Space News & Blog Articles

Over the last few years I have been renovating my home. Building on Earth seems to be a fairly well understood process, after all we have many different materials to chose from. But what about future lunar explorers. As we head closer toward a permanent lunar base, astronauts will have very limited cargo carrying capability so will have to use local materials. On the Moon, that means relying upon the dusty lunar regolith that covers the surface. Researchers have now developed 20 different methods for creating building materials out of the stuff. They include solidification, sintering/melting, bonding solidification and confinement formation. But of all these, which is the best?

Apollo astronauts reported the surface of the Moon to be covered in a fine, powdery material, similar in texture to talcum powder. The material, known as the lunar regolith is thought to have formed by the constant bombardment from meteoroids over millions of years. The impacts bombarded the rocks on the Moon’s surface breaking them down into fine grains. The layer varies in depth across the surface from 5 metres to 10 metres and consists mostly of silicon dioxide, iron oxide, aluminium dioxide and a few other minerals. The fine nature of the dust makes it difficult for astronauts and machinery alike to operate on the surface and its sharp contours make it somewhat hazardous.

After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Click to enlarge. Credit: NASA

Any future engineers that visit the Moon to construct habitats will need to somehow employ the use of this material in their work. A paper published in the journal Engineering by Professor Feng from the Tsinghua University has conducted a review of possible techniques. Almost 20 techniques have been employed and these have been categorised into four main processes. 

In what I can only assume to be a process similar to concrete and its reaction with water, reaction solidification takes regolith particles and reacts them with other compounds. These will have to be transported to the Moon and, when mixed with regolith, will solidify. The process would create a solid material where regolith comprises 60% to 95% of the overall mixture. 

An alternative approach involves sintering or melting the regolith by subjecting it to high temperatures. The approach can create solid material composed of entirely regolith however, temperatures in excess of 1,000 degrees are required and this in itself will pose challenges and safety concerns on the lunar surface. 

Astrobiologists continue to work towards determining which biosignatures might be best to look for when searching for life on other worlds. The most common idea has been to search for evidence of plants that use the green pigment chlorophyll, like we have on Earth. However, a new paper suggests that bacteria with purple pigments could flourish under a broader range of environments than their green cousins. That means current and next-generation telescopes should be looking for the emissions of purple lifeforms.

“Purple bacteria can thrive under a wide range of conditions, making it one of the primary contenders for life that could dominate a variety of worlds,” said Lígia Fonseca Coelho, a postdoctoral associate at the Carl Sagan Institute (CSI) and first author of “Purple is the New Green: Biopigments and Spectra of Earth-like Purple Worlds,” published in the Monthly Notices of the Royal Astronomical Society: Letters.

Artist’s concept of Earth-like exoplanets, which strikes the careful balance between water and landmass. Credit: NASA

According to NASA’s Exoplanet Archive, 5612 extrasolar planets have been found so far, as of this writing, and another 10,000 more are considered planetary candidates, but have not yet been confirmed. Of all those, there are just over 30 potentially Earth-like worlds, planets that lie in their stars’ habitable zones where conditions are conducive to the existence of liquid water on surface.

But Earth-like has a broad meaning, ranging from size, mass, composition, and various chemical makeups. While being within a star’s habitable zone certainly means there’s the potential for life, it doesn’t necessarily mean that life could have emerged there, or even if it did, the life on that world might look very different from Earth.

“While oxygenic photosynthesis gives rise to modern green landscapes, bacteriochlorophyll-based anoxygenic phototrophs can also colour their habitats and could dominate a much wider range of environments on Earth-like exoplanets,” Coelho and team wrote in their paper. “While oxygenic photosynthesis gives rise to modern green landscapes, bacteriochlorophyll-based anoxygenic phototrophs can also colour their habitats and could dominate a much wider range of environments on Earth-like exoplanets.”