Planets in the Solar System

Inner Planets: The Terrestrial Planets Terrestrial planets are Earth-like planets (in Latin, terra means Earth) made up of rocks or metals with a hard surface — making them different from other planets that lack a solid surface. Similar density to Earth (range from 3.9 to over 5.5 g/cm³) Terrestrial planets also have a molten heavy metal core, few moons, and topological features such as valleys, volcanoes and craters.

MERCURY It is the closest planet to the Sun, which makes it difficult to see from Earth. It is easiest to see it at sunset and sunrise. About one third the size of Earth and has no moons. Rotation period of 59 days and about 88 days to complete its orbit around the Sun. Atmosphere: Very Little, consisting mostly of OXYGEN, SODIUM, and HYDROGEN. Temperatures range from -173°C to 427°C (This is the largest day-night temperatura difference among the planets).

MERCURY Surface: Like the moon, it is covered with craters and plains. Planetwide system of cliffs calles scarps. Interior: There is no seismic activity which makes it hard to determine. Its high density suggests that it has a large nickel-iron core. Its small magnetic field indicates that some of its core is molten.

VENUS It is the second planet from the Sun and has no moons. It has the highest albedo (percentage of sunlight that is reflected by the surface of the planet). This, and its close proximity to Earth, makes it the brightest planet in the sky. There are thick clous around the planet, preventing astronomers from seeing the surface directly. They use radar technology to map the planet. In 2006, signs were found that indicate that Venus has been, and may still be, volcanically active. Retrograde rotation: Rotates slowly (243 Earth days) and clockwise.

VENUS The atmosphereic pressure is 92 times larger than Earth´s. The atmosphere is composed primarily of CARBON DIOXIDE and small amounts of NITROGEN and WATER VAPOR. Greenhouse effect: High concentration of CO₂ traps the infrared radiation (464°C) Interior: It is probable that the internal structure is similar to Earth´s. Astronomers theorize that Venus has a liquid metal core that extends halfway to the Surface. It has no measureable magnetic field, probably because of its slow rotation.

Compare Clouds in Earth and Venus Made of water vapor and ice Made of sulfuric acid (acid rain)

MARS Fourth planet from the Sun and has two moons (Phobos and Deimos). Mars is a planet that shows climate change on a large scale. Although its atmosphere used to be thick enough for water to run on the surface, today that water is either scarce or non-existent. The climate of Mars comes from a variety of factors, including its ice caps, water vapor and dust storms. At times, giant dust storms can blanket the entire planet and last for months, turning the sky hazy and red. The atmosphere of Mars is about 100 times thinner than Earth's, and it is 95 percent carbon dioxide. There is no Greenhouse Effect. Southern hemisphere: heavily cratered highland region. (Northern hemisphere has sparsely cratered plains). Largest volcano: Olympus Mons (three times higher than Mt. Everest).

MARS Tectonics: A great canyon (Valles Marineris) lies on the equator. It is 10 times the length of the Grand Canyon and more tan 3 times its depth. Erosional features: Suggest that liquid water once existed on the surface. Astronomers think that the atmosphere was once much warmer, thicker, and richer in carbon dioxide, allowing liquid water to run through the planet. Ice caps: Cover both poles on Mars. Both caps are made of carbon dioxide ice, sometimes called dry ice. Water ice lies beneath these ice caps. Interior: Its internal structure is still unknown. Because it has no magnetic field, astronomers think that the core is probably solid.