Survey
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download 9terrestrial5s
Document related concepts
Observations and explorations of Venus wikipedia , lookup
Sample-return mission wikipedia , lookup
Colonization of Mars wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Giant-impact hypothesis wikipedia , lookup
Planets in astrology wikipedia , lookup
Transcript
The Terrestrial Planets Astronomy 311 Professor Lee Carkner Lecture 9 Early Missions to the Inner Planets 1962 -- Mariner 2 Venus Fly-by 1973 Mariner 10 Venus/Mercury Fly-by 1964 -- Mariner 4 Mars Fly-by 1970 Venera 7 Venus lander first successful landing on another planet 1975 Viking 1 and 2 Mars lander first successful landing on Mars Planetary Missions First wave of exploration from 1960-1979 Very large number of Soviet missions, most were failures Venus: 15 successes, 31 missions Smaller number of US missions, but higher success rate Mercury: 2 successes, 2 mission Venus: 6 successes, 7 missions We are now starting to see other countries get more involved with space exploration Most notably Japan and The European Union Sources of Information for the Inner Planets Mercury: Mariner 10 and MESSENGER -- Venus: Soviet Venera landers -- surface conditions Magellan -- Mars: Viking, Pathfinder, Spirit, Opportunity -Viking, Global Surveyor, Odyssey, Recon Orbiter -- maps of the surface Inner Planet Facts Mercury Diameter: 0.38 Mass: 0.06 Orbital Radius: 0.4 Venus Diameter: 0.95 Mass: 0.82 Orbital Radius: 0.7 Earth Diameter: 1 Mass: 1 Orbital Radius: 1 Mars Diameter: 0.53 Mass: 0.11 Orbital Radius: 1.5 Determining Planetary Properties Mass Distance Can find directly with radar Diameter Can get from the angular diameter and the distance Determining Planetary Properties (cont.) Average Density Atmospheric composition take a spectrum of the atmosphere, look for the spectral signature of elements Scale Models We want to make a scale model to try to understand astronomical distances Need to find the scale scale = (real size) / (model size) example: miles per inch or light years per cm Once you have the scale you can find the model size for any real object (model size) = (real size) / scale The Planets That Weren’t There should have been 2 other inner planets A planet about the size of Mars may have hit the Earth a few billion years ago, the debris formed into the Moon Jupiter’s gravity disrupted the planetesimals between Mars and Jupiter so they never formed a planet The Moon Most of our information comes from the 6 Apollo landings (11-17, excluding 13) Moon facts Diameter: 0.27 Mass: 0.01 Orbital Radius (from Earth): 0.003 Moons of the Inner Planets Venus and Mercury have no moons Earth has one large moon Mars has two moons, Phobos and Deimos Inner planets may be too small to capture moons easily It is difficult to gravitationally capture something Asteroids Millions of small bodies orbit the Sun, most between Mars and Jupiter (the asteroid belt) Our information comes from 2 sources: Pieces of asteroids that have fallen to Earth For example: NEAR orbiting Eros Hayabusa landing on Itokawa Asteroid Facts Asteroids Diameter: <0.08 Mass: <0.0002 Orbital Radius: 2.8 Most have orbits within the asteroid belt (~2-3.5 AU) Sizes of the Inner Planets Sizes relative to Earth Earth: 1 (diameter = 13,000 km) Venus: 0.95 Mars: 0.53 Mercury: 0.38 Moon: 0.27 Asteroid: <0.08 All are small compared to the gas giants (Neptune is ~4 times the diameter of the Earth and ~64 times the volume) Atmospheres Mars Surface pressure = Composition = 95 % CO2, 3 % N (also water vapor, oxygen) Venus: Surface pressure = Composition = 96 % CO2, 4 % N (also sulfur compounds such as sulfuric acid, H2SO4) Atmospheres (cont.) Earth: Surface pressure = Composition = 77 % N, 21 % O2 (also water vapor, CO2, trace elements) Why are the atmospheres of Venus, Mars and the Earth so different? The Earth can regulate its atmosphere through the carbonate-silicate cycle, the other planets cannot The Carbonate-Silicate Cycle Atmosphere Water + CO2 (rain) CO2 Volcano CO2 + silicate (subvective melting) Ocean Carbonate + silicate (Sea floor rock) Carbonate + water (stream) CO2 and Greenhouse Effect Water washes CO2 out of atmosphere where it is eventually deposited as rock CO2 is a greenhouse gas More CO2 = higher temperature Carbonate-Silicate Feedback Hot Cool more CO2 washes out cools off less CO2 washes out heats up CO2 and the Inner Planets Venus: all the water boiled off and was disassociated thick CO2 atmosphere and high temperatures Mars: no way to get CO2 out of rocks thin CO2 atmosphere and low temperatures Earth: mild temperature and atmosphere Composition Density of rock (silicates) ~3000 kg/m3 What makes up the difference? Iron “Rocky” planets could also be called the “metal” planets Interior Structure Composition (cont.) Earthquake studies indicate that the Earth has a iron core Earth has a density gradient, heavier materials near the center, lighter near the surface We believe that the other inner planets have a similar structure Next Time Read Chapter 8 but just the Mercury parts Summary Inner or Terrestrial region 4 planets (Mercury, Venus, Earth, Mars) 1 large moon (The Moon) thousands of asteroids Information from 30 years of space missions Size Earth and Venus about the same Mars, Mercury, the Moon, 1/2 -1/4 size of the Earth Asteroids few km Summary (cont.) Composition silicate rock crust iron-silicate mantle iron core each planet has different proportions of each Atmosphere Mercury, Moon, asteroids -- none Venus -- no water means CO2 is in atmosphere Mars -- no plate tectonics means CO2 is in rocks Earth -- carbonate-silicate cycle balances greenhouse effect
