Mercury

1
Mercurys CratersHow They Are And What They Are

• Lindsay Johannessen
• PTYS 495

2
From the Beginning

• How do craters form?
• What kinds of craters are there?
• What are the circumstances of how these craters
  form?
• What does this tell us about our history?

3
On Mercury, How Is It Different?

• Most common types?
• Dispersion throughout region and numbers!
• The biggies Why are they so interesting?
• Amazing effects on Mercury!

4
How Do Craters Form?

• Craters occur on any and every solid bodied mass
  in the Universe.
• Craters shapes and sizes depend on three things
• - Mass density of projectile object and of
  impacted surface.
• - Diameter of projectile object.
• - Velocity of projectile object.

5
What Kinds Exist?

• Simple Craters
• Single ridged with ejectoblanket
• No caving rims
• Retains excavation stage shape
• Complex Craters
• Have central peak
• Outer rims collapse to enlarge diameter
• Larger in general
• Double and Multi-ringed Craters
• Larger than central peak complex
• Have second (sometimes multi) internal ring
• caused from reverberation of impact

6
Formation of Simple Craters

• Impact occurs
• Seismic waves travel through
• impactor and impacted
• Crush, melt and vaporize most
• of the impactor
• Excavation crater is left
• as main crater

7
Formation of Complex Craters

• Same initial process as
• simple craters
• From bigger impacts come
• bigger results
• Central peak and secondary
• Rings form from reverberation
• of initial impact

8
What These Craters Tell Us

• Given consistent information
• Date ranges for bombardment periods
• Possible surface structure
• Quantifiable forces involved in impacts

9
Mercurian Craters

• Generally larger and more violent than what we
  usually see in our Solar System
• Mercurys Gravitational Pull
• 370 cm/sec²
• Average impact speed for
• Asteroid 34km/sec
• Comet 87 km/sec

10
Size of Craters on Mercury

• Simple craters on Mercury
• Range up to approx. 10 km in Diameter
• (19 km on the Moon and 3 km on Earth)
• Complex Craters
• Range from 10km up to 200km with a central peak
• Range from about 200km to 750km with Double Ring
• Range from 750km to 1500 and up with multiple
  rings.

11
The Largest Craters on Mercury

• The Caloris Basin is known to be the largest
  crater basin in the Solar System.
• Effects of the larger impacts are
• as great as planetary change.
• Antipodal changes in the surface
• of the planet are a major side
• effect of this large impact.

12
What These Craters Mean for Scientists

• By studying all effects of Mercurys impact
  history, we can discern eras of impacting,
  possible sources of impacting, (i.e. asteroid
  belts, comets, etc), and ascertain the
  historical records of Mercury through
  observation, data collection and analysis.