Hydrology Mars

liquid water cannot exist on surface of mars due low atmospheric pressure, less 1% of earth s, except @ lowest elevations short periods. 2 polar ice caps appear made largely of water. volume of water ice in south polar ice cap, if melted, sufficient cover entire planetary surface depth of 11 meters (36 ft). permafrost mantle stretches pole latitudes of 60°. large quantities of water ice thought trapped within thick cryosphere of mars. radar data mars express , mars reconnaissance orbiter show large quantities of water ice @ both poles (july 2005) , @ middle latitudes (november 2008). phoenix lander directly sampled water ice in shallow martian soil on july 31, 2008.

photomicrograph opportunity showing gray hematite concretion, nicknamed blueberries , indicative of past existence of liquid water

landforms visible on mars suggest liquid water has existed on planet s surface. huge linear swathes of scoured ground, known outflow channels, cut across surface in 25 places. these thought record of erosion caused catastrophic release of water subsurface aquifers, though of these structures have been hypothesized result action of glaciers or lava. 1 of larger examples, ma adim vallis 700 km (430 mi) long, greater grand canyon, width of 20 km (12 mi) , depth of 2 km (1.2 mi) in places. thought have been carved flowing water in mars s history. youngest of these channels thought have formed few million years ago. elsewhere, particularly on oldest areas of martian surface, finer-scale, dendritic networks of valleys spread across significant proportions of landscape. features of these valleys , distribution imply carved runoff resulting precipitation in mars history. subsurface water flow , groundwater sapping may play important subsidiary roles in networks, precipitation root cause of incision in cases.

along crater , canyon walls, there thousands of features appear similar terrestrial gullies. gullies tend in highlands of southern hemisphere , face equator; poleward of 30° latitude. number of authors have suggested formation process involves liquid water, melting ice, although others have argued formation mechanisms involving carbon dioxide frost or movement of dry dust. no partially degraded gullies have formed weathering , no superimposed impact craters have been observed, indicating these young features, possibly still active. other geological features, such deltas , alluvial fans preserved in craters, further evidence warmer, wetter conditions @ interval or intervals in earlier mars history. such conditions require widespread presence of crater lakes across large proportion of surface, there independent mineralogical, sedimentological , geomorphological evidence.

composition of yellowknife bay rocks. rock veins higher in calcium , sulfur portage soil (curiosity, apxs, 2013).

further evidence liquid water once existed on surface of mars comes detection of specific minerals such hematite , goethite, both of form in presence of water. in 2004, opportunity detected mineral jarosite. forms in presence of acidic water, demonstrates water once existed on mars. more recent evidence liquid water comes finding of mineral gypsum on surface nasa s mars rover opportunity in december 2011. believed amount of water in upper mantle of mars, represented hydroxyl ions contained within minerals of mars s geology, equal or greater of earth @ 50–300 parts per million of water, enough cover entire planet depth of 200–1,000 m (660–3,280 ft).

on march 18, 2013, nasa reported evidence instruments on curiosity rover of mineral hydration, hydrated calcium sulfate, in several rock samples including broken fragments of tintina rock , sutton inlier rock in veins , nodules in other rocks knorr rock , wernicke rock. analysis using rover s dan instrument provided evidence of subsurface water, amounting as 4% water content, down depth of 60 cm (24 in), during rover s traverse bradbury landing site yellowknife bay area in glenelg terrain. in september 2015, nasa announced had found conclusive evidence of hydrated brine flows on recurring slope lineae, based on spectrometer readings of darkened areas of slopes. these observations provided confirmation of earlier hypotheses based on timing of formation , rate of growth, these dark streaks resulted water flowing in shallow subsurface. streaks contain hydrated salts, perchlorates, have water molecules in crystal structure. streaks flow downhill in martian summer, when temperature above −23 degrees celsius, , freeze @ lower temperatures.

researchers believe of low northern plains of planet covered ocean hundreds of meters deep, though remains controversial. in march 2015, scientists stated such ocean might have been size of earth s arctic ocean. finding derived ratio of water deuterium in modern martian atmosphere compared ratio on earth. amount of martian deuterium 8 times amount exists on earth, suggesting ancient mars had higher levels of water. results curiosity rover had found high ratio of deuterium in gale crater, though not high enough suggest former presence of ocean. other scientists caution these results have not been confirmed, , point out martian climate models have not yet shown planet warm enough in past support bodies of liquid water.

polar caps

mars has 2 permanent polar ice caps. during pole s winter, lies in continuous darkness, chilling surface , causing deposition of 25–30% of atmosphere slabs of co2 ice (dry ice). when poles again exposed sunlight, frozen co2 sublimes. these seasonal actions transport large amounts of dust , water vapor, giving rise earth-like frost , large cirrus clouds. clouds of water-ice photographed opportunity rover in 2004.

the caps @ both poles consist (70%) of water ice. frozen carbon dioxide accumulates comparatively thin layer 1 metre thick on north cap in northern winter only, whereas south cap has permanent dry ice cover 8 metres thick. permanent dry ice cover @ south pole peppered flat floored, shallow, circular pits, repeat imaging shows expanding meters per year; suggests permanent co2 cover on south pole water ice degrading on time. northern polar cap has diameter of 1,000 km (620 mi) during northern mars summer, , contains 1.6 million cubic kilometres (380,000 cu mi) of ice, which, if spread evenly on cap, 2 km (1.2 mi) thick. (this compares volume of 2.85 million cubic kilometres (680,000 cu mi) greenland ice sheet.) southern polar cap has diameter of 350 km (220 mi) , thickness of 3 km (1.9 mi). total volume of ice in south polar cap plus adjacent layered deposits has been estimated @ 1.6 million cubic km. both polar caps show spiral troughs, recent analysis of sharad ice penetrating radar has shown result of katabatic winds spiral due coriolis effect.

the seasonal frosting of areas near southern ice cap results in formation of transparent 1-metre-thick slabs of dry ice above ground. arrival of spring, sunlight warms subsurface , pressure subliming co2 builds under slab, elevating , rupturing it. leads geyser-like eruptions of co2 gas mixed dark basaltic sand or dust. process rapid, observed happening in space of few days, weeks or months, rate of change rather unusual in geology – mars. gas rushing underneath slab site of geyser carves spiderweb-like pattern of radial channels under ice, process being inverted equivalent of erosion network formed water draining through single plughole.