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