The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from other planets in the Solar System. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of . About 97.5% of the water is saline; the remaining 2.5% is fresh water. Most fresh water, about 68.7%, is present as ice in ice caps and glaciers. The mass of the oceans is approximately 1.35 metric tons or about 1/4400 of Earth's total mass. The oceans cover an area of with a mean depth of , resulting in an estimated volume of .
Hydrosphere
Earth
Earth | Hydrosphere
Yes, Yes, 71% is covered with water The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from other planets in the Solar System. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world Yes, there is abundance of water on Earth's surface and this is a unique feature that distinguishes it from other planets.
what factor limits the number of eclipses each year
user
The alignment of the Sun, Moon and Earth.
assistant
what is this phenomena ?
user
A solar eclipse occurs when a portion of the Earth is engulfed in a shadow cast by the Moon which fully or partially blocks sunlight.
assistant
what are the different types of it ?
user
There are four types of solar eclipses.
assistant
what is their frequency ?
user
Between two and five solar eclipses occur every year.
assistant
what is their duration ?
user
The longest eclipse that has been calculated thus far is 7 minutes 29 seconds.
assistant
does it follow any path ?
user
Yes, the Moon's umbra moves rapidly from west to east across the Earth.
assistant
talk about the planet you mentioned above ?
user
It is the third planet from the Sun and the only astronomical object known to harbor life.
assistant
talk about its surface ?
user
Of the total surface area of Earth about 70.8%, is below sea level an/d covered by ocean water. The pedosphere is the outermost layer of Earth's continental surface and is composed of soil and subject to soil formation processes.
assistant
how is its atmosphere ?
user
It is composed of 78.084% nitrogen, 20.946% oxygen, 0.934% argon, and trace amounts of carbon dioxide and other gaseous molecules.
assistant
is there water on this planet ?
user
The hydrosphere (from Greek ὕδωρ "hydōr", "water" and σφαῖρα "sphaira", "sphere") is the combined mass of water found on, under, and above the surface of a planet, minor planet or natural satellite. Although Earth's hydrosphere has been around for about 4 billion years, it continues to change in shape. This is caused by seafloor spreading and continental drift, which rearranges the land and ocean. It has been estimated that there are of water on Earth. This includes water in liquid and frozen forms in groundwater, oceans, lakes and streams. Saltwater accounts for 97.5% of this amount, whereas fresh water accounts for only 2.5%.
Hydrosphere | Introduction
Of this fresh water, 68.9% is in the form of ice and permanent snow cover in the Arctic, the Antarctic and mountain glaciers; 30.8% is in the form of fresh groundwater; and only 0.3% of the fresh water on Earth is in easily accessible lakes, reservoirs and river systems. The total mass of Earth's hydrosphere is about 1.4 × 10 tonnes, which is about 0.023% of Earth's total mass. At any given time, about 20 × 10 tonnes of this is in the form of water vapor in the Earth's atmosphere (for practical purposes, 1 cubic meter of water weighs one tonne).
Hydrosphere | Introduction
The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from other planets in the Solar System. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of . About 97.5% of the water is saline; the remaining 2.5% is fresh water. Most fresh water, about 68.7%, is present as ice in ice caps and glaciers. The mass of the oceans is approximately 1.35 metric tons or about 1/4400 of Earth's total mass. The oceans cover an area of with a mean depth of , resulting in an estimated volume of .
Earth | Hydrosphere
The hydrosphere plays an important role in the existence of the atmosphere in its present form. Oceans are important in this regard. When the Earth was formed it had only a very thin atmosphere rich in hydrogen and helium similar to the present atmosphere of Mercury. Later the gases hydrogen and helium were expelled from the atmosphere. The gases and water vapor released as the Earth cooled became its present atmosphere. Other gases and water vapor released by volcanoes also entered the atmosphere. As the Earth cooled the water vapor in the atmosphere condensed and fell as rain. The atmosphere cooled further as atmospheric carbon dioxide dissolved in to rain water.
Hydrosphere | Water cycle
Water is a chemical substance that is composed of hydrogen and oxygen (H2O) and is vital for all known forms of life. In typical usage, "water" refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor, or steam. Water covers 71% of the Earth's surface. On Earth, it is found mostly in oceans and other large bodies of water, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds, and precipitation. Oceans hold 97% of surface water, glaciers, and polar ice caps 2.4%, and other land surface water such as rivers, lakes, and ponds 0.6%.
Nature | Water on the Earth
A planet cannot have a hydrosphere—a key ingredient for the formation of carbon-based life—unless there is a source for water within its stellar system. The origin of water on Earth is still not completely understood; possible sources include the result of impacts with icy bodies, outgassing, mineralization, leakage from hydrous minerals from the lithosphere, and photolysis. For an extrasolar system, an icy body from beyond the frost line could migrate into the habitable zone of its star, creating an ocean planet with seas hundreds of kilometers deep such as GJ 1214 b or Kepler-22b may be. Maintenance of liquid surface water also requires a sufficiently thick atmosphere.
Circumstellar habitable zone | Other considerations
In turn this further caused the water vapor to condense and fall as rain. This rain water filled the depressions on the Earth's surface and formed the oceans. It is estimated that this occurred about 4000 million years ago. The first life forms began in the oceans. These organisms did not breathe oxygen. Later, when cyanobacteria evolved, the process of conversion of carbon dioxide into food and oxygen began. As a result, Earth's atmosphere has a distinctly different composition from that of other planets and allowed for life to evolve on Earth.
Hydrosphere | Water cycle
The current atmospheric reservoir of water, though important as a conduit, is insignificant in volume with the WEG no more than . Since the typical surface pressure of the current atmosphere (~) is less than the triple point of HO, liquid water is unstable on the surface unless present in sufficiently large volumes. Furthermore, the average global temperature is ~, even below the eutectic freezing point of most brines. For comparison, the highest diurnal surface temperatures at the two MER sites have been ~.
Water on terrestrial planets of the Solar System | Mars
Earth's hydrosphere contains ~1.46×10 kg (3.22×10 lb) of HO and sedimentary rocks contain ~0.21×10 kg (4.6×10 lb), for a total crustal inventory of ~1.67×10 kg (3.68×10 lb) of HO. The mantle inventory is poorly constrained in the range of 0.5×10–4×10 kg (1.1×10–8.8×10 lb). Therefore, the bulk inventory of HO on Earth can be conservatively estimated as 0.04% of Earth's mass (~2.3×10 kg (5.1×10 lb)).
Water on terrestrial planets of the Solar System | Earth
This is water that evaporates from the oceanic surface (502,800 km) and from land (74,200 km). The same amount of water falls as atmospheric precipitation, 458,000 km on the ocean and 119,000 km on land. The difference between precipitation and evaporation from the land surface (119,000 - 74,200 = 44,800 km/year) represents the total runoff of the Earth's rivers (42,700 km/year) and direct groundwater runoff to the ocean (2100 km/year). These are the principal sources of fresh water to support life necessities and man's economic activities."Water is a basic necessity of life. Since 2/3 of the Earth is covered by water, the Earth is also called the blue planet and the watery planet.
Hydrosphere | Water cycle
While the majority of Earth's surface is covered by oceans, those oceans make up just a small fraction of the mass of the planet. The mass of Earth's oceans is estimated to be 1.37 × 10 kg, which is 0.023% of the total mass of Earth, 6.0 × 10 kg. An additional 0.5 × 10 kg of water is estimated to exist in ice, lakes, rivers, groundwater, and atmospheric water vapor. A significant amount of water is also stored in Earth's crust, mantle, and core. Unlike molecular HO that is found on the surface, water in the interior exists primarily in hydrated minerals or as trace amounts of hydrogen bonded to oxygen atoms in anhydrous minerals.
Origin of water on Earth | Earth's water inventory
Earth is the only known planet with seas of liquid water on its surface, although Mars possesses ice caps and similar planets in other solar systems may have oceans. Earth's of sea contain about 97.2 percent of its known water and cover more than 70 percent of its surface. Another 2.15% of Earth's water is frozen, found in the sea ice covering the Arctic Ocean, the ice cap covering Antarctica and its adjacent seas, and various glaciers and surface deposits around the world. The remainder (about 0.65% of the whole) form underground reservoirs or various stages of the water cycle, containing the freshwater encountered and used by most terrestrial life: vapor in the air, the clouds it slowly forms, the rain falling from them, and the lakes and rivers spontaneously formed as its waters flow again and again to the sea.
Sea | Physical science
The total mass of water, regardless of phase (e.g. liquid, solid, gas), that exists within an ecosphere. It's possible for the hydrosphere to be highly distributed throughout other component spheres such as the geosphere and atmosphere.
Ecosphere (planetary) | <a href="Hydrosphere">Hydrosphere</a>
The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth are vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the Solar System; if it were slightly closer to or farther from the Sun (about 5%, or about 8 million kilometers), the conditions which allow the three forms to be present simultaneously would be far less likely to exist. Earth's gravity allows it to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a temperature buffer (greenhouse effect) which helps maintain a relatively steady surface temperature.
Water | Water and habitable zone
Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers.
Water | On Earth
This sphere represents all water on Earth, wherever it is and in whatever form within the water cycle.
Outline of Earth | Earth's <a href="hydrosphere">hydrosphere</a>
Estimates based on Venus's levels of deuterium suggest that the planet has lost anywhere from of surface water up to "an Earth's ocean's worth".
Water on terrestrial planets of the Solar System | Venus
Travis Barman at Lowell Observatory in Flagstaff, Arizona analyzed the emission spectrum of this planet, and believes that its atmosphere contains water, although previous research suggests that the atmosphere is composed mostly of silicate clouds.
HD 209458 | Planetary system
Evapotranspiration is the term used by hydrologists in reference to the three processes together, transpiration, sublimation and evaporation. Marq de Villiers has described the hydrosphere as a closed system in which water exists. The hydrosphere is intricate, complex, interdependent, all-pervading and stable and "seems purpose-built for regulating life." De Villiers claimed that, "On earth, the total amount of water has almost certainly not changed since geological times: what we had then we still have. Water can be polluted, abused, and misused but it is neither created nor destroyed, it only migrates. There is no evidence that water vapor escapes into space.""Every year the turnover of water on Earth involves 577,000 km of water.
Hydrosphere | Water cycle
Liquid water is present on Earth, covering 71% of its surface. Liquid water is also occasionally present in small amounts on Mars. Scientists believe liquid water is present in the Saturnian moons of Enceladus, as a 10-kilometre thick ocean approximately 30–40 kilometres below Enceladus' south polar surface, and Titan, as a subsurface layer, possibly mixed with ammonia. Jupiter's moon Europa has surface characteristics which suggest a subsurface liquid water ocean. Liquid water may also exist on Jupiter's moon Ganymede as a layer sandwiched between high pressure ice and rock.
Water | Liquid water
However, carbon planets will probably be devoid of water, which cannot form because any oxygen delivered by comets or asteroids will react with the carbon on the surface. The atmosphere on a relatively cool carbon planet would consist primarily of carbon dioxide or carbon monoxide with a significant amount of carbon smog.
Carbon planet | Definition
Not only does the hydrological cycle determine patterns of precipitation, it also has an influence on the movement of energy throughout the climate system. The "hydrosphere" proper contains all the liquid water on Earth, with most of it contained in the world's oceans. The ocean covers 71% of Earth's surface to an average depth of nearly , and can hold substantially more heat than the atmosphere. It contains seawater with a salt content of about 3.5% on average, but this varies spatially. Brackish water is found in estuaries and some lakes, and most freshwater, 2.5% of all water, is held in ice and snow.
Climate system | Components of the climate system
One factor in estimating when water appeared on Earth is that water is continually being lost to space. HO molecules in the atmosphere are broken up by photolysis, and the resulting free hydrogen atoms can sometimes escape Earth's gravitational pull (see: Atmospheric escape). When the Earth was younger and less massive, water would have been lost to space more easily. Lighter elements like hydrogen and helium are expected to leak from the atmosphere continually, but isotopic ratios of heavier noble gases in the modern atmosphere suggest that even the heavier elements in the early atmosphere were subject to significant losses.
Origin of water on Earth | History of water on Earth
The gaseous outer layers of Jupiter and Saturn transition smoothly into oceans of supercritical hydrogen. The atmosphere of Venus is 96.5% carbon dioxide, which is a supercritical fluid at its surface.
Ocean | Non-water surface liquids
The origin of water on Earth is the subject of a body of research in the fields of planetary science, astronomy, and astrobiology. Earth is unique among the rocky planets in the Solar System in that it is the only planet known to have oceans of liquid water on its surface. Liquid water, which is necessary for life as we know it, continues to exist on the surface of Earth because the planet is at a distance, known as the habitable zone, far enough from the Sun that it does not lose its water to the runaway greenhouse effect, but not so far that low temperatures cause all water on the planet to freeze.
Origin of water on Earth | Introduction
The current Venusian atmosphere has only ~200 mg/kg HO(g) in its atmosphere and the pressure and temperature regime makes water unstable on its surface. Nevertheless, assuming that early Venus's HO had a ratio between deuterium (heavy hydrogen, 2H) and hydrogen (1H) similar to Earth's Vienna Standard Mean Ocean Water (VSMOW) of 1.6×10, the current D/H ratio in the Venusian atmosphere of 1.9×10, at nearly ×120 of Earth's, may indicate that Venus had a much larger HO inventory. While the large disparity between terrestrial and Venusian D/H ratios makes any estimation of Venus's geologically ancient water budget difficult, its mass may have been at least 0.3% of Earth's hydrosphere.
Water on terrestrial planets of the Solar System | Venus
The concept of the habitable zone (or Liquid Water Zone) defining a region where water can exist on the surface, is based on the properties of both the Earth and Sun. Under this model, Earth orbits roughly at the centre of this zone or in the "Goldilocks" position. Earth is the only planet currently confirmed by humankind to possess large bodies of surface water. Venus is on the hot side of the zone while Mars is on the cold side. Neither are known to have persistent surface water, though evidence exists that Mars did have in its ancient past, and it is speculated that the same was the case for Venus.
Earth analog | Surface water and hydrological cycle
To allow water to be liquid for long periods of time, a planet —or moon— must orbit within the habitable zone (HZ), possess a protective magnetic field, and have the gravitational pull needed to retain an ample amount of atmospheric pressure. If the planet's gravity cannot sustain that, then all the water will eventually evaporate into outer space. A strong planetary magnetosphere, maintained by internal dynamo action in an electrically conducting fluid layer, is helpful for shielding the upper atmosphere from stellar wind mass loss and retaining water over long geological time scales. A planet's atmosphere forms from outgassing during planet formation or is gravitationally captured from the surrounding protoplanetary nebula.
Ocean world | Atmospheric models
A sizable quantity of water would have been in the material that formed the Earth. Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. Hydrogen and helium are expected to continually escape (even to the present day) due to atmospheric escape. Part of the ancient planet is theorized to have been disrupted by the impact that created the Moon, which should have caused melting of one or two large regions of the Earth. Earth's present composition suggests that there was not complete remelting as it is difficult to completely melt and mix huge rock masses.
Hadean | Atmosphere and oceans
Most water in the Earth's atmosphere and crust comes from the world ocean's saline seawater, while freshwater accounts for nearly 1% of the total. Because the oceans that cover roughly 71% of the area of the Earth reflect blue light, the Earth appears blue from space, and is often referred to as the "blue planet" and the "Pale Blue Dot". An estimated 1.5 to 11 times the amount of water in the oceans may be found hundreds of kilometers deep within the Earth's interior, although not in liquid form. The oceanic crust is young, thin and dense, with none of the rocks within it dating from any older than the breakup of Pangaea.
Water distribution on Earth | Introduction
Water has a much lower condensation temperature than other materials that compose the terrestrial planets in the Solar System, such as iron and silicates. The region of the protoplanetary disk closest to the Sun was very hot early in the history of the Solar System, and it is not feasible that oceans of water condensed with the Earth as it formed. Further from the young Sun where temperatures were cooler, water could condense and form icy planetesimals. The boundary of the region where ice could form in the early Solar System is known as the frost line (or snow line), and is located in the modern asteroid belt, between about 2.7 and 3.1 astronomical units (AU) from the Sun.
Origin of water on Earth | Extraplanetary sources
There is no life without water. It has been described as the "universal solvent" for its ability to dissolve many substances, and as the "solvent of life". Water is the only common substance to exist as a solid, liquid, and gas under conditions normal to life on Earth. The Nobel Prize winner Albert Szent-Györgyi referred to water as the "mater und matrix": the mother and womb of life. The abundance of surface water on Earth is a unique feature in the Solar System. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean, having a depth of .
Marine life | Water
Since Venus only has a fraction of the water on Earth (less than half the Earth's water content in the atmosphere, and none on the surface), water would have to be introduced either by the aforementioned method of introduction of hydrogen, or from some other extraplanetary source.
Terraforming of Venus | Introduction of water
The origin and development of water on terrestrial planets, Venus, Earth, Mars, and the closely related Earth's Moon, varies with each planetary body, with the exact origins remaining unclear. Additionally, the terrestrial dwarf planet Ceres is known to have water ice on its surface.
Water on terrestrial planets of the Solar System | Introduction
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. 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, or be close enough to their primary star to be stripped of these light elements. Otherwise, they would form a warmer version of an ice giant instead, like Uranus and Neptune.
Ocean world | Exoplanets
The water cycle refers to the transfer of water from one state or reservoir to another. Reservoirs include atmospheric moisture (snow, rain and clouds), streams, oceans, rivers, lakes, groundwater, subterranean aquifers, polar ice caps and saturated soil. Solar energy, in the form of heat and light (insolation), and gravity cause the transfer from one state to another over periods from hours to thousands of years. Most evaporation comes from the oceans and is returned to the earth as snow or rain. Sublimation refers to evaporation from snow and ice. Transpiration refers to the expiration of water through the minute pores or stomata of trees.
Hydrosphere | Water cycle
Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir. Shifts in the oceanic temperature distribution can cause significant weather shifts, such as the El Niño–Southern Oscillation.
Earth | Hydrosphere
Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients. Its chemical formula is HO, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. "Water" is the name of the liquid state of HO at standard ambient temperature and pressure. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds are formed from suspended droplets of water and ice, its solid state.
Water | Introduction
At 800 atmospheres of pressure the surface atmosphere, with its load of dissolved oxygen and sulphur oxides, is compressed to a density a little less than the density of liquid water (1182 kilograms per cubic meter). Only when the density of the planet's air is a little less than the density of liquid water will the raindrops descend slowly; otherwise, they would come down like meteors and make life on Tenebra impossible.
Close to Critical | Setting
Only 2.5% of the water in the hydrosphere is fresh water and only 0.25% of that water is accessible for our use.
Hydrosphere | Specific fresh water availability
The deuterium to hydrogen ratio for ocean water on Earth is known very precisely to be (1.5576 ± 0.0005) × 10. This value represents a mixture of all of the sources that contributed to Earth's reservoirs, and is used to identify the source or sources of Earth's water. The ratio of deuterium to hydrogen may have increased over the Earth's lifetime as the lighter isotope is more likely to leak to space in atmospheric loss processes. However no process is known that can decrease Earth's D/H ratio over time. This loss of the lighter isotope is one explanation for why Venus has such a high D/H ratio, as that planet's water was vaporized during the runaway greenhouse effect and subsequently lost much of its hydrogen to space.
Origin of water on Earth | Earth
The atmospheric pressure at Earth's sea level averages , with a scale height of about . A dry atmosphere is composed of 78.084% nitrogen, 20.946% oxygen, 0.934% argon, and trace amounts of carbon dioxide and other gaseous molecules. Water vapor content varies between 0.01% and 4% but averages about 1%. The height of the troposphere varies with latitude, ranging between at the poles to at the equator, with some variation resulting from weather and seasonal factors. Earth's biosphere has significantly altered its atmosphere. Oxygenic photosynthesis evolved , forming the primarily nitrogen–oxygen atmosphere of today. This change enabled the proliferation of aerobic organisms and, indirectly, the formation of the ozone layer due to the subsequent conversion of atmospheric into.
Earth | Atmosphere
Liquid water is not present within the ringwoodite, rather the components of water (hydrogen and oxygen) are held within as hydroxide ions.
Water distribution on Earth | Water in Earth's mantle
The total volume of water on Earth is estimated at 1.386 billion km³ (333 million cubic miles), with 97.5% being salt water and 2.5% being fresh water. Of the fresh water, only 0.3% is in liquid form on the surface. In addition, the lower mantle of inner earth may hold as much as 5 times more water than all surface water combined (all oceans, all lakes, all rivers).
Water distribution on Earth | Distribution of saline and fresh water
In particular, xenon is useful for calculations of water loss over time. Not only is it a noble gas (and therefore is not removed from the atmosphere through chemical reactions with other elements), but comparisons between abundances of its nine stable isotopes in the modern atmosphere reveal that the Earth lost at least one ocean of water early in its history, between the Hadean and Archean eras. Any water on Earth during the later part of its accretion would have been disrupted by the Moon-forming impact (~4.5 billion years ago), which likely vaporized much of Earth's crust and upper mantle and created a rock-vapor atmosphere around the young planet.
Origin of water on Earth | History of water on Earth
The rock vapor would have condensed within two thousand years, leaving behind hot volatiles which probably resulted in a majority carbon dioxide atmosphere with hydrogen and water vapor. Afterwards, liquid water oceans may have existed despite the surface temperature of due to the increased atmospheric pressure of the CO atmosphere. As cooling continued, most CO was removed from the atmosphere by subduction and dissolution in ocean water, but levels oscillated wildly as new surface and mantle cycles appeared. There is also geological evidence that helps constrain the time frame for liquid water existing on Earth. A sample of pillow basalt (a type of rock formed during an underwater eruption) was recovered from the Isua Greenstone Belt and provides evidence that water existed on Earth 3.8 billion years ago.
Origin of water on Earth | History of water on Earth
Long before the discovery of water on asteroids on comets and dwarf planets beyond Neptune, the Solar System's circumstellar disks, beyond the snow line, including the asteroid belt and the Kuiper Belt were thought to contain large amounts of water and these were believed to be the Origin of water on Earth. Given that many types of stars are thought to blow volatiles from the system through the photoevaporation effect, water content in circumstellar disks and rocky material in other planetary systems are very good indicators of a planetary system's potential for liquid water and a potential for organic chemistry, especially if detected within the planet forming regions or the habitable zone.
Extraterrestrial liquid water | Water rich circumstellar disks
This would be consistent with the thermodynamic estimate of around two Earth masses of water vapor within 3AU of the solar accretionary disk, which would exceed by a factor of 40 the mass of water needed to accrete the equivalent of 50 Earth hydrospheres (the most extreme estimate of Earth's bulk HO content) per terrestrial planet. Even though much of the nebular HO(g) may be lost due to the high temperature environment of the accretionary disk, it is possible for physisorption of HO on accreting grains to retain nearly three Earth hydrospheres of HO at temperatures. This adsorption model would effectively avoid the Os/Os isotopic ratio disparity issue of distally-sourced HO.
Water on terrestrial planets of the Solar System | Accretion of water by Earth and Mars
Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology. The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1.386 × 10 cubic kilometers (3.33 × 10 cubic miles).
Water | On Earth
Because Earth's D/H ratio has increased significantly over time, the D/H ratio of water originally delivered to the planet was lower than at present. This is consistent with a scenario in which a significant proportion of the water on Earth was already present during the planet's early evolution.
Origin of water on Earth | Earth
The action of plate tectonics traps vast amounts of CO, thereby reducing greenhouse effects, and leading to a much cooler surface temperature, and the formation of solid rock and liquid water.
Origin of water on Earth | History of water on Earth
It was long thought that Earth’s water did not originate from the planet’s region of the protoplanetary disk. Instead, it was hypothesized water and other volatiles must have been delivered to Earth from the outer Solar System later in its history. Recent research, however, indicates that hydrogen inside the Earth played a role in the formation of the ocean. The two ideas are not mutually exclusive, as there is also evidence water was delivered to Earth by impacts from icy planetesimals similar in composition to asteroids in the outer edges of the asteroid belt.
Origin of water on Earth | Introduction
The atmosphere of Venus is 96.5% carbon dioxide and 3.5% nitrogen. The surface pressure is 9.3 MPa (93 bar) and the surface temperature is 735 K, above the critical points of both major constituents and making the surface atmosphere a supercritical fluid. The interior atmospheres of the solar system's gas giant planets are composed mainly of hydrogen and helium at temperatures well above their critical points. The gaseous outer atmospheres of Jupiter and Saturn transition smoothly into the dense liquid interior, while the nature of the transition zones of Neptune and Uranus is unknown. Theoretical models of extrasolar planet Gliese 876 d have posited an ocean of pressurized, supercritical fluid water with a sheet of solid high pressure water ice at the bottom.
Supercritical fluid | Planetary atmospheres
Despite its Earth-like composition, the planet's equilibrium temperature is around , far too hot for liquid water or life. Depending on the amount of cloud cover in the atmosphere of HD 219134 b, the actual temperature may be somewhat lower, but nowhere near the range for liquid water.
HD 219134 b | Mass, radius and temperature
If liquid water is present in the atmosphere of HD 154672 b, it could possibly convert between gaseous and liquid phases as the planet moves along its orbit. The high eccentricity of the planet's orbit suggests that either the Kozai mechanism (there is an exchange between the inclination of a planet and its eccentricity) is at work, or that the planet's orbit was distorted by the unstable orbit of other planets that used to be part of the HD 154672 system. HD 154672 b had, at the time of its 2008 discovery, an orbital period larger than 90% of all discovered planets.
HD 154672 b | Characteristics
In the current, oxygen-rich atmosphere most hydrogen is converted into water before it has an opportunity to escape. Instead, most of the hydrogen loss comes from the destruction of methane in the upper atmosphere.
Earth | Upper atmosphere
Because water is much denser than any gas, this means that water will flow into the "depressions" formed as a result of the high density of oceanic crust. (On a planet like Venus, with no water, the depressions appear to form a vast plain above which rise plateaux). Since the low density rocks of the continental crust contain large quantities of easily eroded salts of the alkali and alkaline earth metals, salt has, over billions of years, accumulated in the oceans as a result of evaporation returning the fresh water to land as rain and snow. As a result, the vast bulk of the water on Earth is regarded as "saline" or "salt water", with an average salinity of 35‰ (or 4.5%, roughly equivalent to 34 grams of salts in 1 kg of seawater), though this varies slightly according to the amount of runoff received from surrounding land.
Water distribution on Earth | Introduction
Little erosion meant that liquid water had probably not played a large role in the planet's geomorphology for billions of years. Furthermore, the variations in the radio signal from the spacecraft as it passed behind the planet allowed scientists to calculate the density of the atmosphere. The results showed an atmospheric pressure less than 1% of Earth's at sea level, effectively precluding the existence of liquid water, which would rapidly boil or freeze at such low pressures. Thus, a vision of Mars was born of a world much like the Moon, but with just a wisp of an atmosphere to blow the dust around.
Water on Mars | Historical background
However, the current understanding of Earth's formation allows for less than 1% of Earth's material accreting after the Moon formed, implying that the material accreted later must have been very water-rich. Models of early Solar System dynamics have shown that icy asteroids could have been delivered to the inner Solar System (including Earth) during this period if Jupiter migrated closer to the Sun.
Origin of water on Earth | Extraplanetary sources
A significant amount of surface hydrogen has been observed globally by the Mars Odyssey GRS. Stoichiometrically estimated water mass fractions indicate that—when free of carbon dioxide—the near surface at the poles consists almost entirely of water covered by a thin veneer of fine material. This is reinforced by MARSIS observations, with an estimated of water at the southern polar region with Water Equivalent to a Global layer (WEG) deep. Additional observations at both poles suggest the total WEG to be , while the Mars Odyssey NS observations places the lower bound at ~ depth. Geomorphic evidence favors significantly larger quantities of surface water over geologic history, with WEG as deep as .
Water on terrestrial planets of the Solar System | Mars
Venus's atmosphere has therefore received a great deal of attention from those studying climate change on Earth. There are no geologic forms on the planet to suggest the presence of water over the past billion years. However, there is no reason to suppose that Venus was an exception to the processes that formed Earth and gave it its water during its early history, possibly from the original rocks that formed the planet or later on from comets. The common view among research scientists is that water would have existed for about 600 million years on the surface before evaporating, though some such as David Grinspoon believe that up to 2 billion years could also be plausible.
Atmosphere of Venus | Evolution
Water on Mars exists today almost exclusively as ice, with a small amount present in the atmosphere as vapour. Some liquid water may occur transiently on the Martian surface today but only under certain conditions. No large standing bodies of liquid water exist because the atmospheric pressure at the surface averages just 600 pascals (0.087 psi)—about 0.6% of Earth's mean sea level pressure—and because the global average temperature is far too low (210 K (−63 °C)), leading to either rapid evaporation or freezing. Features called recurring slope lineae are thought to be caused by flows of brine — hydrated salts.
Extraterrestrial liquid water | Mars
Highlands samples were estimated for the Lunar magma ocean at 1320-5000 ppm wt of HO in the beginning. The urKREEP sample estimates a 130-240 ppm wt of H2O, which is similar to the findings in the current Highland samples (before modeling). Pyroclastic Glass sample beads were used to estimate the water content in the mantle source and the bulk silicate Moon. The mantle source was estimated at 110 ppm wt of HO and the bulk silicate Moon contained 100-300 ppm wt of HO.
Water on terrestrial planets of the Solar System | Earth's moon
Hydrated silicates on the surface transport water into the mantle at convergent plate boundaries, where oceanic crust is subducted underneath continental crust. While it is difficult to estimate the total water content of the mantle due to limited samples, approximately three times the mass of the Earth's oceans could be stored there. Similarly, the Earth's core could contain four to five oceans' worth of hydrogen.
Origin of water on Earth | Earth's water inventory
Water is a transparent, tasteless, odorless, and nearly colorless chemical substance. Its chemical formula is HO, meaning that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. Water is the name of the liquid state of HO at standard ambient temperature and pressure. Water at the surface of the Earth moves continually through the water cycle of evaporation, transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Water seldom exists in a pure form, it almost always contains dissolved substances, and usually other matter in suspension.
Underwater environment | Physical characteristics
However, much of the water could be derived from Mercury-sized planetary embryos that formed in the asteroid belt beyond 2.5 AU. Mars's original D/H ratio, as estimated by deconvolving the atmospheric and magmatic D/H components in Martian meteorites (e.g., QUE 94201), is ×(1.9+/-0.25) the VSMOW value. The higher D/H and impact modeling (significantly different from Earth due to Mars's smaller mass) favor a model where Mars accreted a total of 6% to 27% the mass of the current Earth hydrosphere, corresponding respectively to an original D/H between ×1.6 and ×1.2 the SMOW value. The former enhancement is consistent with roughly equal asteroidal and cometary contributions, while the latter would indicate mostly asteroidal contributions.
Water on terrestrial planets of the Solar System | Accretion of water by Earth and Mars
The mean mass of water vapor is estimated as 1.27 kg and the dry air mass as 5.1352 ±0.0003 kg."
Atmosphere of Earth | Density and mass
Most water is found in various kinds of natural body of water.
Natural environment | Water on Earth
The remaining atmosphere, at around 3 bars (about three times that of Earth), would mainly be composed of nitrogen, some of which will dissolve into the new oceans of water, reducing atmospheric pressure further, in accordance with Henry's law. To bring down the pressure even more, nitrogen could also be fixated into nitrates.
Terraforming of Venus | Introduction of hydrogen
It is therefore necessary that objects forming beyond the frost line–such as comets, trans-Neptunian objects, and water-rich meteoroids (protoplanets)–delivered water to Earth. However, the timing of this delivery is still in question. One theory claims that Earth accreted (gradually grew by accumulation of) icy planetesimals about 4.5 billion years ago, when it was 60 to 90% of its current size. In this scenario, Earth was able to retain water in some form throughout accretion and major impact events. This hypothesis is supported by similarities in the abundance and the isotope ratios of water between the oldest known carbonaceous chondrite meteorites and meteorites from Vesta, both of which originate from the Solar System's asteroid belt.
Origin of water on Earth | Extraplanetary sources
When combined with its quantity, water vapor then has a relevant dew point and frost point, unlike e. g., carbon dioxide and methane. Water vapor thus has a scale height a fraction of that of the bulk atmosphere, as the water condenses and exits, primarily in the troposphere, the lowest layer of the atmosphere. Carbon dioxide () and methane, being non-polar, rise above water vapor. The absorption and emission of both compounds contribute to Earth's emission to space, and thus the planetary greenhouse effect. This greenhouse forcing is directly observable, via distinct spectral features versus water vapor, and observed to be rising with rising levels.
Water vapor | In Earth's atmosphere
Dry air from Earth's atmosphere contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and traces of hydrogen, helium, and other "noble" gases (by volume), but generally a variable amount of water vapor is also present, on average about 1% at sea level.
Atmosphere | Composition
An ocean world, ocean planet, water world, aquaplanet or panthalassic planet is a type of terrestrial planet that contains a substantial amount of water either at its surface or within a subsurface ocean. The term "ocean world" is also used sometimes for astronomical bodies with an ocean composed of a different fluid, such as lava (the case of Io), ammonia (in a eutectic mixture with water, as is likely the case of Titan's inner ocean) or hydrocarbons like on Titan's surface (which could be the most abundant kind of exosea). Earth is the only astronomical object known to have bodies of liquid water on its surface, although several exoplanets have been found with the right conditions to support liquid water.
Ocean world | Introduction
"HD 189733 A" has one known planet, designated HD 189733 b, a gaseous giant 13% larger than Jupiter close enough to complete an orbit every two days. Using spectrometry it was found in 2007 that this planet contains significant amounts of water vapour. This planet is the second extrasolar planet where definitive evidence for water has been found. The chemical signature of water vapour was detected in the atmosphere of this planet. Although HD 189733b with atmospheric temperatures rising above is far from being habitable, this finding increases the likelihood that water, an essential component of life, would be found on a more Earth-like planet in the future.
HD 189733 | Planetary system
In this model, the planet would have a pressurised ocean of water (in the form of a supercritical fluid) separated from the silicate core by a layer of ice kept frozen by the high pressures in the planetary interior. Such a planet would have an atmosphere containing water vapor and free oxygen produced by the breakdown of water by ultraviolet radiation.
Gliese 876 d | Mass, radius, and temperature
An additional complication is that the ~25% lower brightness of the young Sun would have required an ancient atmosphere with a significant greenhouse effect to raise surface temperatures to sustain liquid water. Higher CO content alone would have been insufficient, as CO precipitates at partial pressures exceeding , reducing its effectiveness as a greenhouse gas.
Water on Mars | Early Noachian era (4.6 Ga to 4.1 Ga)
The water must have been supplied by meteorites from the outer asteroid belt and some large planetary embryos from beyond 2.5 AU. Comets may also have contributed. Though most comets are today in orbits farther away from the Sun than Neptune, computer simulations show that they were originally far more common in the inner parts of the Solar System.
History of Earth | Oceans and atmosphere
The amount of water lost seems proportional with the planet mass, since the diffusion-limited hydrogen escape flux is proportional to the planet surface gravity. During a runaway greenhouse effect, water vapor reaches the stratosphere, where it is easily broken down (photolyzed) by ultraviolet radiation (UV). Heating of the upper atmosphere by UV radiation can then drive a hydrodynamic wind that carries the hydrogen (and potentially some of the oxygen) to space, leading to the irreversible loss of a planet's surface water, oxidation of the surface, and possible accumulation of oxygen in the atmosphere. The fate of a given planet's atmosphere strongly depends on the extreme ultraviolet flux, the duration of the runaway regime, the initial water content, and the rate at which oxygen is absorbed by the surface.
Ocean world | Atmospheric models
However, the current best estimate of the nebular D/H ratio spectroscopically estimated with Jovian and Saturnian atmospheric CH is only 2.1×10, a factor of 8 lower than Earth's VSMOW ratio. It is unclear how such a difference could exist, if physisorption were indeed the dominant form of HO accretion for Earth in particular and the terrestrial planets in general.
Water on terrestrial planets of the Solar System | Accretion of water by Earth and Mars
Some water may be retained at the poles and there may be occasional rainstorms, but for the most part the planet would be a dry desert with large dunefields covering its equator, and a few salt flats on what was once the ocean floor, similar to the ones in the Atacama Desert in Chile. With no water to serve as a lubricant, plate tectonics would very likely stop and the most visible signs of geological activity would be shield volcanoes located above mantle hotspots. In these arid conditions the planet may retain some microbial and possibly even multicellular life. Most of these microbes will be halophiles and life could find refuge in the atmosphere as has been proposed to have happened on Venus.
Future of Earth | Loss of oceans
Mineralogical evidence from zircons has shown that liquid water and an atmosphere must have existed 4.404 ± 0.008 billion years ago, very soon after the formation of Earth. This presents somewhat of a paradox, as the cool early Earth hypothesis suggests temperatures were cold enough to freeze water between about 4.4 billion and 4.0 billion years ago. Other studies of zircons found in Australian Hadean rock point to the existence of plate tectonics as early as 4 billion years ago. If true, that implies that rather than a hot, molten surface and an atmosphere full of carbon dioxide, early Earth's surface was much as it is today.
Origin of water on Earth | History of water on Earth
Thus extrasolar planets (or moons) in the Goldilocks position with substantial atmospheres may possess oceans and water clouds like those on Earth. In addition to surface water, a true Earth analog would require a mix of oceans or lakes and areas not covered by water, or "land". Some argue that a true Earth analog must not only have a similar position of its planetary system but also orbit a solar analog and have a near circular orbit such that it remains continually habitable like Earth.
Earth analog | Surface water and hydrological cycle
The atmosphere contains 0.04% water. In areas with no fresh water on the ground surface, fresh water derived from precipitation may, because of its lower density, overlie saline ground water in lenses or layers. Most of the world's fresh water is frozen in ice sheets. Many areas suffer from lack of distribution of fresh water, such as deserts.
Fresh water | Water distribution
Extraterrestrial liquid water (from the Latin words: "extra" ["outside of, beyond"] and "terrestris" ["of or belonging to Earth"]) is water in its liquid state that naturally occurs outside Earth. It is a subject of wide interest because it is recognized as one of the key prerequisites for life as we know it and thus surmised as essential for extraterrestrial life. With oceanic water covering 71% of its surface, Earth is the only planet known to have stable bodies of liquid water on its surface, and liquid water is essential to all known life forms on Earth. The presence of water on the surface of Earth is a product of its atmospheric pressure and a stable orbit in the Sun's circumstellar habitable zone, though the origin of Earth's water remains unknown.
Extraterrestrial liquid water | Introduction
The Archean atmosphere is thought to have nearly lacked free oxygen. Astronomers think that the Sun had about 70–75 percent of the present luminosity, yet temperatures on Earth appear to have been near modern levels after only 500 Ma of Earth's formation (the faint young Sun paradox). The presence of liquid water is evidenced by certain highly deformed gneisses produced by metamorphism of sedimentary protoliths. The moderate temperatures may reflect the presence of greater amounts of greenhouse gases than later in the Earth's history. Alternatively, Earth's albedo may have been lower at the time, due to less land area and cloud cover.
Archean | Environment
Studies of zircons have found that liquid water must have existed as long ago as 4.4 billion years ago, very soon after the formation of the Earth. This requires the presence of an atmosphere. The cool early Earth theory covers a range from about 4.4 to about 4.1 billion years.
Hadean | Atmosphere and oceans
In addition, since liquids can not exist without pressure, an atmosphere allows liquid to be present at the surface, resulting in lakes, rivers and oceans. Earth and Titan are known to have liquids at their surface and terrain on the planet suggests that Mars had liquid on its surface in the past.
Atmosphere | Terrain
Multiple geochemical studies have concluded that asteroids are most likely the primary source of Earth's water. Carbonaceous chondrites–which are a subclass of the oldest meteorites in the Solar System–have isotopic levels most similar to ocean water. The CI and CM subclasses of carbonaceous chondrites specifically have hydrogen and nitrogen isotope levels that closely match Earth's seawater, which suggests water in these meteorites could be the source of Earth's oceans. Two 4.5 billion-year-old meteorites found on Earth that contained liquid water alongside a wide diversity of deuterium-poor organic compounds further support this. Earth's current deuterium to hydrogen ratio also matches ancient eucrite chondrites, which originate from the asteroid Vesta in the outer asteroid belt.
Origin of water on Earth | Asteroids
Approximately 71% of Earth's surface, an area of some 361 million square kilometers (139.5 million square miles), is covered by ocean. The average salinity of Earth's oceans is about 35 grams of salt per kilogram of sea water (3.5%).
Hydrosphere | Introduction
Lighter molecules move faster than heavier ones with the same thermal kinetic energy, and so gases of low molecular weight are lost more rapidly than those of high molecular weight. It is thought that Venus and Mars may have lost much of their water when, after being photodissociated into hydrogen and oxygen by solar ultraviolet radiation, the hydrogen escaped. Earth's magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the magnetic polar regions due to auroral activity, including a net 2% of its atmospheric oxygen.
Atmosphere | Atmospheric escape
Travis Barman is an astronomer at the Lowell Observatory in Arizona, in the United States. While studying a combination of the previously published Hubble Space Telescope measurements and new theoretical models, Barman found strong evidence for water absorption in the atmosphere of HD 209458 b. A planet about 150 light years away from earth, HD 209458 b was known previously to contain an evaporating hydrogen atmosphere, along with oxygen and carbon. Though the planet is only 7 million kilometers away from its star, the planet is not hot enough to break the water molecules. HD 209458 b, a transiting planet, passes in front of its star, where it can be viewed from earth every three and a half days.
Travis Barman | Introduction
Astronomers emphasised that the discovery of water in the atmosphere of K2-18b does not mean the planet can support life or is even habitable, as it probably lacks any solid surface or an atmosphere that can support life. Nevertheless, finding water in a habitable zone exoplanet helps understand how planets are formed. A study led by astronomers from the University of Cambridge considered the interior structure of the planet and found a range of possible solutions, from a rocky core with a thick hydrogen envelope to a planet primarily made up of water with a thinner atmosphere. A subset of these solutions could allow for liquid water on the surface of the planet, albeit at temperatures and pressures higher than STP.
K2-18b | Discovery of water
The now heavier cold and dry air sinks down to ground as well; the atmospheric thermodynamic engine thus establishes a vertical convection, which transports heat from the ground into the upper atmosphere, where the water molecules can radiate it to outer space. Due to the earth rotation and the resulting Coriolis forces, this vertical atmospheric convection is also converted into a horizontal convection, in the form of cyclones and anticyclones, which transport the water evaporated over the oceans into the interior of the continents, enabling vegetation to grow. Water in Earth's atmosphere is not merely below its boiling point (100 °C), but at altitude it goes below its freezing point (0 °C), due to water's highly polar attraction.
Water vapor | In Earth's atmosphere
The D/H isotopic ratio is a primary constraint on the source of HO of terrestrial planets. Comparison of the planetary D/H ratios with those of carbonaceous chondrites and comets enables a tentative determination of the source of HO. The best constraints for accreted HO are determined from non-atmospheric HO, as the D/H ratio of the atmospheric component may be subject to rapid alteration by the preferential loss of H unless it is in isotopic equilibrium with surface HO. Earth's VSMOW D/H ratio of 1.6×10 and modeling of impacts suggest that the cometary contribution to crustal water was less than 10%.
Water on terrestrial planets of the Solar System | Accretion of water by Earth and Mars
It is also possible that terrestrial planets had magma oceans at some point during their formation as a result of giant impacts. Hot Neptunes close to their star could lose their atmospheres via hydrodynamic escape, leaving behind their cores with various liquids on the surface. Where there are suitable temperatures and pressures, volatile chemicals that might exist as liquids in abundant quantities on planets include ammonia, argon, carbon disulfide, ethane, hydrazine, hydrogen, hydrogen cyanide, hydrogen sulfide, methane, neon, nitrogen, nitric oxide, phosphine, silane, sulfuric acid, and water. Supercritical fluids, although not liquids, do share various properties with liquids. Underneath the thick atmospheres of the planets Uranus and Neptune, it is expected that these planets are composed of oceans of hot high-density fluid mixtures of water, ammonia and other volatiles.
Ocean | Non-water surface liquids
However, a fair fraction of material should have been vaporized by this impact, creating a "rock vapor atmosphere" around the young planet. The rock vapor would have condensed within two thousand years, leaving behind hot volatiles which probably resulted in a heavy atmosphere with hydrogen and water vapor. Liquid water oceans existed despite the surface temperature of because at an atmospheric pressure of above 27 atmospheres, caused by the heavy atmosphere, water is still liquid. As cooling continued, subduction and dissolving in ocean water removed most from the atmosphere but levels oscillated wildly as new surface and mantle cycles appeared.
Hadean | Atmosphere and oceans
Isotopic ratios provide a unique "chemical fingerprint" that is used to compare Earth's water with reservoirs elsewhere in the Solar System. One such isotopic ratio, that of deuterium to hydrogen (D/H), is particularly useful in the search for the origin of water on Earth. Hydrogen is the most abundant element in the universe, and its heavier isotope deuterium can sometimes take the place of a hydrogen atom in molecules like HO. Most deuterium was created in the Big Bang or in supernovae, so its uneven distribution throughout the protosolar nebula was effectively "locked in" early in the formation of the Solar System.
Origin of water on Earth | Geochemical analysis of water in the Solar System
A small amount of water vapor is present in the atmosphere. There are no bodies of liquid water on the Martian surface because its atmospheric pressure at the surface averages —about 0.6% of Earth's mean sea level pressure—and because the temperature is far too low, () leading to immediate freezing. Despite this, about 3.8 billion years ago, there was a denser atmosphere, higher temperature, and vast amounts of liquid water flowed on the surface, including large oceans. It has been estimated that the primordial oceans on Mars would have covered between 36% and 75% of the planet. On November 22, 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars.
Life on Mars | Liquid water
Exoplanets with moderate densities (more dense than Jovian planets, but less dense than terrestrial planets) suggests that such planets like GJ1214b and GJ436 are composed of primarily water. Internal pressures of such water-worlds would result in exotic phases of water forming on the surface and within their cores.
Planetary core | Hot ice planets
On July 11, 2007, a team led by Giovanna Tinetti published the results of their observations using the Spitzer Space Telescope concluding there is solid evidence for significant amounts of water vapor in the planet's atmosphere. Follow-up observations made using the Hubble Space Telescope confirm the presence of water vapor, neutral oxygen and also the organic compound methane. Later, Very Large Telescope observations also detected the presence of carbon monoxide on the day side of the planet. It is currently unknown how the methane originated as the planet's high temperature should cause the water and methane to react, replacing the atmosphere with carbon monoxide.
HD 189733 b | Water vapor, oxygen, and organic compounds