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 Mercury  36.2 million miles from the sun Earth  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 Daytime  750 K ( F° ) Nighttime  90 K ( 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