Planetary Geology Lecture Outline - Mercury

'Odd' facts:

• strong magnetic field despite small size.
• have not been able to detect any Fe in surface materials (yet large iron core?).
• has O2 in thin atmosphere.
• spins slowly (59 days vs. 88 days orbit around sun).
• ice at the poles?

Internal construction:

• 3500 km diameter core and 4880 km diameter total, greater density. How do we know size of core?
• strong magnetic field source?
• evidence of isostatic response - implications? Rheid or fluid interior.

Surface terranes:

• densely cratered terrane with intercrater plains (oldest terrane)
• Caloris basin: about 3.6 billion years old, focusing on other side creating hilly & lineated terrane, polygonal fractures part of basin.
• contractional wrinkle ridges: character? origin?
• smooth plains: youngest, similar to maria.

History:

• accretion and differentiation, development of anorthositic crust (magma ocean)?
• intense bombardment and formation of intercrater plains
• formation of Caloris basin
• continued cooling and contraction
• minor bombardment and atmosphere development

half globe imageCaloris basinBach quadrangle

Additional references:

• Source of above images: http://nssdc.gsfc.nasa.gov/photo-gallery/
• Nelson, R. M., Nov. 1997, Mercury: The Forgotten Planet; Scientific American, p. 56-67

Reading: text chapter on Venus

Discussion questions for next time:

Venus has surface temperatures in the realm of metamorphic conditions on earth where rocks flow ductilely. Yet brittle structures (faults) abound. Why? There is the standard answer, and another somewhat neglected possibility.

How does the distribution of volcanism on Venus differ from that on earth, and what does that suggest about the tectonic style?

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