The Terrestrial Planets The four planets closest to the sun. Mercury, Venus, Earth, and Mars The terrestrial planets are much like Earth. The four inner planets: Are relatively small and dense Have rocky surfaces (crusts), mantels, and iron cores
More on the First Four Mercury and Mars have crusts that are scarred by craters. Earth and Venus do not have craters because their surface is continually eroded. Common characteristics of the terrestrial planets: Higher temperature than outer planets Have few (if any) moons No rings around the terrestrial planets
Mercury Characteristics: Smallest and closest to the sun Dense with large Iron core Fastest moving planet - 88 day revolution Temperature and Atmosphere: It takes 88 days for sunrise to sunset During the day, temperature = 430 deg. C At night, temperature = 170 deg. C Virtually NO atmosphere - temp makes particles move fast, little gravity makes it easy for particle to escape into space
Venus Characteristics: The brightest object in Earth’s night sky (with the exception of the moon) Rotates in the opposite direction to which it revolves around the sun Rotation rate is VERY slow - takes 243 days to rotate on its axis (a day is longer than a year!) Temperature and Atmosphere: Difficult to study because of clouds Atmosphere is so thick that pressure is 90x greater than that on Earth Atmosphere is made mainly of CO2 which traps heat and increases surface temp Surface temp is 470 deg. C
Earth Earth = Suitable atmosphere and temperature for water to exist as liquid! H2O supports tens of thousands of different species of living organisms and has shaped the surface through erosion. Has gravity to hold most gas molecules = thick atmosphere Geologically alive!
Mars Characteristics: Most Earth-like of all planets Weathering of iron-rich rock give it red tint Has largest volcano in solar system (Olympus Mos) Atmosphere and Temperature: Thin atmosphere and distance = temp range of -140 deg. C to 20 deg. C Atmosphere is mainly CO2 (much like Venus but much thinner) No liquid water on Mars - but thought that there once was Mars also has seasons due to the tilt of its axis
Asteroids Beyond Mars is a region known as the asteroid belt Astronomers have discovered more than 10,000 asteroids and more are thought to exist Asteroid are: >1 kilometer in diameter Only 3 are larger than 500 kilometers across It used to be thought that asteroids were fragments of a shattered planet - not what is thought today
Scientific Discovery• It is said that Scientific Discovery can happen in different ways: • Discovery by accident • Theories predict phenomena that scientists try to find• Uranus (Yoor uh nus) and Neptune were discovered by these two methods• Uranus discovered by chance - thought it was a dim star• Neptune was found when someone predicted that there was something affecting Uranus’ orbit.
Gas Giants• The “Gas Giants” are the next four planets in the Solar System • Jupiter, Saturn, Uranus, and Neptune• Common Characteristics: • Much colder than terrestrial planets • More massive than terrestrial planets • Composed of mainly Hydrogen and Helium • No solid surface - intense pressure means that H and He exist in liquid form • Small dense cores of metal and rock
Jupiter• The first planet beyond the asteroid belt and the largest/massive planet in the solar system• Jupiter could hold more than 1,300 Earths and is named for the ruler of the Roman Gods• Jupiter is composed of mainly H and He• Atmosphere: • Clouds on Jupiter move fast because Jupiter moves fast • Brown bands are colder and move faster than the white bands • The great red spot is a giant storm on Jupiter, caught between bands of warm and cold air • These storms don’t dissipate like they do on Earth - the Great Red Spot was first observed in 1664
Jupiter’s Moons/Fun Facts• Jupiter has over 50 moons! • Ganymede and Callisto are the size of Mercury • Io and Europa are the size of Earth’s moon• Ganymede, Io, and Europa have metal cores and rocky mantels (Io is covered in active volcanoes - Ganymede, Europa, and Callisto are covered in ice)• Scientists believe that the ice on Europa rests on top of a liquid salt water ocean• FUN FACTS: • One day on Jupiter is less than 10 hours on Earth • It takes almost 12 Earth years for Jupiter to revolve around the sun • The Great Red Spot is the size of three Earths
Saturn• The second largest planet in the solar system and known for its rings! • Rings are ice particles or ice covered rock - most are snowball sized • Rings are 274,000 kilometers in diameter yet only tens of meters thick• Atmosphere: • Largest atmosphere of any in the solar system • Saturn has the lowest average density of any planet • Atmosphere is made of H and He • Scientists think that He condenses and as He raindrops fall towards the center of the planet, their energy is changed to heat
Uranus• Uranus is another Gas Giant which is extremely cold and has an atmosphere made of H and He• Like other Gas Giants, it is assumed that Uranus has a rocky core surrounded by a thick mantel layer of liquid water and dissolved ammonia• Uranus has rings, although they are not as impressive or reflective as Saturn’s rings• Uranus is tiled on its side, and it rotates in the complete opposite direction that it revolves around the sun• The northern and southern hemispheres alternate between being exposed to the sun for years - causing disturbances on the surface
Uranus’ Moons/Fun Facts• Uranus has more than 20 moons• FUN FACTS: • Uranus is thought to have been tilted on its side by a collision with another planet sized object • The rings and moons of Uranus follow the irregular rotation of the planet • One day on Uranus is about 17 Earth hours • It takes almost 84 Earth years for Uranus to revolve around the sun • Blue-Green color comes from methane in the atmosphere
Neptune• Neptune has approximately the same size and composition of Uranus• Neptune has clearly visible cloud patterns in its atmosphere, and gets the blue tint from methane in the atmosphere• Neptune has large storms in its atmospere which last for many years • The Great Dark Spot was identified by Voyager 2 in 1989 and then disappeared in 1994
Neptune’s Moons/Fun Facts• Neptune has 8 moons• Triton is the largest moon - has a thin atmosphere and an icy crust• FUN FACTS: • Neptune also has a small band of coal colored rings • One day on Neptune is about 15 Earth hours • It takes almost 165 Earth years for Neptune to revolve around the sun.
Pluto – A Planet No More • Pluto is small and dense - much like the moons of the Gas Giants• Pluto is made up of a mixture of ice and rock• Pluto has a single moon - Charon - which is almost identical in size (almost like a double planet)• Pluto is now considered a “dwarf planet” and is not recognized as having official planet standing