incorporated into larger Martian and lunar modular bases. Particularly if we are talking about a set of livable modules with living rooms, laboratories and sleeping rooms that were mentioned in my previous article on the Moon settlements. And by developing those bases farther we can actually start approaching terraforming. By farther expanding lunar basses until they reach the scale of lunar settlements. Some technologies and ideas can help us with it.
An interesting recent development was done by Harvard University, who has devised a way to terraform Mars by placing sheets of silica aerogel on the planet’s surface to warm it up. The “silica aerogel greenhouse shields” were devised by Robin Wordsworth, Ronald L Kerber and Charles Cockell. Those shields are intended to replicate the greenhouse effect. They would be made from silica aerogel, transparent material with low thermal conductivity.
And by spreading them across the surface it would be possible to recreate the greenhouse effect by trapping heat that would warm the ground below. A thin layer of this gel (97% of which is air) is enough to raise the temperature of the Martian surface to above the melting point of water. Additionally blocking the hazardous ultraviolet radiation and allowing enough visible light for photosynthesis to occur. "We show that widespread regions of the surface of Mars could be made habitable to photosynthetic life in the future via a solid-state analogue to Earth's atmospheric greenhouse effect," says the development team. The practicality of such shields lies in their ability to be applied to specific areas and then be easily scaled up. They can range from a few square meters to entire planetary regions. “The scientists conducted a number of experiments in Mars-like environments to test the warming potential of the sheets. It found that the layers of silica aerogel measuring two to three centimeters thick were enough to warm the surface to the melting point of liquid water or higher. Other tests that explored the effects of the sheet covering over time found that they could warm up several meters below surface level to allow for liquid water for years after years.” Also, the research has estimated that there is a number of nutrients readily available on Mars, with even greater amounts of iron and sulfur than those found on Earth. The main challenge would be finding ways to manufacture the product on site.
Another very interesting idea of terraforming Mars and populating it with life involves introducing terrestrial bacteria on Mars. It derives from the fact that our own Earth had its first life in a single-celled form that survived on the diet of sulfur. Most of our atmosphere at that time consisted of carbon dioxide, methane, and other greenhouse gases, leaving the air toxic for us and most of the modern flora and fauna. “Then, about 2 and a half billion years ago, something happened. With what amounts to a snap of the fingers in geologic timescales, the atmosphere was pumped full of oxygen in what we call the Great Oxygenation Event. The abundance of oxygen meant that new, more diverse kinds of life could take a hold on the young planet, such as Eukaryotes. Fast-forward a few billion years, and complicated, multicellular life like ourselves are walking around the planet.” It is most likely that most of that oxygen came from cyanobacteria – tiny blue-green, single-celled life that first had photosynthesis. With oxygen being a byproduct of their life cycle. Thus, the scientists hope to recreate the Great Oxygenation Even with the help of those bacteria.
As previously mentioned, Mars has an atmosphere that is 95 percent carbon dioxide, providing half of the necessary nutrition for cyanobacteria. The other ingredient – water, would be harder to come by, but it still exists on Mars in the form of ice and hopefully in beneath the Martian surface. We would start with areas where we know liquid water exists and dump many cyanobacteria there. Together with some other microbes that produce greenhouse gases. NASA has already started with preliminary tests, the Mars Ecopoiesis Test Bed is a proposal for a device to be included with the future robotic missions to Mars. It resembles a drill with a hollow chamber inside. It would bury itself in the Martian soil, preferably somewhere with liquid water. Then it would release a container full of cyanobacteria into the chamber with sensors detecting whether microbial life would produce oxygen or other byproducts. It was already tested in a simulated Martian environment here on Earth, yielding positive results.
A more advanced approach to terraforming that could potentially be the next step and would still be resistant to both radiation and meteoroids. Though it should be established only after the initial base was developed to maximum capacity and, preferably, after a fully-fledged underground base has been established. Those would be about creating large-scale greenhouse domes. They would serve a two-fold purpose. First, providing a constant supply of food to the inhabitants.
Second, being able to make the first considerable advancements in planting the flora and recreating the near-natural cycle of Earth. With enough oxygen, moisture and right temperature of the air to sustain a sizable green land. Thus, we would see how the plant and animal life would adapt to the Martian environment. This stage would most likely be the culmination of colonization efforts in the foreseeable future. With subsequent steps involving recreating the magneto-sphere near to what it is on Earth as well as an atmosphere similar to ours. Coupled with enough water and oxygen to completely reshape the planet. This would require technologies that we do not possess yet.
The term that is used to describe the greenhouses on other planets is paratettaforming. The basic idea is about building a sustainable eco-system capable of supporting a hospitable atmosphere and life-cycle for long-term habitation. And even though terraforming may seem like a distant dream, converting a portion of another planet is far more reachable and feasible. “The idea is to create an enclosure around a certain part of a planet to alter the environment within. This concept was originally coined by British mathematician Richard L.S. Taylor in a 1992 study, "Paraterraforming – The world house concept. Using this method, sections of a planet that are otherwise inhospitable or cannot be terraformed as a whole could be made suitable for human habitation. It would be especially useful on planets or moons that had little to no atmosphere, and where much of the surface is subject to lethal levels of heat and radiation.” Hypothetically, such colonies would be able to have enough resources for thousands and even hundreds of thousands (if developed to a larger capacity) inhabitants.
With all likelihood, such a process would involve 3D printing and In-situ Resource Utilization (ISRU) (use of the local resources to manufacture everything) at least at the early stages. Including building materials, energy, breathable air, and potable water. The core idea of it is to create enclosed settlements that could be built on-site without the need to import a lot of prefabricated parts or building materials. Once that is done they would be able to achieve a degree of self-sufficiency. The bases would need to have enough protection against radiation and extreme conditions, not to mention close proximity to resources and energy. The bases would have to be built in locations that afford natural protection against meteoroids (and dust storms in case of Mars) and are also resource-rich.
There is also a possibility of using magnetic shielding. The concept was proposed by the civil engineer – Marco Peroni at the 2018 American Institute of Aeronautics and Astronauts (AIAA) SPACE and Astronautics Forum and Exposition. It included a modular-based architecture, with hexagonally-shaped units being grouped together in a spherical configuration beneath an apparatus that resembled a torus. Which would be made of high-voltage electric cables, generating an electromagnetic field to protect against radiation. It would be capable of generating a magnetic field of 8 microteslas (0.08 gauss). Compared to Earth's 25 to 65 microteslas (0.25 to 0.65 gauss). The apparatus would need to be strengthened further in order to keep the inhabitants safe, but it would still be in the early stages of development.
It is very similar to Solenoid Moon-base concept, proposed by Peroni in 2017. Which was about transparent domes enclosed by a toroid-shaped structure and high-voltage cables as well.
The initial construction would most likely rely upon regolith and aluminum insulation. This combination would be both cheap and effective for radiation and meteoroids protection. In addition, those would be scalable and it would be possible to expand such domes as a settlement develops. There are propositions and plans for creating large transparent domes. However, it is extremely important to consider all of the environmental factors before starting a large-scale production along with the availability of the local resources. Not to mention that we are very likely to see new materials and technologies developed that would prove to be more efficient as construction materials on other planets. Continuous progress in space exploration should bring us closer to terraforming. Even though we are very far from it right now we can possibly start with adapting isolated portions of other planets and hopefully learn how we can transform them in their entirety.