The Inner Planets 20.3

Mercury Closest planet to the sun. 2nd smallest planet Only spacecraft ever sent to Mercury was Mariner 10 in 1974-1975. It flew around the planet and sent back pictures of 45% of Mercury’s surface. Mercury looks like our moon- many craters and cliffs.

Mercury Facts Rev around the Sun-87 days Rotation 58 days, 15 hours Diameter- 4878 Kilometers, 3048 miles No moons No rings Orbital Speed 47.89 km/s .387AU from sun

Atmosphere of Mercury Most gases on Mercury escaped, because of its low gravitational pull. However, the gases that remain form a very thin atmosphere composed of: Hydrogen and Helium, which we probably captured by Mercury from the sun’s solar winds Sodium and Potassium, which came up from the crust.

Temperature of Mercury Because Mercury is so close to the sun and has hardly any atmosphere, its temperatures are extreme. Surface temperature during the day reaches 450 C, 842 F and –170 C, -274 F at night.

Second Planet from the Sun Venus Second Planet from the Sun

Venus Facts Revolution- 224.7 days Rotation- 243 days Diameter- 12,104 Km, or 7565miles Orbital Speed- 35.03 km/s No moons No rings .723 AU from sun

Earth’s Twin Venus is called the Earth’s twin because it is very similar in mass and size. The major difference is the atmosphere- Venus is covered by a thick, dense cloud of mostly carbon dioxide. This atmosphere is 90 times heavier than the Earth’s atmosphere which makes the atmospheric pressure at sea level on Venus 90 times that of Earth’s.

Atmosphere Since the atmosphere is mostly carbon dioxide, its atmosphere is highly toxic. This is because the carbon dioxide mixes with sulfur to create sulfur dioxide, which is acid rain. This make the atmosphere appear yellow. Clouds on Venus are so thick that they only let in 2% of the sunlight that strikes Venus. However, the atmosphere is so thick that all that heat is trapped creating a greenhouse effect.

Temperature on Venus Temperatures on Venus normally remain around 470 C which is 878 F.

Explorers of Venus In 1970 the first exploration on Venus occurred by the Russians. Their spacecraft called the Venera probe began to photo and mapped Venus’s surface

Magellan The US followed by sending the Magellan in 1990 which mapped the surface of Venus with intense radar. This showed the surface to have huge craters, faults, volcanoes with visible lava.

Mars 4th Planet from the sun

The Red Planet Revolution: 686.98 days Rotation: 24 hours, 37 minutes Diameter: 6794 km, or 4246.25 miles Orbital Speed: 24 .13 km/s 2 moons No rings 1.525 AU from sun

Why is it called the red planet? Iron oxide in the weathered rocks on its surface give it’s a reddish appearance. Mars also has polar ice caps that are visible and get larger during the Martian winter and shrink during the summer. Is it water? Yes and No- the southern polar ice cap is made of frozen carbon dioxide, the northern polar ice cap is made of water frozen into ice.

Mariner 9 Orbited Mars in 1971-1972 Revealed long channels that could have contained flowing water Found largest volcano in the solar system, Olympus Mons

Viking 1 1976 landed on Mars with 2 probes, and 2 orbiters The 2 orbiters Photographed the entire surface of Mars The 2 probes landed and conducted experiments. Found No Evidence of LIFE.                                                  

Atmosphere of Mars Much thinner than Earth’s Composed of mostly carbon dioxide, some nitrogen, and argon. This leads to temperature on the surface ranging from 35 C, 95 F to –170 C, -274 F. There are also strong winds storms that can cover the entire planet at one time.

Moons of Mars The moons of Mars are heavily cratered and very small Phobos is 25 km in diameter. It’s orbit is expected to have it impact Mars in 50 million years. Deimos is 13 km in diameter.

Phobos and Deimos Named for the Greek war god Ares Phobos means “fear” Deimos means “panic”

Olympus Mons

Polar Ice Caps of Mars