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Mercury – Craters.

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Presentation on theme: "Mercury – Craters."— Presentation transcript:

1 Mercury – Craters

2 Mercury – Craters Craters are shallower More gravity
Craters are separated by smooth areas

3 Caloris Impact Basin Giant crater Very old
Subsequent lava flows inside it Shock waves created “chaotic terrain” on other side of Mercury

4 Volcanism on Mercury Volcanic Vent Crater Flat plains
Extinct Volcanoes Discovered on Mercury Many “plains” look like they were caused by volcanism Volcanic Vent Crater Flat crater floor Flat plains

5 Scarps on Mercury Giant cliffs ~ few km tall Hundreds of km wide

6 Scarps – Cracks in the Crust
Large metal core Hot initially Metal expands when hot Core cooled Metal shrinks Portions of the surface “fell” Cracks on the surface rock metal

7 Venus Images visible ultraviolet

8 How We Know What We Know Magellan Akatsuki Venus Express Venera 9
Many early spacecraft – limited success Venera – Soviet Landers – 60’s and 70’s Magellan – ’89 – Radar Mapping Venus Express (ESA) –2006 to 2014 Akatsuki (Japan) – Since 2015 Akatsuki Venus Express Venera 9

9 Venus – Basic Facts Q. 35: Temperature of Venus
Size – Slightly smaller than Earth Mass – Slightly less massive than Earth Comparable density to Earth Orbit: 0.723 AU, nearly circular Venus year = 225 Earth Days Rotation: Backwards every 243 Earth Days 2 Venus Days ~ 1 Venus Year Atmosphere – Thick – 93  Earth pressure Mostly Carbon Dioxide (CO2) Q. 35: Temperature of Venus

10 Venera – Surface Images of Venus
Rocks similar to Earth rocks

11 Venus – Temperature and Climate
Surface temperature: K – hotter than hell Hottest planet – strong greenhouse effect (CO2) Uniform temperature – thick atmosphere No water Surface – too hot for water or ice Atmosphere – no water Clouds – cover planet entirely in visible light Clouds are sulfuric acid (H2SO4) “Rain” of acid, but evaporates before it hits the ground Lightning – cause unknown – more than Earth

12 Venus in Radar Clouds block views of surface
Magellan mapped 98% in radar Continents and “seas” Craters – rare, like Earth Mountains Volcanoes

13 Venus Surface Features and Composition
Continents are made of light rocks No water in “seas” Craters are uniformly distributed (?) Suggests entire planet was resurfaced < 1 billion years ago No evidence of plate tectonics – all one plate Probably thicker crust? Composition similar to Earth

14 Mountains and Craters on Venus
Comparable in number and size to Earth No small craters (thicker atmosphere) Q. 36: Volcanism on Venus

15 Volcanoes on Venus Several objects that look like volcanoes

16 Volcanoes on Venus At present, no actual volcanoes have been seen erupting, but . . . Comparable in size to Earth Sulfur compounds in the atmosphere indicate recent activity Lots of evidence of recent eruptions Lava makes pancake-like lava outflows Generally agreed – Venus is still geologically active, like Earth

17 Venus vs. Earth Why is Venus’s atmosphere so different from Earth?
Early Venus: H2O oceans, CO2 atmosphere Lots of water evaporates Water is greenhouse gas Water dissociated by UV Hydrogen and Oxygen lost CO2 continues greenhouse Early Earth: H2O oceans, CO2 atmosphere Little water evaporates Some CO2 dissolves in ocean CO2 combines with rocks Plants convert CO2 to O2 Runaway greenhouse effect

18 Mars Images Q. 37: Mars’s Appearance

19 How We Know What We Know Many early missions (before 2000)
Mars Odyssey (’01-present) Mars Express (’03-present) Mars Exploration Rovers (’04-’18) Mars Reconnaissance Orbiter (’06-present) Mars Phoenix Lander (’08) Mars Science Laboratory (’12-present) MAVEN (’14-present) Mars Orbiter Mission (’14-present) ExoMars Trace Gas Orbiter (’16-present) InSight (’18-present) More missions planned (’20 and beyond)

20 Current Spacecraft at Mars
Mars Orbiter Mission Mars Odyssey ExoMars TGO InSight Mars Reconn-aissance Orbiter Mars Science Laboratory MAVEN Mars Express

21 Mars – Basic Facts Size – Half the size of Earth
Twice the size of Mercury Mass – 1/10 of Earth’s Slightly less dense than Earth Orbit: 1.38 AU, fairly eccentric Mars year = 1.9 Earth years Rotation: Once every 24 hours 40 minutes Atmosphere – Thin – < 1% Earth pressure Mostly Carbon Dioxide (CO2) Too thin for appreciable greenhouse effect

22 Mars – Pictures from the Surface

23 Mars – Pictures from the Surface
Rocks and sand Reddish color due to iron oxide – aka rust

24 Mars – Climate Sun Mars Mars Mild summer north Severe winter south
Mild winter north Severe summer south Q. 37: Climate on Mars

25 Mars – Climate Sun Mars Mars Colder than Earth (far from Sun)
130 K – 290 K Pressure fluctuates seasonally Southern hemisphere is more extreme

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