Heating Mars with nanorods

Should mankind actually succeed in venturing to Mars to colonize it, there are a few key problems. The red planet has an atmosphere that is hostile to life – not only because of the lack of oxygen. The temperatures are also extremely unpleasant and can range from 20 degrees plus to minus 150 degrees Celsius. The heat from the sun disappears as quickly as it arrived, as it cannot be stored. However, there are a number of ideas for introducing warming – a kind of climate change on Mars. So far, these are all purely hypothetical. A new idea from researchers at the University of Chicago now promises to be much more effective than previous proposals. The team led by Edwin Kite, Associate Professor specializing in planetary science and in charge of Solar System and Exoplanet Habitability Research (SSEH), wants to use nano-sized rods, so-called nanorods made of metal.

Hope for ice melt

However, the study published in the journal ScienceAdvances only examines the basic plausibility of the idea. It would also only be a first step, as this alone would not make real life possible on Mars. The nanorods are intended to thicken the planet's atmosphere. If this succeeds, it could trap more solar heat and eventually, it is hoped, melt the water ice beneath the surface. In the model, the idea is already 5000 times more effective than other hypothetical plans for warming Mars. These rely primarily on greenhouse gases, as we know them similarly – and in the negative context of global warming –.

Kite's nanorod idea, which was developed by Master's student Samaneh Ansari, takes a different approach. It relies on nanorods, each nine micrometers long, which could be produced from existing Martian iron and aluminium. They are smaller than normal Martian dust (they resemble glitter) and are to be injected into the atmosphere as aerosols. In contrast to normal dust, they remain in the atmosphere ten times longer. In sufficient quantities, this would allow sunlight to continue to pass through to the planet, but would trap the resulting heat more strongly than before. According to Ansari, the calculation using the MarsWRF climate model and other models shows that a release of 30 liters of nanorods per second – over a constant period of time – could trigger an ice melt with a temperature increase of 10 degrees Celsius. "After a few months, the atmospheric pressure would then rise by at least 20 percent, with the evaporation of carbon dioxide at least doubling the atmospheric pressure over longer periods of time," write the research team.

First nanorods, then plants

However, it would still not be possible to breathe such air. But perhaps, say the researchers, it could lay the foundations for this. Microorganisms and useful plants could already be planted that could gradually supply oxygen to the atmosphere – in the same way as they have done for the earth throughout its geological history. But the time horizon is long. In addition, the astronauts would have to produce enormous quantities of nanorods. "You'd still need millions of tons to warm the planet, but that's five thousand times less than previous proposals for global warming of Mars," says Kite. "That greatly strengthens the feasibility of the project."

Ansari is at least enthusiastic about what could be possible with nanomaterials on the red planet. "How light interacts with objects in the sub-wavelength range is fascinating. Importantly, the development of nanoparticles can lead to optical effects that go far beyond what is usually expected from such small particles," says the researcher. The current Martian dust is counterproductive here: its composition and size are more likely to cause the planet to cool down even further. Another good thing about the nanorods is that they can be produced using existing raw materials on the planet, instead of having to bring large quantities of gas or other substances to the red planet first.

(mma)