One-third of Mars’ surface has shallow groundwater, but it is currently too cold for life to harness it. Proposals to use greenhouse gases to heat Mars require large amounts of raw materials that are scarce on the Martian surface. But a new study shows that artificial aerosols made from materials readily available on Mars (such as conductive nanorods about 9 micrometers long) could heat Mars more than 5,000 times more effectively than the best gases.
This artist’s impression shows what Mars looked like about 4 billion years ago. Image credit: M. Kornmesser / ESO.
Mars geoengineering is a concept that frequently appears in science fiction.
But real-world researchers are also investigating techniques that could melt and release frozen groundwater, potentially making the Martian environment more hospitable to life.
Many of these strategies involve warming through greenhouse gases, but the Earth lacks the ingredients needed to produce them.
“A once habitable Martian surface is crossed by dry river valleys, but the current icy soil is too cold for Earth-derived life,” said Dr Samaneh Ansari of Northwestern University and his colleagues.
“Rivers may have flowed as far back as 600,000 years ago, suggesting the beginnings of a habitable planet.”
“Many methods have been proposed to heat the Martian surface by closing the spectral window centered on wavelengths of 22 and 10 micrometers, through which the surface would be cooled by thermal infrared radiation rising into space.”
“Modern Mars has a thin carbon dioxide atmosphere that provides a greenhouse effect of only 5 Kelvin through absorption in the 15 micrometer wavelength range, and Mars clearly lacks sufficient condensed or mineralized carbon dioxide to restore a temperate climate,” the researchers said.
“It is possible to close the spectral window using man-made greenhouse gases (e.g. chlorofluorocarbons), but this would require volatilizing about 100,000 megatons of fluorine, which is only present in trace amounts on the Martian surface.”
“An alternative approach is suggested by natural Martian dust aerosols, which are, after all, the result of the slow breakdown of iron-rich minerals on the Martian surface.”
“Due to its small size (effective radius of 1.5 micrometers), Martian dust rises to high altitudes (at an altitude of 15-25 km, where the dust mass mixing ratio peaks) and is consistently visible in the Martian sky, present at altitudes of up to 60 km or more.”
“Natural Martian dust aerosols reduce daytime surface temperatures because the composition and shape properties of man-made dust can be modified. For example, nanorods, which are about half the wavelength of upwelling thermal infrared light, should interact strongly with that infrared light.”
In the new paper, Dr Ansari and his co-authors propose an alternative strategy for heating Mars: aerosolizing 9-micrometre-long nanorods made from iron and aluminium, which are available on Mars.
The bars are about the same size as natural Martian dust — essentially a bit smaller than glitter — and should fly up into the air when dispersed.
However, other properties of the rod-shaped material mean it should settle 10 times slower than natural dust.
The researchers evaluated their proposal using a version of the MarsWRF global climate model and another complementary 1D model.
The study found that these bars amplify the amount of sunlight reaching the Martian surface and prevent heat from escaping.
In fact, a sustained release of 30 liters of nanorods per second could warm the entire planet by more than 30 Kelvin above baseline temperature, enough to melt the ice.
After a few months, atmospheric pressure will rise by 20%, creating conditions to initiate a feedforward loop involving the volatilization of carbon dioxide.
It’s worth noting that the nanorod process will still take centuries, and Mars certainly won’t be a suitable place for human habitation.
“The increase in Martian temperature alone will not be sufficient to make the Martian surface habitable for oxygenic photosynthetic organisms,” the scientists said.
“On the other hand, establishing a photosynthetic biosphere on the Martian surface, possibly with the help of synthetic biology, might increase the chances of human thriving in the solar system.”
Team work Published in today’s journal Scientific advances.
_____
Samaneh Ansari others2024. Nanoparticles could keep Mars warm. Scientific advances 10(32);doi: 10.1126/sciadv.adn4650
Source: www.sci.news
