This was originally a formal analytical report which I wrote for a technical communications class. More research was put in to this report than in anything I have ever written, though my teacher seemed to think that my sources are not credible and that the whole idea was impossible and "science fiction." There were originally a few images withing the text, but I cannot figure out how to upload them to my satisfaction on this site. The captions for the images are still present within the text, so hopefully you can use the links in the captions to find the pictures.
INTRODUCTION
The idea of space exploration and colonization has captivated the human race ever since we could first imagine a place outside of Earth. When Neil Armstrong became the first person to step foot on the Moon in 1969, the whole world watched him say that now famous line: “That's one small step for man; one giant leap for mankind.” Now, with our home planet rapidly approaching its own carrying capacity* for human life, we must make what is possibly the biggest step in human history and become a multi-planet species.Of course, we do not currently have the technology needed to sustain life for millions in either orbital satellites* or bases on other celestial* bodies. What we do already have, however, is the capability to take a powerful natural force and wield it to begin to make Mars a permanently habitable place for human life. This force is, of course, is the Greenhouse Effect (See Appendix A).
In recent years, scientists have noticed that an increase in our planet's surface temperature has lead to climate changes throughout the world. Some of the most drastic changes include: “Glaciers are melting, plants and animals are being forced from their habitat, and the number of severe storms is increasing.” (An Inconvenient Truth) Why is our planet suddenly undergoing these massive climate changes after millions of years of relative stability? Most scientists today believe that it is because of the rapid increase in our production of greenhouse gases* (An Inconvenient Truth). At this point, you may be asking yourself, “What does any of this have to do with living on Mars?” The answer to this question is simple: the very principles that make it dangerous for us to use CFCs* and burn fossil fuels (An Inconvenient Truth) here on Earth, are what will allow the human race to turn Mars from a dead frozen planet, into one capable of supporting life.
Since a project of this magnitude has never been completed in human history, any timetable given would, of course, be purely hypothetical. The number of possible variables is so staggering that it would be completely unethical for me to present an accurate time line for the completion of this project. Therefore, I have decided to comprehensively cover:
- The specific greenhouse gases that should be used for maximum efficiency
- All stages involved in raising the Martian surface temperature with greenhouse gases
- How to release these gases into the Martian atmosphere*
Since I am obviously not a qualified expert in any of the fields involved in this project, the information I have compiled in this report comes from a wide array of astronomers, environmental scientists, geologists, astrobiologists*, chemists, and physicists.
COLLECTED DATA
The amount of greenhouse gases in any planet's atmosphere is one of the biggest factors in determining how much of heat will remain with that planet, and how much will be lost to space (Refer to Appendix A). We now know that carbon dioxide (CO2) is a powerful greenhouse gas, but there are also many others, both natural and man-made, which vary in their effectiveness.
Natural Greenhouse Gases
Many of the gases that are naturally in our atmosphere function as greenhouse gases. Possibly the most well-known of these is carbon dioxide.
CO2 Carbon dioxide is a gas which is found throughout our solar system and is possibly the gas that has had the biggest impact on the formation of life on Earth due to its large role in the Greenhouse Effect. Carbon dioxide is especially prevalent on Mars, composing about 95% of the Red Planet's atmosphere (Darling). Why then is Mars not a warm, inhabitable planet if its atmosphere is made up of mostly carbon dioxide? Scientists believe that Mars was once a place capable of supporting life, but somehow underwent a reverse Greenhouse Effect, cooling the planet enough to literally freeze a large amount of this carbon dioxide into dry ice (Darling). When the majority of the planets gaseous carbon dioxide became dry ice,* the atmosphere thinned significantly, reducing the effectiveness of the Greenhouse Effect. It is therefore believed, that an increase of as little as 4 degrees Celsius would be enough to evaporate much of this dry ice, allowing it to rejoin the Martian atmosphere and once again add to the Greenhouse Effect (Hurtak).
H2O Water vapor also works as a greenhouse gas. On Earth, it is estimated water vapor contributes to roughly 60% of our Greenhouse Effect, compared to only 20% by carbon dioxide. (Uherek) This is because the Earth is made up mostly of water. On planets with less water, water vapor plays much less of a part in the Greenhouse Effect. For instance, on Mars, though there is an abundance of water throughout the planet, most of it is permanently frozen as ice, and therefore very little of it exists in the atmosphere as water vapor (Mars, Water On). However, both Earth-based and Mars-orbiting telescopes have determined that water vapor exists in small amounts on Mars in the forms of clouds and fog (Mars, Water On). It is believed that once Mars is made warmer, much of the ice that exists all over the planet will melt into water, forming massive oceans, much like we have on Earth.
CH4 Methane is another important natural greenhouse gas both on Earth and Mars. While both water vapor and carbon dioxide are cycled constantly through the water and carbon cycles, methane remains in a planet's atmosphere for only about 9 to 15 years before being broken down by radiation from the Sun (EPA). However, methane is also more than 20 times more effective than carbon dioxide as a greenhouse gas over a hundred year period (EPA). On Earth, the majority of methane is produced through the decomposition of dead plants and animals. A significant increase in the amount of methane on our planet in recent years is linked to human activities such as coal mining, agricultural production, and landfills (EPA). Trace amounts of the Earth's total methane production comes from volcanic activity. While Mars does contain several volcanoes (including Olympos Mons, the largest volcano in our solar system) other gases, such as sulfur, which are discharged during volcanic activity are not found on Mars, leading to much debate over the Red Planet's recent methane production (BBC News).
Man-Made Greenhouse Gases
While our planet evolved to the comfortable temperature it is today through natural greenhouse gases, this process took millions, if not billions of years to occur naturally. It is completely unacceptable for humans to wait that long for the Greenhouse Effect to transform Mars into a habitable place for us. Since we are now just learning about the effects of releasing too many greenhouse gases into our own atmosphere, it has been theorized that the introduction of just a few of these man-made greenhouse gases could cause a runaway greenhouse effect on Mars, changing the whole planet's climate in a much shorter time period. Many of the man-made greenhouse gases whose use has been restricted on Earth because of environmental hazards will help drastically shorten the time-period involved in warming Mars through the Greenhouse Effect.
CFCs Chlorofluorocarbons are any gasses with a mixture of chlorine, fluorine, and carbon. Developed in the 1930s, CFCs have an incredible array of desirable traits. They are non-toxic, non-flammable, and non-reactive with other chemical compounds (CIESIN). Also, their stable thermodynamic principles allow them to be easily converted from gas to liquid, or liquid to gas, making them perfect for use as a coolant in refrigerators, air conditioners, and aerosol propellants (Hopwood). CFCs by themselves are not particularly powerful greenhouse gases. They do, however, add to the Greenhouse Effect by breaking down ozone* (O3) in the atmosphere. The Ozone Layer around the Earth helps filter excess radiation, specifically ultraviolet radiation (UV), from the Sun. When CFCs interact with radiation from the Sun, they rise into the upper atmosphere of the planet and react with the ozone, disintegrating the CFCs and converting the ozone into oxygen (O2), which does not filter ultraviolet radiation (Khemani). This adds to the Greenhouse Effect because more radiation from sunlight is then making it to the Earth's surface and being trapped by other greenhouse gases in the atmosphere. Because of this, CFCs can be used to raise a planet's temperature, but are not ideal.
HFC*s Hydrofluorcarbons are similar to chlorofluorocarbons in that they are composed of fluorine and carbon, but rather than having chlorine like CFCs, HFCs have hydrogen. Used in refrigerators and air conditioners, HFCs have many of the same properties as CFCs and so are often used as a substitute. The main difference between HFCs and CFCs is that HFCs do not react with ozone (Hopwood). They are, however, more powerful as greenhouse gases than CFCs, and because of this, they are regulated almost as strictly as CFCs themselves. While this may be a problem here on planet Earth, HFCs are ideal for use in increasing the Greenhouse Effect on Mars because they do not deplete ozone, and are anywhere from 4,000 to 10,000 times as effective as carbon dioxide as a greenhouse gas (Greenhouse Gases: Some Definitions).
PFC*s Perfluorcarbons are incredibly potent greenhouse gases that are mostly produced as byproducts of aluminum smelting (Greenhouse Gases: Some Definitions). PFCs are composed solely of different combinations of fluorine and carbon, both of which are key components of the majority of potent greenhouse gases. While they have many of the same properties and uses as CFCs and HFCs, they are more expensive to produce, and as a result are not used as commercially. One specific PFC, perfluoropropane (C3F8), is currently regarded by astrobiologists as one of the ideal greenhouse gases to be used on Mars (Young). It has a lifespan of 2,600 years, does not react with ozone, and is 7,000 times more effective as a greenhouse gas than carbon dioxide (Perflurocarbons [PFCs]).
Methods of Releasing Greenhouse Gases Into Martian Atmosphere
There are many proposed methods of releasing greenhouse gases into Mars' atmosphere. Each method would potentially release different types of greenhouse gases, and therefore a combination of all would likely be the most effective and produce the greatest results.Drilling to Release Water Vapor Many astronomers today believe that while liquid water no longer exists on the surface of Mars, it may remain under the surface where high pressure and proximity to the planet's core may have kept it from freezing (See Figure 1) (David).
Figure 1 Cross Section of Martian Surface
Source: “The Quest to Terraform Mars.” by: D.M. Hurtak, M.S.Sc. The Academy for Future Science. Retrieved November 22, 2009 from http://www.affs.org/html/the_quest_to_terraform_mars.html
When these pockets of liquid water are drilled into, the high pressure will cause the hot water to shoot to the planet's surface, hopefully evaporating some of Mars' frozen carbon dioxide on the way. Even if no other frozen greenhouse gases are released back into the atmosphere, water vapor will certainly be released from this process, (Hurtak) and the liquid water which will pool on Mars' surface will be constantly recycled throughout the planet due to the Water Cycle. If there are not sufficient amount of liquid water under Mars' frozen surface, drilling could also encounter pockets of trapped greenhouse gases that could be released into the atmosphere (Hurtak).
Orbital Mirrors One method of releasing greenhouse gases into Mars' atmosphere is to warm the Red Planet's south pole in order to melt the dry ice polar caps that have formed. Doing so will release a large amount of carbon dioxide gas into Mars' atmosphere, thickening it by a significant amount. One way of melting this ice cap is to build mirrors which would orbit around mars and redirect sunlight at the Martian south pole. The problems with this plan, of course, are size, cost, and material limitations due to the enormous size the mirrors would have to be in order to be effective. It is estimated that a mirror with a radius of 125 kilometers would be sufficient to melt the area below the latitude of 70 degrees south, but that such a mirror, if made out of a light-weight aluminum-mylar material, would weigh close to 200,000 tons (Zubrin). Such a monstrosity would have to be made in space, as it would weigh far too much to launch from Earth. If the mirrors could be made from ores mined and refined on Mars, their transportation would be a far simpler issue.
Asteroid* Impact The alternative plan for quickly melting Mars' south pole ice cap would be to capture an asteroid and impact the south pole with it. The friction from such an impact would certainly melt the ice cap, but may provide difficulties with the resulting clouds of dust that could develop following the massive impact. The asteroid would most likely have to be captured from the outer solar system, rather than from the nearby asteroid belt, because it would require less force to move an object in the outer solar system since it is farther away from the sun and therefore less affected by its gravity (See Figure 2) (Zubrin)
Figure 2 Velocity Change Required to Transport Asteroids to Mars
Source: “Technological Requirements for Terraforming Mars.” by: Robert M. Zubrin and Christopher P. McKay. Retrieved November 22, 2009 from http://www.users.globalnet.co.uk/~mfogg/zubrin.htm
To make this plan truly effective, an asteroid made largely of ammonia is required as ammonia is a strong greenhouse gas. When the asteroid impacts the southern pole, not only does the frozen carbon dioxide and water melt, but the ammonia from the asteroid also becomes a part of the atmosphere, aiding in the Greenhouse Effect. It is estimated that a single asteroid consisting of 10 billion tons of ammonia would be enough to melt 1 trillion tons of water, raise the entire planet's temperature by 3 degrees Celsius, and additionally, form an ammonia shield that would protect the planet from UV radiation (Zubrin). Since the average lifespan of ammonia is slightly less than a hundred years, more asteroids would need to be imported to Mars in order for this plan to work by itself. This is certainly the fastest method devised for bringing Mars' surface temperature to a habitable level, but it also involves the most amount of risk since each 10 billion ton asteroid would impact the Martian surface with the amount of force of 70,000 megaton hydrogen bombs; (Zubrin) making it almost impossible for there to be any kind of habitation while the process of impacting Mars with asteroids is still going on.
Martian Industrialization A far safer method of releasing greenhouse gases into Mars' atmosphere would be to set up factories that actually create the greenhouse gases on Mars. The main purpose of these factories would be to produce a mixture of CFCs, HFCs, and PFCs which are then released into the atmosphere where they will add to the Greenhouse Effect. This is a more reasonable approach to introducing man-made greenhouse gases to Mars than simply developing them on Earth and transporting them to Mars for several reasons. First, a very large quantity of these gases will be needed in order to quickly produce a noticeable temperature difference and the transportation of such large quantities is unrealistic due to costs and the amount of travel time involved. Second, Establishing factories on Mars before it is ready for human habitation allows us to begin readying the planet for our future occupation. This means there will be minimal time wasted in setting up our habitats once Mars is ready to support life. There are a few different options to consider while determining how best to power these factories since there are no fossil fuels, and there will be limited other resources available for our use on Mars. One possibility it to create nuclear power plants on Mars which will run these factories, and can eventually be used to power other devices. The drawback to this, however, is that thousands of workers are currently needed to run a single nuclear power plant, (Zubrin) and therefore, temporary human habitats would need to be set up, either in orbit or on the surface. Another way of powering the factories is with a combination of solar and wind power. Since we are just now beginning to understand how to effectively tame reusable energy sources, it may be a good idea to invest in as many reusable sources of energy as possible for use on Mars. The downfalls of this idea are the high costs and low amounts of energy generated compared to nuclear reactors.
Methane Producing Organisms Once Mars has been changed enough to support life for even the most basic life forms, primitive bacteria can be imported from Earth in order to organically produce a variety of greenhouse gases including carbon, methane, and ammonia. The recent discovery of methane on Mars suggests that some form of methanogens* may already exist and be producing methane from deep below the Martian surface (Darling). Methanogens are anaerobic*, meaning they can live without oxygen, but being fairly strict anaerobes, they do not survive for very long in environments rich in oxygen. On Earth, they are found living and thriving in some of the most extreme environments, including volcanic hot springs, oceanic volcanic vents, swamps and marshes, and even the stomachs and intestines of humans, cows, and termites (Meeres). Being some of the oldest organisms on Earth, methanogens have adapted to these extreme environments and the many different species of methanogens can be classified based on their environmental preferences. There are: thermophilic*, psychrophilic*, halophilic*, acidophilic*, alkaliphilic*, and hyperthermophilic* (Meeres). The ability of methanogens to live in extreme conditions makes them ideal candidates for introduction to Mars while it is still incapable of supporting more complex life.
Stages of Terraforming Process
While there are a multitude of different plans for terraforming Mars with greenhouse gases, it will be a long and difficult process, possibly taking centuries before humans can live unaided on Mars. The Red Planet will change drastically as the different plans are put into effect, and each major change will allow humans to utilize a different method to make the planet habitable.Current Stage Mars is uninhabitable right now for several different reasons. The atmosphere is about one percent as dense as Earth's, resulting in a surface pressure which is less than one percent of that on Earth (Darling). This thin atmosphere, although made up almost entirely of carbon dioxide, does not effectively use the Greenhouse Effect, trapping only about 5ºC (Darling). The average Martian temperature is -55ºC, but because of Mars' very elliptical orbit, the temperature changes drastically from -133ºC to 27ºC (Darling). Both the north and south Martian poles contain water ice and dry ice, the amounts of which change depending on the season (Darling). It is estimated that a 4ºC raise in Mars' atmosphere would begin a process that would eventually lead to the 55ºC change required for liquid water to exist (Hurtak).
Orbital Mirror and Asteroid Impact Stage The first step to terraforming Mars is to raise the temperature and thicken the atmosphere so that both are similar to the atmosphere of Earth. Any change in the temperature or the density of the Martian atmosphere will cause the other to change as the two factors strongly affect one another because of the Greenhouse Effect. Of the plans covered in this report, the Asteroid Impact and the Orbital Mirror plans are the two most effective and drastic plans. They should therefore, be the first methods used. Construction of a massive mirror should be started within Earth's orbit while an asteroid composed of mostly ammonia is located. The mirror would have to built in space rather than on Earth because it would be too massive to reach the escape velocity required to be free of Earth's gravity. (Zubrin). It would take a great deal of time to find a single asteroid of the proper size (roughly 5 billion tons) and composition in the outer reaches of our solar system, and even more time to capture and redirect one. While an asteroid near to the orbits of Uranus or Neptune would be much easier to move due to their distance from the sun, they would also take longer to arrive at Mars, in some cases up to 50 years (Zubrin). This long period of preparation time would allow for the construction and positioning of the orbital mirror, which would be working to evaporate the water and carbon dioxide ice at Mars' poles, thickening the atmosphere with these two greenhouse gases. As the asteroid impact is a chaotic and potentially dangerous method, the next stages of the terraforming process cannot be launched until after the impact, by which time Mars will already have undergone drastic changes.
Industrialization Stage The impact from an asteroid composed of about 5 billion tons of ammonia is estimated to be enough to melt half a trillion tons of water and raise Mars' surface temperature by 1.5ºC (Zubrin). This plus the amount of carbon dioxide and water evaporated by the orbital mirror will have increased the density of the atmosphere, increasing the surface pressure and the amount of heat trapped in Mars' atmosphere through the Greenhouse Effect. Immediately after the asteroid impact is the ideal time to start the Industrialization plan because the amount of ammonia in the atmosphere from the impact will block UV rays for a little less than a century (Zubrin). Any humans on the planet would still have to wear space suits to combat the low pressure, temperature, and lack of oxygen, but they would not have to worry about being exposed to excess radiation from the sun. When humans arrive on Mars for this step of the process, they should immediately begin assembling the power sources that will be used. With the recent advancements being made in the field of reusable energy, wind or solar power will likely be the main sources of energy on Mars. If this technology has not advanced to the level where it would adequately meet the requirement for use on Mars, then nuclear reactors would have to be built. Reusable energy sources are more desirable than nuclear reactors because they require less maintenance, cutting down on the amount of people required to live on Mars before it inhabitable and the costs involved in transporting, compensating, and providing livable conditions for these workers. Once power sources have been established on Mars, factories whose main purpose would be to release CFCs, HFCs, and PFCs into the atmosphere should be set up. With enough of these factories steadily producing these powerful greenhouse gases, Mars could be transformed into a warm and wet planet in less than a century (Zubrin). When combined with the other methods of releasing greenhouse gases into the atmosphere, fewer factories producing lower amounts of CFCs, HFCs, and PFCs would be needed. Since fewer greenhouse gas producing factories would be needed, some factories could be setup to manufacture drilling equipment in preparation for the next stage. This Industrialization Stage would require a great deal of planning, including massive amounts of training in order to prepare non-astronauts for the harsh conditions of space, and would quite possibly be the most expensive stage overall.
Drilling Stage With the introduction of the greenhouse producing factories on Mars, there would not be a noticeable change in either Mars' surface temperature or its atmospheric pressure. Unlike the first stage, which requires lots of preparation time but has immediate results, both the Industrialization and the Drilling stages need to be in effect for decades before Mars will undergo a noticeable change. Since a large amount of time will be needed for the Industrialization Stage, the Drilling Stage should be put in to effect immediately after the completion of the factories. There are two major benefits of this stage following the establishing of the factories. The first is that this will give the workers who assembled the factories something to do rather than simply being sent back to Earth. The second is that liquid water is believed to exist about 800 meters under Mars' frozen surface (Hurtak); if liquid water is found, it will not only release water vapor into the atmosphere, but also provide a source of fresh water for those living on Mars to use. The drilling equipment would have to either be flown assembled from Earth, or in parts to be assembled in factories upon reaching Mars. Many of the workers who were involved in setting up the factories could be taught to use the drilling equipment under the supervision of astronomers and geologists who determine where to drill in order to release the most greenhouse gases. The Drilling Stage is the least effective stage of the entire terraforming process, but it is also the cheapest and has the added benefit of possibly providing water and mapping out wells for future habitation on Mars.
Appendices
Appendix A: Process Description of The Greenhouse Effect
The Greenhouse Effect is the process by which light and energy from the Sun reaches the Earth (or another celestial body with an atmosphere), is converted to heat, and is then unable to freely leave the planet's atmosphere. This process is absolutely necessary for a planet to retain heat and therefore support life. The audience this process description is intended for is comprised of people who are skeptical or unaware of the plausibility of using greenhouse gasses to heat Mars to an inhabitable temperature.
This process description is not intended for use by the main audience of my formal analytical report (NASA), because it is a very basic process. Instead, this explanation of the Greenhouse Effect is meant to be used by my secondary audience.
To fully understand this process, one must have a general understanding of how the Earth's surface absorbs radiation from the Sun, which is then radiated back into space from the Earth's surface. Thanks to greenhouse gasses in the upper atmosphere, some of this heat that would be lost to space is trapped in the lower atmosphere, keeping our planet at a liveable temperature. One must also understand what, specifically greenhouse gasses are and the role they play in the Greenhouse Effect. A greenhouse gas is any atmospheric gas that reflects infrared radiation given off by the Earth as a result of being heated by the Sun. These include carbon dioxide, methane, nitrous oxide, water vapor, ozone, and CFCs.
This process occurs all day everyday on Earth, but on planets like Mars, which has a thin atmosphere, lacking the thick covering of greenhouse gasses that Earth has, there is no Greenhouse Effect. This is why the presence of greenhouse gasses in the atmosphere is crucial for a planet to retain its heat. Some planets, such as Venus, have thick atmospheres full of greenhouse gasses. Some, like Mars, have very thin atmospheres whose greenhouse gasses trap very little heat. Earth is a comfortable middle ground between Venus, which is far too hot to be habitable, and Mars, which is far too cold. Whatever the levels of greenhouse gasses in a planet's atmosphere, the planet must also be close enough to a star so that it receives appropriate radiation.
Stages In The Process:
Once a planet is close enough to a star and has an adequate level of greenhouse gasses, some of the star's emitted radiation will pass through the planet's atmosphere while some is reflected back in to space by the atmosphere. In order for this step to take place, the planet's atmosphere must not be too reflective, or not enough radiation will pass though it.
The radiation that is not reflected into space by the atmosphere will mostly be absorbed by the planet's surface, (some is reflected by the planet's surface) warming it temporarily. The planet then gives off its own infrared radiation, or heat.
The infrared radiation generated by the planet is then lost to space, unless there are greenhouse gasses present. In this case, the greenhouse gasses act as insulation for the planet, reflecting heat back towards the planet and keeping it warm. The amount of greenhouse gasses present in the atmosphere determines the amount of heat that is lost to space and the amount that is re-radiated in the planet's direction.
Glossary
Acidophilic: Classification of methanogens that live in environments with high acid concentrations (pH less than 4).
Alkaliphilic: Classification of methanogens that live in environments with high base concentrations (pH higher than 8).
Anaerobic: Able to live without oxygen in the air. Applies to cells and bacteria. Strict anaerobes cannot live in the presence of oxygen.
Asteroid: Any celestial body ranging from a mile to 480 miles in diameter.
Astrobiologist: Someone who studies life beyond the Earth's atmosphere.
Atmosphere: The gaseous envelope which surrounds any given celestial body.
Carrying Capacity: The maximum number of organisms of a particular species that can be supported in a given environment.
Celestial: Of or pertaining to the sky and space.
CFC: Any of various halocarbon compounds consisting of carbon, hydrogen, chlorine, and fluorine.
Dry Ice: Carbon dioxide in its solid form.
Greenhouse Effect: See Appendix A
Greenhouse Gas: Any gas which adds to the Greenhouse Effect.
Halophilic: Classification of methanogens that lives in environments with high salt (NaCl) concentrations.
HFC: Any of various halocarbon compounds consisting of carbon, hydrogen, and fluorine, but which do not contain chlorine.
Hyperthermophilic: Classification of methanogens that lives in extremely high temperatures, typically about 176-235ºF.
Lunar: Of or pertaining to a moon as opposed to other celestial bodies.
Methanogens: Methane producing bacteria.
Ozone: An unstable, poisonous molecule composed of three oxygen atoms which absorbs ultraviolet radiation.
PFC: Any of various compounds which are made entirely out of carbon and fluorine.
Psychrophilic: Classification of methanogens that lives in cold temperatures typically about 28-60ºF.
Runaway Greenhouse Effect: The result of an unbalanced Greenhouse Effect in which there are too many greenhouse gases.
Satellite: Any body that orbits a planet. May be natural, ie. the moon, or man-made, ie. a space station.
Terraform: The act of making any celestial body that is not the Earth inhabitable by humans or more Earth-like.
Terrestrial: Of or pertaining to the Earth as opposed to any other celestial body.
Thermophilic: Classification of methanogens that live in high temperatures typically about 131-176ºF.
Works Cited
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