lies on the surface of parts of Meridiani Planum. Mapped from orbit by the TES instrument on Mars Global Surveyor, hematite abundances range from 5% (blue) to 20% (red). Because hematite needs liquid water to form, its presence indicates Meridiani has seen much liquid water in the past. The background image is a THEMIS daytime infrared mosaic. Spirit’s right front wheel became stuck, which slowed its movements, but also churned up the largest amount of bright soil discovered so far in the mission . Spirit's instruments confirmed that those soils had a salty chemistry dominated by ironbearing sulfates. The salts may record the past presence of water, as they are easily mobilized and concentrated in liquid solution. What are the major geological features of Mars? Differences in cratering across surface Giant shield volcanoes Evidence of tectonic activity What geological evidence tells us that water once flowed on Mars? Features that look like dry riverbeds Some craters appear to be eroded Rovers have found rocks that appear to have formed in water What geological processes shaped our Moon? Early cratering still present Maria resulted from volcanism What geological processes shaped Mercury? Cratering and volcanism similar to Moon Tectonic features indicate early shrinkage What are the major geological features of Venus? Venus has few craters - young surface Dominated by volcanism Also has tectonics but little or no erosion Terrestrial planets’ atmospheres are generated through internal volcanism or comet impacts Initially composed of H2O, CO2, SO2, N2 There is no clear upper boundary of Earth’s atmosphere, it gets less dense as you go up, “fading” to interplanetary space. Ofcially, NASA considers above 60km to be “space.” However, small amounts of gas are present even above 300 km. If the Earth were the size of a basketball, the lower layer atmosphere (which contains 90% of the air, the clouds) would be no thicker than a sheet of paper wrapped around its surface. What features of Earth’s atmosphere are important for life? Significant O2 Protects from harmful radiation from space Gamma-rays, X-rays UV - Ozone layer Greenhouse effect Provides right conditions for liquid water on the surface Earth’s atmosphere provides protection from harmful radiation Gamma-rays and X-rays are absorbed by O2 very high in the atmosphere Ultraviolet light absorbed by ozone (O3) in the stratosphere (ozone layer) Why does Earth have liquid surface water? Earth’s surface is the right temperature (and pressure) for liquid water Located at an optimal distance from the Sun Atmosphere provides moderate greenhouse effect Other planets are Too hot: Venus, Mercury Too cold: Jovians, Pluto Too small (no air): Mercury, Moon Venus: Hot & Inhospitable Massive amounts of CO2 in Venus’ atmosphere creates a very strong greenhouse effect Doesn’t cool off at night! Sulfuric acid rain evaporates before it ever reaches the ground! No weather -only a slow steady breeze Little erosion Surface probes sent to Venus only survived for a few minutes Most of Earth's CO2
You've reached the end of your free preview.
Want to read all 3 pages?
- Fall '09
- Solar System, Planet