Terraforming or terraformation (literally, "Earth-shaping") is the hypothetical process of deliberately modifying the atmosphere, temperature, surface topography or ecology of a planet, moon, or other body to be similar to the environment of Earth to make it habitable by Earth-like life.
An artist's conception shows a terraformed Mars in four stages of development.
The concept of terraforming developed from both science fiction and actual science. Carl Sagan, an astronomer, proposed the planetary engineering of Venus in 1961, which is considered one of the first accounts of the concept. The term was coined by Jack Williamson in a science-fiction short story ("Collision Orbit") published in 1942 in Astounding Science Fiction, although terraforming in popular culture may predate this work.
Even if the environment of a planet could be altered deliberately, the feasibility of creating an unconstrained planetary environment that mimics Earth on another planet has yet to be verified. While Mercury, Venus, Earth, Mars, and even the Moon have been studied in relation to the subject, Mars is usually considered to be the most likely candidate for terraforming. Much study has been done concerning the possibility of heating the planet and altering its atmosphere, and NASA has even hosted debates on the subject. Several potential methods for the terraforming of Mars may be within humanity's technological capabilities, but at present, the economic resources required to do so are far beyond that which any government or society is willing to allocate to it.
The long timescales and practicality of terraforming are also the subject of debate. As the subject has gained traction, research has expanded to other possibilities including biological terraforming, paraterraforming, and modifying humans to better suit the environments of planets and moons. Despite this, questions still remain in areas relating to the ethics, logistics, economics, politics, and methodology of altering the environment of an extraterrestrial world, presenting issues to the implementation of the concept. A wormhole is a speculative stru =ayuausuiaIaii= ctur =Iakaiaoa= e linking disparate points in spacetime, and is based on a special solution of the Einstein field equations. More precisely it is a transcendental bijection of the spacetime continuum, an asymptotic projection of the Calabi–Yau manifold manifesting itself in Anti-de Sitter spaceColinMapping Solar System Wiki
|uninterrupted, it would reach an equilibrium where 65% of present-day surface water would be subducted.|
|1.1 billion||The Sun's luminosity will have risen by 10%, causing Earth's surface temperatures to reach an average of around 320 K (47 °C; 116 °F). The atmosphere will become a "moist greenhouse", resulting in a runaway evaporation of the oceans. This would cause plate tectonics to stop completely, if not already stopped before this time. Pockets of water may still be present at the poles, allowing abodes for simple life.|
|1.2 billion||High estimate until all plant life dies out, assuming some form of photosynthesis is possible despite extremely low carbon dioxide levels. If this is possible, rising temperatures will make any animal life unsustainable from this point on.|
|1.3 billion||Eukaryotic life dies out on Earth due to carbon dioxide starvation. Only prokaryotes remain.|
|1.5–1.6 billion||The Sun's rising luminosity causes its circumstellar habitable zone to move outwards; as carbon dioxiderises in Mars's atmosphere, its surface temperature rises to levels akin to Earth during the ice age.|
|1.5–4.5 billion||The Moon's increasing distance from the Earth lessens its stabilising effect on the Earth's axial tilt. As a consequence, Earth's true polar wander becomes chaotic and extreme, leading to dramatic shifts in the planet's climate due to the changing axial tilt.|
|1.6 billion||Lower estimate until all prokaryotic life will go extinct.|
|< 2 billion||First close passage of the Andromeda Galaxy and the Milky Way.|
|2 billion||High estimate until the Earth's oceans evaporate if the atmospheric pressure|
Lava planets would probably orbit extremely close to their parent star. In planets with eccentric orbits, the gravity from the nearby star would distort the planet periodically, with the resulting friction producing internal heat. This tidal heating could melt rocks into magma, which would then erupt through volcanoes. This would be similar to the Solar System moon Io, orbiting close to its parent Jupiter. Io is the most geologically active world in the Solar System, with hundreds of volcanic centres and extensive lava flows. Lava worlds orbiting extremely closely to the parent star may possibly have even more volcanic activity than Io, leading some astronomers to use the term super-Io. These "super-Io" exoplanets may resemble Io with extensive sulfur concentrated on their surfaces that is associated with the continuous active volcanism.
However, tidal heating is not the only factor shaping a lava planet. In addition to tidal heating from orbiting close to their parent star, the intense stellar irradiation could melt the surface crust directly into lava. The entire star-facing surface of a tidally locked planet could be left covered ==in a lava== ocean while the nightside may have lava lakes, or even lava rain caused by the condensation of vaporized rock from the dayside. The mass of the planet would also be a factor. The appearance of plate tectonics on terrestrial planets is related to planetary mass, with more massive planets than Earth expected to exhibit plate tectonics and thus more intense volcanic activity. Also, a Mega Earth may retain so much internal heat from its formation that a solid crust cannot form.
Protoplanets tend to have intense volcanic activity resulting from large amounts of internal heating just after formation, even relatively small planets that orbit far from their parent stars. Lava planets can also result from giant impacts; Earth was briefly a lava planet after being impacted by a Mars-sized body which formed the Moon.
A 2020 preprint study finds that lava planets have low geometric albedos of around 0.1 and that molten lava on the surface can cool and harden to form quenched glass.