19.2.1 - Terraforming

Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization

First Edition

Robert A. Freitas Jr., Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization, First Edition, Xenology Research Institute, Sacramento, CA, 1979; http://www.xenology.info/Xeno.htm

If living space is in short supply on the home planet, one logical alter-native is to move some of the population and growth activities to other worlds. The typical habitable solar system will have from 7-13 planets and as many moons, but it is highly unlikely that more than one of these has a natural environment tolerable to interplanetary pioneers. As with Sol's family of worlds, most will be too hot or too cold or too dry or too wet to permit immediate habitation.

Terraforming is a form of planetary engineering on a grand scale. Just as buildings and cities are designed to suit human comfort, it is entirely feasible to consider the modification of planetary environments to suit human (or alien) needs.¹⁹⁷⁷ Worlds which are unearthlike can be made more earthlike and may then be colonized and exploited by man.

There have been many proposals and suggestions as to how to go about terraforming the planets and moons of our own solar system. Only a few of these will be considered briefly here, because it turns out that in all cases the energy and mass requirements are well within the operating budgets of Type I planetary civilizations. In other words, from the point of view of a Type II culture terraforming techniques should represent a fairly primitive technology.

Perhaps inspired by Poul Anderson's short story entitled “The Big Rain,“ published in 1955, Dr. Carl Sagan in 1961 proposed a terraforming project to modify the environment of Venus.¹⁴⁸¹ Our sister planet has a hellish climate, with temperatures upwards of 750 °C and pressures of 90 atm at the surface. To prepare it for human habitation it will be necessary to lower the surface temperature and pressure, and to elevate by at least two orders of magnitude the fraction of molecular oxygen present in the atmosphere. Most of the air is carbon dioxide, and this must be eliminated as well.

Sagan suggests the injection of blue-green algae into the Venusian atmosphere at high altitudes where it is relatively cool. These tiny organisms would consume the CO₂ by growing more algae cells with water and aerial nutrients. Molecular oxygen would be expired as a waste product. Over a period of several years the carbon dioxide level begins to drop, thus reducing the green-house effect and cooling the planet overall.²⁶³³ When the ground was sufficiently cool, cargo landers armed with fusion bombs could be de-orbited and set down on the surface. These machines, able to burrow like moles and detonate beneath the surface, may be used to trigger new volcanic chains in order to help percolate more water into the dry atmosphere.²⁸³⁶ Eventually the first “big rain“ will fall. Says Sagan: “The heat-retaining clouds will partly clear away, leaving an oxygen-rich atmosphere and a temperature cool enough to sustain hardy plants and animals from Earth.“

How reasonable is the astronomer's proposal? In 1970 a number of biologists conducted experiments to see if earthly algae would actually grow under the extreme initial conditions found on Venus.^2847,2846 It was discovered that the most suitable strain is Cyanidium caldarium, a single-celled form that is found in hot springs on Earth. This algae produced oxygen vigorously in a hot, high-pressure atmosphere of CO₂. In a typical experiment the researchers found that each million algae cells were increasing the oxygen concentration in the test tank by 380% per day.

To terraform the atmosphere of Venus is not a very difficult undertaking from the standpoint of energy and mass requirements. If we dispatch an armada of 500 seeding probes to our neighbor world, each armed with a thousand in-dependently-targetable payload capsules containing 1 ton of Cyanidium caldarium per capsule, this would result in the dispersal of a kilogram of living blue-green algae cells over each square kilometer of the planet's surface. The total mission mass is about 10⁹ kg, and the total energy required is about 10¹⁸ joules -- both well within the budgetary limitations of a Type I civilization.

Small, airless terrestrial worlds such as Luna are also suitable for terraforming projects. Richard R. Vondrak of the Department of Space Physics and Astronomy at Rice University recently suggested a method for creating a comfortable artificial lunar atmosphere.⁶⁵⁶ The present lunar air has a total mass of about 10 tons. This arises mainly from outgassing from the interior, without which the entire atmosphere would quickly be swept away by the solar wind.

Vondrak calculates that if the atmosphere of the Moon was increased to a mass of at least 100,000 tons it would be driven into a “long-lived state“ which would drastically reduce losses to the solar wind. According to him:

To produce a breathable “shirtsleeve“ atmosphere, about 10¹⁸ kilograms of O₂ must be pumped into the lunar environment. This should require a total energy expenditure of about 10²⁴ joules. Again, both mass and energy figures lie within the budget of an ambitious mature Type I civilization.

A wide variety of Martian terraforming techniques have been proposed from time to time. Joseph A. Burns and Martin Harwit of the Center for Radiophysics and Space Research at Cornell University once speculated that the proper positioning of large masses in orbit around the planet would alter its equinoctal precession period.¹²⁸² This would cause a perpetual “Spring“ season planetwide, similar to that predicted by Sagan's "Long Winter" model of the Martian climate.¹²⁶⁷

One scheme involves pushing Phobos from its present equatorial orbit to a new one inclined 45° to the Martian equator. The total energy required to exe cute this maneuver would be about 10²³ joules. Unfortunately, Burns and Harwit admit, the orbit of Phobos would begin to precess and might foil the entire scheme. Their second proposal involves capturing roughly 25% of the matter in the nearby asteroid belt and using that mass instead of Phobos to swing Mars around. While this might work, at least two orders of magnitude of energy would be required.

Carl Sagan may have hit upon the cheapest way to terraform Mars.¹²⁸⁸ He suggests that about 10¹⁰ tons of low albedo matter -- such as lampblack or dark-colored vegetation -- be transported to the permanent Martian polar icecaps over a period of about a century. The caps would be less reflective and would thus absorb more of the sun's energy. The ice would warm and thaw, increasing the atmospheric pressure (and the greenhouse effect) and speeding north-south convective stirring of the planetary atmosphere. A minimum of 10²¹ joules would be needed to accomplish this feat, and hundreds of years. There are ways to do it faster. An enormous orbiting mirror could be stationed in polar orbit to melt the icecaps by reflected or concentrated sunlight, or thermonuclear bombs could be set off to achieve similar effects perhaps in a matter of decades.¹⁹⁷⁸

A more complete analysis was undertaken by a study group at NASA-Ames in 1976. Entitled On the Habitability of Mars: An Approach to Planetary Eco-synthesis, the final report of the study attempted to pin down the specific requirements for successful terraforming of the Red Planet.¹⁹²⁶ It was concluded that “no fundamental limitation to the ability of Mars to support terrestrial life has been identified.“

The scientists proposed a two-pronged attack on the problem. First, atmospheric mass should be increased by vaporizing the polar icecaps or the subsurface permafrost. If the reflectivity of the icecaps was reduced by only 5% for a period of 100 years, a kind of runaway de-ice age might be triggered “and a new high temperature climatic regime established.“ Secondly, mechanisms of genetic engineering currently available or under development could be used to construct organisms far better adapted to grow on Mars than any present terrestrial organism. In principle, the entire gene pool of the Earth might be available for the construction of an ideally adapted oxygen-producing photosynthetic Martian organism.

It was estimated that the creation of an oxygen atmosphere using known terrestrial photosynthetic lifeforms might take hundreds of thousands of years. But by altering the environment of Mars and by seeding it with appropriately bioneered organisms, the length of time to project completion could be reduced a thousandfold. Total energy expenditure for the NASA-Ames scheme: Roughly 10²⁴-10²⁵ joules.

Academician N.N. Semenov, a Soviet scientist, suggests that the water locked in permafrost and polar icecaps by subjected to simple electrolysis.²⁸⁴⁹ Water molecules would be split into oxygen, which could be released into the Martian air eventually to result in a breathable atmosphere, and hydrogen, which could be collected and used for fuel in fusion power plants needed to operate the electrolysis factories. Earthlike air would result from the electrolysis of about 15% of all water believed to be present at the Martian surface, at a cost of about 10²³ joules.

If water proves to be too scarce or too difficult to exploit, scientists are ready with the most grandiose scheme proposed to date. Saturn's rings are believed to consist primarily of flying chunks of water-ice. These icy boulders could be gathered together and welded into “a string of huge, frozen pearls, each the rival of Phobos.“²⁸²⁸ Properly outfitted with propulsion and automated guidance systems, the caravan of giant icebergs majestically peel away from Saturn in a long, steep dive sunward. What happens next has been eloquently described by Freeman Dyson: