History of Mercury

Spring 2003

Introduction

• The telescopic view - surface skin like Moon, but interior must be Earthlike: Paradox
  • "Anomalously dense" / 3/2 history
  • General surface similarity to Moon: microscopically and history recorded
  • Surprising - 80% core, 500 km shell of silicate material
• The Apollo-era scientific influence - Moon seemed standard, Mercury bizarre

Mariner 10 Findings and Interpretations

• Geometry and Timing of the Mission - Mag field - Columbo
• Impact record extraordinarily like Moon's
  • Zooming in
  • 
  • 
  • outgoing hemisphere
  • 
  • 
• Nature and history of interior extraordinarily like Earth's
• Thus, contrast between outside and inside enhanced!
• Key open issues: composition, timing of internal heating to keep dynamo going
• Establishment of coordinate system

Microwave Emission

• Mitchell and de Pater paper

Compositional Implications

• Jeanloz et al. paper
• 

History

1. Early differentiation and accretion, or giant impact and reaccumulation of debris minus much silicate material? (Mercury, Wetherill, p670)
2. How to sustain dynamo for magnetic field? Very low heat flow and low volcanism? (Jeanloz et al. 1995)
3. Intercrater plains
   • Mercury, Moon, Mars - different
   • 
   • 
4. Resurfacing recorded along with cratering
   • What cause? Episodic?
   • Eolian - No, Mars example
   • Impact - higher gravity, like Mars
   • Volcanism - OK. Big basins. Phase not recognized on Moon
5. LHB
   • Was resurfacing, but not necessarily episodic
   • LHB, however, did end abruptly
6. Interplanetary correlations
   • Heavy bombardment
   • Similar large craters - areal difference x4?
7. Scarps
   • Large core - compression
   • Dynamic coupling - solar torque
8. Caloris event
   • Basin formation ejecta
   • 
   • Post-formational compression and extension
   • 
   • Hilly and lineated terrain
9. Q? Rapid response due to thin shell? - "overfilling"
10. Smooth plains
    • Relatively little albedo differences between plains and uplands. Why?
    • Jeanloz, et al argue lower in iron than lunar uplands, and especially deficient in basalt in smooth plains
    • geologic units
    • Caloris
      • + some albedo
      • Volume enormous (compare with Orientale) and overlies other impact debris
      • 1 radii out
      • Color differences in some areas
      • Volcanic origin of plains or impact sheets?
      • Crater floor fillings
11. Q? Significant difference in composition compared to Moon? Less iron, more sulfur?
12. Bowl-shaped craters on Moon, Mars, Mercury
13. Crater age comparison

Post Mariner 10 developments

• Lunar paradigm reshaped by Hartmann, Clementine, Prospector. Moon is bizarre, Mercury more mainstream.
• Emission spectra: Millimeter radio emission points to low iron crust unlike Moon. Suggests potential differences, eg sulfur
• Current volatiles
  • Sodium and other emissions - solar wind interactions? Sprague (1996) argues high sulfur abundance, as well as alkali metals generally, and thus the conspicuous emissions.
• Widespread polar deposits of cold-trapped ice discovered by Earth-based radar

The Future

• Further radar discoveries
• Orbiters! Messenger

- Bruce Murray -

GPS homepage - Home - General Info - Schedule - Assignments - Reading - Lectures - Tutorials - Labs - Brainteasers - Projects - References

Back to top

These pages are currently maintained by Aharonson & Schorghofer.
Last updated 06/05/2003