139-614: Mars is the fourth planet from the Sun. Mars also commonly refers to: Mars may also refer to: Mars Mars is the fourth planet from the Sun . The surface of Mars is orange-red because it is covered in iron(III) oxide dust, giving it the nickname " the Red Planet ". Mars is among the brightest objects in Earth's sky , and its high-contrast albedo features have made it
278-427: A 1:1 mixture of HCl and H 2 O, the system separates completely into two separate liquid phases. Hydrochloric acid forms an azeotrope with boiling point 108.58 °C at 20.22 g HCl per 100 g solution; thus hydrochloric acid cannot be concentrated beyond this point by distillation. Unlike hydrogen fluoride, anhydrous liquid hydrogen chloride is difficult to work with as a solvent, because its boiling point
417-430: A chlorine derivative of perchloric acid (HOClO 3 ), similar to the thermally unstable chlorine derivatives of other oxoacids: examples include chlorine nitrate (ClONO 2 , vigorously reactive and explosive), and chlorine fluorosulfate (ClOSO 2 F, more stable but still moisture-sensitive and highly reactive). Dichlorine hexoxide is a dark-red liquid that freezes to form a solid which turns yellow at −180 °C: it
556-414: A chlorofluorinating agent, adding chlorine and fluorine across a multiple bond or by oxidation: for example, it will attack carbon monoxide to form carbonyl chlorofluoride, COFCl. It will react analogously with hexafluoroacetone , (CF 3 ) 2 CO, with a potassium fluoride catalyst to produce heptafluoroisopropyl hypochlorite, (CF 3 ) 2 CFOCl; with nitriles RCN to produce RCF 2 NCl 2 ; and with
695-489: A classical albedo feature it contains. In April 2023, The New York Times reported an updated global map of Mars based on images from the Hope spacecraft . A related, but much more detailed, global Mars map was released by NASA on 16 April 2023. The vast upland region Tharsis contains several massive volcanoes, which include the shield volcano Olympus Mons . The edifice is over 600 km (370 mi) wide. Because
834-583: A common subject for telescope viewing. It is classified as a terrestrial planet and is the second smallest of the Solar System 's planets with a diameter of 6,779 km (4,212 mi). In terms of orbital motion, a Martian solar day ( sol ) is equal to 24.6 hours, and a Martian solar year is equal to 1.88 Earth years (687 Earth days). Mars has two natural satellites that are small and irregular in shape: Phobos and Deimos . The relatively flat plains in northern parts of Mars strongly contrast with
973-747: A dangerously powerful and unstable oxidizer. Near the end of the nineteenth century, E. S. Smith patented a method of sodium hypochlorite production involving electrolysis of brine to produce sodium hydroxide and chlorine gas, which then mixed to form sodium hypochlorite. This is known as the chloralkali process , first introduced on an industrial scale in 1892, and now the source of most elemental chlorine and sodium hydroxide. In 1884 Chemischen Fabrik Griesheim of Germany developed another chloralkali process which entered commercial production in 1888. Elemental chlorine solutions dissolved in chemically basic water (sodium and calcium hypochlorite ) were first used as anti- putrefaction agents and disinfectants in
1112-445: A fluoride ion donor or acceptor (Lewis base or acid), although it does not dissociate appreciably into ClF 2 and ClF 4 ions. Chlorine pentafluoride (ClF 5 ) is made on a large scale by direct fluorination of chlorine with excess fluorine gas at 350 °C and 250 atm, and on a small scale by reacting metal chlorides with fluorine gas at 100–300 °C. It melts at −103 °C and boils at −13.1 °C. It
1251-422: A global magnetic field, the types and distribution of auroras there differ from those on Earth; rather than being mostly restricted to polar regions as is the case on Earth, a Martian aurora can encompass the planet. In September 2017, NASA reported radiation levels on the surface of the planet Mars were temporarily doubled , and were associated with an aurora 25 times brighter than any observed earlier, due to
1390-488: A high ratio of deuterium in Gale Crater , though not significantly high enough to suggest the former presence of an ocean. Other scientists caution that these results have not been confirmed, and point out that Martian climate models have not yet shown that the planet was warm enough in the past to support bodies of liquid water. Near the northern polar cap is the 81.4 kilometres (50.6 mi) wide Korolev Crater , which
1529-468: A higher oxidation state than bromination with Br 2 when multiple oxidation states are available, such as in MoCl 5 and MoBr 3 . Chlorides can be made by reaction of an element or its oxide, hydroxide, or carbonate with hydrochloric acid, and then dehydrated by mildly high temperatures combined with either low pressure or anhydrous hydrogen chloride gas. These methods work best when the chloride product
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#17327726805791668-490: A low of 30 Pa (0.0044 psi ) on Olympus Mons to over 1,155 Pa (0.1675 psi) in Hellas Planitia , with a mean pressure at the surface level of 600 Pa (0.087 psi). The highest atmospheric density on Mars is equal to that found 35 kilometres (22 mi) above Earth's surface. The resulting mean surface pressure is only 0.6% of Earth's 101.3 kPa (14.69 psi). The scale height of
1807-784: A low-pressure discharge tube. The yellow [Cl 3 ] cation is more stable and may be produced as follows: This reaction is conducted in the oxidising solvent arsenic pentafluoride . The trichloride anion, [Cl 3 ] , has also been characterised; it is analogous to triiodide . The three fluorides of chlorine form a subset of the interhalogen compounds, all of which are diamagnetic . Some cationic and anionic derivatives are known, such as ClF 2 , ClF 4 , ClF 2 , and Cl 2 F . Some pseudohalides of chlorine are also known, such as cyanogen chloride (ClCN, linear), chlorine cyanate (ClNCO), chlorine thiocyanate (ClSCN, unlike its oxygen counterpart), and chlorine azide (ClN 3 ). Chlorine monofluoride (ClF)
1946-442: A massive, and unexpected, solar storm in the middle of the month. Mars has seasons, alternating between its northern and southern hemispheres, similar to on Earth. Additionally the orbit of Mars has, compared to Earth's, a large eccentricity and approaches perihelion when it is summer in its southern hemisphere and winter in its northern, and aphelion when it is winter in its southern hemisphere and summer in its northern. As
2085-542: A minimum thickness of 6 kilometres (3.7 mi) in Isidis Planitia , and a maximum thickness of 117 kilometres (73 mi) in the southern Tharsis plateau. For comparison, Earth's crust averages 27.3 ± 4.8 km in thickness. The most abundant elements in the Martian crust are silicon , oxygen , iron , magnesium , aluminium , calcium , and potassium . Mars is confirmed to be seismically active; in 2019 it
2224-473: A record of erosion caused by the catastrophic release of water from subsurface aquifers, though some of these structures have been hypothesized to result from the action of glaciers or lava. One of the larger examples, Ma'adim Vallis , is 700 kilometres (430 mi) long, much greater than the Grand Canyon, with a width of 20 kilometres (12 mi) and a depth of 2 kilometres (1.2 mi) in places. It
2363-519: A reduction in oxidation state , which can also be achieved by reducing a higher chloride using hydrogen or a metal as a reducing agent. This may also be achieved by thermal decomposition or disproportionation as follows: Most metal chlorides with the metal in low oxidation states (+1 to +3) are ionic. Nonmetals tend to form covalent molecular chlorides, as do metals in high oxidation states from +3 and above. Both ionic and covalent chlorides are known for metals in oxidation state +3 (e.g. scandium chloride
2502-588: A remnant of that ring. The geological history of Mars can be split into many periods, but the following are the three primary periods: Geological activity is still taking place on Mars. The Athabasca Valles is home to sheet-like lava flows created about 200 million years ago. Water flows in the grabens called the Cerberus Fossae occurred less than 20 million years ago, indicating equally recent volcanic intrusions. The Mars Reconnaissance Orbiter has captured images of avalanches. Mars
2641-408: A result of the increasing molecular weight of the halogens down the group, the density and heats of fusion and vaporisation of chlorine are again intermediate between those of bromine and fluorine, although all their heats of vaporisation are fairly low (leading to high volatility) thanks to their diatomic molecular structure. The halogens darken in colour as the group is descended: thus, while fluorine
2780-460: A result, the seasons in its southern hemisphere are more extreme and the seasons in its northern are milder than would otherwise be the case. The summer temperatures in the south can be warmer than the equivalent summer temperatures in the north by up to 30 °C (54 °F). Martian surface temperatures vary from lows of about −110 °C (−166 °F) to highs of up to 35 °C (95 °F) in equatorial summer. The wide range in temperatures
2919-488: A separate gaseous substance was recognised by the Brabantian chemist and physician Jan Baptist van Helmont . The element was first studied in detail in 1774 by Swedish chemist Carl Wilhelm Scheele , and he is credited with the discovery. Scheele produced chlorine by reacting MnO 2 (as the mineral pyrolusite ) with HCl: Scheele observed several of the properties of chlorine: the bleaching effect on litmus ,
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#17327726805793058-471: A small crater (later called Airy-0 ), located in the Sinus Meridiani ("Middle Bay" or "Meridian Bay"), was chosen by Merton E. Davies , Harold Masursky , and Gérard de Vaucouleurs for the definition of 0.0° longitude to coincide with the original selection. Because Mars has no oceans, and hence no " sea level ", a zero-elevation surface had to be selected as a reference level; this is called
3197-625: A solution of sodium carbonate. The resulting liquid, known as " Eau de Javel " (" Javel water "), was a weak solution of sodium hypochlorite . This process was not very efficient, and alternative production methods were sought. Scottish chemist and industrialist Charles Tennant first produced a solution of calcium hypochlorite ("chlorinated lime"), then solid calcium hypochlorite (bleaching powder). These compounds produced low levels of elemental chlorine and could be more efficiently transported than sodium hypochlorite, which remained as dilute solutions because when purified to eliminate water, it became
3336-486: A storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase global temperature. Seasons also produce dry ice covering polar ice caps . Large areas of the polar regions of Mars While Mars contains water in larger amounts , most of it is dust covered water ice at the Martian polar ice caps . The volume of water ice in
3475-491: A very thick lithosphere compared to Earth. Below this the mantle gradually becomes more ductile, and the seismic wave velocity starts to grow again. The Martian mantle does not appear to have a thermally insulating layer analogous to Earth's lower mantle ; instead, below 1050 km in depth, it becomes mineralogically similar to Earth's transition zone . At the bottom of the mantle lies a basal liquid silicate layer approximately 150–180 km thick. Mars's iron and nickel core
3614-668: A yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent : among the elements, it has the highest electron affinity and the third-highest electronegativity on the revised Pauling scale , behind only oxygen and fluorine. Chlorine played an important role in the experiments conducted by medieval alchemists , which commonly involved the heating of chloride salts like ammonium chloride ( sal ammoniac ) and sodium chloride ( common salt ), producing various chemical substances containing chlorine such as hydrogen chloride , mercury(II) chloride (corrosive sublimate), and aqua regia . However,
3753-452: Is Syrtis Major Planum . The permanent northern polar ice cap is named Planum Boreum . The southern cap is called Planum Australe . Mars's equator is defined by its rotation, but the location of its Prime Meridian was specified, as was Earth's (at Greenwich ), by choice of an arbitrary point; Mädler and Beer selected a line for their first maps of Mars in 1830. After the spacecraft Mariner 9 provided extensive imagery of Mars in 1972,
3892-416: Is hydrogen chloride , HCl, a major chemical in industry as well as in the laboratory, both as a gas and dissolved in water as hydrochloric acid . It is often produced by burning hydrogen gas in chlorine gas, or as a byproduct of chlorinating hydrocarbons . Another approach is to treat sodium chloride with concentrated sulfuric acid to produce hydrochloric acid, also known as the "salt-cake" process: In
4031-441: Is sodium chlorate , mostly used to make chlorine dioxide to bleach paper pulp. The decomposition of chlorate to chloride and oxygen is a common way to produce oxygen in the laboratory on a small scale. Chloride and chlorate may comproportionate to form chlorine as follows: Perchlorates and perchloric acid (HOClO 3 ) are the most stable oxo-compounds of chlorine, in keeping with the fact that chlorine compounds are most stable when
4170-406: Is a light albedo feature clearly visible from Earth. There are other notable impact features, such as Argyre , which is around 1,800 kilometres (1,100 mi) in diameter, and Isidis , which is around 1,500 kilometres (930 mi) in diameter. Due to the smaller mass and size of Mars, the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to
4309-474: Is a pale yellow gas, chlorine is distinctly yellow-green. This trend occurs because the wavelengths of visible light absorbed by the halogens increase down the group. Specifically, the colour of a halogen, such as chlorine, results from the electron transition between the highest occupied antibonding π g molecular orbital and the lowest vacant antibonding σ u molecular orbital. The colour fades at low temperatures, so that solid chlorine at −195 °C
Mars (disambiguation) - Misplaced Pages Continue
4448-399: Is a poor solvent, only able to dissolve small molecular compounds such as nitrosyl chloride and phenol , or salts with very low lattice energies such as tetraalkylammonium halides. It readily protonates electrophiles containing lone-pairs or π bonds. Solvolysis , ligand replacement reactions, and oxidations are well-characterised in hydrogen chloride solution: Nearly all elements in
4587-486: Is a very poor conductor of electricity, and indeed its conductivity is so low as to be practically unmeasurable. Chlorine has two stable isotopes, Cl and Cl. These are its only two natural isotopes occurring in quantity, with Cl making up 76% of natural chlorine and Cl making up the remaining 24%. Both are synthesised in stars in the oxygen-burning and silicon-burning processes . Both have nuclear spin 3/2+ and thus may be used for nuclear magnetic resonance , although
4726-432: Is a very strong fluorinating agent, although it is still not as effective as chlorine trifluoride. Only a few specific stoichiometric reactions have been characterised. Arsenic pentafluoride and antimony pentafluoride form ionic adducts of the form [ClF 4 ] [MF 6 ] (M = As, Sb) and water reacts vigorously as follows: The product, chloryl fluoride , is one of the five known chlorine oxide fluorides. These range from
4865-442: Is a weak ligand, weaker than water, a few compounds involving coordinated ClO 4 are known. The Table below presents typical oxidation states for chlorine element as given in the secondary schools or colleges. There are more complex chemical compounds, the structure of which can only be explained using modern quantum chemical methods, for example, cluster technetium chloride [(CH 3 ) 4 N] 3 [Tc 6 Cl 14 ], in which 6 of
5004-506: Is almost colourless. Like solid bromine and iodine, solid chlorine crystallises in the orthorhombic crystal system , in a layered lattice of Cl 2 molecules. The Cl–Cl distance is 198 pm (close to the gaseous Cl–Cl distance of 199 pm) and the Cl···Cl distance between molecules is 332 pm within a layer and 382 pm between layers (compare the van der Waals radius of chlorine, 180 pm). This structure means that chlorine
5143-472: Is also produced when photolysing the solid at −78 °C: it is a dark brown solid that explodes below 0 °C. The ClO radical leads to the depletion of atmospheric ozone and is thus environmentally important as follows: Chlorine perchlorate (ClOClO 3 ) is a pale yellow liquid that is less stable than ClO 2 and decomposes at room temperature to form chlorine, oxygen, and dichlorine hexoxide (Cl 2 O 6 ). Chlorine perchlorate may also be considered
5282-432: Is approximately half the diameter of Earth, with a surface area only slightly less than the total area of Earth's dry land. Mars is less dense than Earth, having about 15% of Earth's volume and 11% of Earth's mass , resulting in about 38% of Earth's surface gravity . Mars is the only presently known example of a desert planet , a rocky planet with a surface akin to that of Earth's hot deserts . The red-orange appearance of
5421-766: Is completely molten, with no solid inner core. It is around half of Mars's radius, approximately 1650–1675 km, and is enriched in light elements such as sulfur , oxygen, carbon , and hydrogen . Mars is a terrestrial planet with a surface that consists of minerals containing silicon and oxygen, metals , and other elements that typically make up rock . The Martian surface is primarily composed of tholeiitic basalt , although parts are more silica -rich than typical basalt and may be similar to andesitic rocks on Earth, or silica glass. Regions of low albedo suggest concentrations of plagioclase feldspar , with northern low albedo regions displaying higher than normal concentrations of sheet silicates and high-silicon glass. Parts of
5560-429: Is divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian "continents" and given names like Arabia Terra ( land of Arabia ) or Amazonis Planitia ( Amazonian plain ). The dark features were thought to be seas, hence their names Mare Erythraeum , Mare Sirenum and Aurorae Sinus . The largest dark feature seen from Earth
5699-487: Is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure (about 1% that of the atmosphere of Earth ), and the low thermal inertia of Martian soil. The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight. Mars has the largest dust storms in the Solar System, reaching speeds of over 160 km/h (100 mph). These can vary from
Mars (disambiguation) - Misplaced Pages Continue
5838-658: Is even more unstable and cannot be isolated or concentrated without decomposition: it is known from the decomposition of aqueous chlorine dioxide. However, sodium chlorite is a stable salt and is useful for bleaching and stripping textiles, as an oxidising agent, and as a source of chlorine dioxide. Chloric acid (HOClO 2 ) is a strong acid that is quite stable in cold water up to 30% concentration, but on warming gives chlorine and chlorine dioxide. Evaporation under reduced pressure allows it to be concentrated further to about 40%, but then it decomposes to perchloric acid, chlorine, oxygen, water, and chlorine dioxide. Its most important salt
5977-894: Is extremely dangerous, and poisonous to most living organisms. As a chemical warfare agent, chlorine was first used in World War ;I as a poison gas weapon. In the form of chloride ions , chlorine is necessary to all known species of life. Other types of chlorine compounds are rare in living organisms, and artificially produced chlorinated organics range from inert to toxic. In the upper atmosphere , chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion . Small quantities of elemental chlorine are generated by oxidation of chloride ions in neutrophils as part of an immune system response against bacteria. The most common compound of chlorine, sodium chloride, has been known since ancient times; archaeologists have found evidence that rock salt
6116-551: Is extremely thermally stable, and is sold commercially in 500-gram steel lecture bottles. It is a colourless gas that melts at −155.6 °C and boils at −100.1 °C. It may be produced by the reaction of its elements at 225 °C, though it must then be separated and purified from chlorine trifluoride and its reactants. Its properties are mostly intermediate between those of chlorine and fluorine. It will react with many metals and nonmetals from room temperature and above, fluorinating them and liberating chlorine. It will also act as
6255-515: Is less reactive than fluorine and more reactive than bromine. It is also a weaker oxidising agent than fluorine, but a stronger one than bromine. Conversely, the chloride ion is a weaker reducing agent than bromide, but a stronger one than fluoride. It is intermediate in atomic radius between fluorine and bromine, and this leads to many of its atomic properties similarly continuing the trend from iodine to bromine upward, such as first ionisation energy , electron affinity , enthalpy of dissociation of
6394-442: Is less than +1.395 V, it would be expected that chlorine should be able to oxidise water to oxygen and hydrochloric acid. However, the kinetics of this reaction are unfavorable, and there is also a bubble overpotential effect to consider, so that electrolysis of aqueous chloride solutions evolves chlorine gas and not oxygen gas, a fact that is very useful for the industrial production of chlorine. The simplest chlorine compound
6533-479: Is low, it has a small liquid range, its dielectric constant is low and it does not dissociate appreciably into H 2 Cl and HCl 2 ions – the latter, in any case, are much less stable than the bifluoride ions ( HF 2 ) due to the very weak hydrogen bonding between hydrogen and chlorine, though its salts with very large and weakly polarising cations such as Cs and NR 4 (R = Me , Et , Bu ) may still be isolated. Anhydrous hydrogen chloride
6672-437: Is made by reacting anhydrous sodium perchlorate or barium perchlorate with concentrated hydrochloric acid, filtering away the chloride precipitated and distilling the filtrate to concentrate it. Anhydrous perchloric acid is a colourless mobile liquid that is sensitive to shock that explodes on contact with most organic compounds, sets hydrogen iodide and thionyl chloride on fire and even oxidises silver and gold. Although it
6811-427: Is mostly ionic, but aluminium chloride is not). Silver chloride is very insoluble in water and is thus often used as a qualitative test for chlorine. Although dichlorine is a strong oxidising agent with a high first ionisation energy, it may be oxidised under extreme conditions to form the [Cl 2 ] cation. This is very unstable and has only been characterised by its electronic band spectrum when produced in
6950-415: Is one of the most reactive elements. Chlorine is a weaker oxidising agent than fluorine but a stronger one than bromine or iodine. This can be seen from the standard electrode potentials of the X 2 /X couples (F, +2.866 V; Cl, +1.395 V; Br, +1.087 V; I, +0.615 V; At , approximately +0.3 V). However, this trend is not shown in the bond energies because fluorine
7089-400: Is present in solid crystalline hydrogen chloride at low temperatures, similar to the hydrogen fluoride structure, before disorder begins to prevail as the temperature is raised. Hydrochloric acid is a strong acid (p K a = −7) because the hydrogen bonds to chlorine are too weak to inhibit dissociation. The HCl/H 2 O system has many hydrates HCl· n H 2 O for n = 1, 2, 3, 4, and 6. Beyond
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#17327726805797228-419: Is produced in the atmosphere by spallation of Ar by interactions with cosmic ray protons . In the top meter of the lithosphere , Cl is generated primarily by thermal neutron activation of Cl and spallation of K and Ca . In the subsurface environment, muon capture by Ca becomes more important as a way to generate Cl. Chlorine is intermediate in reactivity between fluorine and bromine, and
7367-401: Is quite slow at temperatures below 70 °C in spite of the very favourable equilibrium constant of 10 . The chlorate ions may themselves disproportionate to form chloride and perchlorate (4 ClO 3 ⇌ Cl + 3 ClO 4 ) but this is still very slow even at 100 °C despite the very favourable equilibrium constant of 10 . The rates of reaction for the chlorine oxyanions increases as
7506-510: Is singular due to its small size, low polarisability, and inability to show hypervalence . As another difference, chlorine has a significant chemistry in positive oxidation states while fluorine does not. Chlorination often leads to higher oxidation states than bromination or iodination but lower oxidation states than fluorination. Chlorine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Cl bonds. Given that E°( 1 / 2 O 2 /H 2 O) = +1.229 V, which
7645-567: Is stable to hydrolysis; otherwise, the possibilities include high-temperature oxidative chlorination of the element with chlorine or hydrogen chloride, high-temperature chlorination of a metal oxide or other halide by chlorine, a volatile metal chloride, carbon tetrachloride , or an organic chloride. For instance, zirconium dioxide reacts with chlorine at standard conditions to produce zirconium tetrachloride , and uranium trioxide reacts with hexachloropropene when heated under reflux to give uranium tetrachloride . The second example also involves
7784-519: Is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. It is possible that, four billion years ago, the Northern Hemisphere of Mars was struck by an object one-tenth to two-thirds the size of Earth's Moon . If this is the case, the Northern Hemisphere of Mars would be the site of an impact crater 10,600 by 8,500 kilometres (6,600 by 5,300 mi) in size, or roughly
7923-553: Is the anhydride of perchloric acid (HClO 4 ) and can readily be obtained from it by dehydrating it with phosphoric acid at −10 °C and then distilling the product at −35 °C and 1 mmHg. It is a shock-sensitive, colourless oily liquid. It is the least reactive of the chlorine oxides, being the only one to not set organic materials on fire at room temperature. It may be dissolved in water to regenerate perchloric acid or in aqueous alkalis to regenerate perchlorates. However, it thermally decomposes explosively by breaking one of
8062-430: Is the anhydride. It is thus an effective bleach and is mostly used to make hypochlorites . It explodes on heating or sparking or in the presence of ammonia gas. Chlorine dioxide (ClO 2 ) was the first chlorine oxide to be discovered in 1811 by Humphry Davy . It is a yellow paramagnetic gas (deep-red as a solid or liquid), as expected from its having an odd number of electrons: it is stable towards dimerisation due to
8201-657: Is thought to have been carved by flowing water early in Mars's history. The youngest of these channels is thought to have formed only a few million years ago. Elsewhere, particularly on the oldest areas of the Martian surface, finer-scale, dendritic networks of valleys are spread across significant proportions of the landscape. Features of these valleys and their distribution strongly imply that they were carved by runoff resulting from precipitation in early Mars history. Subsurface water flow and groundwater sapping may play important subsidiary roles in some networks, but precipitation
8340-472: Is usually made by reaction of chlorine dioxide with oxygen. Despite attempts to rationalise it as the dimer of ClO 3 , it reacts more as though it were chloryl perchlorate, [ClO 2 ] [ClO 4 ] , which has been confirmed to be the correct structure of the solid. It hydrolyses in water to give a mixture of chloric and perchloric acids: the analogous reaction with anhydrous hydrogen fluoride does not proceed to completion. Dichlorine heptoxide (Cl 2 O 7 )
8479-453: The Viking 1 probe in 1976. As of 2023, there are at least 11 active probes orbiting Mars or on the Martian surface. Mars is an attractive target for future human exploration missions , though in the 2020s no such mission is planned. Scientists have theorized that during the Solar System's formation , Mars was created as the result of a random process of run-away accretion of material from
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#17327726805798618-550: The areoid of Mars, analogous to the terrestrial geoid . Zero altitude was defined by the height at which there is 610.5 Pa (6.105 mbar ) of atmospheric pressure. This pressure corresponds to the triple point of water, and it is about 0.6% of the sea level surface pressure on Earth (0.006 atm). For mapping purposes, the United States Geological Survey divides the surface of Mars into thirty cartographic quadrangles , each named for
8757-459: The Mars Express orbiter found to be filled with approximately 2,200 cubic kilometres (530 cu mi) of water ice. Chlorine Chlorine is a chemical element ; it has symbol Cl and atomic number 17. The second-lightest of the halogens , it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is
8896-453: The Martian hemispheric dichotomy , created the smooth Borealis basin that covers 40% of the planet. A 2023 study shows evidence, based on the orbital inclination of Deimos (a small moon of Mars), that Mars may once have had a ring system 3.5 billion years to 4 billion years ago. This ring system may have been formed from a moon, 20 times more massive than Phobos , orbiting Mars billions of years ago; and Phobos would be
9035-471: The Noachian period (4.5 to 3.5 billion years ago), Mars's surface was marked by meteor impacts , valley formation, erosion, and the possible presence of water oceans . The Hesperian period (3.5 to 3.3–2.9 billion years ago) was dominated by widespread volcanic activity and flooding that carved immense outflow channels . The Amazonian period, which continues to the present, has been marked by
9174-656: The Yellowknife Bay area in the Glenelg terrain. In September 2015, NASA announced that they had found strong evidence of hydrated brine flows in recurring slope lineae , based on spectrometer readings of the darkened areas of slopes. These streaks flow downhill in Martian summer, when the temperature is above −23 °C, and freeze at lower temperatures. These observations supported earlier hypotheses, based on timing of formation and their rate of growth, that these dark streaks resulted from water flowing just below
9313-415: The asteroid belt , so it has an increased chance of being struck by materials from that source. Mars is more likely to be struck by short-period comets , i.e. , those that lie within the orbit of Jupiter . Martian craters can have a morphology that suggests the ground became wet after the meteor impact. The large canyon, Valles Marineris (Latin for " Mariner Valleys", also known as Agathodaemon in
9452-473: The neutron activation of natural chlorine. The most stable chlorine radioisotope is Cl. The primary decay mode of isotopes lighter than Cl is electron capture to isotopes of sulfur ; that of isotopes heavier than Cl is beta decay to isotopes of argon ; and Cl may decay by either mode to stable S or Ar. Cl occurs in trace quantities in nature as a cosmogenic nuclide in a ratio of about (7–10) × 10 to 1 with stable chlorine isotopes: it
9591-483: The noble gases xenon and radon do not escape fluorination. An impermeable fluoride layer is formed by sodium , magnesium , aluminium , zinc , tin , and silver , which may be removed by heating. Nickel , copper, and steel containers are usually used due to their great resistance to attack by chlorine trifluoride, stemming from the formation of an unreactive layer of metal fluoride. Its reaction with hydrazine to form hydrogen fluoride, nitrogen, and chlorine gases
9730-401: The protoplanetary disk that orbited the Sun. Mars has many distinctive chemical features caused by its position in the Solar System. Elements with comparatively low boiling points, such as chlorine , phosphorus , and sulfur , are much more common on Mars than on Earth; these elements were probably pushed outward by the young Sun's energetic solar wind . After the formation of the planets,
9869-505: The wind as a dominant influence on geological processes . Due to Mars's geological history, the possibility of past or present life on Mars remains of great scientific interest. Since the late 20th century, Mars has been explored by uncrewed spacecraft and rovers , with the first flyby by the Mariner 4 probe in 1965, the first orbit by the Mars 2 probe in 1971, and the first landing by
10008-414: The 14 chlorine atoms are formally divalent, and oxidation states are fractional. In addition, all the above chemical regularities are valid for "normal" or close to normal conditions, while at ultra-high pressures (for example, in the cores of large planets), chlorine can exhibit an oxidation state of -3, forming a Na3Cl compound with sodium, which does not fit into traditional concepts of chemistry. Like
10147-545: The 1820s, in France, long before the establishment of the germ theory of disease . This practice was pioneered by Antoine-Germain Labarraque , who adapted Berthollet's "Javel water" bleach and other chlorine preparations. Elemental chlorine has since served a continuous function in topical antisepsis (wound irrigation solutions and the like) and public sanitation, particularly in swimming and drinking water. Chlorine gas
10286-473: The Earth's crust is in the form of ionic chloride compounds, which includes table salt. It is the second-most abundant halogen (after fluorine) and 20th most abundant element in Earth's crust. These crystal deposits are nevertheless dwarfed by the huge reserves of chloride in seawater. Elemental chlorine is commercially produced from brine by electrolysis , predominantly in the chloralkali process . The high oxidising potential of elemental chlorine led to
10425-541: The German and Dutch names of oxygen : sauerstoff or zuurstof , both translating into English as acid substance ), so a number of chemists, including Claude Berthollet , suggested that Scheele's dephlogisticated muriatic acid air must be a combination of oxygen and the yet undiscovered element, muriaticum . In 1809, Joseph Louis Gay-Lussac and Louis-Jacques Thénard tried to decompose dephlogisticated muriatic acid air by reacting it with charcoal to release
10564-491: The Greek word χλωρος ( chlōros , "green-yellow"), in reference to its colour. The name " halogen ", meaning "salt producer", was originally used for chlorine in 1811 by Johann Salomo Christoph Schweigger . This term was later used as a generic term to describe all the elements in the chlorine family (fluorine, bromine, iodine), after a suggestion by Jöns Jakob Berzelius in 1826. In 1823, Michael Faraday liquefied chlorine for
10703-478: The Martian ionosphere , lowering the atmospheric density by stripping away atoms from the outer layer. Both Mars Global Surveyor and Mars Express have detected ionized atmospheric particles trailing off into space behind Mars, and this atmospheric loss is being studied by the MAVEN orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface today ranges from
10842-538: The Martian sky a tawny color when seen from the surface. It may take on a pink hue due to iron oxide particles suspended in it. The concentration of methane in the Martian atmosphere fluctuates from about 0.24 ppb during the northern winter to about 0.65 ppb during the summer. Estimates of its lifetime range from 0.6 to 4 years, so its presence indicates that an active source of the gas must be present. Methane could be produced by non-biological process such as serpentinization involving water, carbon dioxide, and
10981-415: The Martian surface is caused by ferric oxide , or rust . It can look like butterscotch ; other common surface colors include golden, brown, tan, and greenish, depending on the minerals present. Like Earth, Mars is differentiated into a dense metallic core overlaid by less dense rocky layers. The outermost layer is the crust, which is on average about 42–56 kilometres (26–35 mi) thick, with
11120-593: The Moon, Johann Heinrich von Mädler and Wilhelm Beer were the first areographers. They began by establishing that most of Mars's surface features were permanent and by more precisely determining the planet's rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars. Features on Mars are named from a variety of sources. Albedo features are named for classical mythology. Craters larger than roughly 50 km are named for deceased scientists and writers and others who have contributed to
11259-400: The Northern Hemisphere of Mars, spanning 10,600 by 8,500 kilometres (6,600 by 5,300 mi), or roughly four times the size of the Moon's South Pole–Aitken basin , which would be the largest impact basin yet discovered if confirmed. It has been hypothesized that the basin was formed when Mars was struck by a Pluto -sized body about four billion years ago. The event, thought to be the cause of
11398-496: The X 2 molecule (X = Cl, Br, I), ionic radius, and X–X bond length. (Fluorine is anomalous due to its small size.) All four stable halogens experience intermolecular van der Waals forces of attraction, and their strength increases together with the number of electrons among all homonuclear diatomic halogen molecules. Thus, the melting and boiling points of chlorine are intermediate between those of fluorine and bromine: chlorine melts at −101.0 °C and boils at −34.0 °C. As
11537-462: The area of Europe, Asia, and Australia combined, surpassing Utopia Planitia and the Moon's South Pole–Aitken basin as the largest impact crater in the Solar System. Mars is scarred by a number of impact craters: a total of 43,000 observed craters with a diameter of 5 kilometres (3.1 mi) or greater have been found. The largest exposed crater is Hellas , which is 2,300 kilometres (1,400 mi) wide and 7,000 metres (23,000 ft) deep, and
11676-419: The atmosphere is about 10.8 kilometres (6.7 mi), which is higher than Earth's 6 kilometres (3.7 mi), because the surface gravity of Mars is only about 38% of Earth's. The atmosphere of Mars consists of about 96% carbon dioxide , 1.93% argon and 1.89% nitrogen along with traces of oxygen and water. The atmosphere is quite dusty, containing particulates about 1.5 μm in diameter which give
11815-406: The atmosphere is small, but enough to produce larger clouds of water ice and different cases of snow and frost , often mixed with snow of carbon dioxide dry ice . Landforms visible on Mars strongly suggest that liquid water has existed on the planet's surface. Huge linear swathes of scoured ground, known as outflow channels , cut across the surface in about 25 places. These are thought to be
11954-467: The broken fragments of "Tintina" rock and "Sutton Inlier" rock as well as in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock . Analysis using the rover's DAN instrument provided evidence of subsurface water, amounting to as much as 4% water content, down to a depth of 60 centimetres (24 in), during the rover's traverse from the Bradbury Landing site to
12093-606: The central Cl–O bonds, producing the radicals ClO 3 and ClO 4 which immediately decompose to the elements through intermediate oxides. Chlorine forms four oxoacids: hypochlorous acid (HOCl), chlorous acid (HOClO), chloric acid (HOClO 2 ), and perchloric acid (HOClO 3 ). As can be seen from the redox potentials given in the adjacent table, chlorine is much more stable towards disproportionation in acidic solutions than in alkaline solutions: The hypochlorite ions also disproportionate further to produce chloride and chlorate (3 ClO ⇌ 2 Cl + ClO 3 ) but this reaction
12232-424: The chlorine atom is in its lowest (−1) or highest (+7) possible oxidation states. Perchloric acid and aqueous perchlorates are vigorous and sometimes violent oxidising agents when heated, in stark contrast to their mostly inactive nature at room temperature due to the high activation energies for these reactions for kinetic reasons. Perchlorates are made by electrolytically oxidising sodium chlorate, and perchloric acid
12371-415: The cratered terrain in southern highlands – this terrain observation is known as the Martian dichotomy . Mars hosts many enormous extinct volcanoes (the tallest is Olympus Mons , 21.9 km or 13.6 mi tall) and one of the largest canyons in the Solar System ( Valles Marineris , 4,000 km or 2,500 mi long). Geologically , the planet is fairly active with marsquakes trembling underneath
12510-429: The dark. Crystalline clathrate hydrates ClO 2 · n H 2 O ( n ≈ 6–10) separate out at low temperatures. However, in the presence of light, these solutions rapidly photodecompose to form a mixture of chloric and hydrochloric acids. Photolysis of individual ClO 2 molecules result in the radicals ClO and ClOO, while at room temperature mostly chlorine, oxygen, and some ClO 3 and Cl 2 O 6 are produced. Cl 2 O 3
12649-424: The deadly effect on insects, the yellow-green colour, and the smell similar to aqua regia . He called it " dephlogisticated muriatic acid air " since it is a gas (then called "airs") and it came from hydrochloric acid (then known as "muriatic acid"). He failed to establish chlorine as an element. Common chemical theory at that time held that an acid is a compound that contains oxygen (remnants of this survive in
12788-576: The delocalisation of the unpaired electron. It explodes above −40 °C as a liquid and under pressure as a gas and therefore must be made at low concentrations for wood-pulp bleaching and water treatment. It is usually prepared by reducing a chlorate as follows: Its production is thus intimately linked to the redox reactions of the chlorine oxoacids. It is a strong oxidising agent, reacting with sulfur , phosphorus , phosphorus halides, and potassium borohydride . It dissolves exothermically in water to form dark-green solutions that very slowly decompose in
12927-574: The development of commercial bleaches and disinfectants , and a reagent for many processes in the chemical industry. Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of them organic chemicals such as polyvinyl chloride (PVC), many intermediates for the production of plastics , and other end products which do not contain the element. As a common disinfectant, elemental chlorine and chlorine-generating compounds are used more directly in swimming pools to keep them sanitary . Elemental chlorine at high concentration
13066-458: The edges of boulders and other obstacles in their path. The commonly accepted hypotheses include that they are dark underlying layers of soil revealed after avalanches of bright dust or dust devils . Several other explanations have been put forward, including those that involve water or even the growth of organisms. Environmental radiation levels on the surface are on average 0.64 millisieverts of radiation per day, and significantly less than
13205-447: The first time, and demonstrated that what was then known as "solid chlorine" had a structure of chlorine hydrate (Cl 2 ·H 2 O). Chlorine gas was first used by French chemist Claude Berthollet to bleach textiles in 1785. Modern bleaches resulted from further work by Berthollet, who first produced sodium hypochlorite in 1789 in his laboratory in the town of Javel (now part of Paris , France), by passing chlorine gas through
13344-482: The first two. Chlorine has the electron configuration [Ne]3s 3p , with the seven electrons in the third and outermost shell acting as its valence electrons . Like all halogens, it is thus one electron short of a full octet, and is hence a strong oxidising agent, reacting with many elements in order to complete its outer shell. Corresponding to periodic trends , it is intermediate in electronegativity between fluorine and bromine (F: 3.98, Cl: 3.16, Br: 2.96, I: 2.66), and
13483-429: The flanks of the volcano Arsia Mons . The caves, named after loved ones of their discoverers, are collectively known as the "seven sisters". Cave entrances measure from 100 to 252 metres (328 to 827 ft) wide and they are estimated to be at least 73 to 96 metres (240 to 315 ft) deep. Because light does not reach the floor of most of the caves, they may extend much deeper than these lower estimates and widen below
13622-545: The free element muriaticum (and carbon dioxide). They did not succeed and published a report in which they considered the possibility that dephlogisticated muriatic acid air is an element, but were not convinced. In 1810, Sir Humphry Davy tried the same experiment again, and concluded that the substance was an element, and not a compound. He announced his results to the Royal Society on 15 November that year. At that time, he named this new element "chlorine", from
13761-609: The gaseous products were discarded, and hydrogen chloride may have been produced many times before it was discovered that it can be put to chemical use. One of the first such uses was the synthesis of mercury(II) chloride (corrosive sublimate), whose production from the heating of mercury either with alum and ammonium chloride or with vitriol and sodium chloride was first described in the De aluminibus et salibus ("On Alums and Salts", an eleventh- or twelfth century Arabic text falsely attributed to Abu Bakr al-Razi and translated into Latin in
13900-456: The ground, dust devils sweeping across the landscape, and cirrus clouds . Carbon dioxide is substantially present in Mars's polar ice caps and thin atmosphere . During a year, there are large surface temperature swings on the surface between −78.5 °C (−109.3 °F) to 5.7 °C (42.3 °F) similar to Earth's seasons , as both planets have significant axial tilt . Mars was formed approximately 4.5 billion years ago. During
14039-456: The heaviest elements beyond bismuth ); and having an electronegativity higher than chlorine's ( oxygen and fluorine ) so that the resultant binary compounds are formally not chlorides but rather oxides or fluorides of chlorine. Even though nitrogen in NCl 3 is bearing a negative charge, the compound is usually called nitrogen trichloride . Chlorination of metals with Cl 2 usually leads to
14178-488: The inner Solar System may have been subjected to the so-called Late Heavy Bombardment . About 60% of the surface of Mars shows a record of impacts from that era, whereas much of the remaining surface is probably underlain by immense impact basins caused by those events. However, more recent modeling has disputed the existence of the Late Heavy Bombardment. There is evidence of an enormous impact basin in
14317-455: The laboratory, hydrogen chloride gas may be made by drying the acid with concentrated sulfuric acid. Deuterium chloride, DCl, may be produced by reacting benzoyl chloride with heavy water (D 2 O). At room temperature, hydrogen chloride is a colourless gas, like all the hydrogen halides apart from hydrogen fluoride , since hydrogen cannot form strong hydrogen bonds to the larger electronegative chlorine atom; however, weak hydrogen bonding
14456-436: The lander showed that the Martian soil has a basic pH of 7.7, and contains 0.6% perchlorate by weight, concentrations that are toxic to humans . Streaks are common across Mars and new ones appear frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with age. The streaks can start in a tiny area, then spread out for hundreds of metres. They have been seen to follow
14595-474: The mineral jarosite . This forms only in the presence of acidic water, showing that water once existed on Mars. The Spirit rover found concentrated deposits of silica in 2007 that indicated wet conditions in the past, and in December 2011, the mineral gypsum , which also forms in the presence of water, was found on the surface by NASA's Mars rover Opportunity. It is estimated that the amount of water in
14734-613: The mineral olivine , which is known to be common on Mars, or by Martian life. Compared to Earth, its higher concentration of atmospheric CO 2 and lower surface pressure may be why sound is attenuated more on Mars, where natural sources are rare apart from the wind. Using acoustic recordings collected by the Perseverance rover, researchers concluded that the speed of sound there is approximately 240 m/s for frequencies below 240 Hz, and 250 m/s for those above. Auroras have been detected on Mars. Because Mars lacks
14873-563: The most reactive chemical compounds known, the list of elements it sets on fire is diverse, containing hydrogen , potassium , phosphorus , arsenic , antimony , sulfur , selenium , tellurium , bromine , iodine , and powdered molybdenum , tungsten , rhodium , iridium , and iron . It will also ignite water, along with many substances which in ordinary circumstances would be considered chemically inert such as asbestos , concrete, glass, and sand. When heated, it will even corrode noble metals as palladium , platinum , and gold , and even
15012-427: The mountain is so large, with complex structure at its edges, giving a definite height to it is difficult. Its local relief, from the foot of the cliffs which form its northwest margin to its peak, is over 21 km (13 mi), a little over twice the height of Mauna Kea as measured from its base on the ocean floor. The total elevation change from the plains of Amazonis Planitia , over 1,000 km (620 mi) to
15151-431: The movement of dry dust. No partially degraded gullies have formed by weathering and no superimposed impact craters have been observed, indicating that these are young features, possibly still active. Other geological features, such as deltas and alluvial fans preserved in craters, are further evidence for warmer, wetter conditions at an interval or intervals in earlier Mars history. Such conditions necessarily require
15290-794: The multiple bonds on alkenes and alkynes as well, giving di- or tetrachloro compounds. However, due to the expense and reactivity of chlorine, organochlorine compounds are more commonly produced by using hydrogen chloride, or with chlorinating agents such as phosphorus pentachloride (PCl 5 ) or thionyl chloride (SOCl 2 ). The last is very convenient in the laboratory because all side products are gaseous and do not have to be distilled out. Many organochlorine compounds have been isolated from natural sources ranging from bacteria to humans. Chlorinated organic compounds are found in nearly every class of biomolecules including alkaloids , terpenes , amino acids , flavonoids , steroids , and fatty acids . Organochlorides, including dioxins , are produced in
15429-567: The nature of free chlorine gas as a separate substance was only recognised around 1630 by Jan Baptist van Helmont . Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element. In 1809, chemists suggested that the gas might be a pure element, and this was confirmed by Sir Humphry Davy in 1810, who named it after the Ancient Greek χλωρός ( khlōrós , "pale green") because of its colour. Because of its great reactivity, all chlorine in
15568-514: The northwest, to the summit approaches 26 km (16 mi), roughly three times the height of Mount Everest , which in comparison stands at just over 8.8 kilometres (5.5 mi). Consequently, Olympus Mons is either the tallest or second-tallest mountain in the Solar System ; the only known mountain which might be taller is the Rheasilvia peak on the asteroid Vesta , at 20–25 km (12–16 mi). The dichotomy of Martian topography
15707-468: The old canal maps ), has a length of 4,000 kilometres (2,500 mi) and a depth of up to 7 kilometres (4.3 mi). The length of Valles Marineris is equivalent to the length of Europe and extends across one-fifth the circumference of Mars. By comparison, the Grand Canyon on Earth is only 446 kilometres (277 mi) long and nearly 2 kilometres (1.2 mi) deep. Valles Marineris was formed due to
15846-458: The other carbon–halogen bonds, the C–Cl bond is a common functional group that forms part of core organic chemistry . Formally, compounds with this functional group may be considered organic derivatives of the chloride anion. Due to the difference of electronegativity between chlorine (3.16) and carbon (2.55), the carbon in a C–Cl bond is electron-deficient and thus electrophilic . Chlorination modifies
15985-605: The oxidation state of chlorine decreases. The strengths of the chlorine oxyacids increase very quickly as the oxidation state of chlorine increases due to the increasing delocalisation of charge over more and more oxygen atoms in their conjugate bases. Most of the chlorine oxoacids may be produced by exploiting these disproportionation reactions. Hypochlorous acid (HOCl) is highly reactive and quite unstable; its salts are mostly used for their bleaching and sterilising abilities. They are very strong oxidising agents, transferring an oxygen atom to most inorganic species. Chlorous acid (HOClO)
16124-842: The past. This paleomagnetism of magnetically susceptible minerals is similar to the alternating bands found on Earth's ocean floors . One hypothesis, published in 1999 and re-examined in October ;2005 (with the help of the Mars Global Surveyor ), is that these bands suggest plate tectonic activity on Mars four billion years ago, before the planetary dynamo ceased to function and the planet's magnetic field faded. The Phoenix lander returned data showing Martian soil to be slightly alkaline and containing elements such as magnesium , sodium , potassium and chlorine . These nutrients are found in soils on Earth. They are necessary for growth of plants. Experiments performed by
16263-406: The periodic table form binary chlorides. The exceptions are decidedly in the minority and stem in each case from one of three causes: extreme inertness and reluctance to participate in chemical reactions (the noble gases , with the exception of xenon in the highly unstable XeCl 2 and XeCl 4 ); extreme nuclear instability hampering chemical investigation before decay and transmutation (many of
16402-418: The physical properties of hydrocarbons in several ways: chlorocarbons are typically denser than water due to the higher atomic weight of chlorine versus hydrogen, and aliphatic organochlorides are alkylating agents because chloride is a leaving group . Alkanes and aryl alkanes may be chlorinated under free-radical conditions, with UV light. However, the extent of chlorination is difficult to control:
16541-566: The radiation of 1.84 millisieverts per day or 22 millirads per day during the flight to and from Mars. For comparison the radiation levels in low Earth orbit , where Earth's space stations orbit, are around 0.5 millisieverts of radiation per day. Hellas Planitia has the lowest surface radiation at about 0.342 millisieverts per day, featuring lava tubes southwest of Hadriacus Mons with potentially levels as low as 0.064 millisieverts per day, comparable to radiation levels during flights on Earth. Although better remembered for mapping
16680-536: The reaction is not regioselective and often results in a mixture of various isomers with different degrees of chlorination, though this may be permissible if the products are easily separated. Aryl chlorides may be prepared by the Friedel-Crafts halogenation , using chlorine and a Lewis acid catalyst. The haloform reaction , using chlorine and sodium hydroxide , is also able to generate alkyl halides from methyl ketones, and related compounds. Chlorine adds to
16819-615: The second half of the twelfth century by Gerard of Cremona , 1144–1187). Another important development was the discovery by pseudo-Geber (in the De inventione veritatis , "On the Discovery of Truth", after c. 1300) that by adding ammonium chloride to nitric acid , a strong solvent capable of dissolving gold (i.e., aqua regia ) could be produced. Although aqua regia is an unstable mixture that continually gives off fumes containing free chlorine gas, this chlorine gas appears to have been ignored until c. 1630, when its nature as
16958-467: The size of Earth's Arctic Ocean . This finding was derived from the ratio of protium to deuterium in the modern Martian atmosphere compared to that ratio on Earth. The amount of Martian deuterium (D/H = 9.3 ± 1.7 10 ) is five to seven times the amount on Earth (D/H = 1.56 10 ), suggesting that ancient Mars had significantly higher levels of water. Results from the Curiosity rover had previously found
17097-422: The south polar ice cap, if melted, would be enough to cover most of the surface of the planet with a depth of 11 metres (36 ft). Water in its liquid form cannot prevail on the surface of Mars due to the low atmospheric pressure on Mars, which is less than 1% that of Earth, only at the lowest of elevations pressure and temperature is high enough for water being able to be liquid for short periods. Water in
17236-461: The southern highlands include detectable amounts of high-calcium pyroxenes . Localized concentrations of hematite and olivine have been found. Much of the surface is deeply covered by finely grained iron(III) oxide dust. Although Mars has no evidence of a structured global magnetic field , observations show that parts of the planet's crust have been magnetized, suggesting that alternating polarity reversals of its dipole field have occurred in
17375-481: The spin magnitude being greater than 1/2 results in non-spherical nuclear charge distribution and thus resonance broadening as a result of a nonzero nuclear quadrupole moment and resultant quadrupolar relaxation. The other chlorine isotopes are all radioactive, with half-lives too short to occur in nature primordially . Of these, the most commonly used in the laboratory are Cl ( t 1/2 = 3.0×10 y) and Cl ( t 1/2 = 37.2 min), which may be produced from
17514-505: The study of Mars. Smaller craters are named for towns and villages of the world with populations of less than 100,000. Large valleys are named for the word "Mars" or "star" in various languages; smaller valleys are named for rivers. Large albedo features retain many of the older names but are often updated to reflect new knowledge of the nature of the features. For example, Nix Olympica (the snows of Olympus) has become Olympus Mons (Mount Olympus). The surface of Mars as seen from Earth
17653-437: The sulfur oxides SO 2 and SO 3 to produce ClSO 2 F and ClOSO 2 F respectively. It will also react exothermically with compounds containing –OH and –NH groups, such as water: Chlorine trifluoride (ClF 3 ) is a volatile colourless molecular liquid which melts at −76.3 °C and boils at 11.8 °C. It may be formed by directly fluorinating gaseous chlorine or chlorine monofluoride at 200–300 °C. One of
17792-513: The surface. However, later work suggested that the lineae may be dry, granular flows instead, with at most a limited role for water in initiating the process. A definitive conclusion about the presence, extent, and role of liquid water on the Martian surface remains elusive. Researchers suspect much of the low northern plains of the planet were covered with an ocean hundreds of meters deep, though this theory remains controversial. In March 2015, scientists stated that such an ocean might have been
17931-430: The surface. "Dena" is the only exception; its floor is visible and was measured to be 130 metres (430 ft) deep. The interiors of these caverns may be protected from micrometeoroids, UV radiation, solar flares and high energy particles that bombard the planet's surface. Mars lost its magnetosphere 4 billion years ago, possibly because of numerous asteroid strikes, so the solar wind interacts directly with
18070-625: The swelling of the Tharsis area, which caused the crust in the area of Valles Marineris to collapse. In 2012, it was proposed that Valles Marineris is not just a graben , but a plate boundary where 150 kilometres (93 mi) of transverse motion has occurred, making Mars a planet with possibly a two- tectonic plate arrangement. Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars Odyssey orbiter have revealed seven possible cave entrances on
18209-586: The thermally unstable FClO to the chemically unreactive perchloryl fluoride (FClO 3 ), the other three being FClO 2 , F 3 ClO, and F 3 ClO 2 . All five behave similarly to the chlorine fluorides, both structurally and chemically, and may act as Lewis acids or bases by gaining or losing fluoride ions respectively or as very strong oxidising and fluorinating agents. The chlorine oxides are well-studied in spite of their instability (all of them are endothermic compounds). They are important because they are produced when chlorofluorocarbons undergo photolysis in
18348-406: The upper atmosphere and cause the destruction of the ozone layer. None of them can be made from directly reacting the elements. Dichlorine monoxide (Cl 2 O) is a brownish-yellow gas (red-brown when solid or liquid) which may be obtained by reacting chlorine gas with yellow mercury(II) oxide . It is very soluble in water, in which it is in equilibrium with hypochlorous acid (HOCl), of which it
18487-507: The upper mantle of Mars, represented by hydroxyl ions contained within Martian minerals, is equal to or greater than that of Earth at 50–300 parts per million of water, which is enough to cover the entire planet to a depth of 200–1,000 metres (660–3,280 ft). On 18 March 2013, NASA reported evidence from instruments on the Curiosity rover of mineral hydration , likely hydrated calcium sulfate , in several rock samples including
18626-420: The widespread presence of crater lakes across a large proportion of the surface, for which there is independent mineralogical, sedimentological and geomorphological evidence. Further evidence that liquid water once existed on the surface of Mars comes from the detection of specific minerals such as hematite and goethite , both of which sometimes form in the presence of water. In 2004, Opportunity detected
18765-569: Was first used as a weapon on April 22, 1915, at the Second Battle of Ypres by the German Army . The effect on the allies was devastating because the existing gas masks were difficult to deploy and had not been broadly distributed. Chlorine is the second halogen , being a nonmetal in group 17 of the periodic table. Its properties are thus similar to fluorine , bromine , and iodine , and are largely intermediate between those of
18904-629: Was probably the root cause of the incision in almost all cases. Along craters and canyon walls, there are thousands of features that appear similar to terrestrial gullies . The gullies tend to be in the highlands of the Southern Hemisphere and face the Equator; all are poleward of 30° latitude. A number of authors have suggested that their formation process involves liquid water, probably from melting ice, although others have argued for formation mechanisms involving carbon dioxide frost or
19043-437: Was reported that InSight had detected and recorded over 450 marsquakes and related events. Beneath the crust is a silicate mantle responsible for many of the tectonic and volcanic features on the planet's surface. The upper Martian mantle is a low-velocity zone , where the velocity of seismic waves is lower than surrounding depth intervals. The mantle appears to be rigid down to the depth of about 250 km, giving Mars
19182-628: Was used as early as 3000 BC and brine as early as 6000 BC. Around 900, the authors of the Arabic writings attributed to Jabir ibn Hayyan (Latin: Geber) and the Persian physician and alchemist Abu Bakr al-Razi ( c. 865–925, Latin: Rhazes) were experimenting with sal ammoniac ( ammonium chloride ), which when it was distilled together with vitriol (hydrated sulfates of various metals) produced hydrogen chloride . However, it appears that in these early experiments with chloride salts ,
19321-434: Was used in experimental rocket engine, but has problems largely stemming from its extreme hypergolicity resulting in ignition without any measurable delay. Today, it is mostly used in nuclear fuel processing, to oxidise uranium to uranium hexafluoride for its enriching and to separate it from plutonium , as well as in the semiconductor industry, where it is used to clean chemical vapor deposition chambers. It can act as
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