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Mercury
Mercury is a heavily cratered planet; its surface is similar to the surface of our Moon. Cratering on Mercury triggered volcanic eruptions that filled much of the surrounding area. Mercury does have a magnetic field (probably generated by a partly-liquid iron core). -
Venus
Venus is also known as the "morning star" or the "evening star" since it is visible and quite bright at either dawn or dusk. It is only visible at dawn or dusk since it is closer to the sun than we are. Like the moon, Venus' appearance from Earth changes as it orbits around the Sun. It goes from full to gibbous to crescent to new and back. -
Venus
The Earth is about 7,926 miles (12,756 km) in diameter. The Earth is the fifth-largest planet in our Solar System (after Jupiter, Saturn, Uranus, and Neptune).
Eratosthenes (276-194 BC) was a Greek scholar who was the first person to determine the circumference of the Earth. He compared the midsummer's noon shadow in deep wells in Syene (now Aswan on the Nile in Egypt) and Alexandria. He properly assumed that the Sun's rays are virtually parallel (since the Sun is so far away). Knowing the dist -
Mars
The surface of Mars is dry, rocky, and mostly covered with iron-rich dust. There are low-lying plains in the northern hemisphere, but the southern hemisphere is dotted with impact craters. The ground is frozen; this permafrost extends for several kilometers. -
Jupiter
Jupiter's diameter is 88,700 miles (142,800 km). This is a little more than 11 times the diameter of the Earth. Jupiter is so big that all the other planets in our Solar System could fit inside Jupiter (if it were hollow). -
Saturn
Saturn's beautiful rings are only visible from Earth using a telescope. They were first observed by Galileo in the 17th century. Saturn's bright rings are made of ice chunks (and some rocks) that range in size from the size of a fingernail to the size of a car. Although the rings are extremely wide (over 1 million km in diameter), they are very thin (about 0.6 miles = 1 km thick). -
Uranus
Uranus' mass is about 8.68 x 1025 kg. This is about 14 times the mass of the Earth. The gravity on Uranus is only 91% of the gravity on Earth. This is because it is such a large planet (and the gravitational force a planet exerts upon an object at the planet's surface is proportional to its mass and to the inverse of its radius squared). A 100-pound person on Uranus would weigh 91 pounds. -
Neptune
Neptune is about 30,775 miles (49,528 km) in diameter. This is 3.88 times the diameter of the Earth. If Neptune were hollow, it could hold almost 60 Earths. Neptune is the fourth largest planet in our Solar System (after Jupiter, Saturn, and Uranus). -
Pluto
Neptune is about 30,775 miles (49,528 km) in diameter. This is 3.88 times the diameter of the Earth. If Neptune were hollow, it could hold almost 60 Earths. Neptune is the fourth largest planet in our Solar System (after Jupiter, Saturn, and Uranus).
