One oft-discussed possibility for the planet Mars is the large-scale transformation of its planetary environment to become more Earth-like – a process known as terraforming.
Extensive geological evidence indicates that Mars once had a much thicker atmosphere and a warmer climate that allowed liquid water to flow across its surface.
More on Mars
In this sense, terraforming Mars would represent an effort to wind back the clock of planetary time to return Mars to a warmer, wetter world.
So how likely is this, and what does the process of terraforming a planet actually involve?
How to terraform a planet
The first step in the terraforming process would be to pump up a more substantial atmosphere for the planet and so warm the surface by trapping heat through the greenhouse effect.
Mars today is so cold that a significant amount of its carbon dioxide air has frozen out onto the surface.
The planet’s poles contain deposits of ‘dry ice’ on top of thicker layers of water ice.
Some proposals have argued nuclear detonations over the poles could vaporise this carbon dioxide (and water) into the atmosphere to kick-start a more powerful process – the warmer Mars gets, the more greenhouse gases return to the atmosphere, causing further warming.
The problem with this nuclear option is that the latest studies estimate there isn’t enough carbon dioxide ice present to provide a significant greenhouse effect.
Another proposal is to build facilities on the surface that mine fluorine-containing minerals to manufacture powerful greenhouse gases like sulphur hexafluoride, which are thousands of times more effective than carbon dioxide.
But fluorine is pretty sparse in Mars rocks.
Creating an artificial greenhouse
So might there be another approach? Samaneh Ansari is a graduate student at Northwestern University in Illinois, and with her team has been exploring the use of artificial aerosols made of very small particles.
If these are manufactured to be about 9µm long (not much smaller than flakes of fine glitter) and very thin, the team say they would allow incoming sunlight to scatter down to the surface, but would then effectively block outgoing infrared wavelengths.
That is to say, such ‘nanorods’ would function very well as greenhouse insulation for the planet.
In fact, the team calculated that such nanorods would be more than 5,000 times more effective than the most powerful greenhouse gases.
These nanorods could be produced from common elements in Martian rocks – iron or aluminium
– and avoid the problems encountered by other proposals.
And because they are so small and light, like Martian dust particles they would be lofted high in the atmosphere and remain for a long period.
Achieving a steady temperature
The team also ran models of the Martian climate to show that if their nanorods were released at a rate of 30 litres (8 gallons) per second – pumped out of a chimney a few tens of metres tall – they could sustain a global warming of Mars of around 30°C (54°F).
This would be enough to drive carbon dioxide ice back into the atmosphere and melt near-surface ice into liquid water across large regions of the planet during summer.
This approach would still require the mining and processing of a lot of Martian rock and so would be a major undertaking.
The authors also stress that this is only a preliminary study and several uncertainties remain.
But what’s exciting is that it represents a novel strategy – and is seemingly more feasible than others – for terraforming Mars in the future.
Lewis Dartnell was reading Feasibility of Keeping Mars Warm with Nanoparticles by Samaneh Ansari et al. Read it online at: arxiv.org/abs/2409.03925.
This article appeared in the December 2025 issue of BBC Sky at Night Magazine
