1 / 21

Mercury

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

ayame
Download Presentation

Mercury

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mercury God of commerce, travel and thievery

  2. 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

  3. 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)

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. Time lapse photo of Mercury over Leeds, England

  21. 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

More Related