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THE INNER PLANETS . MERCURY, VENUS EARTH AND MARS. Why are they called the Inner Planets?. They are called the Inner Planets because they are located inside the ring of asteroids that separate the first four planets from the last four. MERCURY. Closest planet to the Sun No atmosphere
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THE INNER PLANETS MERCURY, VENUS EARTH AND MARS
Why are they called the Inner Planets? • They are called the Inner Planets because they are located inside the ring of asteroids that separate the first four planets from the last four.
MERCURY • Closest planet to the Sun • No atmosphere • Extreme temperatures 425 degrees C during the day and – 170 degrees C at night. (770 and -274 degrees F) • Average distance to Sun – 58 million km (36 million miles) • Diameter – 4,878 km • Mass: 0.055 of Earth’s
MERCURY (con’t) • Surface gravity: 0.38 of Earth’s • Tilt of Axis – 0 degrees • Day: 59 Earth days • Year: 88 Earth days • No moons or rings • Smallest planet
VENUS • Second planet from the Sun • Atmosphere of carbon dioxide and sulfuric acid with high atmospheric pressure • Average temperature: 465 degrees C (869 F) • Average distance from Sun: 108 million km or 67 million miles • Diameter: 12,103 km (7,500 miles) • Mass: 0.81 of Earth’s
VENUS (con’t) • Gravity: 0.91 of Earth’s • Tilt of Axis: 2.6 degrees • Day: 243 Earth days • Year: 225 Earth days • Has no moons or rings • Can be seen in Earth’s sky just before sunrise and just after sunset • Hottest planet
EARTH • Third planet from the sun • Atmosphere of 78% nitrogen and 21% oxygen • Temperature: 15 degrees C (59 F) • Average distance from the Sun: 150 million km (93 million miles) • Diameter: 12,756 km (7,920 miles)
EARTH (con’t) • Mass: 1.0 • Gravity: 1.0 • Tilt of axis: 23.5 degrees • Day: 23 hours 56 minutes • Year: 365.25 days • Fifth largest planet • Supports life • Abundant water in liquid, solid and gas forms
EARTH (con’t) • Tilted axis allows for seasons • Has one large moon and no rings
MARS • Fourth planet from the Sun • Thin atmosphere of mostly carbon dioxide • Temperature: -50 degrees C (-58 F) • Distance from the Sun: 228 million km (141 million miles) • Diameter: 6,794 km (4,220 miles) • Mass: 0.11 of Earth’s • Gravity: 0.38 of Earth’s • Tilt of Axis: 25 degrees
MARS (con’t) • Day: 24 hours 37 minutes • Year: 1.88 Earth years • Seventh largest planet • Called the Red Planet because of the color of its surface • Winds up to 100 km per hr that cause dust storms • May have water in the polar ice caps
MARS (con’t) • Has two small moons and no rings • One moon, Phobos, orbits Mars once every 7 hours. • Deimos, the other moon, orbits every 31 hours.
Where did their name come from? • Mercury – named for the Roman messenger god because it travels so swiftly. • Venus – Named after the Roman goddess of love and beauty. • Earth – Comes from the Greek Mother Earth goddess. • Mars – Named after the Roman god of war.
EXPLORATION • 1974-1975 – Mariner 10 photographed about 45% of Mercury. It detected a weak magnetic field. Messenger, launched in 2004, flew to the planet by 2008 and is orbiting it in 2011. • 1962 – Mariner 2 flew past Venus and sent back info about its atmosphere and rotation. 1970 the Soviet Union landed the first probe on Venus but it stopped working in an hour because of high temperature and pressure. Between 1990-94, the U.S. Magellan used radar to make the most detailed map of Venus so far.
EXPLORATION (con’t) • 1976 – Viking 1 and 2 arrived at Mars. Each had an orbiter and lander. Orbiters photographed the entire planet while the landers touched down on the surface. The Mars Pathfinder carried a robot named Sojourner to test samples of Martian rocks and soil. Global Surveyor sent pictures that may indicate the presence of groundwater. 2002 Mars Odyssey began orbiting Mars.