Regions of Mars could be made habitable within decades using current technology. So say researchers at Harvard University, the California Institute of Technology (Caltech) and the University of Edinburgh who suggest warming just certain areas of the planet – using greenhouse-like shields made from silica aerogels – rather than terraforming it entirely.
The surface of Mars is hostile to life as we know it – it is too cold for liquid water to exist and there is no ozone layer to protect it from ultraviolet radiation. Although researchers have put forward many proposals over the years to make Mars more hospitable, all these would require massive environmental modifications. “Such global terraforming will not be possible for centuries, if ever,” says Robin Wordsworth of the Harvard Paulson School of Engineering and Applied Sciences, who led this new study.
Solid-state greenhouse effect
Wordsworth and colleagues have now put forward a new idea: exploiting a solid-state analogue to the atmospheric greenhouse effect here on Earth. This effect occurs when sunlight is absorbed inside translucent snow or ice layers. It is most pronounced in materials that are partially transparent to visible light but have low thermal conductivity and block infrared light. Unlike Earth’s polar ice caps, the polar ice caps on Mars (which contain a combination of both water ice and frozen carbon dioxide) are much too volatile to make robust solid-state greenhouse shields, say the researchers.
They explain that silica aerogels, which contain nanoscale networks of interconnecting silica clusters, contain over 97% air by volume and have some of the lowest measured thermal conductivities of any known material (of 0.02 W/m/K at 1 bar pressure or 0.01 W/m/K at Martian atmospheric pressure). Thanks to these properties, the materials are already routinely employed in many engineering applications, including in NASA’s Mars Exploration Rovers where thin aerogel layers provided night-time thermal insulation.
In their experiments, Wordsworth and co-workers replicated the surface conditions of Mars in the laboratory. They then placed a layer of silica aerogel particles or tiles on a base that reflects little light surrounded by a thermally insulating material. Next, they exposed the apparatus to visible light from a solar simulator. They measured the broadband light flux incident on the aerogel layer using a pyranometer and the temperature with calibrated glass-bead thermistors.
2-3 cm thick silica aerogel layer is enough
Both the aerogel particles and tile layers received visible flux in the 100-200 W/m2range. To compare, Earth receives on average 342 W/m2and Mars 147 W/m2.
The team found that a 3 cm layer of silica aerogel can increase the temperature of the underlying surface by 45 K when it receives a flux of 150 W/m2. Aerogel tiles, which transmit more visible light, increase temperatures by a further 10 K, reaching over 50 K at just 2 cm thicknesses.
The researchers say they can obtain warming to 0°C or higher under Mars-like insulation levels using a 2-3 cm thick silica aerogel layer. The maximum amount of warming possible is likely even higher since heat is lost in the experimental set up.
They also measured how much UV light the aerogel and tiles absorbed and found that it strongly blocked UVA and UVB radiation (280-400 nm wavelengths) and nearly totally blocked the most hazardous UVC (220-275 nm) radiation.
“The aerogel is effective at transmitting visible light but blocks infrared radiation and is an extremely effective insulator,” says Wordsworth. This makes it very efficient at warming via the solid-state greenhouse effect, while also blocking harmful UV radiation,” he tells Physics World.
Habitation domes and self-sustaining biospheres
The material could be used as a shield to warm up small, sufficiently ice-rich, relatively dust-free regions of Mars’ surface – to build habitation domes, for example, or even self-sustaining biospheres, he adds.
“There are many mid-latitude locations rich in ground ice and low dust accumulation rates within the latitude band where solar flux is high throughout the year (45°S–45°N). We calculated how the Martian subsurface would evolve using our aerogel for one location (Deuteronilus Mensae).
“Assuming the presence of a 2.5-cm-thick aerogel layer, subsurface temperatures down to depths of several metres are high enough to allow liquid water throughout the Martian year after a few years at this location.”
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The long road to Mars
“Small islands of habitability”
“Mars is the most habitable planet in our Solar System besides Earth,” explains Laura Kerber of the Jet Propulsion Laboratory at Caltech. “But it remains a hostile world for many kinds of life. A system for creating small islands of habitability would allow us to transform Mars in a controlled and scalable way.”
The team, reporting its work in Nature Astronomy10.1038/s41550-019-0813-0, now plans to investigate the response of the aerogel shield to the pressure changes expected to occur on heating the Martian surface. “We also plan to perform field tests in analogue, extreme, environmental sites on Earth, such as in the dry valleys of Antarctica or Chile, to increase the realism of our setup,” says Wordsworth.
There are also the all-important philosophical and ethical questions concerning astrobiological planetary protection that will need to be answered before any such technology can realistically be employed. “If you’re going to enable life on the Martian surface, are you sure that there’s not life there already? If there is, how do we navigate that,” he asks. “The moment we decide to commit to having humans on Mars, these questions are inevitable.”
FAQs
Why does NASA use aerogel? ›
NASA turned to the material to keep rocket fuel at cryogenic temperatures and worked with industry to create the world's first practical, flexible aerogel blankets in the 1990s.
Does aerogel protect against radiation? ›“The aerogel is effective at transmitting visible light but blocks infrared radiation and is an extremely effective insulator,” says Wordsworth. This makes it very efficient at warming via the solid-state greenhouse effect, while also blocking harmful UV radiation,” he tells Physics World.
What are the properties of aerogel? ›Aerogels are a unique class of materials that possess intriguing properties such as very light weight, low bulk density, high porosity, heat resistance, very high specific surface area, low dielectric constant, and low refractive index.
How is aerogel made? ›They are created by combining a polymer with a solvent to form a gel, and then removing the liquid from the gel and replacing it with air. Aerogels are extremely porous and very low in density. They are solid to the touch. This translucent material is considered one of the finest insulation materials available.
Can aerogel be used in Mars? ›Aerogel is a Styrofoam-like solid that is 99% air, making it extremely light. It's adept at preventing the transfer of heat as well, making it an excellent insulator; in fact, it's been used for that purpose on all of NASA's Mars rovers.
What problems can aerogel solve? ›Aerogel materials serve a vital role as protective materials needed for many fields, including as electromagnetic interference shielding material for 5G technology, thermally insulating material in high-rise buildings and infrared stealth material for military applications.
Can aerogel stop a bullet? ›Strong Enough To Stop a Bullet in its Track
To collect these delicate particles, each smaller than a grain of sand, aerogel will gradually slow them to a stop without damaging them or altering their shape and chemical composition.
Available in plastic encased strips (optional self-adhesive)that attach easily to the stud, Thermablok maintains its R-value over time, under a wide range of conditions. For this reason, Thermablok has made aerogel insulation available for home and commercial use.
What temperatures can aerogel withstand? ›Maximum operating temperatures for aerogel materials can vary. Silica-based aerogels and composite pyrogels operate until about 650°C. Airloys have maximum operating temperatures of about 300°C.
Is aerogel the best insulation? ›Air in microscopic pores make up the remaining 97% of aerogel's volume. This air has very little room to move, inhibiting both convection and gas-phase conduction. These characteristics make aerogel the world's lowest density solid and most effective thermal insulator.
What is aerogel in physics? ›
Aerogels are a class of synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas, without significant collapse of the gel structure. The result is a solid with extremely low density and extremely low thermal conductivity.
Where is aerogel insulation used? ›Aerogel is a flexible blanket insulation that can reduce energy loss whilst conserving interior space in residential and commercial building applications. It's typically applied for complete coverage in walls, floors and roofs as well as in framing and windows to provide maximum energy efficiency.
Why is aerogel fire resistant? ›The aerogels cannot be ignited under simulated real-scale fire conditions, leaving suppressed smoke emission and reduced potential for flame spread and fire hazards. High thermal insulation and resistance to a 1000 °C flame has been achieved by compositing PBOAs with fumed silica.
How long does aerogel last? ›with aerogel granules to a single glazed window. The predicted performance of this product over a 15 year lifespan is estimated based upon the results of in-situ testing, carried out by the corresponding author prior to this streamlined LCA [20].
Why is aerogel so strong? ›Aerogels are wild materials sometimes called solid smoke. As much as 99% or more of their volume is gas; the rest a gossamer network of molecules surrounding open pores. Their extreme openness means they're incredible insulators, but their structure makes them surprisingly strong as well.
Can we make Mars habitable? ›Terraforming Mars would entail three major interlaced changes: building up the atmosphere by inducing a stronger greenhouse effect and global warming, keeping the planet warm enough to allow liquid water to remain stable on its surface which would support vegetation growth, and protecting the new atmosphere from being ...
What materials can survive on Mars? ›The key life-support compounds O2, N2, and H2O are available on Mars. The soil could be used as radiation shielding and could provide many useful industrial and construction materials. Compounds with high chemical energy, such as rocket fuels, can be manufactured in-situ on Mars.
How can the aerogel sheets help possible farming on Mars? ›The “aerogel” sheets work by mimicking Earth's greenhouse effect, where energy from the sun is trapped on the planet by carbon dioxide and other gases. Spread out in the right places on Mars, the sheets would warm the ground and melt enough subsurface ice to keep plants alive.
What are the advantages and disadvantages of aerogel? ›In fact, Aerogel offers the same quality insulation with 1/3 the thickness of other insulating materials. However, Aerogel is expensive to manufacture and is rigid and brittle in its basic form, so it requires some supporting material.
Is aerogel safe for environment? ›Many aerogels are being used as insulators for houses. Most of these insulators are quite environmentally friendly, being 100% recyclable, not containing any ozone depleting substances, and being made of 30% already recycled content.
How much force can aerogel withstand? ›
The aerogels can withstand a loading of 100 000 N (109 times their own weight) for 60 min and retain their substantial elastic resilience.
Can aerogel protect you from lava? ›Despite technically being a solid, this type of aerogel is made up of 98% air. As a result, it can even insulate against the incredible heat of lava.
Can aerogel replace plastic? ›Researchers at the KTH Royal Institute of Technology in Sweden have developed a wood cellulose aerogel which offers superior thermal performance to typical plastic-based insulation materials.
Can you breathe aerogel? ›Most of the particulate released during aerogel handling was respirable. This means the particles can be inhaled deep into the lungs. Many participants who handled aerogel insulation reported upper respiratory tract irritation, or very dry or chapped skin.
What are the disadvantages of aerogel insulation? ›Disadvantages: Increased density (typically about one-third to one-half the density of water) Decreased clarity (from translucent to foggy to opaque) Decreased surface area (by about half)
Does aerogel insulate against cold? ›The air has little to no room to move, which inhibits convection and conduction, and makes it a great thermal insulator that keeps you warm and toasty. As a side note, aerogel insulation can also impede radiative heat loss, but for cold-weather apparel, convective and conductive heat loss are the primary targets.
What is the best insulation in space? ›Silica gel-based aerogels have emerged as the best alternative to currently used thermal insulation materials. This nanomaterial has provided a solution for the highly demanding thermal requirements of space vehicles and planetary exploration rovers.
How is aerogel waterproof? ›Classic silica aerogels and other oxide-based aerogels are not natively waterproof but can be modified to not only be waterproof, but superhydrophobic. Mechanically strong Airloy® aerogels made by Aerogel Technologies are water-resistant with varying levels of hydrophobicity for different applications.
Does aerogel float on water? ›In fact, silica aerogels treated in this way can not be wet by water, and will float on its surface indefinitely.
What will aerogel be used for in the future? ›Aerogels based on nanoparticles can be used as a photocatalyst, which enables or accelerates chemical reactions (when combined with sunlight) to produce extremely useful products in the modern world, including hydrogen. The optimal material for photocatalysts is titanium dioxide (TiO2), which is also a semiconductor.
What state of matter is aerogel? ›
The aerogel is defined by IUPAC (international union of pure and applied chemistry) as a “gel comprised of a microporous solid in which the dispersed phase is a gas” [56].
How much air does aerogel have? ›An excellent insulator, aerogel has the lowest density of any known solid — one form of this extraordi- nary substance is actually 99.8 percent air and 0.2 percent silica dioxide (by volume).
Is aerogel insulation toxic? ›Most of the particulate released during aerogel handling was respirable and can be inhaled deep into the lungs. Many participants who handled aerogel insulation reported upper respiratory tract irritation, or very dry or chapped skin.
Can you eat aerogel? ›Aeroeggs are not edible. Do not eat. Although Aeroeggs are made from real eggs and in principle egg aerogels could be eaten if prepared properly, these aerogels are supercritically dried in industrial equipment that processes chemicals and that is not food grade making them not edible.
Does aerogel absorb water? ›The aerogel can absorb water up to absorption capacity of 43.87–80.28 g/g. Compared with CMC and CS aerogels, the fabricated aerogel exhibits the highest water absorption capacity.
Does aerogel keep heat in? ›Aerogels can keep out both heat and cold. Some can withstand temperatures between absolute zero and 3,000 degrees Celsius. NASA has used aerogels to insulate space suits and the Mars Rover.
What do they use aerogel for? ›Metal oxide aerogels are used as catalysts in various chemical reactions/transformations or as precursors for other materials. Aerogels made with aluminium oxide are known as alumina aerogels. These aerogels are used as catalysts, especially when "doped" with a metal other than aluminium.
Is aerogel a better insulator than air? ›However, in aerogel, the narrow space in the nanostructure hinders air molecules from moving freely and effectively, and hence prevents convection of the air trapped inside [4], which enables aerogel to be an even better thermal insulator than air.
Is aerogel stronger than steel? ›However, aerographene, which is essentially graphene-based aerogel, has risen up to be in fact the least dense material in existence. With a density of only 0.16 milligrams per cubic centimetre, it can be held by a singular flower. It's also 10 times stronger than steel.
What are the advantages of aerogel insulation? ›High temperatures: Thanks to aerogel's high porosity and low-density properties, aerogel insulation has superior thermal performance, outperforming wool and fibreglass. Thinner insulation blanket: a thinner aerogel insulation blanket can offer the same thermal performance as other types of thicker insulation.
Is aerogel good for the environment? ›
Many aerogels are being used as insulators for houses. Most of these insulators are quite environmentally friendly, being 100% recyclable, not containing any ozone depleting substances, and being made of 30% already recycled content.
Is aerogel insulation any good? ›Aerogels are regarded as one of the most promising high performance thermal insulation materials for building applications today. With a thermal conductivity down to 13 mW/(m K) for commercial products they show remarkable characteristics compared to traditional thermal insulation materials.