- Humanity dreams of becoming an interplanetary species, but no other planet in our solar system can currently support a complex life.
- To make a planet like Mars hospitable for us, we will have to commit ourselves to a massive earth-making effort of decades.
- Much of what makes Earth livable, such as breathable air, tolerable temperatures, and so on, is the result of microbial activity in the early history of the Earth. Can we use microbial life to make the same changes on Mars?
Three billion years ago, Earth would not have been so pleasant to humans. It was covered with active volcanoes, emitting carbon dioxide and water vapor. Unicellular life scraped from a sulfur diet. Most of the atmosphere consisted of carbon dioxide, methane and other greenhouse gases, leaving the air toxic for us and for most of modern life on Earth.
Then, about 2 and a half billion years ago, something happened. With what amounts to a snap of the fingers in geological terms, the atmosphere has been pumped full of oxygen into what we call the Great Oxygenation Event. The abundance of oxygen has meant that more new types of life could take hold of the young planet, such as eukaryotes. A few billion years ahead and a complicated and multicellular life like we are walking the planet.
So where does all this oxygen come from? Today we think that almost all the oxygen on Earth has come out cyanobacteria, small, blue-green, unicellular life that had the innovative idea of using sunlight to cook water and carbon dioxide in sugar to produce energy, ie photosynthesis. Unfortunately for cyanobacteria, photosynthesis makes the unpleasant by-product of oxygen, which they throw away in their environment.
Every breath we take, we owe to the cyanobacteria, and this inflow of oxygen into our environment is ultimately responsible for why the modern Earth is so accommodating for life. But what the Earth gives, the Earth also takes away. Whether because of climate change, nuclear war, a global pandemic or an unknown catastrophe, we would eventually like a new home. But our closest one, the best hope for a new home – Mars – has no oxygen.
It does not have much atmosphere, really.
That said, scientists hope to recreate the Great Oxygenation event on Mars much the same way it happened on Earth; using microbial life to build the environment for us.
Earth Mars with microbes
Representation of an artist of the progression of a terraforming Martian effort.
While Mars may be different from the first Earth in many ways, it has some key features that could make a microbial terraforming project work. Mars has an atmosphere that contains 95% of carbon dioxide, which provides half of the ingredients necessary for cyanobacteria to produce oxygen. The other ingredient, water, is scarcely present on the Red Planet, but we have seen evidence that exists. We know that ice is abundant in the poles, so much so that if we were to melt them, Mars would be covered in an 18-foot deep ocean.
There is already some liquid water that exists on Mars, to be sure – only in very low quantities. We have seen features on Mars called recurring pendent lines, which are dark lines that advance along the sides of the hills during the Martian summer and vanish during the winter. It is thought that these dark lines are flows of water that come and go with the seasons.
This side image of a Martian crater shows recurring slope lines. The dark lines that descend from the slope of the crater come and go with the seasons, which can indicate flowing water.
So, to terraform Mars, we will start with areas where we know that liquid water exists and we discharge many cyanobacteria there. Indeed, it would be an operation a little more sophisticated than the one that sounds, but this is the idea's juice. We would also like to include the microbes that produce greenhouse gases.
Mars has the opposite problem of the Earth; we want to make Mars warmer and thicken its atmosphere, so its polar ice can melt. More water means more opportunities for microbial life to do its job. Not to mention the fact that the current climate on Mars is too cold even for the harshest humans, with an average of around 81 degrees Fahrenheit, although the temperature can vary wildly.
The idea of using microbes to start a terraforming project on Mars is so promising that NASA has already started preliminary tests. The Ecopoiesis test bed of Mars is a proposal for a device to be included in future robotic missions to Mars. It would look something like a drill with a hallowed chamber inside. The drill would have buried itself in the Martian soil, preferably somewhere with liquid water. A container full of cyanobacteria would be released into the chamber and the sensors would detect if the microbial life produces oxygen or other by-products.
The first phase of this project was conducted in a Martian environment simulated here on Earth, and the results were positive. But even so, there are some important challenges that we will have to meet if we want to use Mars Terra in a large-scale microbial way.
The Ecopoiesis test bed of Mars.
Something very necessary for the living planets is missing from Mars: a magnetosphere. Mars had a magnetic field that protected the planet. We found magnetized rocks on the surface that indicate that this was the case, but at some point the magnetic field has disappeared and we do not know for sure what happened. Without a magnetosphere, the planet's surface is bombarded with solar radiation, which will make life wider and more difficult to sustain.
This "solar wind" also blows the Martian atmosphere. So even if we make a coaxial microbial life in the production of oxygen and other gases, many of them will simply float in space.
These images show different elements fleeing from the Martian atmosphere. From left to right, the images show carbon, oxygen and hydrogen that float in space.
Fortunately, these challenges are not insurmountable. In the short term, we will probably build domed habitats to protect both us, our cyanobacteria, and our new atmosphere from the solar wind. In the long run, NASA scientists have proposed to place a powerful magnet in a fixed orbit between Mars and the Sun. This magnet redirects the solar wind, protecting the atmosphere of Mars. While microbial life continues to produce oxygen and greenhouse gases in the atmosphere of Mars, the planet heats up, the shells melt into oceans and Mars could become our second home.
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