Kurzgesagt – In a Nutshell
Sources – Mars Terraforming
Thanks to our experts
Prof. Matthew Caplan
Illinois State University
Dr. Nicola Mari
Planetary Geosciences, University of Pavia.
– Mars is dry and has no soil to grow anything. Its atmosphere is too thin to breathe or protect from radiation, giving you a high cancer risk.
Mars’ dryness is well documented:
#NASA (2018): “Is Mars’ Soil Too Dry to Sustain Life?” (retrieved 2022)
https://www.nasa.gov/feature/ames/is-mars-soil-too-dry-to-sustain-life
Quote: “Mars is 1,000 times drier than even the driest parts of the Atacama, which makes it less likely that microbial life as we know it exists on the planet’s surface, even with some access to water.”
As well as the inadequacy of its surface to support plant growth:
#Christopher Oze et al. (2021): “Perchlorate and Agriculture on Mars”, Soil Systems
https://www.mdpi.com/2571-8789/5/3/37/htm
Quote: “Perchlorate (ClO4−) is globally enriched in Martian regolith at levels commonly toxic to plants [...] The presence of perchlorate was uniformly detrimental to plant growth regardless of growing
medium. Plants in potting soil were able to germinate in 1 wt.% perchlorate; however, these plants showed restricted growth and decreased leaf area and biomass. Some plants were able to germinate in regolith simulant without perchlorate; however, they showed reduced growth. In Martian regolith simulant, the presence of perchlorate prevented germination across all plant treatments.”
And the lack of protection against cosmic radiation:
#NASA (2015): “Real Martians: How to Protect Astronauts from Space Radiation on Mars” (retrieved 2022)
Quote: “Compared to Earth’s atmosphere, the thin Martian atmosphere is a less powerful shield against quick-moving, energetic particles that pelt in from all directions – which means astronauts on Mars will need protection from this harsh radiation environment. [...] Energetic particles can be dangerous to humans because they pass right through the skin, depositing energy and damaging cells or DNA along the way. This damage can mean an increased risk for cancer later in life or, at its worst, acute radiation sickness during the mission if the dose of energetic particles is large enough.”
– So to turn it into a new home for humanity, we have to give it a proper atmosphere, similar to Earth’s. It should be made of 21% oxygen, 79% nitrogen and a tiny bit of CO2, at an average temperature of 14°C and under 1 bar of pressure.
The composition of the atmospheres of the Earth and Mars differ drastically:
#ESA (2018): “Comparing the atmospheres of Mars and Earth” (retrieved 2022)
https://www.esa.int/ESA_Multimedia/Images/2018/04/Comparing_the_atmospheres_of_Mars_and_Earth
At the surface, the annual global temperature average in the past century was about 14 ºC:
#NOAA (2022): “Global Surface Temperature Anomalies” (retrieved 2022)
https://www.ncei.noaa.gov/access/monitoring/global-temperature-anomalies/mean
Challenge 1: The Atmosphere
– Some 4 billion years ago Mars had a nice oxygen-rich atmosphere and was home to vast oceans and rivers. It held onto it for several hundred million years before it got blown away. Ultraviolet rays broke down the atmospheric gases and then the oceans, until they were swept away by solar wind. Today Mars is a dry, barren wasteland.
Scientists think that, shortly after the formation of the planet, the Martian atmosphere was probably much thicker and oxygen-rich:
#University of Oxford (2013): “Mars had oxygen-rich atmosphere 4000m years ago” (retrieved 2022)
https://www.ox.ac.uk/news/2013-06-20-mars-had-oxygen-rich-atmosphere-4000m-years-ago
Quote:”Professor Wood said: 'The implication is that Mars had an oxygen-rich atmosphere at a time, about 4000 million years ago, well before the rise of atmospheric oxygen on earth around 2500 million years ago. As oxidation is what gives Mars its distinctive colour it is likely that the 'red planet' was wet, warm and rusty billions of years before Earth's atmosphere became oxygen rich.' “
Additional hints of oxygen in the ancient Martian atmosphere have been also found by NASA’s Curiosity rover:
#Nina L. Lanza et al. (2016): “Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars”, Geophysical Research Letters
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL069109
Quote: “Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day.”
The ancient Martian atmosphere may have been almost as thick as that of Earth’s today:
#Tokyo Institute of Technology (2017): “Meteorite tells us that Mars had a dense atmosphere 4 billion years ago” (retrieved 2022)
https://www.titech.ac.jp/english/news/2017/039366
Quote: “The research team concluded that Mars had a dense atmosphere 4 billion years ago. The surface air pressure at the time was at least 0.5 bar and could have been much higher. Because Mars had its magnetic field about 4 billion years ago and lost it, the result suggests that stripping by the solar wind is responsible for transforming Mars from a warm wet world into a cold desert world.”
And at the same time, Mars is thought to have been host of oceans of liquid water:
#NASA(2015): “NASA Research Suggests Mars Once Had More Water Than Earth’s Arctic Ocean” (retrieved 2022)
Quote: “Perhaps about 4.3 billion years ago, Mars would have had enough water to cover its entire surface in a liquid layer about 450 feet (137 meters) deep. More likely, the water would have formed an ocean occupying almost half of Mars’ northern hemisphere, in some regions reaching depths greater than a mile (1.6 kilometers).”
#NASA: “Ocean Worlds” (retrieved 2022)
https://www.nasa.gov/specials/ocean-worlds/
Quote: “Mars was once much more Earth-like, with a thick atmosphere, abundant water, and global oceans (as in this artist’s conception). Billions of years ago, Mars lost its protective global magnetic field, leaving it vulnerable to the effects of our Sun: solar wind and space weather.”
However, those conditions didn’t last for long. Also about 4 billion years ago, Mars lost its protective magnetic field. As a result, the particles of the solar wind, helped by the UV light of the Sun, swept away Mars’ atmosphere and water.
#Bruce Jakosky (2022): “How did Mars lose its atmosphere and water?”, Physics Today
https://physicstoday.scitation.org/doi/10.1063/PT.3.4988
Quote: “[Atmosphere and water] were mostly lost to space early in Mars’s history, in processes driven by the Sun’s UV photons and solar wind after Mars lost its magnetic field. [...] Planetary scientists think that the loss of H was much larger early in history when the Sun’s UV radiation intensity was much higher. The stripping of C and O by the solar wind began about 4.1 billion years ago, when the Martian magnetic field shut off with the death of the planet’s dynamo (see Physics Today, October 2021, page 17). At that point in time, no global magnetic field existed to protect the atmosphere from the onslaught of the solar wind.”
– Luckily a sizeable portion of the water is frozen in deep reservoirs and in the polar ice caps, enough to create a very shallow ocean.
The presence of water on Mars is documented:
#NASA: “Ocean Worlds” (retrieved 2022)
https://www.nasa.gov/specials/ocean-worlds/
Quote: “Most of the remaining water on Mars is frozen in the ice caps or trapped beneath the soil, but a small amount of muddy, brackish water can be seen moving down the side of Martian hills in the local summer.”
#American Geophysical Union (2019): “Multiple former ice caps buried under Mars’s north polar circle” (retrieved 2022)
https://news.agu.org/press-release/multiple-former-ice-caps-buried-under-marss-north-polar-ice/
Quote: “The team found layers of sand and ice that were as much as 90 percent water in some places. If melted, the newly discovered ice would be equivalent to a global layer of water around Mars at least 1.5 meters (5 feet) deep, which could be one of the largest water reservoirs on the planet, according to the researchers.”
However, it is thought that Mars has more water underground:
#Christensen, Philip R. (2006): “Water at the Poles and in Permafrost Regions of Mars”, Elements.
Quote: “The poles and mid-latitudes of Mars contain abundant water in ice caps, thick sequences of ice-rich layers, and mantles of snow. The volume of the known reservoir is ≥5 x 106 km3, corresponding to a layer ∼35 m thick over the planet.”
– And enormous amounts of oxygen are bound as minerals in the Martian rocks, like the oxygen in the iron oxides that give the planet its rust-red color, as well as carbon dioxide in carbonates.
Oxygen is abundant in the Martian soil:
#Rebecca Burgher et al. (2000): “Red Mars - Green Mars? Mars Regolith as a Growing Medium”, Proceedings of the Third Annual HEDS-UP Forum, Human Exploration and Development of Space-University Partners (HEDS-UP).
And carbonates have also been found on the surface of Mars:
#Joshua L. Bandfield et al. (2003): “Spectroscopic Identification of Carbonate Minerals in the Martian Dust”, Science.
https://www.science.org/doi/abs/10.1126/science.1088054
Quote: “Thermal infrared spectra of the martian surface indicate the presence of small concentrations (2 to 5 weight %) of carbonates, specifically dominated by magnesite (MgCO3). The carbonates are widely distributed in the martian dust, and there is no indication of a concentrated source. The presence of small concentrations of carbonate minerals in the surface dust and in martian meteorites can sequester several bars of atmospheric carbon dioxide and may have been an important sink for a thicker carbon dioxide atmosphere in the martian past.”
Nitrates have been found as well, although in a significantly smaller proportion (a few hundreds parts per million, this will become important later on):
#Jennifer C. Stern et al. (2015): “Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars”, Proceedings of the National Academy of Sciences
https://www.pnas.org/doi/10.1073/pnas.1420932112
Quote: “We present data supporting the presence of an indigenous source of fixed nitrogen on the surface of Mars in the form of nitrate. This fixed nitrogen may indicate the first stage in development of a primitive nitrogen cycle on the surface of ancient Mars and would have provided a biochemically accessible source of nitrogen. [...] our results support the equivalent of 110–300 ppm of nitrate in the Rocknest (RN) aeolian samples, and 70–260 and 330–1,100 ppm nitrate in John Klein (JK) and Cumberland (CB) mudstone deposits, respectively.”
– To free these gasses, we need to reverse the reactions that lock them away by thermolysis, which happens at temperatures as high as on the surface of the Sun. In short, we want to melt Mars’ surface.
The idea to heat up Mars’ surface at temperatures of several thousands of Kelvin in order to vaporize the regolith and free the volatiles to build up a thicker atmosphere was proposed years ago in this classic paper, where it was estimated that the process would require to heat up the Martian surface to temperatures of several thousand degrees. This would require a heat input of about 10 megajoules per kg of rock:
#Paul Birch (1992): “Terraforming Mars quickly”, Journal of the British Interplanetary Society
https://www.orionsarm.com/fm_store/TerraformingMarsQuickly.pdf
– The best way to do that would be lasers in orbit aiming their beams down on Mars. The most powerful laser today is the ELI-NP, able to produce beams of 10 Petawatts of power, for a split trillionth second.
Currently, the most powerful laser is located at the European Extreme Light Infrastructure - Nuclear Physics (ELI-NP) facilities in Romania:
#Andreas Thoss (2020): “Visiting the most powerful laser in the world”, Laser Focus World
Quote: “ELI NP hosts the most powerful laser in the world with a power of 10 PW.”
The laser is called L4 Aton and can reach a power of 10 petawatts (10·1015 watts) during 150 femtoseconds (150·10–15 seconds, or 0.15 trillionths of a second):
#ELI Beamlines: “Laser L4 Aton” (retrieved 2022)
https://www.eli-beams.eu/facility/lasers/laser-4-aton-10-pw-2-kj/
Quote: “The L4 Aton laser system is designed to generate an extremely high and unprecedented peak power of 10 PW (Petawatt) in pulses with duration of 150 fs.”
#ELI Nuclear Physics: “ELI-NP in a nutshell”(retrieved 2002)
– To melt Mars we need a laser twice as powerful, that runs continuously. The easiest way is to use a solar-pumped laser that can be powered directly with sunlight: At its core are metal-infused glass rods that absorb energy and release it as a laser beam.
Solar-pumped lasers have already been considered for space missions. The main idea is to use the solar light to generate a laser beam directly, instead of having to produce huge amounts of electricity first:
#Ulrich Wittroock (2013): “Perspective of Solar Pumping of Solid State Lasers for ESA Missions”, ESA/University of Münster.
https://nebula.esa.int/sites/default/files/neb_study/1154/C4000106760ExS.pdf
Quote: “The basic idea behind solar pumping of solid state lasers is simple and convincing: To short-cut the process of converting the energy of visible solar radiation to electrical energy and the subsequent conversion of this electrical energy to near-infrared or visible laser radiation by semiconductor lasers.
Using solar radiation for directly pumping solid state lasers instead of light from the semiconductor lasers would eliminate the two conversion steps from light energy to electrical energy and backwards. By eliminating these two conversion steps, one could hope for simpler, more robust systems that have higher efficiencies.”
The main problem with these systems is their low solar-to-laser conversion efficiency. However, some theoretical calculations have suggested that a solar-pumped laser equipped with a “black body cavity” (basically a “box” that captures and reuses much of the otherwise lost solar power) could achieve solar-to-laser efficiencies of up about 30%:
#Walter H. Christiansen and J. Marcos Sirota (1991): “Solar-powered blackbody-pumped lasers”, Proceedings of the Eighth International Symposium on Gas-Flow and Chemical Lasers.
Quote: “A concept for a solar-powered laser is presented which utilizes an intermediate blackbody cavity to provide a uniform optical pumping environment for the lasant, typically CO or CO2 or possibly a solid state laser medium. High power cw blackbody- pumped lasers with efficiencies on the order of 20% or more are feasible. The physical basis of this idea is reviewed. Small scale experiments using a high temperature oven as the optical pump have been carried out with gas laser mixtures. Detailed calculations showing a potential efficiency of 35% for blackbody pumped Nd:YAG system are discussed.”
As will be shown below, creating a suitable oxygen atmosphere by vaporizing the Martian regolith will require a total of about 3·1025 joules, or 3·1010 petajoules. If we aim for 50 years (~ 1.6·109 sec), this implies a power of about 20 petawatts, twice as much as the ELI-NP laser.
– If we build an array of mirrors in space, about 11 times the size of the United States, we can focus enough sunlight onto them to melt Mars.
We want to get this power directly from the Sun using a solar-pumped laser with an assumed solar-to-laser efficiency of about 30%. This implies that we need to collect about 60 petawatts of solar power, or 60 petajoules per second.
The solar luminosity (energy radiated by the Sun every second) is about L = 3.8·1026 watts:
#NASA (2018): “Sun Fact Sheet” (retrieved 2022)
https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
And Mars is at an average distance from the Sun of about R = 2.3·1011 km:
#NASA (2021): “Planetary Fact Sheet - Metric” (retrieved 2022)
https://nssdc.gsfc.nasa.gov/planetary/factsheet/
This means that, at the orbit of Mars, we get a flux of solar energy (energy per unit time and unit area) of
I = L/(4πR2) = 570 W/m2
(which is about 40% of the solar flux received at Earth). Since we need to collect 60 petawatts of solar power, that would require
60·1015/570 ~ 1014 m2 = 108 km2
of mirrors. That is equivalent to the area of a circle of 5,650 km in radius (about 90% of the radius of the Earth), or to about 11 times the land area of the US:
#US Census Bureau (2010): “State Area Measurements and Internal Point Coordinates” (retrieved 2022)
https://www.census.gov/geographies/reference-files/2010/geo/state-area.html
– As the lasers hit the surface, about 750 kg of oxygen and some carbon dioxide emerge from every cubic meter of rock melted. If we are efficient our lasers only need to melt through the top 8 meters of the surface to get enough oxygen.
The density of Mars rock is about 2500 kg per cubic meter:
#NASA (2017): “New Gravity Map Suggests Mars Has a Porous Crust”
https://mars.nasa.gov/news/8295/new-gravity-map-suggests-mars-has-a-porous-crust/
Quote: “The researchers mapped the density of the Martian crust, estimating the average density is 2,582 kilograms per meter cubed”
When pyrolyzing the Martian rock, we can expect an extraction efficiency of oxygen of around 30% in mass:
#Paul Birch (1992): “Terraforming Mars quickly”, Journal of the British Interplanetary Society
https://www.orionsarm.com/fm_store/TerraformingMarsQuickly.pdf
#Rebecca Burgher et al. (2000): “Red Mars - Green Mars? Mars Regolith as a Growing Medium”, Proceedings of the Third Annual HEDS-UP Forum, Human Exploration and Development of Space-University Partners (HEDS-UP).
And an efficiency of 30% in mass means that each cubic meter has the potential for 2500·0.3 = 750 kg of oxygen.
On Earth, the atmosphere exerts a pressure at the surface of 1 bar, i.e. 100,000 pascals, or 100,000 newtons per square meter. Under a surface gravity of 9.8 m/s2, this equals the weight of about 10,000 kg of air per square meter.
In terms of the fraction of molecules (equivalent to the volume fraction in the case of an ideal gas), 21% of Earth’s atmosphere is oxygen. By mass, the fraction of oxygen is about 23%:
#McGill University (2007): “Earth’s atmosphere” (retrieved 2022)
https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/e/Earth%2527s_atmosphere.htm
Quote: “The above composition percentages are done by volume. Assuming that the gases act like ideal gases, we can add the percentages p multiplied by their molar masses m, to get a total t = sum (p·m). Any element's percent by mass is then p·m/t. When we do this to the above percentages, we get that, by mass, the composition of the atmosphere is 75.523% nitrogen, 23.133% oxygen, 1.288% argon, 0.053% carbon dioxide, 0.001267% neon, 0.00029% methane, 0.00033% krypton, 0.000724% helium, and 0.0000038 % hydrogen.”
This means that, on the Earth’s surface, oxygen exerts a pressure of about 230 mbar, or 23,000 pascal. This is the oxygen pressure that we’ll need on Mars.
Mars has a lower surface gravity of 3.7 m/s2:
#NASA (2021): “Planetary Fact Sheet - Metric” (retrieved 2022)
https://nssdc.gsfc.nasa.gov/planetary/factsheet/
So we need more gas to reach the same pressure. Specifically:
23,000/3.7 = 6,200 kg of oxygen per square meter of Martian surface.
At a release rate of 0.3 kg of O2 per kg of rock burned, getting 6,200 kg of O2 from the Martian regolith means melting about 20,000 kg of rock. With a density of 2,500 kg/m3, this amounts to 8 cubic meters of rock. Since all numbers here are given by square meter, what we need is to melt the top 8 meters of Martian surface.
Mars has a radius of about 3,400 km:
#NASA (2021): “Planetary Fact Sheet - Metric” (retrieved 2022)
https://nssdc.gsfc.nasa.gov/planetary/factsheet/
Which implies a total surface of
4π·(3,400 km)2 = 1.45·108 km2 = 1.45·1014 m2.
Melting 8 meters of Martian surface amounts to melting a total of 8 · 1.45·1014 m3 = 11.6·1014 m3 of rock. At a density of 2500 kg/m3, this equals to about 3·1018 kg. If, as stated above, to melt 1 kg we need about 10 megajoules, the total energy requirement for the whole Martian surface will be of 3·1025 joules, or 3·1010 petajoules, as advanced before.
– After they pass, the ground cools quickly. A strange snow falls: the ashes from all the elements that solidify as they cool down, like silicon and iron. Mars is still a cold planet at this point.
The laser will heat the Martian surface, but only in those areas being worked out at a given moment. After having vaporized the rock, the surface will rapidly cool down at a temperature close to the usual one of –65 degrees Celsius, or about 210 K:
#NASA (2021): “Planetary Fact Sheet - Metric” (retrieved 2022)
https://nssdc.gsfc.nasa.gov/planetary/factsheet/
In these conditions, elements like iron and silicon (see the composition of Martian oxides below) would freeze very quickly and return to their solid state.
#Rebecca Burgher et al. (2000): “Red Mars - Green Mars? Mars Regolith as a Growing Medium”, Proceedings of the Third Annual HEDS-UP Forum, Human Exploration and Development of Space-University Partners (HEDS-UP).
– A happy side effect of this inferno is that all the water in the polar ice caps and even deep underground rise into the sky as hot steam, forming clouds that rain down over the entire planet. They would wash out the nastier gasses from the atmosphere, like chlorine, and carry away harmful elements that accumulated on the surface. In the end, they would form shallow oceans, saltier than on Earth. We might need to do some extra clean-up afterwards.
Rains on Mars would have an important role in cleaning the atmosphere.
#Paul Birch (1992): “Terraforming Mars quickly”, Journal of the British Interplanetary Society
https://www.orionsarm.com/fm_store/TerraformingMarsQuickly.pdf
#USGS: “Why is the ocean salty?” (retrieved 2022)
https://www.usgs.gov/faqs/why-ocean-salty
Quote: “The two ions that are present most often in seawater are chloride and sodium. These two make up over 90% of all dissolved ions in seawater. The concentration of salt in seawater (its salinity) is about 35 parts per thousand; in other words, about 3.5% of the weight of seawater comes from the dissolved salts.”
In Mars, more than 0.5% and about 3% of the rock is chlorine and sodium, respectively:
#Rebecca Burgher et al. (2000): “Red Mars - Green Mars? Mars Regolith as a Growing Medium”, Proceedings of the Third Annual HEDS-UP Forum, Human Exploration and Development of Space-University Partners (HEDS-UP).
At a salt concentration of 3.5% in mass, melting 8 meters of Martian rock with density of 2,500 kg/m3 implies that we would be left with
2,500 * 0.035 * 8 = 700 kg/m2 of salts.
If, as mentioned above, the frozen water in the polar caps is enough to create a shallow global ocean 1.5 meters deep, and if all those minerals ended up dissolved in water, that would imply a salinity of the order of 700/1500 ~ 40% in weight, i.e. more salty than the Dead Sea:
#NASA (2014): “Saltiest Pond on Earth” (retrieved 2022)
https://earthobservatory.nasa.gov/images/84955/saltiest-pond-on-earth
Quote: “With a salinity level over 40 percent, Don Juan is significantly saltier than most of the other hypersaline lakes around the world. The Dead Sea has a salinity of 34 percent; the Great Salt Lake varies between 5 and 27 percent. Earth’s oceans have an average salinity of 3.5 percent.”
Although, as pointed out above, there may be more water hidden in the Martian soil.
– It would take about 50 years of continuous lasering to create our oxygen atmosphere.
In the calculations above we’ve shown two things: 1) That our 20 PW laser will take 50 years in melting the first 8 meters of Martian surface, 2) and that melting the first 8 meters of Martian surface should free an amount of oxygen that, under Martian gravity, creates the same pressure that the atmospheric oxygen on Earth.
– The resulting atmosphere is nearly 100% oxygen and only 0.2 bars. It’s hard to breathe and very flammable.
Humans can breathe air at much lower pressure than 1 bar. It won’t feel different if it is compensated by increasing the fraction of oxygen within the air. For example, a person breathing at half pressure (0.5 bar) would be able to produce the same amount of exercise if the oxygen fraction is doubled (to 42%).
Astronauts and high altitude pilots breathe pure oxygen at a minimum pressure as low as 0.2 bar:
https://www.nasa.gov/sites/default/files/atoms/files/dressing_for_altitude.pdf
Quote: “Likewise, U-2 and ER-2 pilots also breathe ABO [“aviator’s breathing oxygen”, nearly pure oxygen used by high-altitude pilots] and wear pressurized suits. At 30,000 feet, atmospheric pressure is 4.3 psia [“pounds per square inch absolute”, equivalent to about 7 kilopascals]. [...] When comparing air pressure psi, at sea level Earth’s surface air pressure is about 14.7 psia. At about 9.1 kilometers (30,000 feet), air pressure is 4.3 psia. Astronauts on spacewalks use suits pressurized at 4.3 psia, and the pressure in high-altitude pilot suits varies with the altitude but rarely goes above 3 psi.”
The new Martian atmosphere would be nearly pure oxygen at just enough pressure for humans to breathe without difficulty. And although most of it will be oxygen, we will have some CO2, too.
Today, 95% of the present day Martian atmosphere is CO2, but the atmosphere is so thin (the total pressure just amounts to 6 or 7 millibars) that this adds up to very little:
#Arizona State University: “Mars Education: Atmosphere” (retrieved 2022)
https://marsed.asu.edu/mep/atmosphere
Quote: “Relative to Earth, the air on Mars is extremely thin. Standard sea-level air pressure on Earth is 1,013 millibars. On Mars the surface pressure varies through the year, but it averages 6 to 7 millibars. That's less than one percent of sea level pressure here.”
However, other reservoirs of CO2 are available:
#Joshua L. Bandfield et al. (2003): “Spectroscopic Identification of Carbonate Minerals in the Martian Dust”, Science.
https://www.science.org/doi/abs/10.1126/science.1088054
Quote: “Thermal infrared spectra of the martian surface indicate the presence of small concentrations (2 to 5 weight %) of carbonates, specifically dominated by magnesite (MgCO3).”
If we assume a proportion of about 5% in weight of carbonates in the Martian rock, and that the vaporization will free about 50% of that mass in the form of CO2 (as it would happen with e.g. MgCO3), after melting 8 meters of Martian surface we would get about 2,500·8·0.025 = 500 kg of CO2 per square meter. At the Martian gravity of 3.7 m/s2, this implies a pressure of about 0.02 bar in CO2.
Similar figures have been found in other works:
#Bruce M. Jakosky and Christopher S. Edwards (2018): “Inventory of CO2 available for terraforming Mars”, Nature Astronomy
– To make it similar to earth and a lot safer, we need to add a lot of nitrogen, which Mars is lacking sadly. We have to import it. The ideal source is Titan, a large moon of Saturn, covered in a thick atmosphere that’s almost entirely nitrogen. We just have to move 3000 trillion tons from the outer solar system to Mars.
Earth’s atmosphere is a 10,000 kg/m2 column of gas that produces 1 bar of pressure under 1g of gravity. By mass, about 75% is nitrogen, i.e. 7500 kg/m2. In other words, we need 750 mbar of nitrogen, or 75,000 Pa. At Martian gravity, this means that we need about 20,000 kg/m2 of nitrogen. Multiplying by the surface of Mars (1.45·1014 m2, computed above) this implies a total of about 3·1018 kg of nitrogen, i.e. 3,000 trillion tons.
As pointed out at the beginning, nitrogen is probably scarce in the Martian soil. But these would be available in Titan:
#NASA (2021): “Titan: In Depth” (retrieved 2022)
https://solarsystem.nasa.gov/moons/saturn-moons/titan/in-depth/
Quote: “Titan's atmosphere is mostly nitrogen (about 95 percent) and methane (about 5 percent), with small amounts of other carbon-rich compounds.”
– While that’s not easy, it is doable. To process that much of Titan’s atmosphere, we have to construct giant automated factories, powered by our lasers, on its surface to suck in the atmosphere and compress it into a liquid. This gets pumped into bullet-shaped tanks, which a mass driver shoots all the way to the red planet, where they explode and mix with the oxygen. We’ve already been able to send individual missions to Saturn in just a few years. With enough resources, it should be possible to complete the task within 2 generations.
The Cassini-Huygens mission left the Earth on October 1997 and landed on Titan on January 2005, i.e. reached Saturn’s moon just 7 years:
#NASA (2021): “Cassini Mission – Timeline” (retrieved 2022)
https://solarsystem.nasa.gov/missions/cassini/the-journey/timeline/#launch-from-cape-canaveral
Counting on another 7 years on average to return to Mars, the trip of a single spaceship could be completed in about 15 years. Preparing during the years of melting and launching simultaneously as many spaceships as needed to bring all that nitrogen from Titan, it should be reasonable to have the mission completed in two generations (about 60 years, or about another half a century).
– Of course it would be much more convenient to have nitrogen left over from terraforming Venus on the side, which we explained in detail in another video.
If you enjoy terraforming planets, watch our previous video:
#Kurzgesagt (2021): “How To Terraform Venus (Quickly)”.
– So, about a century after the start of the terraforming process, we have a breathable atmosphere that has the right gases. If the liberated CO2 isn't enough to warm it up to temperatures we can stand, we just add a bit of super greenhouse gasses.
If we spend about 50 years melting through the Martian surface to release oxygen via thermolysis, and another 50 years adding nitrogen from Titan, then we would have the correct Earth-like atmosphere after about 100 years.
Our atmosphere now contains about 0.2 bars of oxygen, 0.75 bars of nitrogen and about 0.02 bars of CO2. Given that Mars is further from the Sun that the Earth, and given the fact that we have to warm the planet starting at a much lower temperature, it has been argued that such an amount of CO2 by itself won’t suffice to warm up the atmosphere to temperatures allowing for stable liquid water:
#Bruce M. Jakosky and Christopher S. Edwards (2018): “Inventory of CO2 available for terraforming Mars”, Nature Astronomy
Quote: “Models of greenhouse warming by CO2 have not yet been able to explain the early warm temperatures that are thought to have been necessary to produce liquid water in ancient times. However, such models are much more straightforward at lower pressures and for the current solar output. For an atmosphere of 20 mbar, as an example, they predict a warming of less than 10 K. This is only a small fraction of the ~60 K warming necessary to allow liquid water to be stable. It would take a CO2 pressure of about 1 bar to produce greenhouse warming that would bring temperatures close to the melting point of ice [7,43]. This is well beyond what could be mobilized into the Mars atmosphere.”
We’d have other advantages, however. Our process has released water vapor as well (which is a potent greenhouse gas, too) and our laser has heated temporarily the atmosphere, which should help kickstarting the warming process. And if this is not enough, we could achieve the desired warming by releasing a tiny amount of “super greenhouse gasses”:
# M. F. Gerstell et al (2001): “Keeping Mars warm with new super greenhouse gases”, PNAS.
https://www.pnas.org/doi/10.1073/pnas.051511598
Quote: “We suggest that a 70-K greenhouse effect might be maintainable with as little as 5 × 1022 m−2 column amount of a mixture of “designer” greenhouse molecules. This molecular column corresponds to about 240 parts per billion by volume in Earth's atmosphere”
Challenge 2: Biosphere
– Installing a biosphere onto a new planet is very difficult. Unexpected interactions between species or sudden diseases can destabilize it to the point of collapse.
Ecosystems are complex and come become fragile if the interactions among species are not properly balanced:
#Encyclopedia Britannica (2022): “Biodiversity loss” (retrieved 2022)
https://www.britannica.com/science/biodiversity-loss
Quote: “Biodiversity loss also threatens the structure and proper functioning of the ecosystem. Although all ecosystems are able to adapt to the stresses associated with reductions in biodiversity to some degree, biodiversity loss reduces an ecosystem’s complexity, as roles once played by multiple interacting species or multiple interacting individuals are played by fewer or none. As parts are lost, the ecosystem loses its ability to recover from a disturbance (see ecological resilience). Beyond a critical point of species removal or diminishment, the ecosystem can become destabilized and collapse.”
– We would probably begin by seeding our young oceans with phytoplankton. Without competition, it would bloom rapidly, filling up the oceans to become the bottom of an aquatic food chain. They can be followed by tiny zooplankton, then by fish. Maybe even sharks and whales. If things go well, life in the oceans will thrive.
We are trying to recreate the aquatic food chain, level by level. The base is phytoplankton.
#NOAA (2019): “Aquatic food webs” (retrieved 2022)
https://www.noaa.gov/education/resource-collections/marine-life/aquatic-food-webs
Quote: “Phytoplankton and algae form the bases of aquatic food webs. They are eaten by primary consumers like zooplankton, small fish, and crustaceans. Primary consumers are in turn eaten by fish, small sharks, corals, and baleen whales. Top ocean predators include large sharks, billfish, dolphins, toothed whales, and large seals.”
#Japan Agency for Marine-Earth Science and Technology (2016): “Mechanism of Resilience in Communities with Different Size Distributions” (image, retrieved 2022)
Phytoplankton gain sustenance by photosynthesis, like plants. This is useful for our terraforming efforts as it can be used to regulate the levels of carbon dioxide or oxygen in the atmosphere by changing how quickly phytoplankton grows.
#NOAA (2021): “What are phytoplankton?” (retrieved 2022)
https://oceanservice.noaa.gov/facts/phyto.html
Quote: “Phytoplankton, also known as microalgae, are similar to terrestrial plants in that they contain chlorophyll and require sunlight in order to live and grow. Most phytoplankton are buoyant and float in the upper part of the ocean, where sunlight penetrates the water.”
– Life on land is harder. Plants need nutrient-filled ground to sink their roots into. But most of the surface is the congealed remains of lava and ashes. We could wait for thousands of years for water and wind to grind it down into finer sands or try to do it manually.
Mars’ potential for providing the nutrients needed for agriculture has been considered in the literature:
#Laura E.Fackrell et al. (2021): “Development of martian regolith and bedrock simulants: Potential and limitations of martian regolith as an in-situ resource”, Icarus
https://www.sciencedirect.com/science/article/abs/pii/S0019103520304061
Quote: “Soil on Mars is known to contain the majority of planet essential nutrients, but many questions of both the benefits (e.g. bioavailability of present nutrients) and limitations (e.g. extent of toxins) of Martian soil as a plant growth medium remain unanswered. It may be necessary to augment Mars soil with other regolith and bedrock materials (e.g. phyllosilicates, carbonates) to produce a medium appropriate for plant growth.”
And the fertility of volcanic soil on Earth is well known:
#British Geological Survey (2022): “Living with volcanoes” (retrieved 2022)
https://www.bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/living-with-volcanoes
Quote: “Volcanic environments can be good locations for farming. Volcanic deposits are enriched in elements such as magnesium and potassium. When volcanic rock and ash weathers, these elements are released, producing extremely fertile soils. Thin layers of ash can act as natural fertilisers, producing increased harvests in years following an eruption.”
However, we need to prepare the rock for plant growth.
– But we want to be quick. And we have a big laser. Turning the beam on and off in rapid succession would cause the ground to quickly heat up and contract, which breaks it into smaller and smaller pieces. Add a bit of water, and you get a sort of dark mud.
Rock fracturing using pulsed lasers has been demonstrated:
#Xiaomeng Shi et al. (2020): “Enhanced rock breakage by pulsed laser induced cavitation bubbles: preliminary experimental observations and conclusions”, Geomechanics and Geophysics for Geo-Energy and Geo-Resources.
Quote: “High-power laser has been considered as a potential method of rock breakage through melting. [...] Cavitation is the rapid formation and collapse of vapour bubbles within a liquid. The irradiation of a pulsed laser beam with the energy density beyond the breakdown threshold of a liquid could induce cavitation bubbles in the liquid.The energy of the laser beam converts into highly pressurised cavitation bubbles. When the cavitation bubbles explode near rock surface, the explosions induce dynamic force to break the rock. In this paper, a series of tests using continuous and pulsed laser beams to break rocks in both air and water are presented. [...] The study leads to the conclusion that the pulsed laser induced cavitation in water is potentially an effective way for laser rock cutting technology with industrial applications.”
#Yijiang Wang et al. (2020): “Experimental study of thermal fracturing of Hot Dry Rock irradiated by moving laser beam: Temperature, efficiency and porosity”, Renewable Energy
https://www.sciencedirect.com/science/article/abs/pii/S0960148120310600
Quote: “Results indicate that rock temperature and the corresponding temperature gradients near the laser beam spots are strongly dependent on the laser power, beam diameter and irradiation time. The high temperature generated by the laser irradiation melts and cracks the HDR samples. The removed mass, cracked mass and size of grooving kerf induced by laser irradiation are also related to various irradiation conditions.”
– Into this mud, we can mix fungi and nitrogen-fixing bacteria. They’re able to absorb nitrogen and convert it into nitrate compounds to feed plants.
Fungi have been proposed as a method of turning bare asteroid rock into soil that plants can grow on.
#NASA (2021): “Making Soil for Space Habitats by Seeding Asteroids with Fungi” (retrieved 2022)
https://www.nasa.gov/directorates/spacetech/niac/2021_Phase_I/Making_Soil_for_Space_Habitats/
Quote: “Instead, we propose to create soil from carbon-rich asteroid material, using fungi to physically break down the material and chemically degrade toxic substances. We will use fungi to help turn asteroid material into soil. The basic idea is to inoculate carbonaceous asteroid material with fungi to initiate soil formation. Fungi are excellent at breaking down complex organic molecules, including those toxic to other life forms.”
Nitrogen is an essential nutrient for plants. On Earth, bacteria fix the atmospheric oxygen into the soil, where it becomes a crucial resource for plants:
#Encyclopedia Britannica: “Nitrogen-fixing bacteria” (retrieved 2022)
https://www.britannica.com/science/nitrogen-fixing-bacteria
Quote: “nitrogen-fixing bacteria, microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen (inorganic compounds usable by plants). More than 90 percent of all nitrogen fixation is effected by these organisms, which thus play an important role in the nitrogen cycle.”
– The first plants we want to bring are native to volcanic islands on Earth, since they are perfectly suited to the laser-blasted Martian landscape.
Right after a volcanic eruption the rock cannot be easily infiltrated by new water and isn’t ready to host a wide variety of plants. However, some “volcanic” species are able to thrive. In doing so, they transform the soil and allow a renewed widespread vegetation:
#B. Magnússon et al. (2014): “Plant colonization, succession and ecosystem development on Surtsey with reference to neighbouring islands”, Biogeosciences.
https://bg.copernicus.org/articles/11/5521/2014/
Quote: “Plant colonization and succession on the volcanic island of Surtsey, formed in 1963, have been closely followed. In 2013, a total of 69 vascular plant species had been discovered on the island; of these, 59 were present and 39 had established viable populations. [...] The first species to colonize Surtsey in 1965 was the sea rocket (Cakile maritima), dispersed to the island by sea currents.”
#Danny Dwi Saputra et al. (2022): “Recovery after volcanic ash deposition: vegetation effects on soil organic carbon, soil structure and infiltration rates”, Plant and Soil.
https://link.springer.com/article/10.1007/s11104-022-05322-7
Quote: “Post-eruption volcanic ash thickness varied between land-use systems and was influenced by the plots slope position rather than canopy cover. The average soil texture and porosity did not vary significantly between the periods. Surface volcanic ash and soil layers initially had low aggregate stability and limited soil infiltration, demonstrating hydrophobicity. While Corg slowly increased from low levels in the fresh volcanic ash, surface litter layer, aggregate stability, and soil infiltration quickly recovered.”
Nutrient transfer could also be considered. The process of transferring nutrient-rich soil to areas that cannot support plant growth is called soil transplantation.
#Netherlands Institute of Ecology: “Soil Transplantation” (recovered 2022)
https://nioo.knaw.nl/en/soil-transplantation
Quote: “Transporting soil from a donor area and spreading this soil over another area is what we call soil transplantation. Soil from a donor area is distributed (transplanted) thinly over the surface of a different area. Soil transplantation is often used to speed up nature development on former arable lands, using soil from nature reserves to kick-start nature in the new location.”
– Eventually, the enriched mud becomes the foundation for grasslands and forests. In Mars’ lower gravity, trees can become very tall very fast. Their roots gather the nutrients they need and then dig deeper to turn more rocks into soil, forming a self-sustaining ecosystem.
Plants grown in gravitational accelerations similar to that of Mars’ surface have been able to form roots normally:
#F. Javier Medina et al. (2021): “Understanding Reduced Gravity Effects on Early Plant Development Before Attempting Life-Support Farming in the Moon and Mars”, Frontiers in Astronomy and Space Sciences
https://www.frontiersin.org/articles/10.3389/fspas.2021.729154/full
Quote: “Fundamental novel findings were obtained from this experiment. Firstly, seedlings grown under Mars gravity exhibited a conspicuous root gravitropic response, and, consequently, a balanced distribution of the phytohormone auxin throughout the root, indicative of a regular auxin polar transport”
On Earth, tree height is limited by gravity, so it’s natural to assume that lower gravity would give taller trees:
#George W. Koch (2004): “The limits to tree height”, Nature
Quote: “Our regression analyses of height gradients in leaf functional characteristics estimate a maximum tree height of 122–130 m barring mechanical damage, similar to the tallest recorded trees of the past. As trees grow taller, increasing leaf water stress due to gravity and path length resistance may ultimately limit leaf expansion and photosynthesis for further height growth, even with ample soil moisture.”
– At this point we can slowly introduce more plant varieties, insects and animals. Not mosquitoes though. The new biosphere needs to be maintained to prevent it from falling out of balance. If plants grow too quickly and absorb too much carbon dioxide, the planet cools down too much. If key species die out, we could see populations collapse faster than they could recover. On Earth, other species would move in to fill the void, but our Martian biosphere is not as flexible.
It is thought that, on Earth, the rapid growth of the first oxygen-producing cyanobacteria about 2 billion years ago displaced so much greenhouse gasses from the atmosphere that it caused a long period of global cooling:
#Kartik Aiyer (2022): “The Great Oxidation Event: How Cyanobacteria Changed Life”, American Society for Microbiology.
https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change
Quote: “Researchers have hypothesized on the impact of the great oxidation event on the earth’s climate by painstakingly estimating geochemical and isotopic signatures of molecules in the earth’s early atmosphere, using mass-modeling and conducting studies involving redox-sensitive transition metal isotopes. These studies indicate that the chemistry of the earth’s atmosphere changed dramatically as oxygen levels rose and replaced methane (methane is still present today, but in very minute amounts). Further, it is hypothesized that accumulation of oxygen in the atmosphere led to one of the earliest ice ages on earth. Methane is a greenhouse gas, since it traps heat from sunlight and warms the planet. As methane was displaced by oxygen, global temperatures cooled sufficiently to generate ice sheets that extended all the way from the poles to the tropics.”
#Caltech (2005): “Evolutionary Accident Probably Caused The Worst Snowball Earth Episode, Study Shows” (retrieved 2025)
Quote: “cyanobacteria (or blue-green algae) suddenly evolved the ability to break water and release oxygen about 2.3 billion years ago. Oxygen destroyed the greenhouse gas methane that was then abundant in the atmosphere, throwing the global climate completely out of kilter. [...] This was bad for the climate because the oxygen destabilized the methane greenhouse. Kopp and Kirschvink's model shows that the greenhouse may have been destroyed in as little as 100,000 years, but almost certainly was eliminated within several million years of the cyanobacteria's evolution into an oxygen-generating organism. Without the methane greenhouse, global temperatures plummeted to -50 degrees Celsius.
A similar disruption would be even easier to cause on Mars.
Certain species play such an important role in the ecosystem that they are known as ‘keystone species’. Disruptions to these species will affect all the other species in the ecosystem, or even cause their collapse.
#Encyclopedia Britannica: “Keystone species” (retrieved 2022)
https://www.britannica.com/science/keystone-species
Quote: “keystone species, in ecology, a species that has a disproportionately large effect on the communities in which it occurs. Such species help to maintain local biodiversity within a community either by controlling populations of other species that would otherwise dominate the community or by providing critical resources for a wide range of species. The name keystone species, coined by American zoologist Robert T. Paine in 1969, was derived from the practice of using a wedge-shaped stone to support the top of an arch in a bridge or other construction. Just as other stones in the construction depend on the keystone for support, other species in a biological community depend on the presence of a keystone species to maintain the community’s structure.”
Challenge 3: The long future
– There is a problem we have not addressed: Mars’ core does not produce a magnetic field, so it does not have enough protection from solar radiation or cosmic rays. This becomes dangerous for the long term health of Martian populations. So as a final step, we need an artificial magnetic field. It doesn’t have to be huge like Earth’s. It just needs to deflect the solar wind enough to not touch Mars.
The defencelessness of Mars against cosmic radiation is well documented:
#Jingnan Guo (2021): “Directionality of the Martian Surface Radiation and Derivation of the Upward Albedo Radiation”, Geophysical Research Letters
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL093912
Quote: “Interplanetary space is filled with energetic particles that can affect the health of astronauts, for example, by causing late-arising cancer and possibly hereditary diseases. Mars lacks a global magnetic field and its atmosphere is very thin compared to Earth's. Thus its surface is exposed to such space radiation which presents risks to future humans on Mars.”
And some ideas to create an artificial magnetic field have already been put forward:
#R. A. Bamford et al. (2022): “How to create an artificial magnetosphere for Mars”, Acta Astronautica
https://www.sciencedirect.com/science/article/pii/S0094576521005099
Quote: “If humanity is ever to consider substantial, long-term colonization of Mars, the resources needed are going to be extensive. For a long-term human presence on Mars to be established, serious thought would need to be given to terraforming the planet. One major requirement for such terraforming is having the protection of a planetary magnetic field - which Mars currently does not have. The Earth’s magnetosphere helps protect the planet from the potential sterilizing effects of cosmic rays and also helps retain the atmosphere, which would otherwise b[e] stripped by large solar storms as they pass over the planet. Mars does have small patches of remnant surface magnetic field, but these are localized in the southern hemisphere and are not of sufficient size or magnitude to protect the planet or a colony.”
– The easiest way is a magnetic umbrella far ahead of Mars that splashes the solar wind to the sides. A big, superconducting ring powered by nuclear facilities is all it takes. It would orbit in the Mars-Sun L1 point, keeping it constantly in between the Sun and Mars and protect the new atmosphere. And that’s it!
The Lagrange point L1 of a planet is a point located between the Sun and the planet and where the gravitational attraction exerted by both bodies “cancel” each other. Such a balance of gravitational forces implies that any small object placed at L1 will remain in equilibrium at L1; i.e. the object will orbit the Sun at the same angular speed as Mars, and therefore will stay in the same relative position with respect to the Sun and Mars. (Similarly to L1, for any given planet there are other four Lagrange or “equilibrium” points, called L2, L3, L4 and L5)
#NASA (2020): “What is a Lagrange Point?” (retrieved 2022)
https://solarsystem.nasa.gov/resources/754/what-is-a-lagrange-point/
In the case of the Earth, the Lagrange point L1 is located at about 1.5 million km from Earth in the direction of the Sun. In the case of Mars, L1 is located at about 1 million km from Mars.
#R. A. Bamford et al. (2022): “How to create an artificial magnetosphere for Mars”, Acta Astronautica
https://arxiv.org/abs/2111.06887
Quote: “The Mars L1 is 333RM away and the question is then whether Mars would reside within the magnetotail created by the coil.”
(RM above stands for the radius of Mars, which is about 3,400 km)
The idea of generating an artificial magnetic field at L1 was first proposed by NASA researchers here:
#J.L. Green et al. (2017): “A future mars environment for science and exploration”, Planetary Science Vision 2050 Workshop, LPI Contribution No. 1989, Lunar and Planetary Institute, Houston
Quote: “The magnetic field will be increased until the resulting magnetotail of the artificial magnetosphere encompasses the entire planet as shown in Figure 1. The magnetic field direction could also maintain an orientation that keeps it parallel with the impinging solar wind interplanetary field thereby significantly reducing mass, momentum, and energy flow into the magnetosphere and thus also damping internal magnetospheric dynamics. This situation then eliminates many of the solar wind erosion processes that occur with the planet’s ionosphere and upper atmosphere allowing the Martian atmosphere to grow in pressure and temperature over time.”
And it has been considered in subsequent works together with other options:
#R. A. Bamford et al. (2022): “How to create an artificial magnetosphere for Mars”, Acta Astronautica
Quote: “The benefit of L1 location is the coil can potentially be smaller and the magnetic field larger without concern for the magnetic field intensity being a hazard to colonization and operation on the planet due to the distance.”
The possibilities are not completely clear, though, since some researchers have argued that the amount of superconducting material needed to create an artificial magnetosphere at L1 might be too high, at least with present-day superconductors:
#DuPont, Marcus et al. (2021): “Fundamental physical and resource requirements for a Martian magnetic shield”, International Journal of Astrobiology, Volume 20, Issue 3.
Quote: “This non-intuitive result means that the ‘intuitive’ strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. [...] We find that the most feasible design is to encircle Mars with a superconducting wire with a loop radius of ~3400 km.”