Astronomy 1

Weekly Quiz  In place of a quiz this week, you must be able to identify each inner planet and give several facts for each.  So pay attention!!!!

Inner Planets  The 4 inner planets are small and have rocky surfaces  They are known as the terrestrial planets  The are more similar to each other than they are to the outer planets  They all have a core, mantel and crust

Earth  3 rd planet from the sun  Has an atmosphere about 100km above the Earth’s surface that has about 20% oxygen and about 78% nitrogen  The atmosphere and temperature range is suitable for water to exist as a liquid  Approximately 70% is covered with water

Earth  Has enough gravity to hold most of the gas molecules (atmosphere)  Geologically active because the internal heat allows for plate tectonics

Mercury  Closest planet to the sun  Very small (not much larger than our moon)  Has no moons of its own  Geologically dead  Has an iron core  Very little is known about Mercury because it is so close to the sun  Mariner 10 was a space probe that flew by in , but only got a few pictures

Mercury  Very little atmosphere because the sun heated the gas particles and they escaped into space  Very extreme temperatures – sun side reaches 430°C and at night falls to -170°C (has the greatest temp range of all the planets)  Takes 88 days to complete one revolution

Venus  2 nd planet from the sun  Venus can often times be seen easily on Earth – it appears to be a star, but is not because it is reflecting light from the sun  It is the evening star because it can be seen in the west at sunset and the morning star because it can be seen in the east at sunrise  It is known as the Earth’s twin because it is similar is size and composition; however, it is very different in other aspects

Venus  Takes about 7.5 Earth months to revolve around the sun and about 8 months to rotate in its axis So that means that a day on Venus is longer that a year on Venus!  It rotates opposite of other planets and moons in the solar system It rotates from east to west This is called retrograde rotation

Venus  Has a very thick atmosphere – so thick that there is never a sunny day on Venus  This causes the pressure to be 90 times greater than on Earth (it would crush you like a can!)  The clouds are partly sulfuric acid  Has volcanoes, but no other evidence of plate tectonics

Venus  Also because of the thick atmosphere the greenhouse effect is magnified on Venus  The average surface temperature is 460°C  We have had more visits to Venus than any other planet – 19 spacecrafts – one even landed on the surface, but only survived for 23 minutes  Scientists have mapped the surface of Venus and found many volcanoes and strange domes

Mars  4 th planet from the sun  Called the “Red Planet” because it is red from the iron in the soil  The atmosphere is mostly carbon dioxide (similar to Earth before life evolved)  Has on about 1% of the pressure Earth has  Has clouds, but only very thin ones

Mars  Mars is much colder than Earth because it is farther from the sun  The south pole of Mars has frozen carbon dioxide or dry ice  Mars has a tilted axis like Earth, therefore it has seasons like Earth  Many spacecrafts have been sent to Mars – a few have landed and traveled on Mars

Mars  Those probes are still on Mars – that is why there have been no manned mission because scientists are unsure of how to safely return back to Earth  Mars has two very small moons Phobos is only 27km wide (a car could travel across it in 15 minutes) Deimos is only 15km wide Both are covered in craters

Mars  Temperatures range from 35°C to -170°C  There are strong winds that blow across the surface of Mars  Last volcanic eruption was around 100 million years ago  Olympus Mons is the largest volcano in the solar system