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Considering all the logistics involved, it is unlikely that humanity will ever see itself outside the solar system to colonize exoplanets. But the possibility of settling elsewhere in the solar system is not that exaggerated.
NASA is planning an outpost on the Moon. Manned missions to Mars are not far off. Heck, we even already have humans living off the planet (albeit for temporary stays) on the International Space Station.
So, is there anywhere else in the solar system that humans could settle in with us? Well, according to physicist and astrobiologist Pekka Janhunen of the Finnish Meteorological Institute in Finland, the dwarf planet Ceres is not entirely implausible.
Ceres is an interesting rock song. It trails in the asteroid belt between Mars and Jupiter, and with its diameter of 952 kilometers (592 miles), it is considered both the largest known asteroid in the solar system and the only dwarf planet closer to the Sun. than Neptune.
Why Ceres? That ticks many desirable boxes, Janhunen thinks.
“The motivation,” he writes in an article published on arXiv, “is to have a colony with artificial gravity that allows growth beyond the living surface of the Earth, while allowing inhabitants to easily travel between colonies and a reasonably low population density of 500 [people per] square kilometer. “
Mars and the Moon, he argues, might not be the best places for human colonies, because their natural gravity is so different from Earth’s. We know that astronauts face health issues when they return to Earth from a low or zero G environment; we have very little idea of the effects of maturity in low gravity.
An alternative to the planetary colony model is an artificial space colony, orbiting the Sun – a space station rotating to generate enough centrifugal force to mimic a g: Earth’s gravity.
It would also be logistically horrible. If the population becomes too large for a single colony, multiple colonies may be necessary. If multiple colonies orbit the Sun, they could separate, creating other problems, such as travel between colonies. If they are orbiting a common body, collision avoidance becomes an issue.
Janhunen’s solution is pretty neat, really, at least in concept: using Ceres as a base around which the rotating settlement nodes could orbit, connected by a fixed frame.
This would not only solve the problem of keeping the stand nodes together without the potential for collision, but would also solve the problem of materials perfectly, as they could be collected directly from the dwarf planet. Nitrogen is of particular importance, Janhunen said, because it makes up a large part of the Earth’s atmosphere.
But we also know that Ceres is quite salty, and recent research suggests that there could be a lot of water below the surface as well. Solar panels on the surface of the dwarf planet could easily power a space elevator to the satellite.
“Lifting Ceres materials is energetically inexpensive compared to transforming them in habitats, if a space elevator is used,” says Janhunen. “Because Ceres has low gravity and spins relatively fast, the space elevator is doable.”
The radiation shield, he said, could be constructed from 80% silicate regolith (Ceres rock) and water. The habitats would be divided into rural and urban areas, with a soil depth of 1.5 meters up to 4 meters depending on the needs for trees and gardens.
(P. Janhunen, arXiv, 2020)
Because Ceres is so far from the Sun, mirrors could be used to direct sunlight to habitat, to grow crops, for lighting, and for solar power. These mirrors would be hinged to one side of the disc-shaped satellite, like a makeup compact, and could be adjusted to collect the most sunlight as the dwarf planet moves around the Sun.
“We use disk geometry for the mega-satellite because its symmetry eliminates tidal torque so that reaction wheels are not needed to maintain attitude,” Janhunen writes.
“The habitats are illuminated by natural sunlight. The sunlight is collected on the disk by two plane mirrors tilted at a 45 degree angle and concentrated at the desired intensity by parabolic mirrors.”
This could be cultivated, if necessary, by simply adding more habitats on the edge of the former, potentially millions of habitats, for a way of life that could, perhaps, be even better than life on Earth.
After all, there wouldn’t be any natural disasters or unwanted weather conditions, and its modularity would mean it could just keep growing with population. In principle, Ceres could support, according to Janhunen, 10,000 times the current population of Earth.
Of course, this is all very speculative and remains to be tested. Additionally, Janhunen notes that orbital artificial gravity is still a goal that has yet to be met.
Besides, space elevators, giant mirrors, and radiation shielding are enough to protect a space colony. Orbital simulations for Ceres and the logistics of transporting so many humans out of Mars are also factors to consider.
However, once these problems are ironed out, it would only take about 22 years to build a human satellite orbiting Ceres, Janhunen calculates.
“The overall level of difficulty in carrying out this project is probably similar to that of the colonization of Mars,” he writes.
“The delta-v and triptime to Ceres are longer, but on the other hand, planetary landings, atmospheric weather and dust are avoided. On Ceres, it takes a bit of effort to get the materials into orbit using the elevator, but it’s energetically cheap. Once the materials are in high orbit of Ceres, the thermal environment is uniform and energy is easily obtained due to the absence of eclipses. “
It’s definitely worth thinking about, right?
Janhunen’s article, written by the Finnish Center for Excellence in Sustainable Space Research, is available on arXiv.
H / T: Phys.org
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