One-third of Mars’ surface has shallow-buried H2O, but it is currently too cold for use by life.

Proposals to warm Mars using greenhouse gases require a large mass of ingredients that are rare on Mars’ surface.

However, we show here that artificial aerosols made from materials that are readily available at Mars—for example, conductive nanorods that are ~9 micrometers long—could warm Mars >5 × 103 time smore effectively than the best gases.

Such nanoparticles forward-scatter sunlight and efficiently block upwelling thermal infrared. Like the natural dust of Mars, they are swept high into Mars’ atmosphere, allowing delivery from the near-surface.

For a 10-year particle lifetime, two climate models indicate that sustained release at 30 liters per second would globally warm Mars by ≳30 kelvin and start to melt the ice. Therefore, if nanoparticles can be made at scale on (or delivered to) Mars, then the barrier to warming of Mars appears to be less high than previously thought.

More work is needed on the very long-term sustainability of a warmed Mars. Atmospheric escape to space would take at least 300 million years to deplete the atmosphere at the present-day rate .

However, if the ground ice observed at meters to tens of meters depth is underlain by empty pore space, then excessive warming over centuries could allow water to drain away, requiring careful management of long-term warming. Subsurface exploration by electromagnetic methods could address this uncertainty regarding how much water remains on Mars deep underground .

The efficiency of nanoparticle warming suggests that any entity with the goal of strong planet-scale warming would use this approach. This suggests polarization as a technosignature for cold terrestrial worlds with geodynamos.

Nanoparticle warming, by itself, is not sufficient to make the planet’s surface habitable again. Nevertheless, our study suggests that nanoparticle warming may be of interest to the nanophotonics and planetary science communities, among others, and that further investigation might be fruitful.