Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
A Look at Our Solar System: The Sun, the planets and more by Firdevs Duru Week 1 An overview of our place in the universe An overview of our solar system History of the astronomy Physics of motion of the planets Week 2 Our star Sun (physical properties, layers, fusion) Our home Earth (motion, interior, atmosphere, auroras) Our companion Moon (physical properties, eclipses, tidal effects) Week 3 Terrestrial planets (Mercury, Venus, Mars) Physical properties, missions Week 4 Jovian planets (Jupiter, Saturn, Uranus, Neptune) Trans-Neptunian Objects MERCURY and VENUS Terrestrial Planets Huge temperature difference! It gets very hot during the day (88 Earth days) and very cool during the night (88 Earth days). Two spacecraft: Mariner 10 and Messenger Surface u Crater dominated u Not extensive lava flow regions u Impact meteorites Spider o Not as big crater density as in the Moon. o Intercrater plains are seen in between. o Scarps: due to the cracking of the surface when the planets core cooled and shrank. o Volcanic activity ended 3.8 billion years ago. Atmosphere Very tenuous atmosphere. Gasses: sodium, oxygen, helium, potassium and hydrogen. Trapped from solar wind & vaporization of the meteorites. Uneroded old craters: not a thick atmosphere ever. Consequence: heat cannot be retained. Poles always cold (~125 K) –sunlight is almost parallel. Interior Mercury’s density: 5440 kg/m3 70% metals, 30% silicate rock Magnetic Field Origin of Mercury Doppler effect can tell us about the speed and rotation rate of the distant objects When the source and the observer are moving with respect to each other, a change is seen in the spectrum. Venus rotates very slowly! Rotation period: 243 days 1 Venus year = 1.93 Venus day Retrograde rotation: Rotates from east to west. Clouds Extends from 45 to 75 km above the surface. A layer of haze goes down to 30 km. Upper-level winds: 400 km/h relative to the planet. At the surface: 3 km/h Entire atmosphere rotates faster than the solid planet itself. Surface of Venus Radargrams: radio signals sent to Venus. Surface elevation map of Venus VENERA 14 Spacecraft Two features: Ishtar Terra and Aphrodite Terra 15 km between the highest and lowest points Less than 1000 impact craters Some volcanic craters Aurelia Crater Venus shows a lot of volcanic activity Volcanos: Maat Mons, Sif Mons and Gula Mons Pancake-shaped lava domes Most volcanoes are shield volcanoes: large cones and gentle slopes. Characteristic: Caldera or crater at the summit. Coronae Aine and Fotla . Arachnoids Evidence for ongoing volcanic activity at Venus: Level of sulfur dioxide above the clouds show large fluctuations. The orbiting spacecraft have observed bursts of radio energy from planet’s surface. Soviet landers found out basaltic samples implying volcanic activity in the past. Interior No magnetosphere Overall Earth-like composition and a partially molten iron-rich core. Core/mantle structure similar to ours. No plate tectonics. If Venus started off like Earth, why is its atmosphere now so different from Earth’s? On Earth: CO2 level is controlled by its production by volcanic activities (and human activities at some extend) and its absorption by rocks and oceans on the surface. Carbon cycle At Venus, greenhouse gasses never left the atmosphere. Why no water? Venus, closer the Sun, it was warmer at the beginning More water evaporation à increase of water vapor in the atmosphere Ability of oceans and surface rocks to hold CO2 decreases with increasing temperature à more CO2 would enter the atmosphere Greenhouse effect would increase à Heating of the planet à increasing the greenhouse gasses. Finally, oceans would evaporate and all the greenhouse gasses would be in the atmosphere.