As humans continue to explore the possibility of life on Mars, we are met with a series of essential questions, one of the most important being how will we live there?
Scientists and space experts alike have long grappled with this profoundly intricate question, and they are currently investigating a novel solution: terraforming. A popular definition of terraforming is “transforming (a planet) so as to resemble the Earth, especially so that it can support human life” (Oxford Languages). A concept that has long been seen as something out of a science fiction novel, terraforming is rapidly becoming a well-respected theory in the science world, with its potential applications to long-term habitation of Mars.
If you take a look at the “red planet” today, it is hard to believe that it once supported life forms similar to what we know on Earth. Indeed, its landscape of volcanoes, intense dust storms and sublimating dry ice seem anything but homey. With an global average temperature of -81 degrees fahrenheit, a paper thin atmosphere and harsh levels of radiation, if you were to step outside on Mars you would pass out instantly and die shortly after. However, multiple Mars missions have revealed features resembling dry riverbeds and mineral deposits on Mars’s surface that only form in the presence of liquid water, proving that Mars’s climate was once able to support water. Furthermore, the atmosphere must have been thicker so that greenhouse trapping of heat from the sun would warm the planet, allowing water to not freeze. Mars did not remain habitable for long, though. Data from NASA has revealed that Mars’s atmosphere was lost to space due to solar wind and radiation, leaving the planet with no greenhouse effect. This means that light from the sun is radiated directly back out into space, whereas on Earth, that sunlight bounces around our atmosphere, heating it up. Today, Mars’s atmospheric pressure is just .6% of Earth’s.
There have been many suggestions on how to make Mars habitable. We already have the technology to bring humans to Mars and set up small settlements, but not without heavy duty protection. To survive on Mars without extensive equipment, we would need a few capabilities: to be able to breathe, stay conscious and not freeze to death.
On Earth, we have an atmosphere made up of about 21% oxygen, 78% nitrogen and 1% of everything else. Mars’s atmosphere would not need that exact mix, but it would need a similar amount of oxygen to keep us breathing. Luckily, there may be enough water locked up in Mars’s ice to obtain the needed O2. But there probably would not be enough nitrogen, so you would have to wear a gas max and carry around an oxygen tank at all times. Some researchers have suggested that we turn to life forms that have transformed Earth’s atmosphere. For example, cyanobacteria were responsible for converting Earth’s atmosphere into the oxygen-rich one of today through photosynthesis. Since Mars receives little sunlight and experiences severe dust storms, introducing special microorganisms on Mars that photosynthesize in low-light could make the atmosphere breathable for humans. In an experiment conducted on the International Space Station, microorganisms survived in a container with Mars-like conditions for 533 days, demonstrating the effectiveness of this approach. However, this method would take at least a few thousand years to work. In a separate investigation that launched on February 18th, the MOXIE experiment on NASA’s Perseverance rover began its aim to convert CO2 on Mars’s atmosphere into oxygen. Although this may not be feasible for the entire planet, it is a first step in testing the limits of terraforming.
To stay awake and warm, we would need to thicken Mars’s atmosphere by adding mass to it and kickstarting a greenhouse effect that could stabilize the temperature and protect against some of the deadly radiation. According to Bruce Jakosky from The University of Colorado, we would likely initiate this greenhouse effect by using CO2 and water vapor, since they are probably the only greenhouse gasses sufficiently present on Mars’s atmosphere to provide significant greenhouse warming. This brings up a key concern surrounding terraforming Mars: is there enough CO2 on Mars for us to mobilize and put back into the atmosphere? We need more CO2 to warm up Mars than humans have emitted throughout our entire history on Earth. Fortunately, there are multiple locations on Mars that contain CO2 that could then be released. Firstly, Mars’s South Pole contains mainly CO2 ice. By making the planet warmer you would sublimate that ice, hence releasing the CO2. Or, as Elon Musk said on The Late Show with Stephen Colbert, you could drop nuclear weapons over the poles, although this would only double the atmospheric pressure on Mars which is not enough to heat up the planet. Other sources for terraforming could be lying in surface dust and carbon minerals in the crust. But carbon bearing minerals must be heated up to a very high temperature in order to retrieve CO2. If we took this approach, we would have to strip mine the entire planet in order to mobilize the billions of tons of gas needed to terraform the atmosphere; this requires a lot of energy. Furthermore, this would only provide a small fraction of the required pressure and greenhouse warming to make Mars habitable. It is possible that carbonate minerals exist in large quantities beneath Mars’s surface, and future technology may allow us to release this buried CO2, although the extent of these deposits are currently unknown.
Although NASA recognizes Mars as the most promising candidate for terraforming, according to a NASA article published in 2018, Mars does not retain enough CO2 to thicken its atmosphere and warm the planet. Therefore, terraforming Mars’s atmosphere into a hospitable environment humans could explore without life support is not possible using present-day technology. Researchers in the study analyzed the abundance of carbon bearing minerals and the presence of CO2 in polar ice using data from NASA’s Mars Reconnaissance Orbiter, Mars Odyssey spacecraft and Mars Atmosphere and Volatile Evolution spacecraft. However, Elon Musk disagreed with NASA’s study, claiming that there is plenty of CO2 to terraform Mars.
Mobilizing and releasing carbon dioxide on the red planet is not our only hope, though. We could use something more efficient – a super greenhouse gas like hydrochlorofluorocarbons – but we would need to build hundreds of factories on Mars to pump out enough of it to affect the climate. We would then need to add back other necessary gasses to allow us to take off our gas masks and oxygen tanks. Another option is comet collisions. Comets contain large sources of nitrogen, oxygen, and hydrogen, so if you could redirect thousands of comets and crash them into Mars on purpose, that could be a solution, although the repeated collisions would devastate the planet’s surface. Scientists have even imagined using an army of self replicating robots attached to comets to, over the course of years, redirect those comets to eventually impact Mars. But this process would take centuries to complete, as about 10,000 comet collisions are needed to build the quadrillion-ton nitrogen atmosphere. Researchers are also looking into aerogel, a low-density solid that is 99% air, to build structures like greenhouses. Aerogel is a great insulator and is already being used on Mars rovers. In a study published in July 2019, Harvard University professor Robin Wordsworth used a lamp to simulate Mars sunlight on a piece of silica aerogel and was able to significantly heat the surface to a temperature that would melt Mars’s ice. Aerogel is, however, brittle and production methods are questionable.
Finally, we would need to fix Mars’s magnetic field. NASA scientist Dr. Jim Green and his colleagues have theorized that, “a magnetic field placed at a point called L1 between the Sun and Mars, where their gravities roughly cancel out, could in theory encompass Mars and protect it from the solar wind.” This, along with a thicker atmosphere, would shield humans from radiation and allow for the possibility of growing plants and other forms of life.
With new enthusiasm in low-cost space exploration, we may see the technical advances needed to bring us closer to these visions sooner than we think. There are also alternatives to completely changing Mars’s atmosphere. For example, we could perform “paraterraforming” in which we would build a “world house”: a roof instead of a sky. This could be done by covering vast pieces of land with airtight bubbles, tall enough to encapsulate cities and Earth-like natural wilderness. This would also require less material than building an entire atmosphere, although space radiation and bombardment of micro-meteors could cause issues. We could also build centrifuge cities: rotating habitats that simulate gravity on Earth. So, even if terraforming Mars is not entirely possible, it does not mean we will never colonize the planet. According to The Planetary Society’s Jatan Mehta, “near-term Martian explorers would likely live in enclosed structures on the surface or subsurface, built using material from the Red Planet.”
A terraformed Mars is likely not something anyone alive today will live to see. Nevertheless, terraforming the red planet could be the first step to terraforming the galaxy. To really begin the process, we would need to build a city on Mars, which is something we’re not ready to do just yet. As said by the Associate Director of Planetary Sciences at the University of California Berkeley, Robert Lillis, “I think the people who ultimately terraform Mars are going to be martians. They will have been adapted by generations upon generations of living in lower gravity… They will ultimately start to diverge somewhat as a species from us and evolution will slowly take over. They’re still going to be humans.. But they’ll be different enough from us that they’ll be easily identifiable as ‘Martians’ as opposed to ‘Earthers.’” We should also question whether we should go forward with tailoring the solar system to our species’ comfort zone. The consequence of having an extra planet in our back pocket is that we may begin to disregard the Earth because we have another place to go. Yet, it will always be easier to keep the Earth’s environment habitable than to terraform Mars. Currently, the emphasis is on getting the first human mission to Mars. After that, we will need to establish scientific outposts on Mars to show that there’s some level of sustainability as it is today. Still, it is clear that scientific theories of the future are quickly becoming our reality.
