The Solar System

'Inner planets' are traditionally defined as Mercury, Venus, Earth, and Mars.

This is because of a vast difference in orbital distances separating 'Inner' planets from the 'Outer' planets.

It has been theorized that the Asteroid Belt, between the orbits of Mars and Jupiter, is the remains of a fifth inner planet that was destroyed by collisions with other minor 'Planetoids' or asteroids. and earth is cool

The biggest planet in our solar system is Jupiter.Jupiter is the fifth planet from the sun and the largest in the solar system. Named after the ruler of the gods in Roman mythology, Jupiter has 1400 times the volume of Earth but only 318 times more mass. Thus, the mean density of Jupiter is about one-fourth that of Earth, indicating that the giant planet must consist of gas rather than the metals and rocks of which the Earth and other inner planets are composed.
Jupiter is the biggest planet in our Solar System.

It is the largest by mass, volume, and surface area among other statistics. Here are the critical measurements of Jupiter as well as a few other interesting facts about the planet and other bodies in the Jovian system.

Starting with mass, here are Jupiter's measurements: mass 1.8981 x 1027 kg, volume 1.43128 x 1015 km3, surface area 6.1419 x 1010 km2, and a mean circumference of 4.39264 x 105 km. Despite its size, it only has a density of 1.326 g/cm3, which is less than one fourth of Earth's density. The low density is one way scientists are able to determine that it is made mostly of gases and probably does not have a solid core.

Jupiter is not the largest possible planet in the Universe. TrES-4 is about 1.4 times the size of Jupiter. Scientist theorize that a gas gain could get 15 times the size of Jupiter before it began deuterium fusion, making it a brown dwarf star.

On Earth, we are fascinated by the auroras near the north and south poles. On Jupiter, the aurora activity is much more intense and rarely ever stops. The intense radiation, Jupiter's magnetic field, and the abundance of material from the moon Io's volcanoes in Jupiter's ionosphere create a light show that is spectacular yet would become commonplace if you lived there.

The Jovian system includes 63 acknowledged moons along with a few other theorized satellites. The four largest are called the Galilean satellites after their discoverer, Galileo Galilei. They include: Ganymede, the largest moon in our Solar System, Io, the most volcanically active body in our Solar System, Europa, which is suspected of having a massive subsurface ocean, and Callisto. Callisto is also thought to have a subsurface ocean and features some of the oldest surface material in the Solar System.

Jupiter has a violent atmosphere. Winds in the clouds can reach as high as 620 kph. Storms form within hours and can become thousands of km in diameter overnight. One storm, the Great Red Spot, has been raging since at least the late 1600s. The storm shrinks and expands, but has never gotten smaller than 20,000 km in diameter and can be seen from Earth with a medium-sized telescope.
Jupiter

Mars is home to the largest known canyon and mountain in our solar system. Answered by Alma Singleton

(The mountain is a volcano called Olympus Mons.)

1. Rocky Surface
2. Inside the Meteor Belt
3. Mercury, Venus, Earth, and Mars
4. Thin closer to the sun than outer planets are

1. Gas planets
2. Most are bigger planets ( other than Pluto)
3. Uranus, Saturn, Neptune, Jupiter, and Pluto.
4. Called Gas giants

Pluto is a dwarf planet

It's currently thought that Earth and the Moon formed around 4.5 billion years ago. The theory, called the giant impact theory, states that two planets - one named Proto-Earth, about 90% of the current size of Earth, and the other named Theia (after the mother of the Moon goddess in Greek mythology), about the size of Mars, suffered a huge collision. It wasn't a head-on collision though, it was a glancing blow. The impact would have melted both planets, fusing them together to form our present Earth. Theia's dense iron core sank to the centre of Proto-Earth and merged with it's core to form Earth's current core, while the lighter rocks of the two planets merged together to form a thick layer of rock around the core, Earth's mantle.

However, the force of the impact was so violent that it would have spewed up huge amounts of the new Earth's mantle into space. The pieces thrown out would have formed a ring around Earth for a short while, before they coalesced together to form the Moon.

All very well you might say, but where's the evidence that such a huge collision created the Earth and Moon?

• The Moon has roughly the same density, composition etc. as Earth's mantle, with no iron core (or at least a very small one). This makes sense if we consider it was formed from pieces of Earth's mantle thrown out during the giant impact.
• The Moon rocks examined by the Apollo astronauts contain oxygen isotopes in the same ratio as Earth's mantle, and nowhere else in the Solar System - strong evidence they formed in the same event, like the giant impact.
• The Moon contains few volatile elements (things that evaporate easily like potassium). As the ring of debris orbited Earth after the impact, it would have "dried out," i.e. all the volatiles evaporated out of the debris before it came together to form the Moon.
• We have seasons because Earth is tilted over. Earth's tilt is easy to explain if we assume it was knocked over by a giant impact when it formed.