Terraforming of Mars
The terraforming of Mars is a hypothetical procedure that would consist of a planetary engineering project or concurrent projects aspiring to transform Mars from a planet hostile to life to one that could sustainably host humans and other lifeforms free of protection or mediation. The process would involve the modification of the planet's extant climate, atmosphere, and surface through a variety of resource-intensive initiatives, as well as the installation of a novel ecological system or systems.
Justifications for choosing Mars over other potential terraforming targets include the presence of water and a geological history that suggests it once harbored a dense atmosphere similar to Earth's. Hazards and difficulties include low gravity, toxic soil, low light levels relative to Earth's, and the lack of a magnetic field.
Although new techniques have emerged that could raise Mars's average global temperature by tens of degrees within a few decades, the terraforming of Mars is considered to be infeasible using present-day technology. Disagreement exists about whether future technology should render the planet habitable. Reasons for supporting terraforming the planet include allaying concerns about resource consumption and depletion on Earth and arguments that the alteration and settlement of other planets decreases the odds of humanity's extinction. Reasons for objecting to terraforming the planet include ethical concerns about terraforming, and the considerable energy and resource costs that such an undertaking would involve.
Motivation and side effects
Future population growth, demand for resources, and an alternate solution to the doomsday argument may require human colonization of bodies other than Earth, such as Mars, the Moon, and other objects. Space colonization would facilitate harvesting the Solar System's energy and material resources.In many aspects, Mars is the most Earth-like of all the other planets in the Solar System. It is thought that Mars had a more Earth-like environment early in its geological history, with a thicker atmosphere and abundant water that was lost over the course of hundreds of millions of years through atmospheric escape. Given the foundations of similarity and proximity, Mars would make one of the most plausible terraforming targets in the Solar System.
Research on terraforming Mars continues to advance. Mars, once terraformed, could become humanity's last hope in the event of various catastrophes, such as an unlimited nuclear war that could result in high radioactive contamination of the Earth, uncontrolled global warming, or an epidemic of particularly virulent bacteria or viruses.
Side effects of some methods of terraforming include the potential displacement or destruction of any indigenous life if such life exists.
Challenges and limitations
The Martian environment presents several terraforming challenges to overcome and the extent of terraforming may be limited by certain key environmental factors. The process of terraforming aims to mitigate the following distinctions between Mars and Earth, among others:- Reduced light levels
- Low surface gravity
- Unbreathable atmosphere
- Low atmospheric pressure
- Ionizing solar and cosmic radiation at the surface
- Average temperature compared to Earth average of
- Molecular instability — bonds between atoms break down in critical molecules such as organic compounds
- Global dust storms
- No natural food source
- Toxic soil
- No global magnetic field to shield against the solar wind
Countering the effects of space weather
The lack of a magnetic field, its relatively small mass, and its atmospheric photochemistry, all would have contributed to the evaporation and loss of its surface liquid water over time. Solar wind–induced ejection of Martian atmospheric atoms has been detected by Mars-orbiting probes, indicating that the solar wind has stripped the Martian atmosphere over time. The current loss rate of CO2 from Mars's atmosphere to space is equivalent to approximately 1 millibar per billion years. For comparison, while Venus has a dense atmosphere, it has only traces of water vapor as it lacks a large, dipole-induced, magnetic field.
Earth's ozone layer provides additional protection. Ultraviolet light is blocked before it can dissociate water into hydrogen and oxygen.
Low gravity and pressure
The surface gravity on Mars is 38% of that on Earth. It is not known if this is enough to prevent the health problems associated with weightlessness.Mars's atmosphere has about 1% the pressure of the Earth's at sea level. It is estimated that there is sufficient ice in the regolith and the south polar cap to form a atmosphere if it is released by planetary warming. The reappearance of liquid water on the Martian surface would add to the warming effects and atmospheric density, but the lower gravity of Mars requires 2.6 times Earth's column airmass to obtain the optimum pressure at the surface. Additional volatiles to increase the atmosphere's density must be supplied from an external source, such as redirecting several massive asteroids containing ammonia as a source of nitrogen.
Breathing on Mars
Current conditions in the Martian atmosphere, at less than of atmospheric pressure, are significantly below the Armstrong limit of where very low pressure causes exposed bodily liquids such as saliva, tears, and the liquids wetting the alveoli within the lungs to boil away. Without a pressure suit, no amount of breathable oxygen delivered by any means will sustain oxygen-breathing life for more than a few minutes. In the NASA technical report Rapid Decompression Emergencies in Pressure-Suited Subjects, after exposure to pressure below the Armstrong limit, a survivor reported that his "last conscious memory was of the water on his tongue beginning to boil". In these conditions humans die within minutes unless a pressure suit provides life support.If Mars's atmospheric pressure could rise above, then a pressure suit would not be required. Visitors would only need to wear a mask that supplied 100% oxygen under positive pressure. A further increase to of atmospheric pressure would allow a simple mask supplying pure oxygen. This might look similar to mountain climbers who venture into pressures below, also called the death zone, where an insufficient amount of bottled oxygen has often resulted in hypoxia with fatalities. However, if the increase in atmospheric pressure was achieved by increasing CO2 the mask would have to ensure the external atmosphere did not enter the breathing apparatus. CO2 concentrations as low as 1% cause drowsiness in humans. Concentrations of 7% to 10% may cause suffocation, even in the presence of sufficient oxygen.
In 2021, the NASA Mars rover Perseverance was able to make oxygen on Mars. However, the process is complex and takes a considerable amount of time to produce a small amount of oxygen.
considered various methods of raising Mars' temperature without replenishing the atmosphere with nitrogen. It would then be possible to create a thin atmosphere composed primarily of oxygen, but still capable of supporting human life.
Advantages
Mars exists on the outer edge of the habitable zone, a region of the Solar System where liquid water on the surface may be supported if concentrated greenhouse gases could increase the atmospheric pressure. The lack of both a magnetic field and geologic activity on Mars may be a result of its relatively small size, which allowed the interior to cool more quickly than Earth's, although the details of such a process are still not well understood.There are strong indications that Mars once had an atmosphere as thick as Earth's during an earlier stage in its development, and that its pressure supported abundant liquid water at the surface. Although water appears to have once been present on the Martian surface, ground ice currently exists from mid-latitudes to the poles. The soil and atmosphere of Mars contain many of the main elements crucial to life, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon.
Any climate change induced in the near term is likely to be driven by greenhouse warming produced by an increase in atmospheric carbon dioxide and a consequent increase in atmospheric water vapor. These two gases are the only likely sources of greenhouse warming that are available in large quantities in Mars's environment. Large amounts of water ice exist below the Martian surface, as well as on the surface at the poles, where it is mixed with dry ice, frozen. Significant amounts of water are located at the south pole of Mars, which, if melted, would correspond to a planetwide ocean 5–11 meters deep. Frozen carbon dioxide at the poles sublimes into the atmosphere during the Martian summers, and small amounts of water residue are left behind, which fast winds sweep off the poles at speeds approaching. This seasonal occurrence transports large amounts of dust and water ice into the atmosphere, forming Earth-like ice clouds.
Most of the oxygen in the Martian atmosphere is present as carbon dioxide, the main atmospheric component. Molecular oxygen only exists in trace amounts. Large amounts of oxygen can be also found in metal oxides on the Martian surface, and in the soil, in the form of per-nitrates. An analysis of soil samples taken by the Phoenix lander indicated the presence of perchlorate, which has been used to liberate oxygen in chemical oxygen generators. Electrolysis could be employed to separate water on Mars into oxygen and hydrogen if sufficient liquid water and electricity were available. However, if vented into the atmosphere it would escape into space.