Carl sagan was the first person who proposed to transform Mars outside the field of science fiction. Sagan pointed out in the paper "Planetary Engineering on Mars" of 197 1 that the evaporation of the Arctic ice sheet is likely to produce the Martian atmosphere, which will lead to the greenhouse effect, increase the temperature and greatly increase the possibility of liquid water.
Sagan's work inspired other researchers and futurists to take seriously the idea of transforming Mars into the Earth.
The key question is: Is there enough greenhouse gas and water on Mars to raise its atmospheric pressure to a level similar to that of the Earth?
In 20 18, researchers from the University of Colorado, the University of Boulder and northern arizona university, funded by NASA, found that all available resources on Mars would only increase the atmospheric pressure to about 7% of the earth, far below the pressure needed to make Mars livable.
Now, researchers from Harvard University, NASA's Jet Propulsion Laboratory and Edinburgh University have a new idea. Instead of trying to change the whole planet, why not adopt the method of regional transformation?
Researchers believe that some areas on the surface of Mars can be inhabited by a substance similar to the greenhouse effect of the earth's atmosphere-silica aerogel. Through modeling and experiments, researchers show that silica aerogels with a thickness of two to three centimeters can transmit enough visible light for photosynthesis, prevent harmful ultraviolet radiation, and permanently raise the temperature above the melting point of water without any internal heat source.
This paper was published in Natural Astronomy.
Different from the previous idea of making Mars livable, this regional method of making Mars livable is easier to realize than global atmospheric transformation, and it is something that can be systematically developed and tested by using our existing materials and technologies.
In the solar system, besides the earth, Mars is the most livable planet. But for many species, it is still a hostile world. A system for creating habitable islands will allow us to transform Mars in a controllable and extensible way.
Unlike the polar ice sheet made of frozen water on earth, the polar ice sheet on Mars is a combination of water ice and frozen carbon dioxide. Just like its gaseous form, frozen carbon dioxide absorbs heat and allows sunlight to penetrate. In summer, this solid greenhouse effect will increase the temperature under the ice.
Solid greenhouse effect, what kind of material can minimize the thermal conductivity and transmit as much light as possible?
The researchers focused on silica aerogel, which is one of the most insulating materials ever.
97% of silica aerogel is porous, which means that light can pass through the material, but the nano-layers of silica infrared radiation are interconnected, which greatly slows down the heat conduction. Today, these aerogels have been used in many engineering applications, including NASA's Mars probe.
Figure: A thin translucent material with low thermal conductivity can transmit visible light, but block ultraviolet and infrared rays, which directly replicates the radiation effect of the earth's atmosphere. Due to thermal diffusion, the depth of underground habitable area increases with time. Tav is the average surface temperature.
Silica aerogel is a promising material, because its function is passive, and it can keep an area warm for a long time without a lot of energy or maintenance of moving parts.
By simulating models and experiments on the surface of Mars, the researchers proved that the thin layer of this substance can raise the average temperature in the mid-latitude area of Mars to a temperature similar to that of the Earth. In a large enough area, there is no need for any other technology, just cover the surface and bottom with a layer of this substance, and there will be permanent liquid water.
This material can be used to build a life dome or even a self-sufficient biosphere on Mars.
Next, the research team's goal is to test this material under the climate conditions similar to Mars on Earth, such as the dry valleys in Antarctica or Chile.
References:
1. Baidu encyclopedia
2. Material methods to make Mars livable
3. Using silica aerogels to realize the habitability of Mars through the solid greenhouse effect.
4. Silica aerogels can warm the surface of Mars, just as greenhouse gases warm the earth.