Surface and Subsurface Ices, 14 October 2013!The fact that ices are abundant in the solar system is a largely a space age 1.discovery. !In the 70s, Astronomers believed that water and ice were very rare, and A.that the Earth had the biggest reservoir known anywhere. !Space age craft revealed that most of Jupiter's, Saturn's, and Uranus' a.moons are covered with ice. !It is only close to the sun that ice is rare. !B.Ices in the solar system come mainly in the forms of water, carbon dioxide, 2.methane, and ammonia.!There are other ices mixed in.!A.Different objects have different proportions of different chemicals (and B.ices). !The four main forms are good enough in this class. !a.Ice on Earth:!3.There is a considerable amount of ice on Earth, but mostly not where A.people live. !The biggest reservoir of ice is Antarctica. !a.There is no vegetation around here.!1.There is an active volcano in this area called Mount Erebus which 2.spouts off a few times every decade. !There is ice on Newfoundland and in the sea around it !b.There is ice on top of mountain ranges:!c.Flat Iron Mountains !1.Mount Rainier!2.Himalayas!3.The Grand Tetons in Wyoming !4.The California coast is one of the few places on Earth where where ice d.is rare. !Ice ages: times when there was a lot of ice growing!B.There have been ices ages repeatedly over many millions of years of the a.Earth's history. !The most recent ice age ended about 10,000 years ago. !b.There was substantial glaciers 8,000 years ago which have been 1.getting smaller ever since. !Ice ages are an important process in the dynamics of a planet, they have c.shaped the Earth's surface: !The Missouri and Ohio rivers are where they are because that is 1.where the terminal output from the glaciers was (where the end ofthe glacier was).!The great lakes were carved by ice. !2.New England was under ice during the ice age. !A.Evidence of Ice on the Moon: !4.Small areas of the Moon have hills that look structurally like pingoes. !A.Pingoes: Mounds of soil covered in ice with mysterious origins.!a.On earth, they are only found in the tundra (for example: in the arctic, 1.and in the Mackenzie Delta in northern Canada). !No two authors agree with one another as to how these are formed. !2.Any student who solves this problem to the satisfaction of experts A.in the specialty, gets an instant A for the entire course, regardless of anything else.!Pingoes are said to occur on Earth when permafrost melts. If this is true, b.there could have been permafrost on the Moon. !Permafrost is ice that does not melt in summer –"it is permanent. !1.Experts claim that these hills cannot be called pingoes because the 2.moon has no water, but this is backwards reasoning since we do not know that the moon has always been dry. !The moon must have intercepted comets with ice on them at A.some point, and it doesn't take more than a couple of weeks to make a pingo. !People have also discovered ice near the poles of the Moon.!B.Head and tail valleys on the Moon are found in the same area as pingoes. !C.These are a valley with a big head, flow features, an a long tail. !a.These are caused by permafrost under the surface of a planet melting 1.into water and flowing away down a hill. !Head and tail valleys are evidence of permafrost on Mars and Earth.!b.The moon might not have had permafrost, but this is evidence that 1.the moon had some subsurface frost at some point in the last billion years, probably from a comet.!Ice on Mars: !5.Polar ice caps: !A.The polar ice caps of mars are clearly visible through a telescope, so a.they were discovered in the 1600s. !Images of Mars' ice caps from the Hubble space telescope and 1.spacecraft orbiting Mars are superior, however.!Also visible through a telescope: A notch in the north polar ice cap. !2.This is due to lowlands on Mars' surface.!A.The ice caps come and go with the seasons. !b.They have cores of water with a frosting of carbon dioxide over them. !c.The snow pattern on the polar ice cap has arcs in it– it's a spiral. !d.There are a few ideas proposed to explain this, and some are 1.plausible, but nothing has been proven. ! Any student who solves this problem to the satisfaction of experts A.in the specialty, gets an instant A for the entire course, regardless of anything else.!Icicles hang from the edge of Mars' ice caps:!B.Since 1976, some astronomers have claimed that water could not exist a.in a liquid state on Mars due to the planet's low air pressure. !This idea is correct in theory, but wrong in practice. !1.Icicles are formed by drops of water freezing, and then other drops A.of water flowing down those frozen drops. These drops eventually give an icicle a pointy shape. !This means that there must be liquid water on Mars for minutes or B.even hours at a time. !Experts must have the evaporation rate wrong.!C.Other astronomers think that there used to be rivers on Mars, although b.there is no water in them now. !There are recent images of channels which are thought to have been 1.carved by dripping water.!Some images of Mars also appear to have a small, temporary A.stream in them. !There is also evidence of permafrost on Mars: !c.There are head and tail valleys (see description in "Evidence of Ice on 1.the Moon")!Some craters on Mars have a big apron around them with curlicue 2.edges. !These are caused when an impact melts the ice just under the A.surface of Mars: !The liquid mud flows away in all directions carrying a lot of dirt a.with it. !Either the water freezes in Mars' cold temperatures or b.evaporates in Mar's low air pressure, leaving curlicue-shaped cliffs where the flow stopped. !Ice is the dominant substance in the outer solar system away from the sun: !6.Moons of Jupiter that are covered in ice: !A.Europa, no 2 moon of Jupiter!a.Europa's surface ice is thought to be roughly 10 kilometers thick. !1.Under the ice of Europa is a global ocean that is a warmer 2.temperature. !Since this ocean is warm enough for chemical reactions and A.contains every chemical compound that is necessary for life, it is considered the most likely place to hunt for life.!Ganymede, no 3 moon of Jupiter !b.Some of Ganymede's surface ice is covered with grooves which 1.appear to be compression fractures.!Callisto no 4 moon of Jupiter !c.Moons of Saturn that are covered in ice: !B.Dione!a.There is white stuff on this moon that is thought to be snow. !1.Rhea!b.Iapetus!c.Has a surface with is half white and half black, and the white part is
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