Scientist illustrations of
hypothetical ocean planets with
two natural satellites.
An ocean planet, aquaplanet or water
world[1] is a hypothetical type of
exoplanet wherein the surface is
completely covered by water, and a
substantial portion of its mass is water.
Formation
Planetary objects that form in the outer
Solar System begin as a comet-like
mixture of roughly half water and half
rock by mass. Simulations of Solar System
formation and of extra-solar system
formation have shown that planets are
likely to migrate inward (i.e., toward the
star) as they form.[2][3][4] Outward
migration may also occur under particular
conditions.[4] Inward migration presents
the possibility that icy planets could move
to orbits where their ice melts into liquid
form, turning them into ocean planets.
This possibility was first discussed in the
professional astronomical literature by
Marc Kuchner[5] and Alain Léger[6] in
2003.
Structure
Although 70.8% of all Earth's surface is
covered in water,[7] water accounts for
just some 0.05% of Earth’s mass. There
are worlds where more than 10% of the
mass may be water. This may be the case,
for example, for all the six innermost
planets orbiting the star Kepler-11.[8]
These planets may have oceans hundreds
of kilometres deep.[9] Their abyssal
depths would be so deep and dense that
even at high temperatures the pressure
would turn the water into ice. The
immense pressures in the lower regions
of these oceans could lead to the
formation of a mantle of exotic forms of
ice. This ice would not necessarily be as
cold as conventional ice. If the planet is
close enough to its star that the water
reaches its boiling point, the water will
become supercritical and lack a well-
defined surface.[6] Even on cooler water-
dominated planets, the atmosphere can
be much thicker than that of Earth, and
composed largely of water vapor,
producing a very strong greenhouse
effect. Such planets would have to be
small enough not to be able to retain a
thick envelope of hydrogen and helium,
otherwise they would form a warmer
version of an ice giant instead, like Uranus
and Neptune.
Smaller ocean planets would have less
dense atmospheres and lower gravity;
thus, liquid could evaporate much more
easily than on more massive ocean
planets. Theoretically, such planets could
have higher waves than their more
massive counterparts due to their lower
gravity.
Examples
The extrasolar planet GJ 1214 b is the
most likely known candidate for an ocean
planet.[10][11] Many more such objects
are expected to be discovered by Kepler,
such as the recently discovered ocean
planet candidate Kepler-22b.
Possibilities for
colonization
An ocean planet has no dry surface
landmasses. One of two processes would
be required:
1. Constructing an artificial surface, either
from a network of large platforms or
series of floating settlements.
2. Constructing artificial islands from solid
materials gathered elsewhere. This is not
viable if the ocean is hundreds or
thousands of miles deep.
See also
v
hypothetical ocean planets with
two natural satellites.
An ocean planet, aquaplanet or water
world[1] is a hypothetical type of
exoplanet wherein the surface is
completely covered by water, and a
substantial portion of its mass is water.
Formation
Planetary objects that form in the outer
Solar System begin as a comet-like
mixture of roughly half water and half
rock by mass. Simulations of Solar System
formation and of extra-solar system
formation have shown that planets are
likely to migrate inward (i.e., toward the
star) as they form.[2][3][4] Outward
migration may also occur under particular
conditions.[4] Inward migration presents
the possibility that icy planets could move
to orbits where their ice melts into liquid
form, turning them into ocean planets.
This possibility was first discussed in the
professional astronomical literature by
Marc Kuchner[5] and Alain Léger[6] in
2003.
Structure
Although 70.8% of all Earth's surface is
covered in water,[7] water accounts for
just some 0.05% of Earth’s mass. There
are worlds where more than 10% of the
mass may be water. This may be the case,
for example, for all the six innermost
planets orbiting the star Kepler-11.[8]
These planets may have oceans hundreds
of kilometres deep.[9] Their abyssal
depths would be so deep and dense that
even at high temperatures the pressure
would turn the water into ice. The
immense pressures in the lower regions
of these oceans could lead to the
formation of a mantle of exotic forms of
ice. This ice would not necessarily be as
cold as conventional ice. If the planet is
close enough to its star that the water
reaches its boiling point, the water will
become supercritical and lack a well-
defined surface.[6] Even on cooler water-
dominated planets, the atmosphere can
be much thicker than that of Earth, and
composed largely of water vapor,
producing a very strong greenhouse
effect. Such planets would have to be
small enough not to be able to retain a
thick envelope of hydrogen and helium,
otherwise they would form a warmer
version of an ice giant instead, like Uranus
and Neptune.
Smaller ocean planets would have less
dense atmospheres and lower gravity;
thus, liquid could evaporate much more
easily than on more massive ocean
planets. Theoretically, such planets could
have higher waves than their more
massive counterparts due to their lower
gravity.
Examples
The extrasolar planet GJ 1214 b is the
most likely known candidate for an ocean
planet.[10][11] Many more such objects
are expected to be discovered by Kepler,
such as the recently discovered ocean
planet candidate Kepler-22b.
Possibilities for
colonization
An ocean planet has no dry surface
landmasses. One of two processes would
be required:
1. Constructing an artificial surface, either
from a network of large platforms or
series of floating settlements.
2. Constructing artificial islands from solid
materials gathered elsewhere. This is not
viable if the ocean is hundreds or
thousands of miles deep.
See also
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