Chapter 8, Review 5 (page 184)

Q: Define each of the four major geological processes: impact cratering, volcanism, tectonics, erosion


Impact Cratering: The excavation of bowl-shaped depressions (impact craters) by asteroids or comets striking a planet’s surface.  Impacts can have devastating effects on planetary surfaces, with impactors able to vaporize solid rock and excavate large, generally circular, craters.  At the large extreme, impact basins are formed when the lithosphere is cracked to allow for flooding by lava.  At the small extreme, micrometeorites pulverize surface rock on bodies without significant atmospheres.  Impact cratering is the most universal of the geological processes.


Volcanism: The eruption of molten rock, or lava, from a planet’s interior onto its surface.  Eruptions occur when underground lava finds a path through the lithosphere to the surface.  It occurs in planets with high internal temperatures and thin lithospheres.  In addition to resurfacing, outgassing through volcanic activity is responsible for the atmospheres of the terrestrial planets.  Volcanism is a feature of the larger worlds that have retained internal heat.


Tectonics: The disruption of a planet’s surface by internal force and stress.  Compression of the crust can create mountain ranges; when the crust is pulled apart valleys and cliffs form.  Tectonics is a feature of the larger worlds that have retained internal heat.


Erosion: The wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather.  Examples include wind, rain, ice, rivers, and glaciers.  Erosion is found on planets with substantial atmospheres and faster rotation.


Chapter 9, Review 2 (page 210)

Q: Describe the interior structure of Jupiter.  Contrast Jupiter’s interior structure with the structures of the other Jovian planets.  Why is Jupiter denser than Saturn?  Why is Neptune denser than Saturn?


The Essential Cosmic Perspective Fig. 9.4


The interior structures of Jupiter and Saturn are similar in composition- both contain a core of rocks, metals, and hydrogen compounds, layers of metallic hydrogen, liquid hydrogen, and gaseous hydrogen, and the visible cloud tops.  However, Jupiter’s core is significantly larger than Saturn’s, and Jupiter contains a much thicker layer of metallic hydrogen and comparatively thinner layers of hydrogen in the liquid and gaseous states.  Jupiter is compositionally quite different from Uranus and Neptune.  Beneath their visible clouds, Uranus and Neptune have a thin layer of gaseous hydrogen, beneath which is a layer of liquid nitrogen.  Beneath this is a sea of water, methane, and ammonia.  The cores of these two planets are believed to be rock.


Jupiter is denser than Saturn because it is more compressed.  Think of it like stacking pancakes.  If you have three pancakes in your stack, they are all still fairly fluffy.  But if you add 10 more pancakes to the top, you’ll start to squish down the bottom ones.  Add 10 more, and the bottom ones will get even more squashed.  The more pancakes you add to the stack, the more compressed the bottom ones will get.  So if you have 100 pancakes in a stack, it won’t be as tall as if you just measured the height of one pancake and multiplied it by 100.  This is because in the stack, gravity is pushing down on the top layers and pressing them down onto the bottom layers.  The bottom layers have nowhere to go, so they become compressed.  Same mass (we’re not changing the mass of the pancake) squished into less space means that the density increases.  Same deal with Jupiter- the more gas you add to it, the more compressed its lower layers will be.  More compressed = same amount of stuff squished into a smaller amount of space = more densely packed.  So Jupiter is denser than Saturn.


Neptune is denser than Saturn because it is made of different material.  Neptune has more higher-density material than Saturn does.  If you have a shoebox full of popcorn and a shoebox full of pennies, the one full of pennies weighs more even though it is the same size as the shoebox full of popcorn.  For the same amount of space, pennies have more weight.  The same can be said of the material that makes up Neptune.  If you filled a shoebox with a slice of Neptune from top to bottom, and another shoebox of Saturn from top to bottom, the box of Neptune would weigh more because there is different stuff in each of the boxes.


Chapter 10, Review 2 (page 321)

Q: Define and distinguish among each of the following: asteroid, comet, meteor, meteorite.


Comet: A relatively small, icy object that orbits a star.  Comets can be thought of as “dirty snowballs”- mixtures of ice and rock.  They ‘live’ far from the sun, in the regions of the outer Solar System called the Kuiper Belt, outside the orbit of Pluto, and the Oort Cloud, a sphere of objects surrounding our system and reaching halfway to the nearest star.  The orbit of a comet might take it near the sun if its ellipse is particularly eccentric, in which case we see it as a large glowing dusty object in the sky, often for weeks or even months at a time.


Asteroid: A rocky planetesimal orbiting a star.  Asteroids in our Solar System are located in the Asteroid Belt, between the orbits of Mars and Jupiter.  They can range in size from a small rock to 500 kilometers, about half the size of Pluto.


Meteor: A flash of light in the sky caused by a particle entering the atmosphere, whether the particle comes from an asteroid or a comet.  Meteors are more commonly called “shooting stars.”  When a bit of material enters Earth’s atmosphere, it is moving at such high velocity that part of it (if it is large) or all of it (if it is small, the more likely scenario) vaporizes due to the intense heat.  Just like when you rub your hands together to warm them up, two things moving against each other create heat.  It is this heat that vaporizes the particle and causes the streak across the sky- the meteor.


Meteorite: Of the four things listed here, a meteorite is the only one that you could pick up off the ground.  A meteorite is any piece of rock that has fallen from space to the ground- it could be all or part of an asteroid, a bit of a comet, or even a rock from another planet.  There are many examples of meteorites- a lot of them are in museums, one particularly famous one of a few years ago, originating from Mars and picked up in Antarctica, was thought to contain evidence of past life, and every once in awhile you hear about someone’s car getting smashed by a rock falling out of the sky from space.


Chapter 11, Review 10 (page 252)

Q: What are oxidation reactions?  If there were no life on Earth, would Earth’s atmosphere still contain significant amounts of oxygen or ozone?


Oxidation reactions: chemical reactions that remove oxygen from the atmosphere.  Examples include fire, rust, and the browning of fruits and vegetables.  When an oxidation reaction occurs with the surface of the Earth, it creates the rusty reddish appearance of some of Earth’s rock layers.  The origin of oxygen in Earth’s atmosphere is believed to be early photosynthesis.  Plants emit oxygen as a waste product, and there was a point in Earth’s biological history where the rate of photosynthesis was putting oxygen into the atmosphere much much faster than either an oxidation reaction or another process (like an animal breathing) could remove it.  If there was no life on Earth, it would not have an oxygen atmosphere.  Ozone consists of three oxygen atoms, so if there was no oxygen to begin with there would not be anything to form ozone with.  No life, no oxygen.  No oxygen, no ozone.