Planets

M E R C U R Y

Mercury is the smallest planet in our solar system. It’s just a little bigger than Earth’s moon. It is the closest planet to the sun, but it’s actually not the hottest. Venus is hotter.

Along with Venus, Earth, and Mars, Mercury is one of the rocky planets. It has a solid surface that is covered with craters. It has a thin atmosphere, and it doesn’t have any moons. Mercury likes to keep things simple.

This small planet spins around slowly compared to Earth, so one day lasts a long time. Mercury takes 59 Earth days to make one full rotation. A year on Mercury goes by fast. Because it’s the closest planet to the sun, it doesn’t take very long to go all the way around. It completes one revolution around the sun in just 88 Earth days. If you lived on Mercury, you’d have a birthday every three months!

(This is Mercury's northern horizon as seen by
the MESSENGER spacecraft during its third flyby.)

A day on Mercury is not like a day here on Earth. For us, the sun rises and sets each and every day. Because Mercury has a slow spin and short year, it takes a long time for the sun to rise and set there. Mercury only has one sunrise every 180 Earth days! 

(Retrieved from: https://spaceplace.nasa.gov/all-about-mercury/en/)

V E N U S

Venus is the second planet from the sun, is named for the Roman goddess of love and beauty. The planet — the only planet named after a female — may have been named for the most beautiful deity of her pantheon because it shone the brightest of the five planets known to ancient astronomers.

In ancient times, Venus was often thought to be two different stars, the evening star and the morning star — that is, the ones that first appeared at sunset and sunrise.

(Venus in close up)

Venus is the hottest world in the solar system. Although Venus is not the planet closest to the sun, its dense atmosphere traps heat in a runaway version of the greenhouse effect that warms Earth. As a result, temperatures on Venus reach 870 degrees Fahrenheit (465 degrees Celsius), more than hot enough to melt lead. Probes that scientists have landed there have survived only a few hours before being destroyed. 

(Retrieved from: http://www.space.com/44-venus-second-planet-from-the-sun-brightest-planet-in-solar-system.html)

E A R T H

Earth is a rocky, terrestrial planet. It has a solid and active surface with mountains, valleys, canyons, plains and so much more. Earth is special because it is an ocean planet. Water covers 70% of Earth's surface. It is the only planet in our solar system that supports life.

A day on earth lasts a little a little under 24 hours. One year on earth lasts 365. 25 days. That extra 0. 25 extra means every four hours we need to add one day in our calendar. We call it a leap day (in a leap year).

(This Apollo 11 picture taken by an astronaut in 1969
shows the Earth rising over the moon.)

The earth's atmosphere is made mostly of nitrogen and has plenty of

oxygen for us to breathe. The atmosphere also protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface as meteorites.

(Retrieved from:https://spaceplace.nasa.gov/all-about-earth/en/)

M A R S

( NASA's Mars Exploration Rover Opportunity took this picture
with its panoramic camera near "Solander Point" on Mars.)

Mars is a cold desert world. It is half the size of Earth. Mars is sometimes called the Red Planet because of the rusty iron in the ground. It has 2 moons: Phobos and Deimos.

Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons, and weather. It has a very thin atmosphere made of carbon dioxide, nitrogen, and argon.

There are signs of ancient floods on Mars, but now water mostly exists in icy dirt and thin clouds. On some Martian hillsides, there is evidence of liquid salty water in the ground.

Scientists want to know if Mars may have had living things in the past. They also want to know if Mars could support life now or in the future. We have sent 20 spacecraft to visit Mars and Mars is the planet that we've sent rovers too. They drive around Mars, taking pictures and measurements.

(Retrieved from: https://spaceplace.nasa.gov/all-about-mars/en/)

J U P I T E R

Jupiter is the biggest planet in our solar system. It's similar to a star, but it never got big enough to start burning. It is covered in swirling cloud stripes. It has big storms like the Great Red Spot, which has been going for hundreds of years. Jupiter is a gas giant and doesn't have a solid surface, but it may have a solid inner core about the size of Earth. Jupiter also has rings, but they're too faint to see very well.

(This picture taken by Voyager 2 shows the Great Red Spot.)

Jupiter is a gas giant. It's made mostly of Hydrogen and Helium. It also have a thick atmosphere. One day on Jupiter goes by in just 10 hours and one year in Jupiter is the same as 11.8 Earth years. 

(Retrieved from: https://spaceplace.nasa.gov/all-about-jupiter/en/)

S A T U R N 

Saturn isn’t the only planet to have rings, but it definitely has the most beautiful ones. The rings we see are made of groups of tiny ringlets that surround Saturn. They’re made of chunks of ice and rock. Like Jupiter, Saturn is mostly a ball of hydrogen and helium.When Galileo Galilei saw Saturn through a telescope in the 1600s, he wasn't sure what he was seeing. At first he thought he was looking

(The Cassini spacecraft took this picture of Saturn's
rings. You can see the grey and tan colors.)

at three planets, or a planet with handles. Now we know those "handles" turned out to be the rings of Saturn.

One day on Saturn lasts 10.7 hours and one year on Saturn is the same as 29.5 earth years. Saturn has 53 moons. It also has 9 unconfirmed moon we need to learn more about. 

(Retrieved from: https://spaceplace.nasa.gov/all-about-saturn/en/_)

U R A N U S

Uranus was discovered bin 1781 by William Herschel in Great Britain. Uranus is made of water, methane, and ammonia fluids above a small rocky center. Its atmosphere is made of hydrogen and helium like Jupiter and Saturn, but it also has methane. The methane makes Uranus blue.


Uranus also has faint rings. The inner rings are narrow and dark. The outer rings are brightly colored and easier to see. Like Venus, Uranus rotates in the opposite direction as most other planets. And unlike any other planet, Uranus rotates on its side.

(This picture shows Uranus surrounded by its four major rings and
by 10 of its moons. This image has colors added to show the
different altitudes and thicknesses of clouds in the atmosphere.)

One day on Uranus lasts a little over 17 hours and one year on Uranus is the same as 84 earth years. It has 27 moons. 

(Retrieved from: https://spaceplace.nasa.gov/all-about-uranus/en/

N E P T U N E

Neptune is dark, cold, and very windy. It's the last of the planets in our solar system. It's more than 30 times as far from the sun as Earth is. Neptune is very similar to Uranus. It's made of a thick soup of water, ammonia, and methane over an Earth-sized solid center. Its atmosphere is made of hydrogen, helium, and methane. The methane gives Neptune the same blue color as Uranus. Neptune has six rings, but they're very hard to see.One day in Neptune goes by 16 hours and Neptune has such a long

(Clouds streak across Neptune.)

journey around the sun it takes 164 earth hours to go around once. It was discovered in 1864 by Urbain Le Verrier, John Couch Adams and Johann Gale. Only Voyager 2 has visited Neptune.

(Retrieved from: https://spaceplace.nasa.gov/all-about-neptune/en/)