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91-562: Gullies on Mars may be due to recent flowing water. Many are present in the Gorgonum Chaos. Gullies occur on steep slopes, especially craters. Gullies are believed to be relatively young because they have few, if any craters, and they lie on top of sand dunes which are young. Usually, each gully has an alcove, channel, and apron. Although many ideas have been put forward to explain them, the most popular involve liquid water either coming from an aquifer or left over from old glaciers . There

182-410: A certain time of the year, sunlight will melt snow with the resulting water producing gullies. Direct evidence for these snowpacks was recently discovered for the first time, showing that this mantle is indeed composed of <~1% dust and ice Changes observed within gullies over multiple Mars Years shows that dusty ice being exposed today is disappearing, and potentially melting to form channels within

273-516: A decline in basic activity level and information usage at 1000 ppm, when compared to 500 ppm. However a review of the literature found that a reliable subset of studies on the phenomenon of carbon dioxide induced cognitive impairment to only show a small effect on high-level decision making (for concentrations below 5000 ppm). Most of the studies were confounded by inadequate study designs, environmental comfort, uncertainties in exposure doses and differing cognitive assessments used. Similarly

364-519: A few years when liquid water cannot exist. The timing of gully activity is seasonal and happens during the period when seasonal frost is present and defrosting. These observations support a model in which currently active gully formation is driven mainly by seasonal CO 2 frost. Simulations described in a 2015 conference, show that high pressure CO 2 gas trapping in the subsurface can cause debris flows. The conditions that can lead to this are found in latitudes where gullies occur. This research

455-540: A gas, it may lubricate dry material to flow especially on steep slopes. In some years frost, perhaps as thick as 1 meter, triggers avalanches. This frost contains mostly dry ice, but also has tiny amounts of water ice. Observations with HiRISE show widespread activity in southern hemisphere gullies, especially in those that appear fresh. Significant channel incision and large-scale mass movements have been seen. Sinuous channels which were thought to need liquid water for their formation have even been seen to form over just

546-611: A glass state similar to other members of its elemental family, like silicon dioxide (silica glass) and germanium dioxide . Unlike silica and germania glasses, however, carbonia glass is not stable at normal pressures and reverts to gas when pressure is released. At temperatures and pressures above the critical point, carbon dioxide behaves as a supercritical fluid known as supercritical carbon dioxide . Table of thermal and physical properties of saturated liquid carbon dioxide: Table of thermal and physical properties of carbon dioxide (CO 2 ) at atmospheric pressure: Carbon dioxide

637-438: A great deal of fine dust particles. Water vapor will condense on the particles, then fall down to the ground due to the additional weight of the water coating. When Mars is at its greatest tilt or obliquity, up to 2 cm of ice could be removed from the summer ice cap and be deposited at midlatitudes. This movement of water could last for several thousand years and create a snow layer of up to around 10 meters thick. When ice at

728-748: A group of researchers found that gullies are preferentially distributed on areas with some ground ice rather than no ice at all. A large data set of gullies was used in this study. As soon as gullies were discovered, researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found. Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water. With continued observations many more changes were found in Gasa Crater and others. Channels widened by 0.5 to 1 m; meter sized boulders moved; and hundreds of cubic meters of material moved. It

819-404: A history of the discovery and research on gullies. As research progresses, the cause of Martian gullies has shifted from recent liquid water to pieces of dry ice moving down steep slopes, but research continues. On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers think that the processes carving

910-655: A length of nearly 940 meters. The major issue with the CO 2 frost model is trying to explain the erosion of rocks. Although there is considerable evidence for CO 2 frost transporting loose materials, it seems unlikely that sublimating CO 2 gas can erode and weather rocks to form gullies. Instead, CO 2 frost might only be able to modify pre-existing gullies. Using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and High Resolution Imaging Science Experiment ( HiRISE ) on

1001-491: A mature forest will produce as much CO 2 from respiration and decomposition of dead specimens (e.g., fallen branches) as is used in photosynthesis in growing plants. Contrary to the long-standing view that they are carbon neutral, mature forests can continue to accumulate carbon and remain valuable carbon sinks , helping to maintain the carbon balance of Earth's atmosphere. Additionally, and crucially to life on earth, photosynthesis by phytoplankton consumes dissolved CO 2 in

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1092-477: A molecule touches a surface or touches another molecule, the two bending modes can differ in frequency because the interaction is different for the two modes. Some of the vibrational modes are observed in the infrared (IR) spectrum : the antisymmetric stretching mode at wavenumber 2349 cm (wavelength 4.25 μm) and the degenerate pair of bending modes at 667 cm (wavelength 15.0 μm). The symmetric stretching mode does not create an electric dipole so

1183-410: A possible starting point for carbon capture and storage by amine gas treating . Only very strong nucleophiles, like the carbanions provided by Grignard reagents and organolithium compounds react with CO 2 to give carboxylates : In metal carbon dioxide complexes , CO 2 serves as a ligand , which can facilitate the conversion of CO 2 to other chemicals. The reduction of CO 2 to CO

1274-416: A study on the effects of the concentration of CO 2 in motorcycle helmets has been criticized for having dubious methodology in not noting the self-reports of motorcycle riders and taking measurements using mannequins. Further when normal motorcycle conditions were achieved (such as highway or city speeds) or the visor was raised the concentration of CO 2 declined to safe levels (0.2%). Poor ventilation

1365-469: Is Emiliania huxleyi whose calcite scales have formed the basis of many sedimentary rocks such as limestone , where what was previously atmospheric carbon can remain fixed for geological timescales. Plants can grow as much as 50% faster in concentrations of 1,000 ppm CO 2 when compared with ambient conditions, though this assumes no change in climate and no limitation on other nutrients. Elevated CO 2 levels cause increased growth reflected in

1456-419: Is 304.128(15) K (30.978(15) °C) at 7.3773(30) MPa (72.808(30) atm). Another form of solid carbon dioxide observed at high pressure is an amorphous glass-like solid. This form of glass, called carbonia , is produced by supercooling heated CO 2 at extreme pressures (40–48  GPa , or about 400,000 atmospheres) in a diamond anvil . This discovery confirmed the theory that carbon dioxide could exist in

1547-449: Is a trace gas in Earth's atmosphere at 421  parts per million (ppm) , or about 0.042% (as of May 2022) having risen from pre-industrial levels of 280 ppm or about 0.028%. Burning fossil fuels is the main cause of these increased CO 2 concentrations, which are the primary cause of climate change . Its concentration in Earth's pre-industrial atmosphere since late in

1638-447: Is a weak acid , because its ionization in water is incomplete. The hydration equilibrium constant of carbonic acid is, at 25 °C: Hence, the majority of the carbon dioxide is not converted into carbonic acid, but remains as CO 2 molecules, not affecting the pH. The relative concentrations of CO 2 , H 2 CO 3 , and the deprotonated forms HCO − 3 ( bicarbonate ) and CO 2− 3 ( carbonate ) depend on

1729-436: Is a tendency for gullies to be on poleward facing slopes; these slopes have more shade that would keep snow from melting and allow large snowpacks to accumulate. In general, it is now estimated that during periods of high obliquity, the ice caps will melt causing higher temperature, pressure, and moisture. The moisture will then accumulate as snow in midlatitudes, especially in the more shaded areas—pole facing, steep slopes. At

1820-415: Is an end product of cellular respiration in organisms that obtain energy by breaking down sugars, fats and amino acids with oxygen as part of their metabolism . This includes all plants, algae and animals and aerobic fungi and bacteria. In vertebrates , the carbon dioxide travels in the blood from the body's tissues to the skin (e.g., amphibians ) or the gills (e.g., fish ), from where it dissolves in

1911-414: Is called sublimation . The symmetry of a carbon dioxide molecule is linear and centrosymmetric at its equilibrium geometry. The length of the carbon–oxygen bond in carbon dioxide is 116.3  pm , noticeably shorter than the roughly 140 pm length of a typical single C–O bond, and shorter than most other C–O multiply bonded functional groups such as carbonyls . Since it is centrosymmetric,

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2002-404: Is changes directly from a solid to a gas. This gas builds up pressure because it is trapped between the ice and the frozen ground. Eventually, pressure builds up enough to explode through the ice taking with it soil particles. The dirt particles mix with the pressurized gas and act as a fluid that can flow down the slope and carve gullies. Observations of gullies that are on sand dunes support

2093-404: Is comparable to benzaldehyde or strongly electrophilic α,β-unsaturated carbonyl compounds . However, unlike electrophiles of similar reactivity, the reactions of nucleophiles with CO 2 are thermodynamically less favored and are often found to be highly reversible. The reversible reaction of carbon dioxide with amines to make carbamates is used in CO 2 scrubbers and has been suggested as

2184-628: Is evidence for both theories. Most of the gully alcove heads occur at the same level, just as one would expect of an aquifer. Various measurements and calculations show that liquid water could exist in an aquifer at the usual depths where the gullies begin. One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. Aquifers are layer that allow water to flow. They may consist of porus sandstone. This layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). The only direction

2275-451: Is found in the gas state at room temperature and at normally-encountered concentrations it is odorless. As the source of carbon in the carbon cycle , atmospheric CO 2 is the primary carbon source for life on Earth. In the air, carbon dioxide is transparent to visible light but absorbs infrared radiation , acting as a greenhouse gas . Carbon dioxide is soluble in water and is found in groundwater , lakes , ice caps , and seawater . It

2366-595: Is not observed in IR spectroscopy, but it is detected in Raman spectroscopy at 1388 cm (wavelength 7.20 μm), with a Fermi resonance doublet at 1285 cm . In the gas phase, carbon dioxide molecules undergo significant vibrational motions and do not keep a fixed structure. However, in a Coulomb explosion imaging experiment, an instantaneous image of the molecular structure can be deduced. Such an experiment has been performed for carbon dioxide. The result of this experiment, and

2457-632: Is one of the main causes of excessive CO 2 concentrations in closed spaces, leading to poor indoor air quality . Carbon dioxide differential above outdoor concentrations at steady state conditions (when the occupancy and ventilation system operation are sufficiently long that CO 2 concentration has stabilized) are sometimes used to estimate ventilation rates per person. Higher CO 2 concentrations are associated with occupant health, comfort and performance degradation. ASHRAE Standard 62.1–2007 ventilation rates may result in indoor concentrations up to 2,100 ppm above ambient outdoor conditions. Thus if

2548-410: Is ordinarily a difficult and slow reaction: The redox potential for this reaction near pH 7 is about −0.53 V versus the standard hydrogen electrode . The nickel-containing enzyme carbon monoxide dehydrogenase catalyses this process. Photoautotrophs (i.e. plants and cyanobacteria ) use the energy contained in sunlight to photosynthesize simple sugars from CO 2 absorbed from

2639-470: Is prevented from going down, the only direction the trapped water can flow is horizontally. Eventually, water could flow out onto the surface when the aquifer reaches a break—like a crater wall. The resulting flow of water could erode the wall to create gullies. Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah . However, the idea that aquifers formed

2730-405: Is produced as a by-product. Ribulose-1,5-bisphosphate carboxylase oxygenase , commonly abbreviated to RuBisCO, is the enzyme involved in the first major step of carbon fixation, the production of two molecules of 3-phosphoglycerate from CO 2 and ribulose bisphosphate , as shown in the diagram at left. RuBisCO is thought to be the single most abundant protein on Earth. Phototrophs use

2821-510: Is put to commercial use, mostly in the fertilizer industry and in the oil and gas industry for enhanced oil recovery . Other commercial applications include food and beverage production, metal fabrication, cooling, fire suppression and stimulating plant growth in greenhouses. Carbon dioxide cannot be liquefied at atmospheric pressure. Low-temperature carbon dioxide is commercially used in its solid form, commonly known as " dry ice ". The solid-to-gas phase transition occurs at 194.7 Kelvin and

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2912-425: Is released from organic materials when they decay or combust, such as in forest fires. When carbon dioxide dissolves in water, it forms carbonate and mainly bicarbonate ( HCO − 3 ), which causes ocean acidification as atmospheric CO 2 levels increase. Carbon dioxide is 53% more dense than dry air, but is long lived and thoroughly mixes in the atmosphere. About half of excess CO 2 emissions to

3003-455: Is shown below in the image of Lohse Crater and the image of gullies in Ross Crater. Much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. This ice-rich mantle, a few yards thick, smooths the land, but in places it has a bumpy texture, resembling the surface of a basketball. The mantle may be like a glacier and under certain conditions

3094-602: The Mars Reconnaissance Orbiter researchers studied over 100 Martian gully sites and found no evidence for specific minerals being more likely to be associated with gullies, or with the formation of hydrated minerals that would have been made by recent liquid water. This research adds evidence that liquid water was not involved with gully formation. However, as described above, the amounts of liquid water thought to be generated in near-freezing conditions from melting snowpacks are unlikely to cause chemical weathering in

3185-503: The Precambrian was regulated by organisms and geological features. Plants , algae and cyanobacteria use energy from sunlight to synthesize carbohydrates from carbon dioxide and water in a process called photosynthesis , which produces oxygen as a waste product. In turn, oxygen is consumed and CO 2 is released as waste by all aerobic organisms when they metabolize organic compounds to produce energy by respiration . CO 2

3276-425: The carbonate ion ( CO 2− 3 ): In organisms, carbonic acid production is catalysed by the enzyme known as carbonic anhydrase . In addition to altering its acidity, the presence of carbon dioxide in water also affects its electrical properties. When carbon dioxide dissolves in desalinated water, the electrical conductivity increases significantly from below 1 μS/cm to nearly 30 μS/cm. When heated,

3367-467: The pH . As shown in a Bjerrum plot , in neutral or slightly alkaline water (pH > 6.5), the bicarbonate form predominates (>50%) becoming the most prevalent (>95%) at the pH of seawater. In very alkaline water (pH > 10.4), the predominant (>50%) form is carbonate. The oceans, being mildly alkaline with typical pH = 8.2–8.5, contain about 120 mg of bicarbonate per liter. Being diprotic , carbonic acid has two acid dissociation constants ,

3458-426: The (incorrect) assumption that all dissolved CO 2 is present as carbonic acid, so that Since most of the dissolved CO 2 remains as CO 2 molecules, K a1 (apparent) has a much larger denominator and a much smaller value than the true K a1 . The bicarbonate ion is an amphoteric species that can act as an acid or as a base, depending on pH of the solution. At high pH, it dissociates significantly into

3549-439: The air and water: Carbon dioxide is colorless. At low concentrations, the gas is odorless; however, at sufficiently high concentrations, it has a sharp, acidic odor. At standard temperature and pressure , the density of carbon dioxide is around 1.98 kg/m , about 1.53 times that of air . Carbon dioxide has no liquid state at pressures below 0.51795(10) MPa (5.11177(99) atm ). At a pressure of 1 atm (0.101325 MPa),

3640-443: The atmosphere are absorbed by land and ocean carbon sinks . These sinks can become saturated and are volatile, as decay and wildfires result in the CO 2 being released back into the atmosphere. CO 2 is eventually sequestered (stored for the long term) in rocks and organic deposits like coal , petroleum and natural gas . Nearly all CO2 produced by humans goes into the atmosphere. Less than 1% of CO2 produced annually

3731-632: The changes occur in the winter and spring, experts are tending to suspect that gullies were formed from carbon dioxide ice (dry ice). Recent studies describe using the High Resolution Imaging Science Experiment (HiRISE) camera on MRO to examine gullies at 356 sites, starting in 2006. Thirty-eight of the sites showed active gully formation. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon dioxide frost and temperatures that would not have allowed for liquid water. When dry ice frost changes to

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3822-558: The climate changes, this ice can sublimate into the thin Martian atmosphere. Sublimation is when a substance goes directly from a solid state to a gas state. Dry ice on Earth does this. So when the ice at the base of a steep wall sublimates, a spatulate depression results. Also, more ice from higher up the wall will tend to flow downward. This flow will stretch the surface rocky debris thereby forming transverse crevasses. Such formations have been termed "washboard terrain" because they resemble

3913-484: The conclusion of theoretical calculations based on an ab initio potential energy surface of the molecule, is that none of the molecules in the gas phase are ever exactly linear. This counter-intuitive result is trivially due to the fact that the nuclear motion volume element vanishes for linear geometries. This is so for all molecules except diatomic molecules . Carbon dioxide is soluble in water, in which it reversibly forms H 2 CO 3 (carbonic acid), which

4004-862: The condition. There are few studies of the health effects of long-term continuous CO 2 exposure on humans and animals at levels below 1%. Occupational CO 2 exposure limits have been set in the United States at 0.5% (5000 ppm) for an eight-hour period. At this CO 2 concentration, International Space Station crew experienced headaches, lethargy, mental slowness, emotional irritation, and sleep disruption. Studies in animals at 0.5% CO 2 have demonstrated kidney calcification and bone loss after eight weeks of exposure. A study of humans exposed in 2.5 hour sessions demonstrated significant negative effects on cognitive abilities at concentrations as low as 0.1% (1000   ppm) CO 2 likely due to CO 2 induced increases in cerebral blood flow. Another study observed

4095-406: The day warms. Things are quite different as fall approaches, for the pole-facing slopes remain in the shade all day. Shade causes snow to accumulate through the fall and winter seasons. In the spring at certain point, the ground will be warm enough and the air pressure high enough for liquid water to form at certain times of the day. There may be sufficient water to produce gullies by erosion. Or,

4186-566: The dispersing effects of wind, it can collect in sheltered/pocketed locations below average ground level, causing animals located therein to be suffocated. Carrion feeders attracted to the carcasses are then also killed. Children have been killed in the same way near the city of Goma by CO 2 emissions from the nearby volcano Mount Nyiragongo . The Swahili term for this phenomenon is mazuku . Adaptation to increased concentrations of CO 2 occurs in humans, including modified breathing and kidney bicarbonate production, in order to balance

4277-412: The distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains a great deal of fine dust particles. Water vapor will condense on the particles, then fall down to

4368-485: The dry ice is gone, new channels are visible. These gullies may be caused by blocks of dry ice moving down the steep slope or perhaps from dry ice starts the sand moving. In the thin atmosphere of mars, dry ice will expel carbon dioxide with vigor. Carbon dioxide Carbon dioxide is a chemical compound with the chemical formula CO 2 . It is made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It

4459-541: The effects of blood acidification ( acidosis ). Several studies suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a submarine ) since the adaptation is physiological and reversible, as deterioration in performance or in normal physical activity does not happen at this level of exposure for five days. Yet, other studies show a decrease in cognitive function even at much lower levels. Also, with ongoing respiratory acidosis , adaptation or compensatory mechanisms will be unable to reverse

4550-410: The first one for the dissociation into the bicarbonate (also called hydrogen carbonate) ion ( HCO − 3 ): This is the true first acid dissociation constant, defined as where the denominator includes only covalently bound H 2 CO 3 and does not include hydrated CO 2 (aq). The much smaller and often-quoted value near 4.16 × 10 (or pK a1 = 6.38) is an apparent value calculated on

4641-445: The first place. Some researchers believe that gully formation may involve both dry ice and liquid water, especially in the past. It is estimated that a few million years ago, the tilt of the axis of Mars was 45 degrees instead of its present 25 degrees. Its tilt, also called obliquity, varies greatly because its two tiny moons cannot stabilize it, like our relatively large moon does to the Earth. During such periods of high tilt,

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4732-480: The flow. A team of researchers examined changes in a sand dune gully in Matara Crater (49.5°S; 34.9°E - Noachis quadrangle) for 5 years. Each year there were changes. The changes were in the length of the gully, the curviness of the gully, and changes in the volume both the alcove and the apron. The alcove lost material, while the apron gained. In just one Martian year, the apron went from a length of 800 meters to

4823-469: The gas deposits directly to a solid at temperatures below 194.6855(30) K (−78.4645(30) °C) and the solid sublimes directly to a gas above this temperature. In its solid state, carbon dioxide is commonly called dry ice . Liquid carbon dioxide forms only at pressures above 0.51795(10) MPa (5.11177(99) atm); the triple point of carbon dioxide is 216.592(3) K (−56.558(3) °C) at 0.51795(10) MPa (5.11177(99) atm) (see phase diagram). The critical point

4914-526: The ground due to the additional weight of the water coating. When ice at the top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice. Gully (Mars) Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars . They are named for their resemblance to terrestrial gullies . First discovered on images from Mars Global Surveyor , they occur on steep slopes, especially on

5005-452: The ground in the thin Martian atmosphere. Because the liquid carbon dioxide would throw material over 100 meters, the channels should be discontinuous, but they are not. Eventually, most hypotheses were narrowed to involve liquid water coming from an aquifer , from melting at the base of old glaciers (or snowpacks), or from the melting of ice in the ground when the climate was warmer. Close-up images with HiRISE showed details that support

5096-463: The gullies does not explain the ones found on isolated peaks, like knobs and the central peaks of craters. Also, a type of gully seems to be present on sand dunes. Aquifers need a wide collecting area which is not present on sand dunes or on isolated slopes. Even though most of the original gullies that were seen seemed to come from the same layer in the slope, some exceptions to this pattern have been found. Examples of gullies coming from different levels

5187-428: The gullies formed when the tilt of Mars went to 35 degrees. It has done that many times; the last time just 630,000 years ago. Some steep slopes show other features in addition to gullies. At the base of some gullies there may be curved ridges or depressions. These have been named "spatulate depressions." Along walls, like crater walls, ice often accumulates during certain phases of the Martian climate cycle. When

5278-447: The gullies involve liquid water. When the volumes of the aprons are compared to the rest of the gully, it appears that there is much less volume in the apron; hence, much of the material may have contained water and ice that disappeared. However, this remains a topic of active research. Because the gullies are so young, this would suggest that liquid water has been present on Mars in its very recent geological past, with consequences for

5369-597: The harvestable yield of crops, with wheat, rice and soybean all showing increases in yield of 12–14% under elevated CO 2 in FACE experiments. Increased atmospheric CO 2 concentrations result in fewer stomata developing on plants which leads to reduced water usage and increased water-use efficiency . Studies using FACE have shown that CO 2 enrichment leads to decreased concentrations of micronutrients in crop plants. This may have knock-on effects on other parts of ecosystems as herbivores will need to eat more food to gain

5460-530: The ice that is mixed in the mantle could melt and flow down the slopes and make gullies. Calculations show that a third of a mm of runoff can be produced each day for 50 days of each Martian year even under current conditions. Because there are few craters on this mantle, the mantle is thought to be relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE . The ice-rich mantle may be

5551-421: The idea that a fluid was involved. Images show that channels were formed a number of times. Smaller channels were found in larger valleys, suggesting that after a valley formed another formed at a later time. Many cases showed channels took different paths at different times. Streamlined forms like teadrop-shaped islands were common in some channels. The following group of pictures of gullies illustrate some of

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5642-418: The idea that current gully changes may be caused by dry ice. Some gullies on sand dunes have even been observed to change noticeably in just one year. Dry ice, or solid carbon dioxide, accumulates in the cold winter and then when it is starting to warm up, changes appear in gullies. It is thought that dry ice could be causing a flow in the sand as it sublimates; the carbon dioxide gas released would speed up

5733-476: The land, but in places it has a bumpy texture, resembling the surface of a basketball. Under certain conditions the ice could melt and flow down the slopes to create gullies. Because there are few craters on this mantle, the mantle is relatively young. An excellent view of this mantle is shown below in the picture of the Ptolemaeus Crater Rim, as seen by HiRISE. Changes in Mars's orbit and tilt cause significant changes in

5824-470: The last two million years (between 400,000 and two million years ago) creating conditions suitable for formation of the gullies through ice melt. Today, we have noticed small changes in gullies even though it is not possible for liquid water to exist. However, in the past perhaps water was involved. Indeed, a large team of researchers published a paper in Science that showed that water would have existed where

5915-411: The mantle, and the rock underneath. The third theory is that climate changes may be enough to allow ice deposited from atmospheric vapor into the ground to melt and thus form the gullies. During a warmer climate, the first few meters of ground could thaw and produce a "debris flow" similar to those on the dry and cold Greenland east coast. Since the gullies occur on steep slopes only a small decrease of

6006-403: The molecule has no electric dipole moment . As a linear triatomic molecule, CO 2 has four vibrational modes as shown in the diagram. In the symmetric and the antisymmetric stretching modes, the atoms move along the axis of the molecule. There are two bending modes, which are degenerate , meaning that they have the same frequency and same energy, because of the symmetry of the molecule. When

6097-514: The old fashioned washboards. The parts of gullies and some associated features of gullies are shown below in a HiRISE images. The Phaethontis quadrangle is the location of many gullies that may be due to recent flowing water. Some are found in the Gorgonum Chaos and in many craters near the large craters Copernicus and Newton (Martian crater) . Gullies are found on some dunes. These are somewhat different than gullies in other places, like

6188-530: The potential habitability of the modern surface. On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by the seasonal freezing of carbon dioxide (CO 2 ), and not by that of liquid water as considered earlier. After being discovered, many hypotheses were put forward to explain the gullies. However, as in the usual progression of science, some ideas came to be more plausible than others when more observations were made, when other instruments were used, and when statistical analysis

6279-499: The presence of sufficient oxygen, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour. Concentrations of more than 10% may cause convulsions, coma, and death. CO 2 levels of more than 30% act rapidly leading to loss of consciousness in seconds. Because it is heavier than air, in locations where the gas seeps from the ground (due to sub-surface volcanic or geothermal activity) in relatively high concentrations, without

6370-496: The products of their photosynthesis as internal food sources and as raw material for the biosynthesis of more complex organic molecules, such as polysaccharides , nucleic acids , and proteins. These are used for their own growth, and also as the basis of the food chains and webs that feed other organisms, including animals such as ourselves. Some important phototrophs, the coccolithophores synthesise hard calcium carbonate scales. A globally significant species of coccolithophore

6461-407: The result of climate changes. Changes in Mars's orbit and tilt cause significant changes in the distribution of water ice from polar regions down to latitudes equivalent to Texas. During certain climate periods water vapor leaves polar ice and enters the atmosphere. The water comes back to ground at lower latitudes as deposits of frost or snow mixed generously with dust. The atmosphere of Mars contains

6552-420: The same amount of protein. The concentration of secondary metabolites such as phenylpropanoids and flavonoids can also be altered in plants exposed to high concentrations of CO 2 . Plants also emit CO 2 during respiration, and so the majority of plants and algae, which use C3 photosynthesis , are only net absorbers during the day. Though a growing forest will absorb many tons of CO 2 each year,

6643-592: The same level, just as one would expect if water came out of an aquifer . Various measurements and calculations show that liquid water could exist in aquifers at the usual depths where gullies begin. One variation of this model is that rising hot magma could have melted ice in the ground and caused water to flow in aquifers. Aquifers are layers that allow water to flow. They may consist of porous sandstone. The aquifer layer would be perched on top of another layer that prevents water from going down (in geological terms it would be called impermeable). Because water in an aquifer

6734-412: The seasonal freezing of carbon dioxide (CO 2 ice or 'dry ice'), and not by that of liquid water as thought earlier. The exact cause/causes of these gullies is still under debate. A study supported formation by the melting of ground ice or snowpack as the chief cause. Over 54,000 CTX images were examined which covered about 85% of the surface of the planet. Most of the gully alcove heads occur at

6825-470: The shapes that lead researchers to think that water was involved in creating at least some of the gullies. However, more studies open up other possibilities; a study released in October 2010, proposes that some gullies, the ones on sand dunes, may be produced by a buildup of solid carbon dioxide during cold winter months. On July 10, 2014, NASA reported that gullies on the surface of Mars were mostly formed by

6916-471: The shear strength of the soil particles is needed to begin the flow. Small amounts of liquid water from melted ground ice could be enough to lead to erosion. However, it is likely that ice deposited in the pores of soil in the ground will diffuse back into the atmosphere rather than melt. Similar pore ice diffusion was also observed in-situ at the Phoenix landing site In support for ground ice being involved,

7007-512: The south, high concentrations are found on the northern edge of Argyre basin, in northern Noachis Terra , and along the walls of the Hellas outflow channels. A recent study examined 54,040 CTX images that covered 85% of the Martian surface found 4861 separate gullied landforms (e.g., individual craters, mounds, valleys, etc.), which totaled tens of thousands of individual gullies. It is estimated that CTX can resolve 95% of gullies. This article gives

7098-520: The southern hemisphere. Some studies have found that gullies occur on slopes that face all directions; others have found that the greater number of gullies are found on poleward facing slopes, especially from 30° to 44° S. Although thousands have been found, they appear to be restricted to only certain areas of the planet. In the northern hemisphere, they have been found in Arcadia Planitia , Tempe Terra , Acidalia Planitia , and Utopia Planitia . In

7189-399: The summer rays of the sun strike the mid-latitude crater surfaces straight on, thus the surface remains dry. Note that at high tilt, the ice caps at the poles disappear, the atmosphere thickness, and the moisture in the atmosphere goes up. These conditions cause snow and frost to appear on the surface. However, any snow that falls at night and during the cooler parts of the day disappears when

7280-412: The thin air of the higher altitude. For example, Thaumasia quadrangle is heavily cratered with many steep slopes. It is in the right latitude range, but its altitude is so high that there is not enough pressure to keep ice from sublimating (going directly from a solid to a gas); hence it does not have gullies. A large study done with several years worth of data from Mars Global Surveyor showed that there

7371-509: The top of the mantling layer goes back into the atmosphere, it leaves behind dust, which insulates the remaining ice. When the slopes, orientations, and elevations of thousands of gullies were compared, clear patterns emerged from the data. Measurements of altitudes and slopes of gullies support the idea that snowpacks or glaciers are associated with gullies. Steeper slopes have more shade which would preserve snow. Higher elevations have far fewer gullies because ice would tend to sublimate more in

7462-481: The trapped water can flow is horizontally. The water could then flow out onto the surface when it reaches a break, like a crater wall. Aquifers are quite common on Earth. A good example is "Weeping Rock" in Zion National Park Utah. On the other hand, much of the surface of Mars is covered by a thick smooth mantle that is thought to be a mixture of ice and dust. This ice-rich mantle, a few yards thick, smooths

7553-535: The upper ocean and thereby promotes the absorption of CO 2 from the atmosphere. Carbon dioxide content in fresh air (averaged between sea-level and 10 kPa level, i.e., about 30 km (19 mi) altitude) varies between 0.036% (360 ppm) and 0.041% (412 ppm), depending on the location. In humans, exposure to CO 2 at concentrations greater than 5% causes the development of hypercapnia and respiratory acidosis . Concentrations of 7% to 10% (70,000 to 100,000 ppm) may cause suffocation, even in

7644-474: The walls of craters. Gullies on dunes seem to keep the same width for a long distance and often just end with a pit, instead of an apron. They are often just a few meters across with raised banks along the sides. Many of these gullies are found on dunes in Russell (Martian crater) . In the winter dry ice accumulates on the dunes and then in the spring dark spots appear and dark-toned streaks grow downhill. After

7735-575: The walls of craters. Usually, each gully has a dendritic alcove at its head, a fan-shaped apron at its base, and a single thread of incised channel linking the two, giving the whole gully an hourglass shape. They are estimated to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes, that are themselves considered to be quite young. Linear dune gullies are now considered recurrent seasonal features. Most gullies occur 30 degrees poleward in each hemisphere, with greater numbers in

7826-458: The water begins to gradually lose the conductivity induced by the presence of C O 2 {\displaystyle \mathrm {CO_{2}} } , especially noticeable as temperatures exceed 30 °C. The temperature dependence of the electrical conductivity of fully deionized water without CO 2 saturation is comparably low in relation to these data. CO 2 is a potent electrophile having an electrophilic reactivity that

7917-653: The water may soak into the ground, and later move down as a debris flow. Gullies on Earth formed by this process resemble Martian gullies. The great changes in the tilt of Mars explain both the strong relationship of gullies to certain latitude bands and the fact that the vast majority of gullies exist on shady, pole-facing slopes. Models support the idea that pressure/temperature changes during high obliquity times are enough to allow liquid water to be stable in places where gullies are common. Research published in January 2015 suggests that these seasonal changes could have happened within

8008-546: The water, or to the lungs from where it is exhaled. During active photosynthesis, plants can absorb more carbon dioxide from the atmosphere than they release in respiration. Carbon fixation is a biochemical process by which atmospheric carbon dioxide is incorporated by plants, algae and cyanobacteria into energy-rich organic molecules such as glucose , thus creating their own food by photosynthesis. Photosynthesis uses carbon dioxide and water to produce sugars from which other organic compounds can be constructed, and oxygen

8099-513: Was calculated that gullies could be formed under present conditions with as little as 1 event in 50–500 years. So, although today there is little liquid water, present geological/climatic processes could still form gullies. Large amounts of water or great changes in climate are not needed. However, some gullies in the past may have been aided by weather changes that involved larger amounts of water, perhaps from melted snow. With more repeated observations, more and more changes have been found; since

8190-442: Was described in a later article entitled, "Formation of gullies on Mars by debris flows triggered by CO2 sublimation." In the model, CO 2 ice accumulates in the cold winter. It piles up on a frozen permafrost layer that consists of ice-cemented dirt. When the higher intensity sunlight of spring begins, light penetrates the translucent dry ice layer, consequently warming the ground. The CO 2 ice absorbs heat and sublimates—that

8281-473: Was employed. Even though some gullies resembled debris flows on Earth, it was found that many gullies were on slopes that were not steep enough for typical debris flows. Calculations showed that the pressure and temperatures were not right for liquid carbon dioxide. Moreover, the winding shape of the gullies suggested that the flows were slower than what would be produced in debris flows or eruptions of liquid carbon dioxide. Liquid carbon dioxide would explode out of

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