Despite the fact we don't have the technology yet, we do know some of the key elements needed for terraforming are already present elsewhere in the solar system. Take water, for instance, whose presence in various forms on the Moon and on Mars has already been confirmed.
From water we can generate oxygen. We mostly do it at the time of writing through a process called electrolysis. But the problem with this method is that it requires electricity to work, and generating that on another planet can be quite tricky.
But there's another method to turn water into oxygen. It's called photosynthesis, and it's a process plants have been using for eons here on Earth. In photosynthesis, plants take in carbon dioxide and water, mix them with a bit of sunlight, and turn water into oxygen and CO2 into glucose.
Instant solution, but for it to apply some hard work needs to be done. Since taking plants to an alien planet and expecting them to survive to do their thing is not realistic, some other way to use photosynthesis for space exploration needs to be devised.
A team from the three European organizations (the British University of Warwick, German University of Bremen, and Swiss EPFL), backed by the European Space Agency (ESA), thinks it may just have found a way. It involves using semiconductor materials coated with metallic catalysts to capture sunlight and take oxygen out of the water found on both the Moon and Mars.
The method (a study on the subject was published earlier this month in Nature) requires no electricity, and it is only dependent on the presence of water and sunlight. If properly placed in an area where water can be found, and supplied with enough sunlight (on Mars, where the Sun doesn't shine as bright, mirrors could be used to amplify it), this method could at least supply astronauts with fresh oxygen.
Scientists call this approach artificial photosynthesis, and in the long run I dare speculate it might also play its part in terraforming. Closer to our time, however, it could be adapted to serve various green goals right here on Earth.
We're still a long way from artificial photosynthesis becoming a mature technology (at least several years of intense research are needed, we're told), but when it becomes so, the idea might forever change the worlds around us.