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Every celestial body with mass passing the so called "Wild bound" has round shape. For silicate-rocky bodies this limit coresponds to diameter ~600 km -- a point where the lithostatic presure is higher than 10 000 Bars, the internal structural strenght of the rock could no longer prevent the self-gravity of the body to shape it according to the minimal gravity potential. For these with mainly icy composition -- about 400 km. diameter is the roundness limit.
In the Solar system there are more than 30 such round/solid objects. According to the so called Gravitational planetary criteria, they are planemos -- planetary mass objects; these circling the Sun on independant paths are planets, the rest - (spherical) moons. Nowaday astronomical taxonomy calls traditionally planets only several bigger bodies from this list.
Of these all 30+ discovered:
-Only one (except the Earth) - Venus have about 1 G surface gravity, and could be transformed in close replica of Earth, i.e. trully terraformed.
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-The next two Mars and Mercury have about one third G, and their terraformation should accept this compromise.
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-Eight others, huge moons each + Pluto, have some substantial surface gravity to hold atmosphere for millenia: the Moon(0.17 G), Io(0.18 G), Europa(0.13 G), Ganymede(0.14 G), Callisto(0.13 G), Titan(0.13), Triton(0,08) and Pluto(0.07)
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-TWENTY (and counting!!!) as follows with ~diameter in km./gravity in earths`: Ceres(1000/0.024), Pallas(540/0.03), Vesta(530/0.03), Mimas(400/0.008), Encelladus(500/0.008), Tethys(1050/0.016), Dione(1120/0.02), Rhea(1530/0.026), Iapetus(1460/0.026), Miranda(472/0.008), Ariel(1158/0.02), Umbriel(1190/0.02), Titania(1610/0.038), Oberon(1523/0.034), Charon(1028/0.036), 2004 DW(1600/0.03?), Ixion(1055/0.02?), Varuna(1060/0.02?), Sedna(1180-1800/0.02-0.04?)... , are pieces of low-gravity terra firma with territories of millions of sq.km. each, covered with so usefull and interesting topographic features... If big scale Solar system terraforming colonization commences and unfolds, I think it is inevitable these big round planetoides to be left behind, without big patches of their ground (trenches, chasms, underground cavities, craters...) or the whole surface of some to be converted in human-livable places. They are too unique to be allowed their dismantling for tube words construction materials. Those dozens of system`s sightseengs should remain topologically intact. There is more than enough material in the smaller bodies, in the realm of the countless irregulary shaped planetoids (from ~50 m. to 400 km. in diameter) in the Main belt, KB and OC...
In "Terraforming of Ceres" thread I described the idea for worldwide "Sky oceans" - shifting the places of the atmosphere and hydrosphere. Such and other techniques could be used to be made the dwarf planets habitable, paralelly of plain terraforming of bigger planets and moons, supramundane shells production, tube worlds` construction... whatever is possible, economical and necesarry.
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Sedna has diameter between 1180 and 1800 km., area 4-8 000 000 sq.km., if it has ice/rock composition like the Uranian big moons, than it has surface gravity is from 2 to 4% the Earths`. Not too much different natural conditions than Ceres. Except the distance to the "central heating". In 2075-76 Sedna will pass it`s perihelion at >40 AU, about 5-6000 years after that will reach aphelion at ~1000 AU from the Sun. Let assume 100 AU distance from the sun as initial conditions. With this weak gravity a method for atmosphere retaining should be applied: Sky ocean, world tent/dome/roof, magnetic tech for exospheric manipulation and back-scooping of escaping ions... For the earth-values` illumination of Sedna with sun light at 100 AU, the diameter of the statite magnifying soleta should be 100 times the planetoid`s one, or the scattered solar photons should be collected from 10 000 times bigger area than the illuminated body. Soleta with diameter, say, 150 000 km. That means 17-18 billions of sq.km. Because the 'enlighted' planet is too small an annular support mirror should hold the soleta into position. The optic processor system is made from 'solar sail material' weighting about 0.0003 grams/sq.m. hence the soleta + annulus is about 20 billion tones. The carbon and alluminium necesary could be extracted from Sedna as it is (probably) 50/50 ice/silicate rock+organics. As Sedna goes deeper in the dark, the sedners have 50-60 centuries to grow the soleta 10 times wider and to capture successfuly all the light needed. The shear light flux could be diminished (many-many times)depending the size of the society, industry and ecology planted there. The colony grows incrementaly, untill the closest to full-surface terraforming is achieved. As other icy worlds Sedna will be cold within and warm from the outside in order the firm land to not melt and vaporize in methan/amonia/water vapour/gass...
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In the Oort cloud which is estimated to contain between 1 and 10 trillions of comets, with total mass equaling from one earth`s to one jupiter`s, could be hiding much bigger than Sedna objects. There is no reason why not to be terraformed such supercold objects.
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If and when fusion power becomes available, these objects will make ideal construction material and fuel for interstellar travel.
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If and when fusion power becomes available, these objects will make ideal construction material and fuel for interstellar travel.
Im the Solar system there is more than enough rough material (+ more than enough solar power - even without artificial fusion) for both colonising the whole galaxy with sufficiently big civilization seeds and for producing the whole necessary earth-like surface to utilize the output of the central star entirelly in Dyson collector manner. We don`t need to dismantle the big round bodies-with-personality present here. We could use for such ultimate projects only the enormous host of undersized irregulary shaped bodies in the solar sphere of influence. There are trillions of comets in the Oort cloud with total mass estimated from one earth`s to one jovian. Consisting of primordial stellar material. Plus the asteroids. Meteoroids. The system`s dust. We could mine the sun by plasma ram-scoops. The ready complete planets have unique value. They are places with names. They`ll be protected by environmentalist legislature from this pointless dismantling. If the terraforming itself wouldn`t be prohibited, what to do with them will decide their owners, but even under only economical reasoning -- these worlds being just miniscule part of the system`s living room, hence unique shall possess enormous value as unique touristic destinations.
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In very brutal comparison: No one intends to dig out Hawaii from the bottom of Pasific and use it to Manhattan-form the Yellowstone park, for example, or for interplanetary travel...
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