Worlds For Man - Part 6 - Ceres
Introduction
Ceres is not often thought of as a "planet," and is thus often overlooked. But it is a perfectly respectable "dwarf planet," equal in mass to a medium-sized moon (though much smaller than our own giant Luna). It contains about a third of all the mass in the Asteroid Belt, and hence is the "failed planet" filling the Keplerian orbit. In any long-term human future, Ceres is destined to be an important center of population in the Asteroid Belt.
Orbital Characteristics
Ceres orbits at about 2.76 AU (414 million km) from the Sun, and hence receives about 1/7.6 (between one-seventh and one-eighth) the energy from the Sun as does the Earth per square meter (but the amount at the surface is closer to one-fourth, because Ceres is airless). The orbit has an eccentricity of only about 0.08, and thus varies between about 2.55 AU and 2.99 AU (381 to 447 million km). It is inclined 10 degrees from the solar ecliptic, and is thus a bit out of the main planetary plane (this may be one reason why it never succeeded in coalescing its planet). The orbital period is 4.6 years.
Physical Characteristics
Ceres is about 950 km in diameter, varying from 908 km polar to 974 km equatorial diameter, and is thus more flattened than the Earth. Its mass is 943 quadrillion tons (much less than one-millionth that of the Earth). Density is 2.077, indicating a world made largely out of ices and silicates.
Surface gravity is 0.028 G, so a typical human would weigh only around 3-5 lbs on the surface: very useful for access to and from space, but enough to require a definite orientation with respect to "up" and "down," as a released object would fall 27 centimeters (around a foot) in the first second. A man could easily make or land from a vertical leap of around 100 feet (equivalent to 3 feet on Earth), though the roughly 15 seconds (*kudos to firstashore for spotting my original error) it would take to reach the bottom would make this tedious at the start of the fall, and dreamlike or frightening at the end. Falls of 300-500 feet (9-15' on Earth) would be easily survivable albiet with signficant risk of injury.
Escape velocity is only around 500 meters per second. This is well within the capability of many firearms. Any actual rocketship other than an ion-drive vessel could easily take off and land.
Ceres spins about its axis in a bit over 9 hours. This will be convenient for surface operations, as the Cerean "daytime" is about as long as a naval "watch." The axial tilt is minor, only around 3 degrees, so therefore there would be no real "seasons."
Surface temperature is around 167 degrees K, increasing to a maximum average of 239. Note that this is well below the melting point of water (273 K), which is important for its future colonization.
Geology
Ceres appears to have undergone thermal differentiation into a 100-km deep icy mantle, containing 200 cubic kilometers of water (more than all the fresh water on Earth), over a 350-km deep rocky core. There may or may not be a subterranean ocean between the mantle and the core.
Above the mantle is a thin, dusty crust. This crust is composed largely of hydrated minerals, and probably iron-rich clays (cronstedite) and carbonates (dolomite and siderite). This means that the Cerean crust is rich in hydrogen, oxygen, silicon, iron, calcium, magnesium, and possibly manganese.
Economics
Ceres is positioned between Mars and Jupiter, and is fairly accessible to either, but would cost some extra delta vee owing to its orbital inclination off the ecliptic. The low gravity, however, means that spacecraft would have a fair amount of excess fuel to burn matching vectors with the dwarf planet.
The rich water deposits would be very useful both for agriculture and export. Ceres happens to be in the part of the Asteroid Belt beyond the "snow line," and could ship water to the warmer, dryer asteroids of the Inner Belt, which may lack such resources. Because Ceres is large and thus probably has at least traces of all elements, including those needed for life, an agricultural colony (which could export food) could be supported from purely local resources.
Ceres is probably not mineral-rich, owing to its low density, but mining might be easy owing to its low gravity and its probably dead interior. While the concentration of heavy elements might be too small to be worth exporting, it might be more than sufficient to support an agricultural colony's raw material needs. Thus, rather appropriately given its name, Ceres might become the Belt's main farm-world.
Cerean hydrogen would provide deuterium and tritium plentiful for the needs of agriculture, if fused in a reactor. The presence of tri-helium has never been confirmed, and the solar wind would be weak that far out. Solar power would be a possibility for auxiliary power, and hydrogen and oxygen could thus be separated for chemical fuel cells and rockets. Ceres might have enough uranium and thorium, deep down, for nuclear batteries or even reactors.
The Future
The robot probe Dawn, launched by NASA in 2007, will orbit Ceres for several months in 2015, providing valuable information about the dwarf planet's surface and composition. In half a decade, we will have maps and clues as to valuable mining sites.
Perhaps in the 2030's or 2040's, as we explore Mars, we will also explore Ceres. Manned outposts will follow by the middle of the 21st century, and by the year 2100 there will probably be a thriving little colony or colonies at the more promising sites, growing food for the rest of the Belt.
Ceres will play its role in the human future off Earth.
Ceres is not often thought of as a "planet," and is thus often overlooked. But it is a perfectly respectable "dwarf planet," equal in mass to a medium-sized moon (though much smaller than our own giant Luna). It contains about a third of all the mass in the Asteroid Belt, and hence is the "failed planet" filling the Keplerian orbit. In any long-term human future, Ceres is destined to be an important center of population in the Asteroid Belt.
Orbital Characteristics
Ceres orbits at about 2.76 AU (414 million km) from the Sun, and hence receives about 1/7.6 (between one-seventh and one-eighth) the energy from the Sun as does the Earth per square meter (but the amount at the surface is closer to one-fourth, because Ceres is airless). The orbit has an eccentricity of only about 0.08, and thus varies between about 2.55 AU and 2.99 AU (381 to 447 million km). It is inclined 10 degrees from the solar ecliptic, and is thus a bit out of the main planetary plane (this may be one reason why it never succeeded in coalescing its planet). The orbital period is 4.6 years.
Physical Characteristics
Ceres is about 950 km in diameter, varying from 908 km polar to 974 km equatorial diameter, and is thus more flattened than the Earth. Its mass is 943 quadrillion tons (much less than one-millionth that of the Earth). Density is 2.077, indicating a world made largely out of ices and silicates.
Surface gravity is 0.028 G, so a typical human would weigh only around 3-5 lbs on the surface: very useful for access to and from space, but enough to require a definite orientation with respect to "up" and "down," as a released object would fall 27 centimeters (around a foot) in the first second. A man could easily make or land from a vertical leap of around 100 feet (equivalent to 3 feet on Earth), though the roughly 15 seconds (*kudos to firstashore for spotting my original error) it would take to reach the bottom would make this tedious at the start of the fall, and dreamlike or frightening at the end. Falls of 300-500 feet (9-15' on Earth) would be easily survivable albiet with signficant risk of injury.
Escape velocity is only around 500 meters per second. This is well within the capability of many firearms. Any actual rocketship other than an ion-drive vessel could easily take off and land.
Ceres spins about its axis in a bit over 9 hours. This will be convenient for surface operations, as the Cerean "daytime" is about as long as a naval "watch." The axial tilt is minor, only around 3 degrees, so therefore there would be no real "seasons."
Surface temperature is around 167 degrees K, increasing to a maximum average of 239. Note that this is well below the melting point of water (273 K), which is important for its future colonization.
Geology
Ceres appears to have undergone thermal differentiation into a 100-km deep icy mantle, containing 200 cubic kilometers of water (more than all the fresh water on Earth), over a 350-km deep rocky core. There may or may not be a subterranean ocean between the mantle and the core.
Above the mantle is a thin, dusty crust. This crust is composed largely of hydrated minerals, and probably iron-rich clays (cronstedite) and carbonates (dolomite and siderite). This means that the Cerean crust is rich in hydrogen, oxygen, silicon, iron, calcium, magnesium, and possibly manganese.
Economics
Ceres is positioned between Mars and Jupiter, and is fairly accessible to either, but would cost some extra delta vee owing to its orbital inclination off the ecliptic. The low gravity, however, means that spacecraft would have a fair amount of excess fuel to burn matching vectors with the dwarf planet.
The rich water deposits would be very useful both for agriculture and export. Ceres happens to be in the part of the Asteroid Belt beyond the "snow line," and could ship water to the warmer, dryer asteroids of the Inner Belt, which may lack such resources. Because Ceres is large and thus probably has at least traces of all elements, including those needed for life, an agricultural colony (which could export food) could be supported from purely local resources.
Ceres is probably not mineral-rich, owing to its low density, but mining might be easy owing to its low gravity and its probably dead interior. While the concentration of heavy elements might be too small to be worth exporting, it might be more than sufficient to support an agricultural colony's raw material needs. Thus, rather appropriately given its name, Ceres might become the Belt's main farm-world.
Cerean hydrogen would provide deuterium and tritium plentiful for the needs of agriculture, if fused in a reactor. The presence of tri-helium has never been confirmed, and the solar wind would be weak that far out. Solar power would be a possibility for auxiliary power, and hydrogen and oxygen could thus be separated for chemical fuel cells and rockets. Ceres might have enough uranium and thorium, deep down, for nuclear batteries or even reactors.
The Future
The robot probe Dawn, launched by NASA in 2007, will orbit Ceres for several months in 2015, providing valuable information about the dwarf planet's surface and composition. In half a decade, we will have maps and clues as to valuable mining sites.
Perhaps in the 2030's or 2040's, as we explore Mars, we will also explore Ceres. Manned outposts will follow by the middle of the 21st century, and by the year 2100 there will probably be a thriving little colony or colonies at the more promising sites, growing food for the rest of the Belt.
Ceres will play its role in the human future off Earth.