Colonization of Mercury
Mercury has been suggested as one possible target for space colonization of the inner solar system, along with Mars, Venus, the Moon and the asteroid belt. Permanent colonies would almost certainly be restricted to the polar regions due to the extreme daytime temperatures elsewhere on the planet, although excursions to the other parts of the planet would be feasible with appropriate measures, particularly along the very slowly moving terminator, which would approximate polar conditions or during the long night.
Advantages
Similarity to the Moon
Like the Earth's Moon, Mercury does not have any significant atmosphere. It is close to the Sun and performs slow revolutions with a very small tilt of its axis. Because of this similarity any colonization of Mercury might be performed with the same general technology, approach and equipment as a colonization of the Moon. Bruce Murray referred to Mercury as "A Mini-Earth in Moon's Clothing" [1]
Ice in polar craters
Due to it being the closest planet to the Sun, the surface of Mercury can reach 700 K (427 °C, 800 °F), hot enough to melt lead. However, temperatures at the polar regions are much colder and there may even be deposits of ice inside permanently shaded craters. [2] The polar areas would also not see the extreme variation in temperature between night and day that the rest of Mercury's surface is subjected to.
Solar energy
Being the closest planet to the Sun, Mercury has vast amounts of solar power available. Its solar constant is 9.13 kW/m², 6.5 times that of Earth or the Moon. Because the tilt of its axis of rotation relative to its orbit is so low, approximately 0.01 degrees [3], there is also the possibility of so-called peaks of eternal light, similar to those of the Moon - high points located at the poles of the planet that are continuously radiated by the Sun. Even if they do not exist, it is possible that they could be constructed artificially.
In 1986, C.R. Pellegrino and J.R. Powell proposed covering Mercury with solar power farms, and transferring some of the resulting energy into a form useful for propulsion for interstellar travel. [4]
A longer range proposal has an iceteroid, from the asteroid belt or outer solar system origins, parked in a higher Mercury orbit. The strong solar wind and solar constant could significantly dissociate the H2O. With a higher proportion of the free oxygen falling from orbit and remaining, for a few million replenishment free years there would be an atmosphere. Whether the process could assist colonization remains unproven.
Valuable resources
There are predictions that Mercury's soil may contain large amounts of helium-3, which could become an important source of clean nuclear fusion energy on Earth and a driver for the future economy of the solar system.
Mercury is also theorized to have a crust rich in iron and magnesium silicates, [5] with the highest concentrations of many valuable minerals of any surface in the solar system, in highly concentrated ores. [6]
Geologist Stephen Gillett has suggested this will make Mercury an ideal place to build solar sails, which could launch from the Mercury surface with no propellant, mitigating the gravity well issue; and that this will make Mercury an ideal place to acquire materials useful in building hardware to send to Venus and to terraform Venus. [7]
Considerable gravity
Mercury is bigger than the Moon (with a diameter of 4879 km versus 3476 km) and has a higher density due to its large iron core. As a result, gravity on the surface of Mercury is 0.377 g, [3] more than twice that of the Moon (0.1654 g) and equal to the surface gravity on Mars. Since there is evidence of human health problems associated with extended exposure to low gravity, from this point of view, Mercury might be more attractive for long-term human habitation than the Moon.
Difficulties
The lack of any substantial atmosphere, close proximity to the Sun and long solar day (176 Earth days) would all lead to significant challenges for any future human settlement. A permanent colony would almost certainly be restricted to the polar regions, but temporary excursions toward the equator could take place during the long night. Outside of the possibility of ice at the poles, it is unlikely that the lighter elements needed for life exist on the planet. These would have to be imported.
Mercury is also deep in the Sun's gravitational potential well, requiring a larger velocity change (delta V) to travel to and from Mercury than is needed for other planets, although, in the past, gravity assist orbits using Venus have been used to reach Mercury.
Fictional depictions
Kim Stanley Robinson described a colony on Mercury in his book Blue Mars, which consisted of a city stationed on a set of tracks encircling the planet. As the terminator and habitable band moved from the night side to the sun side due to the rotation of the planet, the track would expand and propel the city, thus always keeping it on the solar horizion for energy generation.
References
- ^ Bruce Murray and Ronald Greeley, "Earthlike Planets: Surfaces of Mercury, Venus, Earth, Moon, Mars", W. H. Freeman, 1981, ISBN 0716711486
- ^ http://nssdc.gsfc.nasa.gov/planetary/ice/ice_mercury.html
- ^ a b http://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html
- ^ Analog, September 1986
- ^ Eric H. Christiansen and W. Kenneth Hamblin, "Exploring the Planets", 2nd ed.; Prentice Hall, 1995, p. 133
- ^ Stephen L. Gillett, "Mining the Moon", Analog, Nov. 1983
- ^ Stanley Schmidt and Robert Zubrin, eds., "Islands in the Sky: Bold New Ideas for Coloning Space"; Wiley, 1996, p. 71-84
See also
- Mercury (planet)
- MESSENGER, a NASA probe launched in 2004, expected to enter Mercury orbit on March 18, 2011. One goal is to study the volatile inventory at the poles.
- Solar System