Topic 2 - the lunar disc

• What is the mean diameter of the moon?

  3500km
• The Moon's surface features are caused by volcanism, tectonics, impact craters and lava flows
• Volcanoes on the Moon were formed when magma rose to the surface through fissures (cracks) in the crust.
• What shape is the moon?

  Oblate spheroid
• Is the moon a natural satellite of Earth?

  Yes.
• What are Maria?


  Dark areas on the moon
• What percentage of the lunar surface is classed as Maria?


  17%
• What is terrae?


  highlands on the moons surface (brighter areas)
• Why do maria appear darker?

  they contain more iron-rich elements
• Which side of the moon are there more maria?

  Near side
• How were Maria formed?

  lava flowing into ancient impact basins
• What can meteorites or comets colliding with the moons surface cause?

  Craters
• When are craters thought to have formed?

  during the moons early evolution
• Can volcanic activity form craters?

  Yes.
• What are some features of a crater?

  Raised rim

  rampart (slope)

  crater floor

  central peak
• What are rays?


  bright streaks that spread out in different directions from the craters
• How are rays formed?


  Surface material ejected from the crater during an impact
• Where can most mountains on the lunar surface be found?

  bordering maria
• How do mountains form on the lunar surface?


  By impacts that released magma under the early lunar surface
• What are long depressions on the moons surface called?

  valleys
• How do valleys form?

  by ancient lava flows, collapsed lava tubes or geological faults
• How long does the moon take to orbit the earth?

  27.3 days
• The orbit and rotational period of the moon are identical
• What is meant by a synchronous rotation?

  Rotation at the same rate as orbit, showing the same face to the body it orbits.
• What is a sidereal month?

  The time the moon orbits the earth in respect to the stars
• How long is a sidereal month?

  27.32 days
• What is a synodic month?

  the period between the same phase of the moon.
• How long is a synodic month?

  29.5 days
• The moon was closer to the earth and spun on its axis more quickly.
• What has slowed down the moon's rotation?

  tidal forces
• The side we see is known as...?

  the near side
• The side we cannot see is known as...?

  the far side
• What are some features of the far side?

  fewer maria

  thicker crust

  more craters
• How can we see up to 59% of the moon surface?


  libration
• What is the co-accretion theory?

  The moon formed at the same time as the earth in a similar place
•  The Moon evolved in a different part of the Solar System and was captured by Earth's gravity is known as...?

  capture theory
• What is fission theory?

   The Earth spun rapidly during its early evolution and Earth material flung out to form the Moon.
• A Mars size object crashed into the early Earth, changing its axis and jettisoning debris into its orbit and the Moon formed from this, is known as the...?

  Giant Impact theory
• What is one piece of evidence that supports the giant impact theory?

   the Moon is made of similar material and rock as the Earth
• Why is the accretion theory flawed?

  does not explain why the moon has a smaller iron core or the angle and elliptical path of the moon's orbit