Discovering Planets & Moons

Discovering Planets & Moons — page 3 — WHY DO WE EXPLORE SPACE Humans are explorers by nature and that desire to explore extends far beyond the boundaries of Earth But our own curiosity is not the only reason to care about what happens in space Our lives are ruled by the Sun and Moon the Sun’s rays heat our planet the Moon’s gravity controls the ocean’s tides and together they set our days and nights Also important is the fact that other objects in space are not stationary and are constantly moving around our planet understanding the objects in the universe and their location helps us to better understand our own planet Although we have not yet found evidence of life on other planets scientists hope to determine if there are other planets that could support life This doesn’t just mean looking for aliens It means that scientists are looking for planets with appropriate temperatures a stable atmosphere and sufficient water together these three things would allow plants or people to grow and thrive As of now humans could not live on any other planet but scientists are always looking to see whether it would be possible Space is made up of matter and elements many of which are also present on Earth In our own ever changing climate however it is important for us to understand the different matter and forces in the universe that could have the potential to give us new forms of energy Our Sun center and its solar system from left to right Pluto a dwarf planet Neptune Uranus Saturn Jupiter Mars Earth Venus and Mercury 6

Discovering Planets & Moons — page 4

Discovering Planets & Moons — page 5 — Mercury SIZE radius 1,516 miles 2,439 7 km MOONS 0 DISTANCE FROM SUN 36 million miles 58 million km TIME TO ORBIT SUN 1 year 88 Earth days COSMIC DATA Like Venus Earth and Mars Mercury is a terrestrial planet Its rocky surface has lots of craters and looks similar to the surface of Earth’s Moon Mercury is an incredibly hot planet during the day and extremely cold at night daytime temperatures can reach 800 degrees Fahrenheit 430 degrees Celsius and at night the temperature can drop to 290 degrees Fahrenheit 180 degrees Celsius One day on Mercury the time it takes for the planet to rotate once takes about 59 Earth days 8

Discovering Planets & Moons — page 6 — Planets According to the International Astronomical Union in order for an object in space to be considered a planet it must orbit a sun but it cannot be a moon of another space object A planet must also be round and large enough to move objects such as asteroids and comets out of its way to continue its orbit Because of the last reason Pluto formerly considered a planet was renamed to the dwarf planet category in 2006 Our solar system has eight objects that are officially classified as planets and are typically ordered by how far away they are from the Sun Mercury Venus Earth Mars Jupiter Saturn Uranus and Neptune There are three different types of planets in our solar system terrestrial gas giant and ice giant The first four planets from the Sun Mercury Venus Earth and Mars are terrestrial planets This type of planet has a rocky solid surface The next two planets Jupiter and Saturn are gas giant planets The opposite of terrestrial planets the gas giant planets are mostly made up of gas The last two planets Uranus and Neptune are ice giant planets because they are primarily made up of ice Mercury is the smallest of the eight planets and is closest to our Sun 9

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