2ObjectivesStudents will be able to describe the characteristics that the inner planets have in common.Students will be able to identify the main characteristics that distinguish each of the inner planets.
3What Do the Inner Planets Have in Common? The inner planets are small and dense and have rocky surfaces.Often called terrestrial planets which means “Earth”All have relatively high densities.Rich in rocky and metallic materials, including iron and silicon.Each has a solid surface.All have atmospheres except Mercury.
4Data Planet Mercury Venus Earth Mars Diameter (km) 4,879 12,104 12,756 6,794Period of rotation (Earth days)58.92441.01.01Average distance from sun0.390.721.52Period of revolution (Earth days)88224.7365.2687Number of moons12
5How Do They Differ?SizeCompositionDistance from the sun
6Mercury Temperature range 430°C to below -170°C Smallest terrestrial planetNot much larger than Earth’s moonInterior made up of dense metal iron430C = 806F-170C = -274FClosest to the sunCraters formed early in the history of the solar systemDue to no water and little atmosphere, craters have not worn away over time
7Surface- flat plains and craters; no water and not much atmosphere Atmosphere- small in mass= weak gravity, gas particles easily escape into space, small amounts of sodium and other gases have been detected around MercuryExploring Mercury- most information comes from space probesMariner 10 flew by Mercury 3 times in 1974 and 1975Mercury Messenger passed Mercury several times and began orbiting in 2011
8Venus Similar in size and mass to Earth, called “Earth’s twin” Density and internal structure similar to EarthThick atmosphereUnusual pattern of rotationHottest surface of any planet
9Atmosphere- so thick that it is always cloudy; at the surface you would be quickly crushed by the weight of its atmosphere; pressure is 90 times greater than the pressure of Earth’s atmosphere; you couldn’t breathe on Venus because its atmosphere is mostly carbon dioxideRotation- takes about 7.5 Earth months to revolve around the sun and 8 months to rotate once on its axis; rotates from east to west; maybe because a large object struck Venus billions of years ago causing it to change direction or Venus’s thick atmosphere could have somehow altered its rotationClouds made up mostly of droplets of sulfuric acidDay is longer than its yearRotation opposite of most planets and moons
10Magellan probe landed in 1990 Venus Express Hot Planet- receives more solar energy than Earth because its closer to the sun; much of the radiation is reflected by Venus’s atmosphere; some radiation reaches the surface and is later given off as heat; carbon dioxide in atmosphere traps heat so well that it has the hottest surface; average surface temperature is 460°C Greenhouse effect- trapping of heat by the atmosphereExploring Venus-Venera 7 landed in 1970Magellan probe landed in 1990Venus Express460C = 860FVenera 7- first probe to land on Venus, survived a few minutes because of high temp and pressureMagellan carried radar instruments which works through clouds so it was able to map nearly the entire surface; confirmed Venus is covered with rock and surface has more than 10,000 volcanoes; lava flows formed plainsVenus express has helped scientists understand how Venus’s clouds form and change
11Earth Only planet in the solar system where you could live easily Has liquid waterSuitable temperature rangeAtmosphere for living things to surviveWater Planet- about 70% of Earth’s surface is covered with water
12Temperature- if Earth were a little closer to the sun, it would be so hot that liquid water would evaporate; if it were a little farther away and colder, water would always be solid iceAtmosphere- has enough gravity to hold on to most gases that make up Earth’s atmosphere; only planet with an atmosphere that is rich in oxygen; like Venus, Earth experiences a greenhouse effect; traps less heat than Venus’s atmosphere; without the atmosphere, Earth would be much colderTemperature- called having “Goldilocks” conditions, not too hot and not too coldOxygen makes up about 20 % of Earth’s atmosphere, rest is nitrogen and small amounts of argon, carbon dioxide and water vapor
13Mars Called the “red planet” Reddish color is due to the breakdown of iron-rich rocks, leaving a rusty dust behindToo cold for liquid waterDoes have water ice now and liquid water in the past
14Atmosphere- more than 95% carbon dioxide; has few clouds but very thin compared to clouds on Earth; temperatures range from-140°C to 20°CWater and Ice- atmosphere is so thin that any liquid water would quickly turn into a gas; water is located in the planet’s two polar ice caps made entirely of frozen water located under the surfaceVolcanoes- some regions have giant volcanoes that are rarely active anymore; Olympus Mons is the largest volcano in the solar systemCould walk around on Mars but you would have to wear an airtight suit and carry your own oxygen140C = -220F20C = 68F
15Mars’s Moons- has two very small moons that are covered with craters 1. Phobos- larger about 22km across2. Deimos- even smaller 13km acrossExploring Mars- recent missions have focused on finding signs of water and possible life on MarsSpirit and Opportunity- found traces of salts and minerals that form in the presence of waterPhoenix mission- took samples of soil and found frozen water near the north polar capMars Express spacecraft- detected methane gas in Mars’s atmosphere