Topic 1.2 - The Moon 0.0 / 5 ? AstronomyThe MoonGCSEEdexcel Created by: goldstar3Created on: 29-05-18 11:44 B) Diameter + Approx Distance Diameter: 3500 km Approx distance: 380,000 km 1 of 12 C) Rotational & Orbital Periods Orbital period: 27.3 days Rotational period: 27.3 days Cycle of phases: 29.5 days 2.2 days needed to return to same position relative to Sun 2 of 12 D) Far side appearance More craters No large seas Very mountainous Luna 3 launched by Russians - 1959 Space probes photograph far side so we know about it 3 of 12 E) Far side not visible from Earth 1 orbit of Earth = 1 full turn 1 Moon 'year' = 1 Moon 'day' 4 of 12 F) Distinguish between seas + highlands Maria are smooth dark grey plains Cover 15% of surface Many almost circular e.g. Sea of Crises Lack of craters suggest youth Terrae are light grey Found in rugged highland regions 5 of 12 G) Origin of seas and craters Seas are volcanic features Were low impact basins where lava flowed and solidified Craters mostly formed from meteoric impact Shock waves caused projectile to vapourise & material below to condense Crust pushed up + out forming rim Many surrounded by rays of material ejected during formation 6 of 12 H) Relative no. of craters implies age Maria are younger than terrae as they have less craters 7 of 12 I) Nature of Rilles & Wrinkle Ridges Rilles: Narrow trenches less than 5km wide Few hundred metres deep 100kms long Straight Faults in lunar crust Sinuous: channels where lava once flowed Wrinkle ridges: elevations up to 200m high in maria 100kms long Up to 30km wide Formed when maria lava cooled & contracted 8 of 12 J) Lack of atmosphere Gravitational field strength is 1/6 of Earth's No atmosphere to scatter sun's light Low surface gravity explains no atmosphere 9 of 12 K) Nature & Purpose of Apollo programme Announced by John F Kennedy in 1961 Main aim: to land a man on the Moon and return him safely to Earth First orbit was Apollo 8 First landing: Apollo 11 in Sea of Tranquility (22hr mission) rock & soil collected ALSEPs: magnetometer to detect lunar magnetic field particle detector to analyse solar wind seismometer to study moonquakes Powered by RTG 12 astronauts walked on the Moon Last mission - Apollo 17 Apollo 13 didn't land due to explosion but made it home 10 of 12 L) Likely origin of the Moon There are various theories: The Moon evolved elsewhere & was captured by Earth's gravity (capture hypothesis) Formed near the Earth (condensation hypothesis) Earth spun rapidly during formation & material flung out formed the moon (fission hypothesis) Most likely: Giant impact hypothesis A gigantic off centre collision between the Earth & Theia Earth's outer layers melted and merged Earth debris was thrown into Earth orbit Cooled to form the Moon 11 of 12 M) Evidence of Giant Impact Hypothesis Relative abundances of isotopes of oxygen almost identical to Earth's Suggest they were formed at the same time Lack of water and other compoinds is similar to the Earth's mantle, these vapourised in the Moon's formation KREEP rich rocks 12 of 12
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