The Terrestrial Planets PDF

Lesson 7 The Inner Planets Copyright © 2020 W. W. Norton & Company Interiors of Terrestrial Planets ▪ Like the Earth the other terrestrial planets (and our Moon) are differentiated. ▪ The relative sizes and layers vary from planet to planet. Figure 22.9b Mercury ▪ Innermost planet closest to t...

Lesson 7 The Inner Planets Copyright © 2020 W. W. Norton & Company Interiors of Terrestrial Planets ▪ Like the Earth the other terrestrial planets (and our Moon) are differentiated. ▪ The relative sizes and layers vary from planet to planet. Figure 22.9b Mercury ▪ Innermost planet closest to the Sun (so also fastest moving) ▪ Nearest planet to the Earth ▪ Left: false color image of heavily cratered surface ▪ Right: topographic map Figure 22.10 Characteristics of Mercury ▪ Temperature at equator varies from −173 oC at night to 427 oC at noon ▪ Possesses a large iron core and magnetic field ▪ Evidence of past volcanic activity, but no active volcanoes ▪ Almost no atmosphere due to smaller mass and effects of the solar wind ▪ Only 5000 km in diameter ▪ Rotation locked to Sun: 3 rotations in 2 orbits ▪ Its year is 88 earth days ▪ Moon-like on the outside (craters) ▪ Earth-like on the inside (dense core, magnetic field) ▪ Although Mercury is not tidally locked to the Sun, its rotational period is tidally coupled to its orbital period. Mercury rotates one and a half times during each orbit. Because of this 3:2 resonance, a day on Mercury is 176 days long ▪ Mercury’s day is longer than its year Figure 22.11 Mercury has Craters ▪ Large faults (scarps) are visible through craters. ▪ Faults are thought to have resulted from shrinking of Mercury ▪ ▪ ▪ Not as dense as on Moon Most of Mercury covered with lava plains (intercrater plains) Mercury has a huge impact basin, the Caloris Basin Because of Mercury’s locked rotation, it has two “hot poles” ▪ Because of Mercury’s locked rotation, it has two “hot poles” – hottest regions on mercury ▪ And Mercury has the last thing you’d expect to find: ice caps ▪ Mercury’s ice seems to be hiding in polar craters ▪ “Spider” Crater ▪ Caloris Basin “Spider” Crater Volcano on Mercury Venus ▪ Flipped on axis, so rotates retrograde—the Sun rises in the west on Venus ▪ Causes could be tidal lock to the earth or sun, or mega impact ▪ Rotates very slowly—243 days ▪ Orbits sun in 223 days ▪ You can jog as fast as Venus Rotates ▪ Dense CO2 atmosphere with 90X the pressure on the Earth and 450° C—hot enough to melt lead ▪ Abundant evidence of volcanic activity Venus’ Atmosphere ▪ Thick CO2 atmosphere ▪ Sulfuric-acid clouds ▪ Cloud cover is constant so we can’t see the surface from the Earth or from orbiting spacecraft in visible wavelengths (left). Figure 22.12 Surface of Venus ▪ Because of thick cloud cover, the surface has only been seen or photographed twice, by probes landed by the USSR. ▪ Example: Image of Venus’s surface from Venera 13(1981). ▪ It survived 127 minutes ▪ Venus has no Plate Tectonics ▪ Earth’s internal heat causes hot material to rise within Earth and plates to move ▪ Venus’ crust is too rigid ▪ Heat builds up and escapes in planet-wide volcanic activity Figure 22.13a Radar Image of Venus ▪ Venus’s surface has been mapped by radar that can penetrate clouds. ▪ Radar mapping shows many volcanic structures and few impact craters, suggesting a young, active surface. ▪ Radar image from Magellan 1989 (right). ▪ Magellan synthetic aperture radar data are combined with radar altimetry to develop a three-dimensional map of the surface to produce an image of Maat Mons (left). Figure 22.13b,c Topography of Venus Venus has Craters Venus is Volcanic “Pancake” Volcanoes Channels on Venus Resemble Rivers, but likely lava flows because venus is too hot for water Mars: The Most Explored Planet ▪ The Red Planet is the most studied planet beyond the Earth. ▪ Currently, it is cold, dry, and covered with rock and dust, but evidence suggests it was warmer and had liquid water at the surface in the past. Figure 22.14 Mars’s Characteristics ▪ Thin atmosphere—about 0.6% of that on the Earth; like Venus, mostly CO2 ▪ Frigid temperatures—average surface temperature of −55 oC (−67 oF) ▪ 24.6-hour day ▪ 25-degree axial tilt ▪ Has more extreme and longer seasons—wind speeds of up to 100 km/h have been recorded. ▪ 1/10 of the Earth’s mass (or 0.38 of the gravity) ▪ CO2 ice caps at poles that melt in summer ▪ ½ size of earth Moons of Mars ▪ Mars has two small irregularly shaped moons, Phobos (left) and Deimos (right) – fear and death, that are probably asteroids that were captured by Mars’s gravity. Figure 22.15 Topographic Maps of Mars ▪ Topography of Mars is varied, but different from Earth. ▪ Shows highlands, lowlands, volcanic structures, and rifts, but no mountain ranges Figure 22.16 Surface of Mars ▪ It contains many distinct provinces, including plains, canyons, and highlands/volcanoes. ▪ Below, Valles Marineris, an enormous rift valley on Mars. Figure 22.17a Olympus Mons ▪ Mars has no currently active volcanos but shows abundant evidence of past activity. ▪ Below: Olympus Mons, a shield volcano and the largest volcano in the Solar System—2.5 times the size of Mauna Loa (Hawaii). ▪ Size is likely because there are no plate tectonics, so hot spot remains in same place. Figure 22.17b Flowing Water on Mars ▪ Spirit and Opportunity proved the past existence of liquid water on Mars. ▪ Many features appear to be the result of the action and presence of water. ▪ Left: Kasie Valles outflow channel. (false color) ▪ Right: Thin laminate rock that appears to have been deposited by flowing water. Figure 22.18a,c Mars from Mariner 9 ▪ Mars from Mariner 9 ▪ Mars Viking MosaicNotice the big rift which Valles Marineris (4000 km long, 50 to 100 km wide) ▪ Huge Landslide in Vallis Marineris ▪ Layered Deposits in Vallis Marineris Active Landslide on Mars ▪ Olympus Mons ▪ Summit of Olympus Mons Phobos over Olympus Mons Mars’ Polar Caps Polar Cliffs on Mars Dunes on Mars Water on Mars Channels on Mars Floods on Mars Where’s the Water Now? Recent Water on Mars? How to Lose an Ocean ▪ If water is exposed to solar UV and particles, it breaks down to H + O (photodissociation) ▪ Happens if water gets into upper atmosphere • Planet gets hot (Venus) • Planet loses atmosphere (Mars) ▪ Oxygen combines with iron and other elements, on Mars Oxygen may also have escaped Landing on Mars Mars as Seen by Viking Mars from Pathfinder Martian Winter Martian Sunset Layered Rocks on Mars Cape St. Vincent Opportunity’s Shadow “my battery is low and it's getting dark” -was supposed to last 90 sols but lasted 15 years Spirit Makes Tracks Digging Out Hole on Mars Wind Erosion on Mars Ice in Martian Crater Martian Glacier? Martian Glacier? Martian Dust Devil Dust Devil Tracks Earth From Mars The Face on Mars A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite Martian Fossils ? Homework Complete the two worksheets in D2L Inner Planets Worksheet Inner Planet Comparison Sheet