TRENDING
Even when the idea of terraforming Mars was originally put forward, the idea was daunting.
Changing the environment of an entire planet is not something to do easily.
Over the following decades, plenty of scientists and engineers have looked at the problem, and most have come to the same conclusion - we’re not going to be able to make Mars anything like Earth anytime soon.
A new paper available in pre-print on arXiv from Slava Turyshev of NASA’s Jet Propulsion Laboratory, is a good explainer as to why. But before we get into the constraints, let’s lay out some milestones.
There are five “end states” of making Mars habitable.
First is the current version - severely cold with minimal atmospheric pressure - not somewhere we can live without massive life support.
Second is a state where the surface pressure rises above the “triple point” of water - roughly 6.1 millibar at 0℃ - at least for a little while.
At this pressure and temperature, all three phases of water can co-exist in equilibrium. Next up is an engineering goal of a “shirtsleeve greenhouse”, where large-scale farming can happen at a local or regional level.
Typically this would involve the use of massive greenhouses, which is actually easier on Mars since the higher pressure (about 100 mbar) inside the domes would help keep the structural integrity against the lower pressure outside the dome.
This method is often called “paraterraforming”, and can be scaled to encompass the entire planet if necessary, at which point it becomes a “world house”. Fraser discusses how we would terraform Mars. Continuing to raise the overall atmospheric pressure would eventually result in a global pressure of 62.7 mbar, which is enough pressure so that human blood wouldn’t boil on the surface at 37℃.
That sounds like a necessity if we’re truly going to “terraform” Mars.
The final step would be a fully breathable atmosphere with a thick nitrogen buffer and around 210 mbar of oxygen (and 500 mbar total pressure), along with a much higher temperature. While those might seem like reasonable goals for a project as massive as terraforming the planet, the scale really gets terrifying when talking about what each of those milestones actually means.
For example, to get to just 1 mbar of pressure, we would need to add 3.89x10^15 kg of gas.
That is almost equivalent to the entire mass of Deimos - Mar’s smaller moon.
Scaling that up to a full breathable atmosphere requires more like 10^18 kg, such as Janus, an irregular moon of Saturn.
To be fair to the optimists out there, there are expected to be hundreds of bodies of that size in the solar system, so for the purpose of giving atmosphere to one of the eight planets, it might be worth sacrificing one. But pressure is only one part of the equation - temperature is the other.
We would have to raise Mars’ temperature by an average 60℃ to reach globally stable water-melting temperatures.
There are several ways to do this, ranging from injecting shortwave-absorbing nanoparticles into the atmosphere to releasing a whole ton of carbon dioxide.