How Are Planets Alike
How are the solar system planets alike and how do they differ?
There are several similarities and differences for the 8 total planets in our solar system of Sol. The terrestrial planets are all composed of solid materials such as rock or silicate, contain metals throughout their crusts, and all possess a solid surface. Another similarity is that all travel around the sun in a oval, or elliptic, orbit, and at various eccentricities. Such planets all have few natural satellites due to the lesser gravitational fields when compared to the Jovian, which also doubles as proof of the unusual nature (it was a fragment of Earth) of the Earth's moon, especially its relative size.
Differences are numerous, largely due to each terrestrial's distance from the Sun. As a result, the temperatures on Mercury and Venus are much hotter, to the point that lead is liquid on the surface of the 2nd planet from the Sun. Size is also quite different with Mercury being the smallest and Earth the largest. All orbit the Sun at a different speed and also have a different number of hours in a day, with the Martian day being close to Earth relatively.
Similarities between the gas giants (Jovians) include all having small cores at their center and massive gravity necessary to maintain their largely gaseous structure. This will be a difficulty for future research opportunities, as the immense pressure that results from the gravity renders their small surfaces uninhabitable by lifeforms accustomed to Earth's level of pressure.
Jovians all have rings around them and are all much greater in size that terrestrial planets due to their compositions, and all possess multiple moons and satellites. Despite their size, they all are relatively light due to their small cores, to the point that Saturn would float if a large enough container of water could encompass it.
Differences are also largely based around size and distance traveled around the Sun, so this is actually also a similarity to terrestrials. Similarly, all planets were formed from the same coalescence of dust and matter from stellar nebulae.