Geologic evolution and cratering history of Mercury
By: G. Neukum, J. Oberst, H. Hoffmann, R. Wagner, B.A. Ivanov
Presented by: Kristin Hepper
Global mosaic
of Mercury
Facts about Mercury• Closest planet to the sun
• Mercury36.2 million miles from the sun• Earth92.96 million miles from the sun
• Smallest planet
• Radius 1,500 mi• Earth’s radius 3,959 mi
The relative radii of the Sun and Planets
The Sun and planets drawn to scale
Temperature
• Daytime750 K
(890.33 F° )
• Nighttime90 K
(-297.67 F°)
Largest range of temperature of any planet
Geologic Features
• Appears lunar-like
• Covered with impact-craters
• Vast smooth plains
• Low density of impact craters
Mercury’s Terrain:2 major types
• Densely cratered(highlands)
• Lightly cratered(low-lands)
Highlands
• High abundance of large craters– Overlapping– Up to tens of kilometers across
• Inter-crater plains– Gently, smoothly-flowing units– Characterized by few craters < 15km in
diameter
Crater 100km across
Oldest geologic units on Mercury…
• Densely cratered terrain
• Inter-crater plains
• Age based on impact craters and their corresponding materials
Multi-ring structure
Caloris
Low-land plains
• Where are they found?
– In and around large multi-ring structures
– North polar region
– Patches in highlands
Origin of low-lands
• Volcanic favored
or
• Caused by ejecta emplacement
Craters
• Similar to lunar counterparts
• Morphology more complex the greater the diameter gets
Crater = a saucer-shaped pit or depression caused by impact
Craters cont…
• Simple Complex crater dimaeter• 10.3 kilometers
• Age of craters
This crater is 10 km wide
Tectonism on Mercury
• NOT tectonically active TODAY
• But was active in the past– How do we know?
• Lineaments
• Lobate scarps
• Volatile deposits
Lineaments
• Linear topographic features of regional extent
• Believed to reflect crustal structure– Ex fault lines, aligned volcanoes, straight
stream courses
Lobate Scarps
• Represent thrusting events
• Caused by rapid cooling and contraction of planet
• 550km• Heights vary from
0.1-2km
Volatile Deposits
• Seen as bright spots in polar areas
• Reflected radar signal is similar to water-ice deposits on earth
• No seasons occur on Mercury
• So temperatures at poles are stable
< 135 K
Volatile- adj. Evaporating readily at normal temperatures and pressures
Composition of Mercury
• IRON– Unlike other terrestrial planets– Concentrated at core
• Multispectral images from Mariner 10 – Smooth plains– Dark-blue albedo areas
Geophysical
• Due to tidal forces, spin rate slowed
• Faulting in the lithosphere
• Also see compressional features
Conclusions
• Mercury’s endogenic processes have long since ceased
• Similar to both the earth and the moon
• Bombardment history– Lunar-like
– Since ~ 3.0Gya cratering has dropped off
– Mercury now experiences a constant level of bombardment
Conclusions cont…
• Experienced tectonic activity in the past
• Little is known about the surface composition
Future Missions to Mercury
• 2009 by ESA– Bepi-Columbo– Includes a lander