Having calcium carbonate in the soil may be easier on life forms because it buffers acids, creating a pH more friendly toward life. Patterned ground Much of the surface of Vastitas Borealis is covered with patterned ground. Sometimes the ground has the shape of polygons. Close-up views of patterned ground in the shape of polygons was provided by the Phoenix lander. In other places, the surface has low mounds arranged in chains. Some scientists first called the features fingerprint terrain because the many lines looked like someone's fingerprint. Similar features in both shape and size are found in terrestrial periglacial regions such as Antarctica. Antarctica's polygons are formed by repeated expansion and contraction of the soil-ice mixture due to seasonal temperature changes. When dry soil falls into cracks sand wedges are made which increase this effect. This process results in polygonal networks of stress fractures. Defrosting In the spring, various shapes appear because frost is disappearing from the surface, exposing the underling dark soil. Also, in some places dust is blown out of in geyser-like eruptions that are sometimes called "spiders." If a wind is blowing, the material creates a long, dark streak or fan. Glaciers Glaciers formed much of the observable surface in large areas of Mars. Much of the area in high latitudes is believed to still contain enormous amounts of water ice. In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris. The ice was probably deposited as snowfall during an earlier climate when the poles were tilted more. Some features in Vastitas Borealis are believed to be ancient glaciers as shown in the pictures below. Layers Where the ice cap is exposed in certain places, it is found to contain many layers. Some are shown in the picture below. Dunes Climate Weather The Phoenix lander provided several months of weather observations from Mare Boreum. Wind speeds ranged from 11 to 58 km per hour. The usual average speed was 36 km per hour. The highest temperature measured during the mission was -19.6 °C, while the coldest was -97.7 °C. Dust devils were observed. Cirrus clouds that produced snow were sighted in Phoenix imagery. The clouds formed at a level in the atmosphere that was around -65 °C, so the clouds would have to be composed