Planets

6.E.1.2 Explain why Earth sustains life while other planets do not based on their properties (including types of surface, atmosphere and gravitational force) and location to the Sun.

The Inner Planets• The inner four planets are called terrestrial

planets. That means that they are like the Earth in some ways. The terrestrial planets Mercury, Venus, Earth, Mars, and the Earth's moon have similar compositions and densities. These planets are close to the sun, rocky, and dense. They are fairly small. They have few moons and no rings. Their environments are oxidized; that is, oxygen dominates the chemistry. Meteors, tectonic activity, and erosion have modified the surfaces of the terrestrial planets.

The Inner Planets(Cont.)

• The atmospheres of the terrestrial planets have changed as a result of sunlight (which produces chemical reactions, such as those that break apart water molecules), escape of light gases, volcanic activity, and in the case of our planet, biological activity.

The inner planets take up only a small part of the solar system. Note that sizes and distances are not drawn to scale.

Venus

Mercury• Mercury is the smallest terrestrial planet and the

planet closest to the Sun, but surprisingly not the hottest. Because it has almost no atmosphere, there is no greenhouse effect to trap the heat, so temperatures vary from extreme hot to extreme cold. In fact it has the widest day/night temperature change in the solar system. Its surface of craters resembles the Moon because it has been bombarded by comets etc. The planet was named for the Roman god Mercury, a winged messenger, and it travels around the Sun faster than any other planet. Mercury is difficult to see from Earth.

Mercury

Facts about Mercury• Size: 0.382 the diameter of Earth; • Diameter: 3,032.4 miles (4,880 km) • Atmosphere: A thin mixture of helium (95%) and hydrogen • Temperature: The sunlit side can reach up to 950°F (510°C) and the

dark side can drop as low as -346°F (-210° C), avg day temp = 662°F, avg night temp= -274°F

• Rotation (1 Day) = 59 Earth days • Revolution (1 Year) = 88 Earth days • Your weight: If you weigh 100 pounds on Earth, you would weigh 38

pounds on Mercury. • Distance from Earth: 57 million miles, at the closest point in its orbit • Mean Distance from Sun: 36 million miles (57.9 million km) • Satellites (moons): 0 • Rings: 0

Venus• Venus is the brightest planet in the sky because it is very

reflective - it is covered in clouds. The clouds are made of droplets of sulfuric acid. It has a tremendous greenhouse effect that does not allow the heat to escape leaving the temperature to hover around 880°F which makes it the hottest planet in the solar system. The extremely high temperature of Venus’s surface is due to the greenhouse effect. Venus is often called Earth's twin because the two planets are close in size, but that's about the only similarity. Venus' rotation is not only extremely slow but it is also backward or retrograde. Venus is named after the Roman goddess of love and beauty and appears as a bright, white disk from Earth.

Venus

Facts about Venus• Size: About 650 miles smaller in diameter than Earth • Diameter: 7,519 miles (12,100 km) • Surface: A rocky, dusty, waterless expanse of mountains, canyons,

and plains, with a 200-mile river of hardened lava • Atmosphere: Carbon dioxide (95%), nitrogen, sulfuric acid, and

traces of other elements • Rotation (1 day) = 243 Earth days (retrograde rotation or

"backward") • Revolution (1 year) = 225 Earth days • Your weight: If you weigh 100 pounds on Earth, you would weigh 88

pounds on Venus. • Satellites (moons): 0 • Rings: 0

Earth

• Earth is the third planet from the sun. It is 5.5 times more dense than water on average. Its inner core is made up of solid iron with a molten outer core that produces it's magnetic field. Earth's atmosphere is made up of 78% Nitrogen, 21% Oxygen, and traces of other elements. Our greenhouse effect regulates the temperature on Earth and is essential for our survival. Also, Earth is not perfectly round; it bulges at the equator and is flatter at the poles.

Earth

Facts about Earth

• Size: Four planets in our solar system are larger and three are smaller than Earth

• Diameter: 7,926.2 miles (12,756 km) • Surface: Earth is made up of water (70%), air, and solid

ground. It appears to be the only planet with water that has an atmosphere.

• Atmosphere: Nitrogen (78%), oxygen (21%), other gases • Rotation of its axis: 24 hours • Rotation around the Sun: 365.25 days • Mean Distance from Sun: 92.9 million miles (149.6

million km) • Satellites (moons): 1 • Rings: 0

Mars

• Mars is the fourth planet from the Sun, situated between Earth and Jupiter. The surface of Mars contains silicon dioxide and iron oxide. The iron oxide is rust, which gives it a reddish color. Mars has two moons Phobos and Deimos. Like our moon, the two moons keep the same side toward Mars as they revolve around the planet. They are small and appear to be captured asteroids. Mars has the largest volcanic mountain in the solar system, Mt. Olympus, which is 2.5 times the size of Mt. Everest. The poles of Mars are covered with frozen water and frozen carbon dioxide producing white polar ice caps. There can be no liquid water due to the thin, low pressure atmosphere which allows water to vaporize.

Mars

Facts about Mars• Size: About one-half the size of Earth in diameter • Diameter: 4,194 miles (6,794 km) • Surface: Canyons, dunes, volcanoes, and polar caps of water ice • Atmosphere: carbon dioxide (95%) • Temperature: as low as -305°F (-187°C) • Rotation of its axis: 24 Earth hours, 37 minutes • Rotation around the Sun: 687 Earth days (almost 2 Earth years) • Your weight: If you weigh 100 pounds on Earth, you would weigh 38

pounds on Mars. • Distance from Earth: 35 million miles (56 million km) at the closest

point in its orbit • Mean Distance from Sun: 141.71 million miles (227.9 million km) • Satellites (moons): 2 • Rings: 0

Asteroid Belt

• A belt of asteroids (fragments of rock and iron) between Mars and Jupiter separate the four inner planets from the four outer planets.

The Outer Planets

• The four planets farthest from the sun—Jupiter, Saturn, Uranus, and Neptune—are called the outer planets of our solar system. Because these planets are much larger than Earth and the other inner planets, and because they are made primarily of gases and liquids rather than solid matter, the outer planets are also called gas giants.

The Outer Planets(Cont.)

• The gas giants are made up primarily of hydrogen and helium, the same elements that make up most of the Sun.

The Outer Planets(Cont.)

• Astronomers believe that hydrogen and helium gases were found in large amounts throughout the solar system when it first formed. However, the inner planets didn't have enough mass to hold on to these very light gases. As a result, the hydrogen and helium initially on these inner planets floated away into space. Only the Sun and the massive outer planets had enough gravity to keep hydrogen and helium from drifting away.

• All of the outer planets have numerous moons. All of the outer planets also have planetary rings, which are rings of dust and other small particles encircling a planet in a thin plane. Only the rings of Saturn can be easily seen from Earth.

Jupiter

• Jupiter is the largest planet in the solar system. Its diameter is about 11 times that of Earth. You could fit over 1,000 Earths inside! It is a giant ball of gas with no solid surface. It does however have a liquid center due to the high pressures forcing it into a liquid and a small solid core. Jupiter has 63 natural satellites (or moons). The largest four are Io, Europa, Ganymede, and Callisto. Viewed through a large telescope, Jupiter is stunningly colorful and looks like a disk covered with bands of blue, brown, pink, red, orange, and yellow. Its most distinguishing feature is the Great Red Spot, an intense, giant windstorm larger in size than Earth, which has continued for centuries without any signs of dying down.

Jupiter

Facts about Jupiter• Size: 11 times the diameter of Earth • Diameter: 88,736 miles (142,800 km) • Surface: A hot ball of gas and liquid • Atmosphere: Whirling clouds of colored dust, mainly of hydrogen

and helium, and small amounts of methane, water, and ammonia. • Temperature: -234°F (-148°C) average • Rotation of its axis: 9 hours and 55 minutes • Rotation around the Sun: 12 Earth years • Weight: If you weigh 100 pounds on Earth, you would weigh 265

pounds on Jupiter. • Distance from Earth: At its closest, 370 million miles (591 million

km) • Mean Distance from Sun: 483.88 million miles (778.3 million km) • Satellites: 63 • Rings: 4

Saturn

• Saturn is the second-largest planet and has majestic rings surrounding it. Saturn's seven rings are flat and lie inside one another. They are made of rock and billions of ice covered particles so they are not solid bodies they are orbiting debris. Ice reflects light, that is why they are so bright and we can see them through a regular telescope from Earth. Saturn's density is lighter than water (0.7) which means if you had a body of water big enough to hold it, it would float! It's composition is 73% Hydrogen and 26% Helium and 1% other which is similar to both Jupiter and the sun.

Saturn

Facts about Saturn• Size: About 10 times larger than Earth in diameter • Diameter: 74,978 miles (120,660 km) • Surface: Liquid and gas • Atmosphere: Hydrogen and helium • Temperature: -288°F (-178°C) • Rotation of its axis: 10 hours, 40 min • Rotation around the Sun: 29 Earth years! • Your weight: If you weigh 100 pounds on Earth, you would weigh

107 pounds on Saturn. • Distance from Earth: 744 million miles at the closest point • Average distance from Sun: 887.14 million miles (1,427 million km) • Satellites (moons): 40+ • Rings: 1,000?

Uranus

• Uranus is a greenish-blue planet, twice as far from the Sun as its neighbor Saturn. It's axis of rotation is sideways and it takes 84 years to revolve around the sun! It has approximately 20 years of daytime and 20 years of nighttime because one pole faces the sun for a couple of decades and then the other for a couple. Uranus wasn't discovered until 1781 by William Herschel.

Uranus

Facts about Uranus• Size: 4 times larger than Earth in diameter • Diameter: 32,193 miles (51,810 km) • Surface: Little is known • Atmosphere: Hydrogen, helium, and methane • Temperature: uniform temperature of -353°F (-214°C) • Rotation of its axis: 17 hours • Rotation around the Sun: 84 Earth years • Distance from Earth: At the closest point, 1,607,000,000 miles • Mean Distance from Sun: 1,784 million miles (2,870 million km) • Satellites: 27 • Rings: 11

Neptune

• Neptune, the 8th planet from the sun, is named for an ancient Roman sea god, and is a stormy blue planet about 30 times farther from the Sun than Earth.

• The Voyager 2 spacecraft flew by Neptune in 1989. It showed that the planet is, basically, a twin of Uranus based on its size, density, and chemical composition. Like Uranus, Neptune is distinctly colored light blue, from the CH4 in its atmosphere. Neptune's period of revolution is 165 years.

Neptune

Facts about Neptune• Size: Almost 4 times the size of Earth in diameter • Diameter: 30,775 miles (49,528 km) • Surface: A liquid layer covered with thick clouds and with constant,

raging storms • Atmosphere: Hydrogen, helium, methane, and ammonia • Temperature: -353°F (-214°C) • Rotation of its axis: 16 hours • Rotation around the Sun: 165 Earth years • Distance from Earth: 2,680,000,000 miles at closest point • Mean Distance from Sun: 2,796.46 million miles (4,497 million km) • Satellites: 13 • Rings: 4

Pluto

• Pluto was the coldest, smallest, and outermost planet in our solar system.

• During each revolution around the sun, Pluto passes inside Neptune's orbit for 20 years, making Neptune the outermost planet for that time.

• We now realize that it is among many other objects in the Kuiper Belt and it doesn't fit the new "planet" definition. It is now called a "dwarf planet".

Pluto

Facts about Little Pluto• Size: Less than one-fifth the size of Earth in diameter • Diameter: 1,423 miles? (2,290 km?) • Surface: A giant snowball of methane and water mixed with rock • Atmosphere: Methane • Temperature: between -369° and -387°F (-223° and -233°C) • Rotation of its axis: 6 days, 9 hours, 18 minutes • Rotation around the Sun: 248 Earth years • Distance from Earth: At the closest point, 2.67 billion miles • Mean Distance from Sun: 3,666 million miles (5,900 million km) • Satellites: 3

Questions

Which planet is closest to the Sun?

A. Earth

B. Mars

C. Mercury

D. Venus

Which planet is most similar in composition to Earth?

A. Jupiter

B. Neptune

C. Saturn

D. Venus

Which property makes Earth unique compared to other planets in the solar system?

A. It orbits the Sun.

B. It has liquid water.

C. It is a rocky planet.

D. It rotates on its axis.

THE END!!!