Mars though close to Mercury’s dimensions to the naked eye, falls a little short. Mercury has a higher density. This causes a slightly stronger gravitational force at Mercury’s surface. The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as rust. In comparison to Earth, Mars has half the radius and only one-tenth the mass of our planet. Mars’ total surface area is only slightly less than the total area of Earth’s dry land.
Mars consists of much of the chemical materials needed to terraform, including abundant carbon dioxide, water (although not as much as on Earth) and oxygen, in the form of per-nitrates in the composition of the soil. Because of the extremely low temperatures and pressures a lot of CO2 is frozen on the poles, most of the water is either frozen or in its gaseous phase and most of the oxygen is bound to the highly reduced metal-oxides on the Martian surface.
It is generally thought that Mars could once have had an environment relatively similar to today’s Earth, during an early stage in its development. This similarity is predominantly associated with the thickness of the atmosphere and abundance of water, both considered to have been lost over the course of hundreds of millions of years. The exact mechanisms which resulted in this change are still unclear, though several mechanisms have been proposed. For instance, the gravity of Mars today indicates that lighter gases in the upper atmosphere would have contributed to this loss, with the atoms dissipating into space. The lack of plate tectonics on Mars today and in the past, indicated by the thorough examination of its surface features is another plausible factor, since this would cause the recycling of gases locked up in sediments back into the atmosphere to occur at a slowed rate. The lack of magnetic field and geologic activity may both be a result of Mars’ smaller size allowing its interior to cool more quickly than Earth’s, though the details of such processes are still not precisely clear. However, none of these processes are likely to be significant over the typical lifespan of most animal species, or even on the timescale of human civilization, and the slow loss of atmosphere could possibly be counteracted with ongoing low-level artificial maintenance activities.
Terraforming Mars entails two or three major interlaced changes: building up the atmosphere and keeping it warm. The existing Martian atmosphere consists mainly of carbon dioxide, a known greenhouse gas, so once the planet begins to heat, more CO2 enters the atmosphere from the frozen reserves on the poles, adding to the greenhouse effect. This means that the two processes of building the atmosphere and heating it would augment one another, and make terraforming easier. However, a large scale, controlled application of certain techniques (explained below) over enough time to achieve sustainable changes would be required to make theory a reality.
Another change that may need to happen is the restoration of the magnetosphere of Mars and due to this if a large solar wind were to occur, then all places not protected by Mars’s magnetospere (most of the northen hemisphere and parts of the lower) would become desolate as the Mars we know today. The process is still not well understood: Venus lacks a magnetosphere and has a very thick atmosphere.
Building the atmosphere
There are many possible techniques of building an atmosphere with the right chemical constituents to make Mars habitable, and some are easier than others to implement. If a technique is too intricate and can’t sustain itself without human intervention then it should not be considered.
Chloro-Fluoro-Carbons (or CFC) are the simplest way for artificial insertion into the Martian atmosphere because of their strong effect as a greenhouse gas. RAP Towers serve a dual process in this regard: as well as scrubbing and sublimating bound CO2, these contain ancillary automated units which essentially pump PFCs into the upper atmosphere.
Seeding of tailored algae and lichens contributes to the process, and darkens the surface so reducing the albedo of the planet. By absorbing more sunlight, the ground warms the atmosphere even more, and the atmosphere gains a new small oxygen contribution from the algae.
Several martian industrial processes also oxidize the metals in the soil, effectively resulting in desired crude metals and oxygen as a byproduct. Imported plants and microbial topsoil also add to the effect.
Dealing with radiation
It was once believed by some that Mars would be uninhabitable to most life-forms because of higher radiation levels. Without a magnetosphere, the sun is thought to have thinned the Martian atmosphere to its current state; the solar wind adding a significant amount of heat to the atmosphere’s top layers which enables the atmospheric particles to reach escape velocity and leave Mars (effectively boiling off the atmosphere). Indeed, this effect has even been detected by Mars-orbiting probes.
Venus, however, showed that the lack of a magnetosphere did not preclude an atmosphere. A thick atmosphere will also provide radiation protection for the surface, as it does at Earth’s polar regions where aurorae form, so the lack of a magnetosphere will not seriously impact the habitability of a terraformed Mars. In the past, Earth has regularly had periods where the magnetosphere changed direction and collapsed for some time. Some scientists believe that in the ionosphere a magnetic shielding was created almost instantly after the magnetosphere collapsed, a principle that applies to Venus as well and would also be the case in every other planet or moon with a large enough atmosphere.
In addition, the radiation isn’t as harmful to living things as commonly believed. Living organisms adapt readily to their environments, and sometimes even change their environment to suit them. High radiation levels might be a shock at first, but it is likely that any adaptive species living on Mars would adapt to its new environment quickly enough to survive.