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Mars. Mars = the god of War Terrain is red because of iron oxides (rust). Mars. Atmosphere and Weather of Mars. Mars’ atmosphere is tenuous: air pressure is only 1% of air pressure of Earth Because of the low air pressure, water can’t exist as a liquid
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Mars = the god of War Terrain is red because of iron oxides (rust) Mars
Atmosphere and Weather of Mars • Mars’ atmosphere is tenuous: • air pressure is only 1% of air pressure of Earth • Because of the low air pressure, water can’t exist as a liquid • Mars atmos. is 95% CO2 and 3% N2 • Temperature averages about -50C (way below freezing) • No ozone layer, so the UV solar radiation dissociates H2) into H2 and O. • H2 escapes, O combines with iron rust, red color • Martian clouds are solid ice crystals of CO2 and H2O
Seasons on Mars • Tilt of axis = 24 degrees, similar to Earth Mars has seasons, as Earth does • One Martian year = 1.88 Earth years • The ellipticity of Mars’s orbit makes seasons more extreme in the southern hemisphere
Polar Ice Caps of Mars • Carbon dioxide ice of polar cap sublimates as summer approaches and condenses at opposite pole. (sublimates = goes directly from solid to gas) Late winter Mid-spring Early summer
Polar Ice Caps of Mars Residual ice of the polar cap remaining during summer is primarily water ice.
Dust Storms on Mars • Seasonal winds can drive dust storms on Mars. • Dust in the atmosphere absorbs blue light, sometimes making the sky look brownish-pink • No trees to stop winds
Dust Devils on Marshttp://marsrovers.jpl.nasa.gov/gallery/press/spirit/20050819a.html
Was Mars’ atmosphere thickerin the past? • Yes – almost certainly • Carbon Dioxide (a greenhouse gas) was produced by volcanos and about 3 billion years ago, the surface of Mars was much hotter • At that time, water probably flowed, and conditions were more similar to Earth
Geology of Mars • Mars has large volcanos and a gigantic rift valley, but no plate tectonics • The crust of Mars is too cold for plate tectonics, and too thick to fracture into plates • Olympus Mons: The largest volcano in the solar system • VallesMarineris: The largest canyon in the solar system • See many features that look like water once flowed on Mars
Olympus Mons • Olympus Mons is largest volcano in solar system • What Hawaii would look like if the plates weren’t moving?
Olympus Mons Three times as tall as Mt. Everest on Earth
Tectonics on Mars • The system of valleys known as Valles Marineris is thought to originate from tectonics.
Cratering on Mars • The amount of cratering differs greatly across Mars’s surface. • Many early craters have been erased.
What geological evidence tells us that water once flowed on Mars?
Dry Riverbeds? • Close-up photos of Mars show what appear to be dried-up riverbeds.
Erosion of Craters • Details of some craters suggest they were once filled with water.
Martian Rocks • Mars rovers have found rocks that appear to have formed in water.
Hydrogen Content • Map of hydrogen content (blue) shows that low-lying areas contain more water ice.
Crater Walls • Gullies on crater walls suggest occasional liquid water flows have happened less than a million years ago.
Small spherical rocks called “blueberries” are thought to be deposits formed by water
Judging from the geology of the river beds and the amount of cratering since, we estimate that liquid water was present around a billion years ago, or more, and froze and/or escaped Mars about 3 billion years ago
Changing Axis Tilt • Calculations suggest Mars’s axis tilt ranges from 0° to 60°. • Such extreme variations can cause climate changes. • Alternating layers of ice and dust in polar regions reflect these climate changes. Earth: axis tilt changes are avoided because we have a very large Moon
Climate Change on Mars • Mars has not had widespread surface water for 3 billion years. • Greenhouse effect probably kept the surface warmer before that. • Somehow Mars lost most of its atmosphere.
Climate Change on Mars • Magnetic field may have preserved early Martian atmosphere. • Solar wind may have stripped atmosphere after field decreased because of interior cooling.
Moons of Mars • Mars has two tiny moons: Phobos and Deimos • They look like asteroids • Phobos: 13 miles across • Deimos: 10 miles across Phobos Deimos
What have we learned? • What is Mars like today? • Mars is cold, dry, and frozen. • Strong seasonal changes cause CO2 to move from pole to pole • dust storms. • Why did Mars change? • Its atmosphere must have once been much thicker for its greenhouse effect to allow liquid water on the surface. • Somehow Mars lost most of its atmosphere, perhaps because of its declining magnetic field.
What have we learned? • What are the major geological features of Mars? • Differences in cratering across surface • Giant shield volcanoes • Evidence of tectonic activity
What have we learned? • What geological evidence tells us that water once flowed on Mars? • Some surface features look like dry riverbeds. • Some craters appear to be eroded. • Rovers have found rocks that appear to have formed in water. • Gullies in crater walls may indicate recent water flows.
“Canals” on Mars Percival Lowell misinterpreted surface features seen in telescopic images of Mars.
Is there Life on Mars? Was there life in the past, when Mars had water?
Life on Mars? • Searches for life on Mars have yielded no evidence that life currently exists on Mars • However, we have only explored a tiny fraction of the surface of Mars • Contamination by spacecraft now a serious issue • We have discovered single-celled life forms on Earth in extreme environments: underwater heat vents, inside glaciers, etc. • Jury still out!
