Ever since the Vikram lander touched down on the lunar surface, there has been a steady flow of data and information from the instruments onboard the lander and the rover.
Separately, the information may look like some scientific hickery-pockery, but when you stitch them together you can read one message: the moon is more habitable than thought earlier.
The biggest supporter of this notion is the data point thrown up by the lander, which sent a probe down 10 cm into the lunar surface and measured the temperature there. It came up with the revelation that when the lunar surface is about 50o C hot, just 8 cm below the surface, it is as cold as minus 10o C. There is more to this data point than the ‘wow’ feeling it evokes.
For a while now, scientists have known that the lunar subsurface is cold. Vikram has only provided proof that the lunar topsoil is a super-insulator.
Regolith shielding
In a 2015 paper titled ‘Determination of temperature variation on lunar surface and subsurface for habitat analysis and design’, published in the journal Acta Astronautica, the authors, Ramesh B Malla and Kevin M Brown, of the University of Connecticut in the US mathematically determined that “the outermost layer of regolith fluff has very strong insulating capabilities causing the temperature to drop 132.3 K (-140.85o C) from the maximum daytime magnitude of 387.1 K (113.95o C) within the first 30 cm at which point it then remains constant with increasing depth.”
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The moon, which has no atmosphere, is directly exposed to the sun. It gets extremely hot (123o C) during daytime and incredibly cold during night (-233o C). To build a habitat there calls for a stupendous amount of insulation. Imagine carrying all the insulating material all the way from the earth! But now, as Vikram has shown, we see that it is not really necessary.
A layer of processed regolith spread on top of the habitat can make the inhabitants nice and comfy inside. Malla and Brown further say that when you have a regolith shielding atop a lunar habitat, the reflection of sunlight from the surrounding area (albedo) raises the temperature of the shielding, with a corresponding drop below a foot of the regolith cover.
Now that the Vikram lander has shown that the temperature drops by 60o C from the top of the 2 cm-thick ‘fluff’ to 8 cm below the ground, one can design a habitat accordingly. The fluff has very low thermal conductivity.
In another research paper, titled ‘Energy requirements of a thermally processed ISRU radiation shield for a lunar habitat’, authors Christopher Spedding et al of the Open University, Walton Hall, UK, note that it is possible to set up MW-scale solar or nuclear power plants and use the energy to “thermally process” construction material (with lunar regolith), “making large, permanent human presence on the moon more easily realisable.”
More good news
The Pragyan rover, on its part, has also helped confirm something heartening — the presence of oxygen in the lunar soil. The ‘Laser Induced Breakdown Spectroscopy’ (LIBS) instrument on the rover, threw laser beams on to the soil and analysed the reflections. It has shown the presence of sulphur, calcium and many metals such as iron, chromium, titanium, manganese and aluminium and oxygen.
The presence of oxygen in the soil, in the form of ilmenite (FeTiO3), means you have an alternative to ice for oxygen production. So, you don’t have to build your house only near an ice-source if you were to settle on the moon. Ice is not present everywhere, but soil is. Ilmenite can be reduced to make oxygen for breathing.
The findings from the lander and the rover go to strengthen a growing branch of science called In-situ resource utilisation (ISRU), alternatively known as ‘space resource utilisation’ (SRU).