Terraforming of Venus

The most simple proposal is to "veil" the planet from the sun, thus dropping the temperature low enough to condense or solidify carbon dioxide which would then need to be removed or stored in some way.

Poul Anderson, a successful science fiction writer, had proposed the idea in his 1954 novelette "The Big Rain", a story belonging to his Psychotechnic League future history.

This hypothetical prospect, known as terraforming, was first proposed by Carl Sagan in 1961, as a final section of his classic article in the journal Science discussing the atmosphere and greenhouse effect of Venus.

[12] Difficulties include the fact that the production of organic molecules from carbon dioxide requires hydrogen, which is very rare on Venus.

[13] Because Venus lacks a protective magnetosphere, the upper atmosphere is exposed to direct erosion by the solar wind and has lost most of its original hydrogen to space.

Another study[21] concluded that under optimal conditions, on average, 1 cubic meter of basalt rock can sequester 260 kg of carbon dioxide.

Futurist Isaac Arthur has suggested using the hypothesized processes of starlifting and stellasing to create a particle beam of ionized hydrogen from the sun, tentatively dubbed a "hydro-cannon".

Another variant method involving bombardment would be to perturb a massive Kuiper belt object to put its orbit onto a collision path with Venus.

Possible workarounds include placing mass drivers on high-altitude balloons or balloon-supported towers extending above the bulk of the atmosphere, using space fountains, or rotovators.

Another side effect to atmospheric-density reduction could be the creation of zones of dramatic weather activity or storms at the terminator because large volumes of atmosphere would undergo rapid heating or cooling.

[29] A shade placed in the Sun–Venus L1 Lagrangian point also would serve to block the solar wind, removing the radiation exposure problem on Venus.

[citation needed] The recently synthesised amorphous carbonia might prove a useful structural material if it can be quenched to Standard Temperature and Pressure (STP) conditions, perhaps in a mixture with regular silica glass.

According to Birch's analysis, such colonies and materials would provide an immediate economic return from colonizing Venus, funding further terraforming efforts.

[31] Birch proposed that solar shades could be used to not merely cool the planet but to also reduce atmospheric pressure as well, by the process of freezing of the carbon dioxide.

He then proposed that the frozen CO2 could be buried and maintained in that condition by pressure, or even shipped off-world (perhaps to provide greenhouse gas needed for terraforming of Mars or the moons of Jupiter).

After this process was complete, the shades could be removed or solettas added, allowing the planet to partially warm again to temperatures comfortable for Earth life.

In addition to this method being less material intensive and potentially more cost effective, this process also produces a net surplus of energy, which could be utilised to power venusian colonies or other aspects of the terraforming effort, while simultaneously contributing to speeding up the cooling of the planet.

Another method to cool down the planet could be with the use of radiative cooling[33] This technology could utilise the fact that in certain wavelengths, thermal radiation from the lower atmosphere of Venus can "escape" to space through partially transparent atmospheric "windows" – spectral gaps between strong CO2 and H2O absorption bands in the near infrared range 0.8–2.4 μm (31–94 μin).

Paul Birch suggests the possibility of colliding Venus with one of the ice moons from the outer solar system,[24] thereby bringing in all the water needed for terraformation in one go.

Simply changing the velocity of these moons enough to move them from their current orbit and enable gravity-assisted transport to Venus would require large amounts of energy.

Therefore, the slow Venerian rotation rate would result in extremely long days and nights, similar to the day-night cycles in the polar regions of earth—shorter, but global.

More recent research has shown, however, that the current slow rotation rate of Venus is not at all detrimental to the planet's capability to support an Earth-like climate.

Rather, the slow rotation rate would, given an Earth-like atmosphere, enable the formation of thick cloud layers on the side of the planet facing the sun.

This in turn would raise planetary albedo and act to cool the global temperature to Earth-like levels, despite the greater proximity to the Sun.

Extrapolating the numbers from those experiments and applying them to Venerian conditions would mean that a space mirror just under 1700 meters in diameter could illuminate the entire nightside of the planet with the luminosity of 10-20 full moons and create an artificial 24-hour light cycle.

Further extrapolation suggests that to achieve illumination levels of about 400 lux (similar to normal office lighting or a sunrise on a clear day on earth) a circular mirror about 55 kilometers across would be needed.

Paul Birch suggested keeping the entire planet protected from sunlight by a permanent system of slated shades in L1, and the surface illuminated by a rotating soletta mirror in a polar orbit, which would produce a 24-hour light cycle.

Scientific research suggests that close flybys of asteroids or cometary bodies larger than 100 kilometres (60 mi) across could be used to move a planet in its orbit, or increase the speed of rotation.

A proposal by Birch involves the use of dynamic compression members to transfer energy and momentum via high-velocity mass streams to a band around the equator of Venus.

[46] Another study proposes the possibility of deployment of a magnetic dipole shield at the L1 Lagrange point, thereby creating an artificial magnetosphere that would protect the whole planet from solar wind and radiation.