Astronomy :Moon and Mercury Notes

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Astronomy Moon and Mercury Notes

• MOON
• Average of 384,000km from Earth.
• Orbit period 27.3 days
• Rotation period 27.3 days.
• Surface gravity 1.62 m/s/s (1/6th of Earth)
• Density 3.3 g/cm3

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Moon Cont

• Axial tilt 6.7 degrees
• Mass 7.35 x 1022kg or .012 of Earths mass.
• Surface Temperature
• 100 K 400 K
• -173 C --- 127 C
• Atmosphere no atmosphere noted on the Moon.

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Surface Features

• Maria flat areas of the moons surface.
• Highlands elevated surfaces which appear lighter
• Craters features formed by meteoritic impact

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Maria

• The 14 Maria have Latin names.
• They include Mare Imbrium (Sea of Showers) Mare
  Nubium (Sea of Clouds) Mare Nectaris (Sea of
  Nectar)

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Rotation of the Moon

• The moon has a synchronous orbit which means its
  own rotation is equal to the period it rotates
  the earth.
• The moon keeps the same side facing earth at all
  times.

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Moons Shape

• The moon is slightly elongated due to the tidal
  effect of Earths gravitational field.

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Lunar Cratering

• Although there is no wind, water, or tectonic
  plates on the moon there is some erosion.
• The erosion comes from meteoritic impacts on the
  moon.

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Crater Formation

• A 1kg object traveling 10 km/s can release as
  much energy as the detonation of 10 kg of TNT.
• The resulting craters diameter is approximately
  10 times greater than the meteoroid that struck
  the moon.

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Crater Formation

• Most craters on the moon are there due to meteor
  impacts.
• Some craters are due to volcanic activity.
• There is no longer volcanic activity on the moon.

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Cratering rates

• A 10 km Crater is formed about once in 10 million
  years.
• A meter sized crater is created once a month.
• Centimeter sized craters are formed every few
  minutes.

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Lunar Surface Composition

• The highlands are made of rocks rich in aluminum.
  They are lighter in color, and lower in density
  than the marias basaltic matter. It contains
  more iron w/ higher density.

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Lunar dust

• The moon is covered by dust similar to talcum
  powder. Its average depth is 20 meters.
• Scientists believe this dust is from ejecta
  material from meteoritic impacts.

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Volcanism on the Moon

• There was volcanic activity early in the moons
  development, but all rock samples taken from the
  moon have been carbon dated to over 3 Billion
  years old. This seems to indicate volcanic
  activity stopped before that.

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Interior of the Moon

• Scientists believe the moon has four main layers
  the core, Asthenosphere, lithosphere, and the
  crust.

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Origins of the Moon

• The Sister Theory (Coformation)- Both the Earth
  and Moon evolved at the same time from the same
  matter in the vicinity.
• The Capture Theory- The moon was captured by the
  Earths gravitational field.
• The Daughter Theory- The Earth was spinning so
  fast the moon material was ripped out of it.
• Impact Theory- A Mars-sized object had a glancing
  blow with the Earth. Material was ejected forming
  the moon.

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Impact Theory
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The Capture Theory
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The Co-Formation Theory
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Moon Phases
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The Moon and Tides
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Tides Continued
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Moon Views
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Mercury

• The angular distance between Mercury and the Sun
  is never greater than 28 degrees.
• It can only be seen without a telescope just
  before dawn or just after sunset, and during a
  solar eclipse.

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Mercury

• The mass of Mercury is 3.3 x 10 23 kg which is
  about .055 Earth masses.
• Mercurys average density is 5400 kg/cubic meter
  only slightly less than Earths.

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Atmosphere

• Mercury has no appreciable atmosphere.
• Its low gravitational field does not have the
  force needed to maintain an atmosphere.

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Mariner 10

• In 1974, Mariner 10 approached within 10,000 km
  of Mercurys surface.
• The pictures taken showed no signs of clouds,
  rivers, dust storms, or other aspects of weather.

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Cratering of Mercury

• Mercury has many craters. Many of those craters
  are double-ringed. The reason for this is not yet
  understood.

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Orbit

• Mercury has three rotations for every two
  revolutions.
• This is called 32 spin-orbit resonance.

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Mercurys Scarps

• Mercury has scarps or (cliffs) that have formed
  due to the interior of the planet cooling. This
  is similar to the wrinkles formed on the skin of
  an old shrunken apple.

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Mercurys Interior

• Mariner 10 found that Mercury has a weak magnetic
  field approximately 1/100 that of Earth.
• Mercury may have a small molten core or a solid
  iron core which is permanently magnetized.
  

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Mercurys History

• Mercury has been geologically dead for
  approximately 4 Billion Years.

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Mercurys Views