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In this talk I will show many features believed to contain water ice and tell about a popular model for how ice moves around on Mars. Knowing where to obtain water is of upmost importance for future Mar<an colonists. 1 This is thought to be an old glacier a?er almost all the ice has gone. What is le? are the moraines—the dirt and debris carried by the glacier. The center is hollowed out because the ice is mostly gone. ESP_028352_2245; 44.2 N and 28.5 E. 2 In contrast, here is a glacier that probably s<ll contains ice. This is similar to alpine glaciers on Earth. ESP_029444_1465; 33.1 S and 106.2 E. 3 This CTX image displays features called Lobate Debris Aprons. They are, in essence, wide glaciers that form along mesas. Debris aprons are quite common in some areas of Mars. The area inside the oval will be enlarged in later pictures. B13_006200_2228; 41.4 N and 14.7 E. 4 This close-up HiRISE image is 6 kilometers across. This mesa appears to have debris aprons almost all around it. ESP_28313_2220; 41.4 N and 14.7 E. 5 Here is the area inside the oval enlarged. It could even be enlarged further. The le? side of the image is brain terrain. Narrow ridges make up open-celled brain terrain. Most of the other, wider ridges are called closed-cell brain terrain. ESP_28313_2220; 41.4 N and 14.7 E. 6 Lineated valley fill is found in valleys and is composed of linear structures. Valley fill is very common in large areas of Mars. It seems to form when lobate debris aprons coalesce. When enlarged it shows a complex of shapes. The next two images will expand a part from the center of this image. P16_007359_2220; 41.3 N and 48.9 E. 7 At this magnifica<on a complex, regular pa_ern emerges. The area in the box will next be enlarged from this HiRISE image. ESP_23815_2215; 41.3 N and 48.9 E. 8 Now, closed-cell and open-cell brain terrain are easily dis<nguished. It is thought that closed-cell brain terrain contains a core of ice. When the core disappears, the center falls, and open-cell brain terrain with its more narrow ridges results. Also, radar studies have discovered much pure water ice preserved under less than 15 meters of material on both lobate debris aprons and lineated valley fill. ESP_23815_2215; 41.3 N and 48.9 E. 9 Craters containing concentric crater fill are very common in certain regions and can easily be iden<fied from orbit. These craters appear to be almost filled with some sort of material. They have several concentric ridges. This is a CTX image and is therefore 30 kilometers across. P17_007714_2184; 38 N and 75.9 E. 10 This enlarged sec<on is 6 kilometers across. Next a part in the lower right will be greatly enlarged. ESP_030526_2185; 38 N and 75.9 E. 11 Now, one can see a great deal of closed-cell brain terrain and small areas of open-cell brain terrain. The surface is similar to what we saw on the surface of lobate debris aprons and lineated valley fill. One would guess that all three may contain water ice. Our knowledge of impact craters gives us clues to the nature of CCF. ESP_030526_2185; 38 N and 75.9 E. 12 When a impact crater forms, a deep bowl usually is formed, along with rims. Some<mes ejecta also results. This basic shape is common on Mars, the moon, the Earth, and actually all around the solar system. About five hundred miles from here, you can see that Meteor Crater has this shape. 13 We have found that if a crater has a certain diameter, it will have a certain depth when it is formed. 14 By comparing calculated depth diameter ra<os with what is observed, we find that much material has been added since the crater was created. It is thought that much of this material contains ice. There is strong evidence that ice-rich dust and snow has fallen from the Mar<an sky many <mes in the past. 15 So 3 features are believed to contain water ice. Radar studies from orbit have already confirmed ice in LDA and LVF. These landscapes can be mapped from orbit. Next, we will examine how water ice may have arrived in these loca<ons. 16 An ice-rich mantle from the sky has been suggested to bring in the ice. In the higher la<tudes, the surface appears very smooth. Fresh craters should be sharp and crisp, but in some places everything is smooth. This smoothness seems to be caused by a mantle layer that is o?en several tens of meters thick. In the next image the smaller of the two big craters is enlarged. D03_028336_1397; 40.164 S and 116.859 E. 17 This covering has layers in some spots and is gone in other spots. ESP_028336_1395; 40.164 S and 116.859 E. 18 The inside wall of the crater has up to 4 layers visible in the smooth mantle. Researchers have found 6 layers at other sites. Its believed that the layers are from different events of mantle falling from the sky. The mantle shown here may be rela<vely recent—maybe only a million years old. That is not very long. The southern highlands of the planet is several billions of years old. The mantle some<mes shows special features such as gullies. ESP_028336_1395; 40.164 S and 116.859 E. 19 This 30 km wide CTX image shows gullies along a scarp in the lower right. P14_006536_1460; 34.666 S and 210.6 E. 20 These gullies are formed almost totally in mantle material. Gullies are one of the most significant discoveries of this century. They are thought to have been made by liquid water. These gullies were probably formed when ice in the mantle melted and flowed down the slope. It may take only a few warm hours for liquid water to make progress at eroding a gully. ESP_28860_1450; 34.666 S and 210.6 E. 21 The wide picture at the le? is a 30 km wide CTX image of part of Milankovic Crater, which is in the far north--almost directly north of Olympus Mons. The box is enlarged at the right in a HiRISE image. The depressions are called scallops. The mantle is very thick this far north. The next image will greatly enlarge the right side of the top scallop. P17_007788_2347; 54.3 N and 212 E. ESP_024943_2345; 54.3 N and 212 E. 22 At this resolu<on we see the surface covered with polygons which are common in ice-rich areas on Earth. ESP_024943_2345; 54.3 N and 212 E. 23 This wide CTX image shows linear pits and a wide view of scalloped terrain. The area under the box is greatly enlarged in the next photo. P18_008030_2217; 41.667 N and 87.188 E. 24 Now we see polygons that are classified as low center polygons. They too are thought to form in ice-rich areas. Examples of these can be seen a few hours drive from here in Rocky Mountain Na<onal Park. Some researchers have suggested that some mel<ng also needs to occur to produce these shapes. Small amounts of liquid water could permit microorganisms to live. ESP_29418_2270; 41.667 N and 87.188 E. 25 So, observa<ons suggest that the mantle is rich in water. Furthermore, the layers in the mantle are evidence of mul<ple events. Next, we will look into a model that explains how ice-rich mantle moves around. 26 The pictures we have looked at have come from the areas outlined in black. There is a popular model that seeks to explain how ice gets to these mid-la<tude areas. Milankovic Crater that we talked about earilier is by itself in the upper le?. 27 Currently Mars is <lted 25 degrees, close to the Earths 23.5 degrees. The arrows show the direc<on of rays of light from the sun. At this <lt the light intensity is not very high at the poles, so as with the Earth, ice accumulates there. The Earth is always fairly close to this angle because of the stabilizing effect of its rather large moon. The puny moons of Mars can not control its <lt, hence its <lt frequently has changed a great deal. 28 When the <lt gets to 45 degrees the light is much more intense at the poles, and water ice is no longer stable. Also, stores of solid carbon dioxide sublimate to make the atmosphere thicker. A thicker atmosphere will also hold more dust. 29 So at <lts of 45 degrees or more, ice is transferred to the mid la<tudes where today we find ice features. The ice moves in the form of ice coated dust grains and snow. A?er a <me, the top of the ice becomes capped with a lag deposit that protects the ice from disappearing. The lag develops as some ice changes to a gas by sublima<on. At other <mes the <lt gets low again, but some ice remains behind due to the protec<ve cap. 30 A half of a year later the sun will be concentrated at the opposite pole. Then, ice is transferred to southern mid-la<tudes. This oscila<on in <lt has occurred many <mes in the past. Layered features and the layers in the mantle may be a result of these numerous shi?s in <lt.

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