Mercury’s Plains and Volcanism

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Mercurys Plains and Volcanism

• Jake Turner
• PTYS 395

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Overview

• What are plains?
• What types of plains does Mercury have?
• Origins of the plains?
• Volcanism?
• How will MESSENGER help?

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What are Plains?

• Flat or smoothly undulating surfaces
• They are a canvas on which other landforms
  devolve.
• Plains are evidence for resurfacing or the
  creation of a smooth surface from a rough surface

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Plains on Mercury

• About 60 of Mercury is believed to be plains.
• Most abundant terrain on Mercury
• More widespread and higher albedo than plains on
  the moon.

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Types of Plains

• Intercrater
• Heavily cratered
• Older then smooth
• 45 of surface is covered by intercrater plains.

• Smooth Plains
• Occur in the highlands between clusters of
  craters.
• Young
• Confined to interior and exterior of impact
  basins and large craters.
• 15 of surface

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Examples of Intercrater Plains
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Examples of Smooth Plains
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Intercrater Plains

• Located between and around clusters of large
  craters in the heavily cratered highlands.
• Age around the period of the heavy bombardment.
• 4-4.2 billion years old
• Volume of plains decreased as age decreased

• Craters less then 50km may have been destroyed by
  the intercrater plains formation.

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Smooth Plains

• Two large concentrations
• Caloris Basin
• Borealis Basin
• 90 are associated with older large impact basins
  
• Similar to lunar Maria
• Age- 3.8 billions years
• End of heavy bombardment

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Origins of the Plains

• 1. Impact Crater Ejecta deposits from large
  basins

• Consists of two parts
• A continuous ejecta blanket
• Discontinues ejecta beyond the continuous ejecta.

• 2. Volcanic deposits

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Origins of the Smooth Plains

• Impact Ejecta Theory
• Smooth plains around the Caloris basin would be
  smooth ejecta deposits.
• Interior smooth plains would be impact melt.
• Other plains would be impact eject or impact
  melt.

• Problem with Impact Ejecta
• Cannot explain why the plains cover 15 of the
  surface compared to 5 on the moon.

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Problems with the Impact Ejecta Theory

• Cannot explain why the plains cover 15 of the
  surface compared to 5 on the moon.
• For example, Smooth plains around Caloris basin
  extend 2000km.
• No such extensive eject deposits exist on the
  moon.
• Mercury has higher surface gravity then moon.

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Smooth PlainsVolcanism

• Smooth plains are younger than the basins they
  occupy or surround.
• Embayments are a common feature of lava flows
• Isnt definitive though, still need composition.

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Smooth Plain Volcanism

• Earth based radar observations show that the
  annulus of smooth plains surrounding Caloris is
  like the Lunar Maria.
• Color images of Tolstoj basin suggest different
  composition.

A
Tolstoj Basin
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Intercrater PlainsVolcanic

• Covers 45 of the surface
• No evidence of source basins
• The frequency of the interior morphologies of
  craters on the intercrater plains is the same as
  the lunar Maria.

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Volcanic Intercrater Plains

• Recalibrated data from Mariner 10 suggest that
  plains have different composition, age, and grain
  size than the surroundings.

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Problems with Volcanism

• Because of Mariner 10s bad lighting and
  resolution conditions volcanic landforms are
  difficult to find.
• Composition not know exactly

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How Messenger will help?

• Better resolution
• Experience with lighting conditions
• Analyze composition more thoroughly and fully

• Early data analysis might suggest relatively
  recent volcanism.

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Biblography

• R.G. StroR.G. Strom, A.L. Sprague, Exploring
  Mercury The Iron Planet (Springer, New York,
  2003)
• Kiefer, Walter and Murray, Brue. Formation of
  Mercurys Smooth Plains. Pasadena, California.
  1987.
• G. Jeffrey Taylor. Mercury Unveiled, Hawaiis
  Institute of Geophysics and Planetology,
  University of Hawaii. http//solarsystem.nasa.gov/
  scitech/display.cfm?T_ID365