With the right technology and spirit of adventure, the Main Asteroid Belt could become the industrial hub of the Solar System.

The science of becoming “interplanetary”: Could humans live in the asteroid belt?
An artist’s concept of the closest known planetary system to our own-Epsilon Eridani. NASA/JPL-Caltech

Key takeaways

  • The Asteroid Belt could become a central hub for mining and manufacturing, thanks to its rich resources and strategic location.
  • Mining asteroids may ensure human survival by providing abundant resources, potentially leading to a post-scarcity era.
  • The discovery of the Asteroid Belt began in the early 1800s, with significant contributions from astronomers like Giuseppe Piazzi and Heinrich Olbers.
  • Establishing human habitats in the Belt will require overcoming harsh conditions, such as cold temperatures, radiation, and low gravity.
  • Self-sustaining habitats using local resources and innovative designs could turn the Belt into a thriving community, complete with Earth-like living conditions.

Welcome back to the continuing “Interplanetary Series.” In earlier chapters, we discussed what it would take to survive on Mercury, Venus, the Moon, and Mars. Today, we’ll look at the main asteroid belt. This vast expanse of space contains numerous big entities that might one day be inhabited by humans.

For decades, futurists and theorists have discussed the possibility of establishing a permanent human presence and infrastructure in the Asteroid Belt. Its enormous resources, along with its strategic location between the inner and outer Solar systems, make it an appealing candidate for future exploration and development.

In fact, asteroid mining is viewed as a method of ensuring human survival and ushering in a post-scarcity era for our society. While the hurdles are undeniably daunting, the advantages are quite appealing. With a little innovation and innovative design, the Belt may become a popular destination for individuals seeking adventure and enjoyment in low gravity.

Someday, intergalactic travelers may hear messages like this:

“Good morning, passengers! Welcome aboard the ferry liner Kirkwood, your one-stop service to Ceres! For those among you that are first-timers, be prepared for fun, adventure, and some of the most luxurious accommodations in the Solar System! While you’re our guest, we insist you take full advantage of the low-gravity environment and the exotic surface!”

“A reminder that making the transition from an Earth-normal gravity environment can be difficult. Report to a clinician if you find yourself experiencing any of the following symptoms: vertigo, dizziness, vomiting, fainting spells, or rapid heart rate. These can be signs that you are having trouble adjusting. But don’t worry, our expert staff will help you find your footing (not a guarantee)!”

Source: NASA/McREL

“Adventure tours include day trips to Ahuna Mons, the highest peak on Ceres, and Occator, the largest crater. We also recommend the multi-day excursions to the famous “bright spots,” Cerealia Facula and the Vinalia Faculae. And be sure to check out the bright spots here, including five-star accommodations, dining, gaming, and recreation centers.”

“Those who are transferring to Vesta or Pallas must first pass through customs and biomonitoring for a second screening. We apologize for the inconvenience but remind people that maintaining public health is a priority here in the Belt. After all, the air we breathe is a shared amenity, so let’s keep it clean and healthy!”

“A reminder that the import of flora and fauna is strictly prohibited. Please respect the local life cycle and not attempt to take seeds or plants from the local biome. All species on Ceres are adapted to the local gravity and are not likely to survive in another environment.”

The discovery of the Asteroid Belt began around 1800 as a result of a problem with the then-current understanding of the Solar System. The Titius-Bode Law, which properly predicted planet orbits, revealed an inexplicable gap between Mars and Jupiter. To address this issue, the United Astronomical Society began watching the gap in the hopes of discovering anything.

The club includes several well-known astronomers, including William Herschel, who discovered Uranus and its moons in the 1780s. Giuseppe Piazzi, the chair of astronomy at the University of Palermo, was invited to join the Society. Ironically, he made the first finding in this location (as predicted by the Titus-Bode Law) before the invitation arrived.

He dubbed the object “Ceres” after the Roman harvest deity and Sicily’s patron god. Fifteen months later, prominent astronomer and Society member Heinrich Olbers found a second object in the same location, which he dubbed 2 Pallas. These items appeared to be nothing more than brightly colored, moving dots.

Herschel proposed a new class of objects named “asteroids” (Greek for “star-like”). By the early 1850s, the terms “asteroids” and “Asteroid Belt” had gained popularity. Since the late nineteenth century, approximately a million artifacts have been identified in the Belt.

The “Main” Belt

The Main Asteroid Belt, located between Mars’ and Jupiter’s orbits, is a torus-shaped area filled with bodies left over from the birth of the solar system. It is called the “Main” Belt to distinguish it from other asteroid populations such as Near-Earth Asteroids (NEAS) and Trojan and Greek asteroids (which circle Jupiter).

Astronomers have currently cataloged 1,113,527 objects in the Belt, with estimations estimating that there might be up to 1.9 million objects measuring 0.6 mi (1 km) or more in diameter. The Belt is 2.2 to 3.2 astronomical units* (AU) from the Sun and around one AU wide.

Source: ESO/M. Kornmesser/Vernazza et al.

The entire mass is calculated as 5.27×1021 lbs (2.39×1021 kg), which is approximately 3% of the Moon’s mass. Ceres, four Vesta, two Pallas, ten Hygiea, and other asteroids have diameters more than 100 kilometers. These four asteroids account for more than half of the Belt’s total mass, with Ceres alone accounting for more than a third.

Contrary to popular belief, the Asteroid Belt is primarily empty space, with objects distributed across a huge volume of space. The major population of the Asteroid Belt is sometimes classified into three zones based on Kirkwood Gaps.

These are named after astronomer Daniel Kirkwood and explain the orbital dimensions of an asteroid based on its semi-major axis. In 1866, he identified gaps in the distances between asteroids. These characterize an asteroid’s orbital dimensions in terms of its semi-major axis. This system has three zones:

  • Zone I is located between the 4:1 and 3:1 resonance gaps, around 2.06 and 2.5 AU from the Sun, respectively.
  • Zone II stretches from the end of Zone I to the 5:2 resonance gap, which is located 2.82 AU from the Sun.
  • Zone III runs from Zone II’s outer border to the 2:1 resonance gap at 3.28 AU from the Sun.

The Asteroid Belt can also be split into inner and outer belts. The inner Belt contains asteroids that orbit closer to Mars than the 3:1 Kirkwood gap (2.5 AU). The outer Belt contains asteroids closer to Jupiter’s orbit. The asteroids at a radius of 2.06 AU from the Sun form the asteroid belt’s inner limit.

The temperature of the asteroid belt fluctuates with its distance from the Sun. Dust particles within the Belt have normal temperatures ranging from -99 °F (-73 °C) at 2.2 AU to -162 °F (-108 °C) at 3.2 AU. However, because to spin, the surface temperature of an asteroid can change significantly when the sides are alternately exposed to solar radiation and then to the stellar background.

The majority of asteroids, like the terrestrial planets, are made of silicate rock, with just a little amount of iron and nickel. The remaining asteroids are a mixture of these and carbon-rich elements. Some of the more distant asteroids contain more ices and volatiles, such as water ice. The Main Belt largely consists of three types of asteroids:

  • C-type asteroids are carbonaceous (carbon-rich), accounting for more than 75% of observable asteroids.
  • S-type asteroids are silicate and metal-rich, and are more prevalent in the Belt’s inner area.
  • M-type asteroids (iron, nickel, and some silicates) make up 10% of the overall population.
Source: NASA

There are also the strange and relatively rare V-type (or basaltic) asteroids, which were formerly thought to have formed on Vesta. However, the discovery of basaltic asteroids with varying chemical compositions implies a different origin, and current asteroid formation models anticipate that V-type asteroids will be more abundant.

*Equal distance between the Earth and the Sun.

Major bodies

As previously stated, the Belt contains millions of known objects, but four planetoids, Ceres, 4 Vesta, 2 Pallas, and 10 Hygiea, account for more than half of its mass. These bodies vary in size, shape, and composition. These bodies are designated as “minor planets” under Resolution 5A: “Definition of ‘planet'” adopted by the IAU’s General Assembly in 2006.

Ceres, the biggest of the four bodies, has a diameter of approximately 584 miles (940 kilometers) and is the only planetoid in the Belt (or Solar System) that has achieved hydrostatic equilibrium (becomes spheroid in shape). This resulted in its reclassification as the lone “dwarf planet” in the Belt, according to the IAU’s 2006 Resolution.

Ceres has a mass of about 20.68×1020 pounds (9.38×1020 kg), which is around 1.28% as massive as the Moon. It is mostly formed of water ice, carbonates, and silicate minerals. These are thought to be classified as a mostly frozen outer crust, an internal ocean of saltwater and rock, and a rocky mantle with a metallic core.

Ceres, the largest massive rock in the Asteroid Belt, is thought to have originated outside of Jupiter’s orbit before migrating to the Belt. Because of its low mass and density, the surface gravity is less than 3% of Earth’s (0.028 g). Its surface is covered by craters measuring between 10 and 60 mi (20 and 100 km), with the biggest spanning 176 miles (284 kilometers) across – the Kerwal Basin.

The surface also displays symptoms of cryovolcanism, as seen by the brilliant patches that appear to be made of water ice and silicates. These characteristics strengthen the argument for interaction between the surface and an internal ocean, maybe as a result of collisions on one side that sparked activity in the interior.

Vesta’s average diameter is 326 miles (525 kilometers), however this changes depending on which axis is used. Vesta has a flattened hexagonal form with dimensions of 355.8 × 346.2 × 277.4 miles (572.6 × 557.2 × 446.4 kilometers). Vesta is one-quarter the mass of Ceres (5.7×1020 pounds (2.59×1020 kg), but its mean density is greater, resulting in a surface gravity of about 2.5% (0.025 g).

Vesta’s silicate and metallic makeup suggests that it evolved in the Asteroid Belt, unlike Ceres. These are divided into a metallic core of iron and nickel measuring 133-140 miles (214-226 kilometers) and a rocky olivine mantle and top crust. The surface is also coated in regolith, or silicate dust, indicating “space weathering.”

Pallas is somewhat smaller and less massive than Vesta, measuring around 318 miles (513 kilometers) in diameter and weighing about 4.4×1020 pounds (2×1020 kg). Based on spectroscopic measurements, Pallas’ surface is made up of silicate minerals with trace quantities of water ice and iron. Its surface gravity is similar to that of Ceres and Vesta, with roughly 2.2% of Earth’s normal gravity (0.022g).

Hygeia has a mean diameter of around 269 mi (434 km) and a mass of around 1.92×1020 lbs (8.75×1019 kg). Like Pallas, it has a roughly spheroid shape but is not massive enough to have achieved hydrostatic equilibrium. Based on spectroscopic observations, the surface appears to be composed primarily of carbonaceous materials similar to those found in C-type meteorites, with evidence of past water ice.

Cold, irradiated, and dusty

To put it simply, the Asteroid Belt is an unfriendly environment. Even the biggest asteroids are airless, thus everything in the Belt is exposed to the vacuum of space. Its distance from the Sun positions it squarely in the “Frost Line,” where temperatures are continuously low enough for volatile chemicals like water, ammonia, methane, carbon dioxide, and carbon monoxide to condense into solid ice grains.

Surface temperatures for dust particles and bigger things in the Belt are similarly high, ranging from -99 °F (-73 °C) at 2.2 AU to -162 °F (-108 °C) at 3.2 AU. However, because to spin, the surface temperature of an asteroid can change significantly when the sides are alternately exposed to solar light and the darkness of space.

Radiation exposure is also a significant risk owing to the absence of atmospheres or planetary magnetic fields. This includes solar radiation, which intensifies significantly during solar flare activity, as well as galactic cosmic rays. Human inhabitants are projected to need to excavate at least 328 feet (100 meters) beneath the surface to assure protection.

The Asteroid Belt, like the Moon and other airless worlds, contains large quantities of regolith. This means that any communities on or within asteroids will have a “dust problem,” in which microscopic shards of silica will pose respiratory health risks, adhere to everything, and interfere with equipment and electronics. And, as always, there is the problem of low gravity.

The gravitational pull on all of the Belt’s main bodies ranges from 2 to 3% of what we experience on Earth. Everywhere else, the circumstances are described as “microgravity,” which is comparable to what astronauts experience on the ISS. According to ISS research, the long-term impacts include muscle and bone density loss, as well as changes in cardiovascular health and organ function.

Another significant concern is the distance between the Main Belt and the Earth. As with Mars, the distance between the Belt’s small planets fluctuates significantly as they round the Sun. For example, between April and December 2021, the distance between Ceres and Earth varied from 3.9 AU to 1.76 AU. Between July 2022 and March 2023, it will vary between 3.6 and 1.6 AU.

In short, the distance between Ceres and Earth more than doubles within a seven to eight-month period. This implies that missions to and from the Belt can only launch during specific times. While this is more convenient than the 26-month launch window with Mars, the distances are roughly four times greater—0.374 AU to 1.67 AU.

For long-term habitation in the Asteroid Belt to become a reality, the settlements will need to be as self-sufficient as possible. But with the right work, the Main Belt could become the mining and manufacturing hub of the Solar System.

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