Colonization of Venus
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2008-07-15T10:59:30Z
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/* Advantages */ changed "closest major obect (besides the moon)" to "closest planet"...
[[Image:Venus-real color.jpg|thumb|right|200px|Venus]]
The '''colonization of [[Venus]]''' has been a subject of much speculation and many works of science fiction since before the dawn of [[spaceflight]], and is still much discussed. With the discovery of Venus' hostile surface environment, attention has largely shifted towards the [[colonization of the Moon]] and the [[colonization of Mars]]. Recently however, papers have surfaced on the feasibility of colonizing Venus beginning from the less hostile cloud-tops, making surface exploration in the beginning unnecessary. This two-part approach to the exploration and colonization of the planet has refocused interest on Venus.
==Reasons for colonization==
{{Space colonization}}
Space colonization is a step beyond [[space exploration]], and implies the permanent or long-term presence of humans in an environment outside Earth. [[Stephen Hawking]] has stated that colonization of space would be [[Space and survival|the best way to ensure the survival]] of [[homo sapiens|humans]] as a species. <ref>{{cite web|url=http://www.usatoday.com/tech/science/space/2006-06-13-hawking-humans-space_x.htm|title=Hawking says humans must go into space to survive|accessdate=20 March| accessyear=2007}}</ref> Other reasons for colonizing space include economic interests, long-term scientific research best carried out by humans, and sheer curiosity. Venus being the second largest [[terrestrial planet]] and Earth's closest neighbour make it a potential target.
==Advantages==
[[Image:Venus Earth Comparison.png|280px|thumb|left|Scale representations of Venus and the Earth shown next to each other. Venus is only slightly smaller.]]
[[Image:Airpressureonvenus.PNG|right|thumb|280px|Air pressure on Venus, beginning at a pressure on the surface 90 times that of Earth and reaching a single bar by 50 kilometres.]]
Venus has certain similarities to [[Earth]] which might make colonization easier in many respects in comparison with other possible destinations. These similarities, and its proximity, have led Venus to be called Earth's "sister planet".
At present it has not been established whether the gravity of Mars, about one-third that of the Earth, would be sufficient to avoid [[bone decalcification]] and loss of muscle tone experienced by astronauts living in an environment of [[microgravity]] (the probe [[Mars Gravity Biosatellite]] will be the first probe to investigate this). In contrast, Venus is close in size and mass to the Earth, resulting in a similar surface gravity (0.904 [[g-force|''g'']]). Most other space exploration and colonization plans face concerns about the damaging effect of long-term exposure to fractional ''g'' or [[zero gravity]] on the human [[musculoskeletal system]]. Humans born on Venus would probably have little difficulty adapting to Earth gravity should there be a reason to visit or return.
Venus's relative proximity makes transportation and communications easier than for most other locations in the solar system. With current propulsion systems, [[launch window]]s to Venus occur every 584 days, compared to the 780 days for Mars. Flight time is also somewhat shorter; the probe [[Venus Express]] which recently arrived at Venus spent slightly over five months en route, compared to nearly six months for [[Mars Express]]. This is because at closest approach, Venus is 45 million km from Earth compared to 56 million km for Mars, making Venus the closest planet to the Earth.
== Difficulties ==
Venus also presents several significant challenges to human colonization. Surface conditions on Venus are extremely difficult. The temperature at the equator averages around 500 °C (932 °F), higher than the [[melting point]] of [[lead]]. The [[atmospheric pressure]] on the surface is also at least ninety times greater than on Earth, which is equivalent to the pressure experienced under a kilometer of water. These conditions have caused missions to the surface to be extremely brief: the probes [[Venera 5]] and [[Venera 6]] for example were crushed by high pressure 18 km above the surface. Following landers such as [[Venera 7]] and [[Venera 8]] succeeded in transmitting data after reaching the surface, but these missions were brief as well, surviving no more than a single hour on the surface. Obtaining materials from the surface for use by an upper-atmosphere colony would be a problem.
Furthermore, [[water]], in any form, is almost entirely absent from Venus. The atmosphere is devoid of molecular [[oxygen]] and is primarily [[carbon dioxide]] in poisonously high concentrations. In addition, the visible clouds comprise, in part, [[sulfuric acid]] and [[sulfur dioxide]] vapor.
==Methods of colonization and exploration==
Given the hostile conditions of Venus, a colony on the Venusian surface in its present form is far beyond current technological capabilities. Some authors suggest overcoming this by [[Terraforming of Venus|terraforming Venus]] - making the planet more earth-like. The energy requirements for all terraforming plans are daunting when compared with our current technology, and the time required could possibly span tens of thousands of years, if not millions. In spite of this seemingly pessimistic time frame, terraforming in this manner offers the potential for exponential growth to remake the industrial base of the human race if humans are to set about the task of settling space en masse. If a large portion or the entire planet could be shaded, Venus would cool to a useful temperature in mere decades. Such methods would include placing sails ([[Solar shade]]s) between Venus and the sun at [[Lagrange points]] between the two, controlled dust clouds in space, and a large number of other ideas.
Others suggest a different approach, however, arguing that rather than attempting to colonize Venus' hostile surface, man might colonize the Venusian atmosphere (the most habitable part of any planet outside Earth). This is because at an altitude of approximately 50 kilometers (in Venus's [[atmosphere of Venus|upper atmosphere]]), the pressure and temperature are Earth-like (1 bar and 0-50 degrees Celsius). In addition, in this region, solar energy is abundant. The [[solar constant]] at the top of Venus's atmosphere is 2,610 [[watt]]s per [[square meter]], 1.9 times that of Earth, and the clouds are reflective enough that solar panels pointing downward towards them would be nearly as effective as those pointing upwards towards the sun. The atmospheric winds at this altitude would drive a floating station around the planet once every 100 hours or so. At higher altitudes this would take even less time, resulting in a 'day' much closer to the 24-hour day experienced on Earth than on the surface of Venus with the 243 days it takes to make a single rotation.
===Exploration and research before colonization===
As Venus has not been studied as much as objects such as the moon and Mars have, further research would have to be conducted on the planet before a human-powered mission could be approved. The probe [[Venus Express]] is currently in orbit around the planet, but other low-cost missions have been proposed to further explore the planet's atmosphere, as the area 50 kilometres above the surface where air pressure is at the same level as Earth has not yet been explored.
One such proposed mission is a solar-powered flyer. Though wind speeds in the upper atmosphere of Venus can reach up to 95 m/s (342 km/h) at the cloud top level, the slightly lower gravity (8.87 m/s<sup>2</sup>) and the higher air pressure alleviate this somewhat, and flying an aircraft on Venus would be easier than one on Mars with its extremely low air pressure. The proposed flyer would base itself at an altitude of about 72 kilometres where the pressure is low enough and solar energy abundant enough that it could recharge itself for temporary incursions lower into the atmosphere for a number of hours. As daytime on Venus persists for over 100 days due to its extremely slow rotation, a flying craft could remain in perpetual sunlight, and would only need to move at a speed of 13.4 km/h at the equator to keep up with the planet's rotation. Exploring the other side of the planet however, would not be possible until sunlight reaches the area, as a solar-powered craft would not have the power to traverse the entire night side without recharging.<ref>{{cite journal|last=Landis, LaMarre, Colozza |first=Geoffrey A., Christopher, Anthony| year=2002| title=Atmospheric Flight on Venus| url=http://gltrs.grc.nasa.gov/citations/all/tm-2002-211467.html | journal=40th Aerospace Sciences Meeting & Exhibit, Reno NV| month=Jan. 14-17}}</ref><ref>{{cite journal|last=Landis, LaMarre, Colozza |first=Geoffrey A., Christopher, Anthony| year=2005| title=Venus Atmospheric Exploration by Solar Aircraft, Paper IAC-02-Q.4.2.03| journal=Acta Astronautica, Vol. 56, No. 8, pp. 750-755| month= April }}</ref>
===Aerostat habitats and floating cities===
[[Geoffrey A. Landis]] has summarized the perceived difficulties in colonizing Venus as being merely from the assumption that a colony would need to be based on the surface of a planet:
:"However, viewed in a different way, the problem with Venus is merely that the ground level is too far below the one atmosphere level. At cloud-top level, Venus is the paradise planet."
He has proposed [[aerostat]] habitats followed by [[Floating cities (science fiction)|floating cities]], based on the concept that breathable air (21:79 Oxygen-Nitrogen mixture) is a lifting gas in the dense Venusian atmosphere, with over 60% of the lifting power that [[helium]] has on Earth.<ref>{{cite journal|last=Landis |first=Geoffrey A.| year=2003| title=Colonization of Venus| url=http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APCPCS000654000001001193000001| journal=Conference on Human Space Exploration, Space Technology & Applications International Forum, Albuquerque NM| month=Feb. 2-6| format={{Dead link|date=May 2008}}}}</ref> In effect, a [[Gas balloon|balloon]] full of human-breathable air would sustain itself and extra weight (such as a colony) in midair. At an altitude of 50 km above Venusian surface, the environment is the most Earth-like in the solar system - a pressure of approximately 1 bar and temperatures in the 0°C-50°C range. Because there is not a significant pressure difference between the inside and the outside of the breathable-air balloon, any rips or tears would cause gases to diffuse at normal atmospheric mixing rates, giving time to repair any such damages. In addition, humans would not require [[pressurized suit]]s when outside, merely air to breathe and a protection from the acidic rain. Alternatively two-part domes could contain a lifting gas like hydrogen or helium (extractable from the atmosphere) to allow a higher mass density<ref name="Terraforming Venus Quickly">{{cite journal| journal=Journal of the British Interplanetary Society| year=1991| title=Terraforming Venus Quickly| first=Paul| last=Birch}}</ref>.
Cloud-top colonization also offers a way to avoid the issue of slow Venusian rotation. At the top of the clouds the wind speed on Venus reaches up to 95 m/s, circling the planet approximately every four Earth days in a phenomenon known as "super-rotation".<ref>[http://gltrs.grc.nasa.gov/reports/2002/TM-2002-211467.pdf Atmospheric Flight on Venus] (pdf) - Geoffrey A. Landis, Anthony Colozza, and Christopher M. LaMarre. paper IAC-02-Q.4.2.03, AIAA-2002-0819, AIAA0, No. 5</ref> Colonies floating in this region could therefore have a much shorter day length by remaining untethered to the ground and moving with the atmosphere. While a [[space elevator]] extending to the surface of Venus is impractical due to the slow rotation, constructing a [[Skyhook (structure)|skyhook]] that extended into the upper atmosphere and rotated at the wind speed would not be difficult compared to constructing a space elevator on Earth.
Since such colonies would be viable in current Venusian conditions, this allows a dynamic approach to colonization instead of requiring extensive terraforming measures in advance. The main challenge would be using a substance resistant to sulfuric acid to serve as the structure's outer layer; ceramics or metal sulfates could possibly serve in this role. (The sulfuric acid itself may prove to be the main motivation for creating the structure in the first place, as the acid has proven to be extremely useful for many different purposes such as [[Lead-acid battery|lead-acid batteries]]. On the other hand, once we have the necessary technology to colonize Venus, such batteries will probably be outdated technology.)
Landis has suggested that as more floating cities were built, they could form a solar shield around the planet, and could simultaneously be used to process the atmosphere into a more desirable form. If made from [[carbon nanotubes]] (recently fabricated into sheet form) or [[graphene]] (a sheet-like carbon [[allotrope]]), the major structural materials can be produced using carbon dioxide gathered in situ from the atmosphere. The recently synthesised [[amorphous carbonia]] might prove a useful structural material if it can be quenched to [[Standard conditions for 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.
===Terraforming===
{{main|Terraforming of Venus}}
[[Image:TerraformedVenus.jpg|thumb|right|250px|Artist's conception of a terraformed [[Venus]]. (credit: Daein Ballard)]]
Terraforming (literally, "Earth-shaping") is the theoretical process of modifying a planet, moon, or other body to a more habitable atmosphere, temperature, or ecology. Venus has been the subject of a number of terraforming proposals. The proposals seek to remove or convert the dense carbon dioxide atmosphere, reduce Venus's 500 °C (770 K) surface temperature, and establish a day/night light cycle closer to that of Earth's.
Most proposals involve deployment of a solar shade and/or a system of orbital mirrors, for the purpose of reducing [[insolation]] and providing light to the dark side of Venus. Another common thread in most proposals involves some introduction of large quantities [[hydrogen]] or [[water]]. Proposals also involve either freezing most of Venus's atmospheric CO<sub>2</sub>, or converting it to other forms.
===Colonies in Venus Orbit===
Another promising pathway to colonization is the use of near-Venus space for the orbital capture and development of comets and asteroids. Although Venus currently has no moons, in the near future it may be practical to nudge smaller bodies into orbit around the inner planets. Venus is especially good for this because [[aerobraking]] in its thick atmosphere can be used to slow these bodies down. Unlike near-Earth space where the danger of [[Impact event|hitting the Earth]] would have severe effects on the civilization, near-Venus space does not suffer from this problem.{{Fact|date=June 2008}} The available free solar energy from the Sun makes Venus a desirable location for industrial development.
It is also a likely precursor to any serious attempt to develop economic activity in the [[gravity well]] of Venus. Resources in Venus orbit would be used to extend activity downward. However a [[space elevator]] would likely not be feasible due to Venus' slow rotation (243 Earth days). A [[Skyhook (structure)|skyhook]] into the atmosphere is however possible.
==Present exploration of Venus==
The [[European Space Agency|ESA]] space probe [[Venus Express]] arrived at the planet in May 2006 and is currently undergoing an approximately 1,000-day mission (initially 500 days prolonged by another 500 in May 2007) to study the atmosphere and clouds in detail.
Future missions include [[JAXA]]'s [[Planet-C]]. The [[MESSENGER]] mission to [[Mercury (planet)|Mercury]] had a flyby of Venus in October 2006 and in June 2007, and the [[BepiColombo]] mission to Mercury also plans a flyby of the planet.
==See also==
* [[Mars Society]]
* [[Colonization of Mars]]
==References==
{{reflist}}
==External links==
*[http://spacemonitor.blogspot.com/2007/05/floating-city-on-venus.html A Floating City on Venus] - article from [http://www.spacemonitor.blogspot.com The Space Monitor]
{{Venus}}
[[Category:Space colonization]]
[[Category:Venus]]
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[[ru:Колонизация Венеры]]
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