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Mercury. God of commerce, travel and thievery. General Information. Named after Roman fleet-footed messenger god Appeared to move quickly across the sky Closest planet to Sun Difficult to observe from Earth Never gets more than 28 degrees from Sun

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God of commerce, travel and thievery

General information
General Information

  • Named after Roman fleet-footed messenger god

    • Appeared to move quickly across the sky

  • Closest planet to Sun

    • Difficult to observe from Earth

    • Never gets more than 28 degrees from Sun

    • Can only be viewed during day or just prior to sunrise or just after sunset

    • Low in sky means 10 X more atmosphere to penetrate than if Sun were directly overhead

  • Second smallest planet (after Pluto)

    • Smaller than Titan and Ganymede

  • Sun would appear 2 ½ X bigger in sky from the surface

Planetary statistics
Planetary Statistics

  • Mean distance from Sun 57,910,000km

    • 0.38 A.U.

    • Highly eccentric (28.6 -43.5 million mi)

  • Orbital Period = 87.96 days

  • Rotational Period = 58.6 days

    • Spin-orbit coupling

    • 2 years to exactly 3 days

  • Axis Tilt = 0.01 degrees (23.5)

  • Diameter = 4880km (12,756km)

  • Mass = 3.303 x 1023 (5.97 x 1024)

    • (.05527 of Earth)

  • Density = 5.42gm/cm3 (5.515gm/cm3)

Planetary statistics1
Planetary Statistics

  • Equatorial surface gravity = 2.78m/sec2 (9.78m/sec2)

  • Visual albedo = 0.10 (.37)

  • Moons = none

  • Surface = heavily cratered

  • Atmosphere = atoms blasted off surface by fierce solar wind

    • Very, very thin

    • Composition

      • Helium 42%

      • Sodium 42%

      • Oxygen 15%

  • Mean surface temperature = 170C (330F)

    • Max temp = 427C (870F)

    • Min temp = -173C (-360F)

    • Most extreme in our SS

Mercury surficial features
Mercury – Surficial Features

  • Heavily cratered surface

    • Represents geological record of SS impact rates

    • Infers no erosional or depositional geologic processes throughout planets history

    • Infers extremely thin atmosphere

    • No liquid water

  • Fault scarps

    • Demonstrate vertical and some horizontal tectonic movement

    • Can be 100’s of kms in length and > 2mi high

    • Probably due to planets cooling history

      • Heating/expansion = normal faulting (tensional stress)

      • Cooling/contraction = reverse (compress. stress)

    • Some may be result of larger impact events

      • Focus of seismic waves antipodal to impact point

Early investigations
Early Investigations

  • Giovanni Schiaparelli

    • 1880’s sketched faint features from telescopic observations

    • Suggested Mercury tidally locked to Sun

      • Much like the Moon is to Earth

  • Pettengill and Dyce

    • 1965 determined Mercury’s rotational period proving it is not tidally locked

  • Speculation rotation was perhaps as quick as 8 hrs

  • Slowly despun over 109 yrs

  • Raised interior temp by 100K

  • Einstein’s Theory of Relativity

    • Newtonian mechanics didn’t fit orbital characteristics

    • Once thought another planet (Vulcan) was reason for orbital perturbations

    • Correctly predicted the precession (very slowly moves backward) of the perihelion of Mercury

Early satellite exploration
Early Satellite Exploration

  • Mariner 10 was the 7th successful launch in the Mariner spacecraft series, and the first to use the gravitational pull of one planet (Venus) to reach another (Mercury)

  • Instruments on board the spacecraft were designed to measure the atmospheric, surface, and physical characteristics of Mercury and Venus

  • Experiments included:

    • Television photography

    • Magnetic field

    • Plasma

    • Infrared radiometry

    • Ultraviolet spectroscopy

    • Radio science detectors

  • An experimental X-band, high-frequency transmitter was flown for the first time on the spacecraft

Mariner 10 cont d
Mariner 10 (cont’d)

  • Mariner 10 reached Mercury on March 29, 1974, passing over the planet at 705 kms (438 mi) above the surface

    • Made a total of three passes during 1974-75

  • Photographs revealed an intensely cratered, Moon-like surface, a faint atmosphere

  • Engineering tests were continued until March 24, 1975, when the supply of attitude-control gas was depleted and the mission was terminated

Mercury internal structure
Mercury – Internal structure

  • About 1/3 the size of Earth

  • Density is comparable to that of Earth

    • Indicates that Mercury has a large core roughly the size of Earth's Moon or about 75% of the planet's radius

    • The core is likely composed of 60 to 70% iron

  • Mariner 10's measurements reveal a dipolar magnetic field

    • Possibly produced by a partially molten core

    • Solid rocky mantle surrounds the core

    • Thin silicate crust of about 100 kms

Surface features and processes
Surface Features and Processes

  • Craters

    • Range from 100m– to 1,300km in diameter

    • Caloris Basin

      • Largest multi-ring basin on Mercury

      • 100km diameter asteroid

      • Concentric mountain rings 3km high

      • Ejecta blanket covers 600-800km

  • Lava flows

    • Post-accretion phase volcanic activity

    • After crustal cooling 3rd phase of flows producing smooth plains

  • Scarps

    • 2nd phase tectonics

    • Thrust faulting

    • Contraction and shrinking of silicate crust

  • Water?

    • 1991 radio waves from Caltech scientists yield bright returns at north pole

    • Axial tilt low = no sun on crater interiors = temp <161C

    • Possibility of ice at or very near surface

Tectonics santa maria rupes
Tectonics – Santa Maria Rupes

  • Sinuous dark feature running through the crater at the center of this image

  • Interpreted to be enormous thrust faults

  • Indicate that the radius of Mercury decreased by 1-2 kms after the solidification and bombardment of the surface

  • Volume change probably was due to the cooling of the planet, following the formation of a metallic core three-fourths the size of the planet

Caloris basin
Caloris Basin

  • Mariner 10 mosaic

  • Terminator enhances relief

  • Note at least 3 concentric rings

    • Many ring mountain blocks are over 3 kms high

  • Secondary mountain rings likely created by impact shock waves

  • Radiating outward are systems of valleys, hills, and other craters

  • Secondary craters surround the Basin

    • Some are in excess of 20 kms diameter

  • The Caloris Basin interior is filled with mostly smooth plains most probably volcanic in nature

Tectonics weird terrain
Tectonics – “Weird Terrain”

  • Hilly, lineated region of Mercury at the antipodal point from the Caloris Basin

  • The shock wave from the Caloris impact was reflected and focused to this antipodal point

  • Result was jumbled crust broken into a series of complex blocks

  • Note orthogonal fracture systems

  • The area covered is about 100 kms (62 mi) on a side

Planetary geologic evolution
Planetary Geologic Evolution

  • Size

    • Mass

    • Radius

  • Chemical Composition

  • Three general phases

    • Highly active

      • Crustal formation and mobility

    • Volcanic

      • Accompanys thickening sub-crustal lithosphere

    • Terminal quiescent

      • Lithosphere too thick to allow volcanism or lateral movement

Mercury s evolutionary factors
Mercury’s Evolutionary Factors

  • Important reference point

  • Planet closest to the Sun

    • Solar wind does not allow substantial atmosphere to form

    • End-member of chemical composition

      • High temperature

      • Refractory elements

      • Few volatiles

  • Larger than Moon evolving at slightly different tempo

  • Mercury

    • ~Same mass and surface gravity as Mars

    • ~Same bulk density of Earth

Messenger s mission timeline
Messenger’s Mission Timeline

  • KEY EVENTS:August 3, 2004 -- MESSENGER Launch August 2005 -- Earth flybyOctober 2006 -- Venus flybyJune 2007 -- Venus flybyJanuary 2008 -- Mercury flybyOctober 2008 -- Mercury flybySeptember 2009 -- Mercury flybyMarch 2011 -- Yearlong science orbit of Mercury begins

Messenger new images
Messenger (New Images)

  • Like the previously mapped portion of Mercury, this hemisphere appears heavily cratered

  • Upper right, Caloris basin, including its western portions never before seen by spacecraft

    • Caloris is one of the largest, and perhaps one of the youngest, basins in the Solar System

    • New image shows the complete basin interior and reveals that it is brighter than the surrounding regions and may therefore have a different composition

  • Darker smooth plains surround Caloris, and many unusual dark-rimmed craters are observed inside the basin

  • Several other multi-ringed basins are seen in this image for the first time

  • Prominent fault scarps (large ridges) lace the newly viewed region

Messenger new images1
Messenger (New Images)

  • One of the highest and longest scarps (cliffs) yet seen on Mercury

    • (The Sun is shining low from the right, so the scarp casts a wide shadow)

  • Compressional tectonic forces in Mercury’s crust have thrust the terrain occupying the right two-thirds of the picture up and over the terrain to the left This image was taken from a distance of only 5,800 kilometers (3,600 miles) from surface of the planet and shows a region about 200 kilometers (about 125 miles) across

Mdis highest res color image even acquired
MDIS – highest res color image even acquired

  • Closest approach, just 200 kms above the surface

  • (500 meters/pixel

  • 120-km diameter Rudaki Crater

  • Younger smooth surface on left

  • Older rougher, bluish terrain on right

  • Orange crater rim

  • Blue-floored crater

  • Dark blue material was ejected from the 105-km diameter crater on the right side

  • A relatively young, small crater then excavated through this blue material to reveal the smooth plains beneath

Mercury s geological history cont d
Mercury’s Geological History (cont’d)

  • This scene is near Mercury's terminator where shadows are long and accentuating height differences

  • Note:

    • Concentric rings

    • Smooth basin floor

    • Large, chaotic ejecta blanket

    • Large number of secondary linear crater chains

  • The large crater is Sullivan crater, a structure about 135 kilometers (84 miles) in diameter also seen during the Mariner 10 mission

    Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington