Difference between revisions of "Terraforming"
(Added link to Paraterraforming, and made a list of books on the subject.) |
(Many changes. Biggest is saying that CO2 is not suitable for a buffer gas since we can only breath if it is present in trace amount.) |
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[[File:Logo-Mars-in-a-shell.jpg|thumb|The planet Mars under a global glas dome. This is certainly not an idea of terraforming, but it gives an idea of the dimensions of the topic.]] | [[File:Logo-Mars-in-a-shell.jpg|thumb|The planet Mars under a global glas dome. This is certainly not an idea of terraforming, but it gives an idea of the dimensions of the topic.]] | ||
| − | '''Terraforming''', or ''Earth-shaping'', is a theoretical process of modifying a planet's atmosphere to make it habitable for humans. In the case of Mars, terraforming would require artificial thickening of the atmosphere | + | '''Terraforming''', or ''Earth-shaping'', is a theoretical process of modifying a planet's atmosphere to make it habitable for humans. In the case of Mars, terraforming would require first warming the planet, then artificial thickening of the atmosphere so pressure suits are not needed, [[water|ice]] melting to increase the H<sub>2</sub>O content of the atmosphere (creating [[clouds|water clouds]]), adding nitrogen as a buffer gas, and greatly increasing the [[oxygen|O<sub>2</sub>]] density to ultimately make the atmosphere breathable. |
==Mars and the "Triple Point" of water== | ==Mars and the "Triple Point" of water== | ||
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[[Image:Phase_diagram_water.png|thumb|right|200px|The phase diagram for water, clearly displaying water's [[triple point]].]] | [[Image:Phase_diagram_water.png|thumb|right|200px|The phase diagram for water, clearly displaying water's [[triple point]].]] | ||
| − | Presently, [[water|ice]] on Mars [[sublimation|sublimes]] as the atmospheric pressure is so low, ice bypasses the liquid phase when heated. Sublimation occurs allowing ice to turn directly into gas (steam). One of the main challenges for future terraforming efforts would be to increase the atmospheric pressure significantly so water can exist as a liquid on the surface of Mars. The atmospheric pressure and ambient temperature will therefore need to be greater than the [[triple point]] of water (thereby existing as ice, liquid and gas). This is just above 0C and 600 Pa. Mars atmospheric pressure is already above 600 Pa. However, close to the triple point, water takes very little energy to turn into a gas, | + | Presently, [[water|ice]] on Mars [[sublimation|sublimes]] as the atmospheric pressure is so low, ice bypasses the liquid phase when heated. Sublimation occurs allowing ice to turn directly into gas (steam). One of the main challenges for future terraforming efforts would be to increase the atmospheric pressure significantly so water can exist as a liquid on the surface of Mars. The atmospheric pressure and ambient temperature will therefore need to be greater than the [[triple point]] of water (thereby existing as ice, liquid and gas). This is just above 0C and 600 Pa. Mars atmospheric pressure is already above 600 Pa. However, close to the triple point, water takes very little energy to turn into a gas, so higher pressures would be required in practice. |
==Methods== | ==Methods== | ||
| − | A life supporting atmosphere needs to contain a "buffer gas", such as nitrogen. Mars is currently lacking in nitrogen, but nitrogen could be sourced from Venus, Saturn's moon Titan, or from comets. | + | Using giant mirrors to reflect light on to Mars would help warm Mars by increasing its insolation. Statites (stationary satellites held up by light pressure) have been suggested to beam light to the north and south poles of Mars. Others have suggested mirrors in sun synchronous orbits to beam light onto the terminator (which would brighten both dawn and dusk). |
| − | (Note that it is likely that Mars has nitrogen in its soil, see [[Atmospheric loss]].) | + | |
| + | A life supporting atmosphere needs to contain a "buffer gas", such as nitrogen. Mars is currently lacking in nitrogen, but nitrogen could be sourced from Venus, Saturn's moon Titan, or from comets. (Note that it is likely that Mars has nitrogen in its soil, see [[Atmospheric loss]].) | ||
| + | |||
| + | Mars could be warmed up using [[Super Greenhouse Gases]] such as perfluorocarbons, which are stable in the atmosphere for long periods of time. | ||
| − | Other greenhouse gasses include [[sulfur hexafluoride]] and 1,1,1-Trichloro ethane. These are very stable and highly effective greenhouse gasses. Use of such gasses to warm the atmosphere would allow the Carbon dioxide frozen into the polar caps and some of the water to evaporate adding to the mass of the atmosphere.If 4 hundredths of a microbar of manufactured greenhouse gas is needed to warm Mars to the point of runaway greenhouse effect, then a mass of manufactured greenhouse gasses equal to about 5.73 times the cargo capacity of the Edmund Fitzgerald (26 000 tonnes) every week for twenty years ( about 150 million tonnes) would be required for the project. | + | Other super greenhouse gasses include [[sulfur hexafluoride]] and 1,1,1-Trichloro ethane. These are very stable and highly effective greenhouse gasses. Use of such gasses to warm the atmosphere would allow the Carbon dioxide frozen into the polar caps and some of the water to evaporate adding to the mass of the atmosphere. If 4 hundredths of a microbar of manufactured greenhouse gas is needed to warm Mars to the point of runaway greenhouse effect, then a mass of manufactured greenhouse gasses equal to about 5.73 times the cargo capacity of the Edmund Fitzgerald (26,000 tonnes) every week for twenty years (about 150 million tonnes) would be required for the project. (Other estimates suggest a somewhat higher amount would be required to make up for the break up of these gases by ultraviolet light. See the [[Super Greenhouse Gases|Super Greenhouse Gas]] page for more discussion.) |
==Pioneer Organisms== | ==Pioneer Organisms== | ||
| − | Certain organisms, such as [[archaea]], [[lichen]], and [[tardigrades]] have been proven capable of surviving extreme environments, such as the vacuum of space. They could gain a foothold on the martian surface after minimal terraforming. The byproducts of their metabolism would contribute to the terraforming efforts. | + | The first creatures to live on the natural Mars landscape would be bacteria. Cyanobacteria (aka blue-green algae), live in water and would produce oxygen. They can live under ice if the ice cover is not too thick. |
| + | |||
| + | Certain organisms, such as [[archaea]], [[lichen]], and [[tardigrades]] have been proven capable of surviving for some time in extreme environments, such as the vacuum of space. They could gain a foothold on the martian surface after minimal terraforming. The byproducts of their metabolism would contribute to the terraforming efforts. | ||
==Long term prospects== | ==Long term prospects== | ||
| − | The ultimate results of terraforming are disputed. Terraforming may have only a temporary effect, even if the effect lasts for some hundred or thousand years. Eventually, the [[solar wind]] may carry away most of the new atmosphere due to the insufficient [[magnetosphere|magnetic field]]s of Mars. It has been suggested that the cost of terraforming a planet would be prohibitive, however to a growing population on the surface of that planet it would most likely be considered a normal colonial function to ensure that daily colonial endeavours have a positive effect on the atmosphere. Artificial magnetic fields might also be created around Mars to reduce atmospheric losses to space. And the solar system contains sufficient resources to replenish martian atmosphere indefinitely, but at a significant energy cost. Building space habitats might be a more practical long term objective for human occupation of space. | + | The ultimate results of terraforming are disputed. Terraforming may have only a temporary effect, even if the effect lasts for some hundred or thousand years. Eventually, the [[solar wind]] may carry away most of the new atmosphere due to the insufficient [[magnetosphere|magnetic field]]s of Mars, tho this would take millions of years. (See [[Atmospheric loss]] for more details.) |
| + | |||
| + | It has been suggested that the cost of terraforming a planet would be prohibitive, however to a growing population on the surface of that planet it would most likely be considered a normal colonial function to ensure that daily colonial endeavours have a positive effect on the atmosphere. | ||
| + | |||
| + | Artificial magnetic fields might also be created around Mars to reduce atmospheric losses to space. And the solar system contains sufficient resources to replenish martian atmosphere indefinitely, but at a significant energy cost. Building space habitats might be a more practical long term objective for human occupation of space. | ||
==Partial terraforming== | ==Partial terraforming== | ||
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|Carbon dioxide (CO<sub>2</sub>)||0.29-11.09 (5.76 average)||>0.15||<10 | |Carbon dioxide (CO<sub>2</sub>)||0.29-11.09 (5.76 average)||>0.15||<10 | ||
|- | |- | ||
| − | | | + | |Nitrogen (N2)||0.01-0.22 (0.114 average)||>1-10||- |
|- | |- | ||
|Oxygen (O<sub>2</sub>)||<0.015||1||>130 | |Oxygen (O<sub>2</sub>)||<0.015||1||>130 | ||
| + | |- | ||
| + | |Argon (Ar) | ||
| + | |0.09 | ||
| + | |0 | ||
| + | |0 | ||
| + | |- | ||
| + | |Carbon Monoxide (CO) | ||
| + | |0.004 | ||
| + | |0 | ||
| + | |0 | ||
| + | |- | ||
| + | |Water (H2O) | ||
| + | |0.0018 | ||
| + | |~10 | ||
| + | |~10 | ||
|} | |} | ||
While full terraforming to make Mars atmosphere suitable for breathable condition for humans can take around 100,000 years, transformations to the atmosphere suitable for plants could take from 100 to several thousands years. Current requirements for plants to grow on Mars are based on atmospheric pressure. Mars polar caps have enough CO<sub>2</sub> to provide 100 mbar (10 kPa) additional atmospheric pressure to the existing 6 millibars. This would be enough to create sustainable growth condition for plants. | While full terraforming to make Mars atmosphere suitable for breathable condition for humans can take around 100,000 years, transformations to the atmosphere suitable for plants could take from 100 to several thousands years. Current requirements for plants to grow on Mars are based on atmospheric pressure. Mars polar caps have enough CO<sub>2</sub> to provide 100 mbar (10 kPa) additional atmospheric pressure to the existing 6 millibars. This would be enough to create sustainable growth condition for plants. | ||
| − | To make using pressure suit unnecessary for humans, atmospheric pressure needs to rise to at least | + | To make using pressure suit unnecessary for humans, atmospheric pressure needs to rise to at least 100 mbar (10 kPa) or 10% of Earth atmospheric pressure. |
| + | |||
| + | To make it so a breathing mask is not required, a pressure of needs to be at least 250 mbar (25% Earth's pressure). This might be composed of 118 mbar of nitrogen, 1 mbar of argon and neon<sub>,</sub> 1 mbar of water vapour and 130 mbar of oxygen (minimal requirement oxygen pressure). Note that the CO2 must be at trace levels for animals to breath. CO2 of 0.05% is the maximum we would want for a breathable atmosphere. (Argon and neon are not needed for life, but can act as a buffer gas.) | ||
| − | + | We would want to increase CO2 partial pressure to warm the planet, but would have to later draw down this CO2 level if we wish to make the plant habitable for animals. | |
[[Paraterraforming]] is a subset of terraforming where terraforming takes place inside huge structures which cover some fraction of the planet's surface. | [[Paraterraforming]] is a subset of terraforming where terraforming takes place inside huge structures which cover some fraction of the planet's surface. | ||
| − | == Books on Terraforming == | + | ==Books on Terraforming== |
| − | "Terraforming: Engineering Planetary Environments", by Martin J. Fogg, ISBN: 1-56091-609-5 is a highly detailed textbook on the subject. It is very hard to find. Perhaps the Mars Society could update it and republish it. | + | "Terraforming: Engineering Planetary Environments", by Martin J. Fogg, ISBN: 1-56091-609-5, is a highly detailed textbook on the subject. It is very hard to find. Perhaps the Mars Society could update it and republish it. |
"New Earths: Restructuring Earth and Other Planets", by James Edward Oberg, ISBN: 0-8117-1007-6. | "New Earths: Restructuring Earth and Other Planets", by James Edward Oberg, ISBN: 0-8117-1007-6. | ||
Revision as of 18:32, 8 May 2021
Terraforming, or Earth-shaping, is a theoretical process of modifying a planet's atmosphere to make it habitable for humans. In the case of Mars, terraforming would require first warming the planet, then artificial thickening of the atmosphere so pressure suits are not needed, ice melting to increase the H2O content of the atmosphere (creating water clouds), adding nitrogen as a buffer gas, and greatly increasing the O2 density to ultimately make the atmosphere breathable.
Contents
Mars and the "Triple Point" of water
Presently, ice on Mars sublimes as the atmospheric pressure is so low, ice bypasses the liquid phase when heated. Sublimation occurs allowing ice to turn directly into gas (steam). One of the main challenges for future terraforming efforts would be to increase the atmospheric pressure significantly so water can exist as a liquid on the surface of Mars. The atmospheric pressure and ambient temperature will therefore need to be greater than the triple point of water (thereby existing as ice, liquid and gas). This is just above 0C and 600 Pa. Mars atmospheric pressure is already above 600 Pa. However, close to the triple point, water takes very little energy to turn into a gas, so higher pressures would be required in practice.
Methods
Using giant mirrors to reflect light on to Mars would help warm Mars by increasing its insolation. Statites (stationary satellites held up by light pressure) have been suggested to beam light to the north and south poles of Mars. Others have suggested mirrors in sun synchronous orbits to beam light onto the terminator (which would brighten both dawn and dusk).
A life supporting atmosphere needs to contain a "buffer gas", such as nitrogen. Mars is currently lacking in nitrogen, but nitrogen could be sourced from Venus, Saturn's moon Titan, or from comets. (Note that it is likely that Mars has nitrogen in its soil, see Atmospheric loss.)
Mars could be warmed up using Super Greenhouse Gases such as perfluorocarbons, which are stable in the atmosphere for long periods of time.
Other super greenhouse gasses include sulfur hexafluoride and 1,1,1-Trichloro ethane. These are very stable and highly effective greenhouse gasses. Use of such gasses to warm the atmosphere would allow the Carbon dioxide frozen into the polar caps and some of the water to evaporate adding to the mass of the atmosphere. If 4 hundredths of a microbar of manufactured greenhouse gas is needed to warm Mars to the point of runaway greenhouse effect, then a mass of manufactured greenhouse gasses equal to about 5.73 times the cargo capacity of the Edmund Fitzgerald (26,000 tonnes) every week for twenty years (about 150 million tonnes) would be required for the project. (Other estimates suggest a somewhat higher amount would be required to make up for the break up of these gases by ultraviolet light. See the Super Greenhouse Gas page for more discussion.)
Pioneer Organisms
The first creatures to live on the natural Mars landscape would be bacteria. Cyanobacteria (aka blue-green algae), live in water and would produce oxygen. They can live under ice if the ice cover is not too thick.
Certain organisms, such as archaea, lichen, and tardigrades have been proven capable of surviving for some time in extreme environments, such as the vacuum of space. They could gain a foothold on the martian surface after minimal terraforming. The byproducts of their metabolism would contribute to the terraforming efforts.
Long term prospects
The ultimate results of terraforming are disputed. Terraforming may have only a temporary effect, even if the effect lasts for some hundred or thousand years. Eventually, the solar wind may carry away most of the new atmosphere due to the insufficient magnetic fields of Mars, tho this would take millions of years. (See Atmospheric loss for more details.)
It has been suggested that the cost of terraforming a planet would be prohibitive, however to a growing population on the surface of that planet it would most likely be considered a normal colonial function to ensure that daily colonial endeavours have a positive effect on the atmosphere.
Artificial magnetic fields might also be created around Mars to reduce atmospheric losses to space. And the solar system contains sufficient resources to replenish martian atmosphere indefinitely, but at a significant energy cost. Building space habitats might be a more practical long term objective for human occupation of space.
Partial terraforming
| Parameter | Mars[1], mbar | Plants[2], mbar | Humans, mbar |
|---|---|---|---|
| Total pressure | 0.30-11.55 (6 average) | >10 | >250 |
| Carbon dioxide (CO2) | 0.29-11.09 (5.76 average) | >0.15 | <10 |
| Nitrogen (N2) | 0.01-0.22 (0.114 average) | >1-10 | - |
| Oxygen (O2) | <0.015 | 1 | >130 |
| Argon (Ar) | 0.09 | 0 | 0 |
| Carbon Monoxide (CO) | 0.004 | 0 | 0 |
| Water (H2O) | 0.0018 | ~10 | ~10 |
While full terraforming to make Mars atmosphere suitable for breathable condition for humans can take around 100,000 years, transformations to the atmosphere suitable for plants could take from 100 to several thousands years. Current requirements for plants to grow on Mars are based on atmospheric pressure. Mars polar caps have enough CO2 to provide 100 mbar (10 kPa) additional atmospheric pressure to the existing 6 millibars. This would be enough to create sustainable growth condition for plants.
To make using pressure suit unnecessary for humans, atmospheric pressure needs to rise to at least 100 mbar (10 kPa) or 10% of Earth atmospheric pressure.
To make it so a breathing mask is not required, a pressure of needs to be at least 250 mbar (25% Earth's pressure). This might be composed of 118 mbar of nitrogen, 1 mbar of argon and neon, 1 mbar of water vapour and 130 mbar of oxygen (minimal requirement oxygen pressure). Note that the CO2 must be at trace levels for animals to breath. CO2 of 0.05% is the maximum we would want for a breathable atmosphere. (Argon and neon are not needed for life, but can act as a buffer gas.)
We would want to increase CO2 partial pressure to warm the planet, but would have to later draw down this CO2 level if we wish to make the plant habitable for animals.
Paraterraforming is a subset of terraforming where terraforming takes place inside huge structures which cover some fraction of the planet's surface.
Books on Terraforming
"Terraforming: Engineering Planetary Environments", by Martin J. Fogg, ISBN: 1-56091-609-5, is a highly detailed textbook on the subject. It is very hard to find. Perhaps the Mars Society could update it and republish it.
"New Earths: Restructuring Earth and Other Planets", by James Edward Oberg, ISBN: 0-8117-1007-6.
"Terraforming: The Creating of Habitable Worlds", by Martin Beech, ISBN: 978-0-387-09795-4.
References
- ↑ Mahaffy, P. R.; Webster, C. R.; Atreya, S. K.; Franz, H.; Wong, M.; Conrad, P. G.; Harpold, D.; Jones, J. J.; Leshin, L. A.; Manning, H.; Owen, T.; Pepin, R. O.; Squyres, S.; Trainer, M.; Kemppinen, O.; Bridges, N.; Johnson, J. R.; Minitti, M.; Cremers, D.; Bell, J. F.; Edgar, L.; Farmer, J.; Godber, A.; Wadhwa, M.; Wellington, D.; McEwan, I.; Newman, C.; Richardson, M.; Charpentier, A. - Abundance and Isotopic Composition of Gases in the Martian Atmosphere from the Curiosity Rover, Nature 341, pp. 263-266. DOI:10.1126/science.1237966
- ↑ Christopher P. McKay, Owen B. Toon & James F. Kasting - Making Mars habitable, Nature 352, pp. 489-496. DOI:10.1038/352489a0
