Test 3 Vocab/Homework

fault

(geological) a place where lithospheric plates slip sideways relative to one another

subduction

(of tectonic plates) the process in which one plate slides under another

plates

(on a planet) pieces of a lithosphere that apparently float upon the denser mantle below

circulation cells

(or Hadley cells) large-scale cells (similar to convection cells) in a planet's atmosphere that transport heat between the equator and the poles

global wind patterns

(or global circulation) wind patterns that remain fixed on a global scale, determined by the combination of surface heating and the planet's rotation

carbonate rock

- a carbon-rich rock, such as limestone, that forms underwater from chemical reactions between sediments and carbon dioxide - on earth, most of the outgassed carbon dioxide currently resides in carbonate rocks

thermosphere

- a high, hot, X-ray-absorbing layer of an atmosphere, just below the exosphere - it begins where the temperature again starts to rise at high altitude

sedimentary rock

- a rock that formed from sediments created and deposited by erosional processes - the sediments tend to build up in distinct layers, or strata

orbital resonance

- a situation in which one object's orbital period is a simple ratio of another object's period, such as 1/2, 1/4, or 5/3 - in such cases, the two objects periodically line up with each other, and the extra gravitational attractions at these times can affect the object's orbits

tidal heating

- a source of internal heating created by tidal friction - it is particularly important for satellites with eccentric orbits such as Io and Europa

stratosphere

- an intermediate-altitude layer of earth's atmosphere that is warmed by the absorption of ultraviolet light from the sun - it begins where the temperature stops dropping and instead begins to rise with altitude - high in the stratosphere, the temperature falls again

aurora

- dancing lights in the sky caused by charged particles entering our atmosphere - called the aurora borealis in the Northern Hemisphere and the aurora australis in the Southern Hemisphere

mid-ocean ridges

- long ridges of undersea volcanoes on earth, along which mantle material erupts onto the ocean floor and pushes apart the existing seafloor on either side - these ridges are essentially the source of new seafloor crust, which then makes its way along the ocean bottom for millions of years before returning to the mantle at a subduction zone

exosphere

- the hot, outer layer of an atmosphere, where the atmosphere "fades away" to space - it is the uppermost region, in which the atmosphere gradually fades away into space

atmospheric structure

- the layering of the planetary atmosphere due to variations in temperature with altitude - for example, earth's atmospheric structure from the ground up consists of the troposphere, stratosphere, thermosphere, and exosphere

lithosphere

- the relatively rigid outer layer of a planet - generally encompasses the crust and the uppermost portion fo the mantle

continental crust

- the thicker lower-density crust that makes up earth's continents - it is made when remelting of seafloor crust allows lower-density rock to separate and erupt to the surface - continental crust ranges in age from very young to as old as about 4 billion years (or more)

heat of accretion

Accretion deposits energy brought in from afar by colliding planetesimals. As a planetesimal approaches a forming planet, its gravitational potential energy is converted to kinetic energy, causing it to accelerate. Upon impact, much of the kinetic energy is converted to heat, adding to the thermal energy of the planet.

vaporization

After outgassing creates an atmosphere, some atmospheric gases may condense to become surface liquids or ices. The subsequent vaporization of these surface liquids (evaporation) and ices (sublimation) therefore represents a secondary source of atmospheric gas. For example, if a planet warms, the rates of vaporization will increase, adding gas to the atmosphere.

WHAT IS AN ATMOSPHERE?

An atmosphere is a layer of gas that surrounds a world. It can create pressure, absorb and scatter sunlight, create wind and weather, interact with the solar wind to create a magnetosphere, and cause a greenhouse effect that can make a planet's surface warmer than it would be otherwise.

WHY DO ATMOSPHERIC PROPERTIES VARY WITH ALTITUDE?

Atmospheric structure is determined by the way atmospheric gases interact with sunlight. On Earth, the basic structure consists of the troposphere, where most greenhouse warming occurs; the stratosphere, where ozone absorbs ultraviolet light from the Sun; the thermosphere, where solar X rays are absorbed; and the exosphere, the extremely low-density outer layer of the atmosphere.

conduction

Conduction is the transfer of heat from hot material to cooler material through contact; it is operating when you touch a hot object. Conduction occurs through the microscopic collisions of individual atoms or molecules when two objects are in close contact, because the faster-moving molecules in the hot material tend to transfer some of their energy to the slower-moving molecules of the cooler material.

convection

Convection is the process by which hot material expands and rises while cooler material contracts and falls, thereby transporting heat upward; it can occur whenever there is strong heating from below. You can see convection in a pot of soup on a hot burner, and you may be familiar with it in weather: Warm air near the ground tends to rise while cool air above tends to fall.

WHY DOES EARTH'S CLIMATE STAY RELATIVELY STABLE?

Earth's long-term climate is remarkably stable because of feedback processes that tend to counter any warming or cooling that occurs. The most important feedback process is the carbon dioxide cycle, which naturally regulates the strength of the greenhouse effect.

solar wind stripping

For any world without a protective magnetosphere, particles from the solar wind can gradually strip away gas particles into space.

WHAT CREATES WIND AND WEATHER?

Global wind patterns are shaped by atmospheric heating and the Coriolis effect caused by a planet's rotation. Convection in the troposphere can lead to the formation of clouds and rain, hail, or snow.

HOW DOES THE GREENHOUSE EFFECT WARM A PLANET?

Greenhouse gases such as carbon dioxide, methane, and water vapor absorb infrared light emitted from a planet's surface. The absorbed photons are quickly reemitted, but in random directions. The result acts much like a blanket, slowing the escape of heat from the planet's surface.

HOW IS HUMAN ACTIVITY CHANGING OUR PLANET?

Human activity is releasing carbon dioxide and other greenhouse gases into the atmosphere, and scientific evidence confirms that this is causing global warming. This warming may have many consequences, including a rise in sea level, an increase in severity of storms, and dramatic changes in local climates.

WHY ARE SMALL ICY MOONS MORE GEOLOGICALLY ACTIVE THAN SMALL ROCKY PLANETS?

Ices deform and melt at much lower temperatures than rock, allowing icy volcanism and tectonics at surprisingly low temperatures. In addition, some jovian moons have a heat source—tidal heating—that is not important for the terrestrial worlds.

thermal escape

If an atom or a molecule of gas in a planet's exosphere achieves escape velocity [Section 4.5], it will fly off into space. The relative importance of thermal escape on any world depends on its size, distance from the Sun, and atmospheric composition. In general, more thermal escape will occur if a planet is small (so that it has a low escape velocity) or close to the Sun (which makes it hotter, so that atoms and molecules of atmospheric gas are moving faster). Lightweight gases, such as hydrogen and helium, escape more easily than heavier gases, such as carbon dioxide, nitrogen, and oxygen.

WHY ARE JUPITER'S GALILEAN MOONS SO GEOLOGICALLY ACTIVE?

Io is the most volcanically active object in the solar system, thanks to an interior kept hot by tidal heating—which occurs because Io's close orbit is made elliptical by orbital resonances with other moons. Europa (and possibly Ganymede) may have a deep, liquid water ocean under its icy crust, also thanks to tidal heating. Callisto is the least geologically active, since it has no orbital resonance or tidal heating, but may also have a subsurface ocean.

Which of the following best describes convection?

It is the process in which warm material expands and rises while cool material contracts and falls.

ARE JOVIAN PLANETS ALL ALIKE?

Jupiter and Saturn are made almost entirely of hydrogen and helium, while Uranus and Neptune are made mostly of hydrogen compounds mixed with metals and rock. These differences arose because all four planets started from ice-rich planetesimals of about the same size, but captured different amounts of hydrogen and helium gas from the solar nebula.

DO JOVIAN PLANETS HAVE MAGNETOSPHERES LIKE EARTH'S?

Jupiter has a magnetic field 20,000 times stronger than Earth's, which leads to an enormous magnetosphere. Many of the particles in Jupiter's magnetosphere come from volcanic eruptions on Io. Other jovian planets also have magnetic fields and magnetospheres, but they are weaker and smaller than Jupiter's.

WHAT GEOLOGICAL ACTIVITY DO WE SEE ON TITAN AND OTHER DISTANT MOONS?

Many medium-size and large moons show a surprisingly high level of past or present volcanism or tectonics. Titan has a thick atmosphere and ongoing erosion, and Enceladus is also geologically active today. Triton, which apparently was captured by Neptune, also shows signs of recent geological activity.

WHAT IS MARS LIKE TODAY?

Mars is cold and dry, with an atmospheric pressure so low that liquid water is unstable; however, a substantial amount of water is frozen in and near the polar caps. Martian weather is driven largely by seasonal changes that cause carbon dioxide alternately to condense and vaporize at the poles, creating pole-to-pole winds and sometimes leading to huge dust storms.

WHY DID MARS CHANGE?

Mars's atmosphere must once have been much thicker with a stronger greenhouse effect, so change must have occurred due to loss of atmospheric gas. Much of the gas probably was stripped away by the solar wind, which was able to reach the atmosphere as Mars cooled and lost its magnetic field. Water was probably lost as ultraviolet light broke apart water molecules in the atmosphere, and the lightweight hydrogen then escaped to space.

Rank the five terrestrial worlds in order of size from smallest to largest.

Moon, Mercury, Mars, Venus, Earth

WHY DO THE JOVIAN PLANETS HAVE RINGS?

Ring particles probably come from the dismantling of small moons formed in the disks of gas that surrounded the jovian planets billions of years ago. Small ring particles come from countless tiny impacts on the surfaces of these moons, while larger ones come from impacts that shatter the moons.

WHAT ARE SATURN'S RINGS LIKE?

Saturn's rings are made up of countless individual particles, each orbiting Saturn independently like a tiny moon. The rings lie in Saturn's equatorial plane, and they are extremely thin. Moons within and beyond the rings create many ringlets and gaps, in part through orbital resonances.

chemical reactions

Some chemical reactions incorporate gas into surface metal or rock. Rusting is a familiar example: Iron rusts when it reacts with oxygen, thereby removing oxygen from the atmosphere and incorporating it into the metal.

HOW DID EARTH'S ATMOSPHERE END UP SO DIFFERENT?

Temperatures on Earth were just right for outgassed water vapor to condense and form oceans. The oceans dissolve carbon dioxide and ultimately lock it away in carbonate rocks, keeping the greenhouse effect moderate. Nitrogen from outgassing remained in the atmosphere. Oxygen and ozone were produced by photosynthesis, which was possible because the moderate conditions allowed the origin and evolution of abundant life.

DO THE MOON AND MERCURY HAVE ANY ATMOSPHERE?

The Moon and Mercury have only very thin exospheres consisting of gas particles released through surface ejection by micrometeorites, solar wind particles, and high-energy solar photons.

condensation

The condensation of gases that then fall as rain, hail, or snow is essentially the reverse of the release of gas by vaporization. On Mars, for example, it is cold enough for carbon dioxide to condense into dry ice (frozen carbon dioxide), especially at the poles.

WHAT IS THE WEATHER LIKE ON JOVIAN PLANETS?

The jovian planets all have multiple cloud layers that give them distinctive colors, fast winds, and large storms. Some storms, such as Jupiter's Great Red Spot, can apparently rage for centuries or longer.

WHAT ARE JOVIAN PLANETS LIKE ON THE INSIDE?

The jovian planets have layered interiors with very high internal temperatures and pressures. All have a core about 10 times as massive as Earth, consisting of hydrogen compounds, metals, and rock. They differ mainly in their surrounding layers of hydrogen and helium, which can take on unusual forms under the extreme internal conditions of the planets.

HOW DO OTHER JOVIAN RING SYSTEMS COMPARE TO SATURN'S?

The other jovian planets have ring systems that are much fainter in photographs. Their ring particles are generally smaller, darker, and less numerous than Saturn's ring particles.

Under what circumstances can differentiation occur in a planet?

The planet must have a molten interior.

heat from radioactive decay

The rock and metal that built the terrestrial worlds contained radioactive isotopes of elements such as uranium, potassium, and thorium. When radioactive nuclei decay, subatomic particles fly off at high speeds, colliding with neighboring atoms and heating them. In essence, this converts some of the mass-energy (E = mc2) of the radioactive nuclei to the thermal energy of the planetary interior.

surface ejection

The tiny impacts of micrometeorites, solar wind particles, and high-energy solar photons can knock individual atoms or molecules free from the surface. This surface ejection process explains the small amounts of gas that surround the Moon and Mercury. It is not a source process for planets that already have substantial atmospheres, because the atmospheres prevent small particles and high-energy solar photons from reaching the surface.

HOW DOES A PLANET GAIN OR LOSE ATMOSPHERIC GASES?

Three sources of atmospheric gas are outgassing, vaporization of ices and liquids, and—on worlds with little atmosphere—surface ejection by tiny impacts of particles and photons. Four loss processes are condensation, chemical reactions with surface materials, the stripping of gas by the solar wind, and thermal escape.

WHAT IS VENUS LIKE TODAY?

Venus has a thick carbon dioxide atmosphere that creates a strong greenhouse effect, explaining why the planet is so hot. It rotates slowly and therefore has a weak Coriolis effect and weak winds, and is far too hot for rain to fall. Its atmospheric circulation keeps temperatures about the same day and night, and its lack of axis tilt means no seasonal changes.

HOW DID VENUS GET SO HOT?

Venus's distance from the Sun ultimately led to a runaway greenhouse effect: Venus became too hot to develop liquid oceans like those on Earth. Without oceans to dissolve outgassed carbon dioxide and lock it away in carbonate rocks, all of Venus's carbon dioxide remained in its atmosphere, creating its intense greenhouse effect.

outgassing

Volcanic outgassing has been the primary source of gases for the atmospheres of Venus, Earth, and Mars. Recall that the terrestrial worlds were built primarily of metal and rock, but impacts of ice-rich planetesimals (from beyond the frost line [Section 8.2]) brought in water and gas that became trapped in their interiors during accretion. Studies of volcanic eruptions show that the most common gases released by outgassing are water (H2O), carbon dioxide (CO2), nitrogen (N2), and sulfur-bearing gases (H2S and SO2).*

WHAT KINDS OF MOONS ORBIT THE JOVIAN PLANETS?

We can categorize the more than 170 known moons as small, medium-size, or large. Most of the medium-size and large moons probably formed with their planet in the disks of gas that surrounded the jovian planets when they were young. Smaller moons are often captured asteroids or comets.

heat from differentiation

When a world undergoes differentiation, the sinking of dense material and rising of less-dense material means that mass moves inward, losing gravitational potential energy. This energy is converted to thermal energy by the friction generated as materials separate by density. The same thing happens when you drop a brick into a pool: As the brick sinks to the bottom, friction with the surrounding water heats the pool—though the amount of heat from a single brick is too small to be noticed.

great red spot

a large-high pressure storm on jupiter

hot spot (geological)

a place within a plate of the lithosphere where a localized plume of hot mantle material rises

runaway greenhouse effect

a positive feedback cycle in which heating caused by the greenhouse effect causes more greenhouse gases to enter the atmosphere, which further enhances the greenhouse effect

Which internal energy source produces heat by converting gravitational potential energy into thermal energy?

accretion and differentiation

The three principal sources of internal heat of terrestrial planets are

accretion, differentiation, and radioactivity.

global warming

an expected increase in earth's global average temperature caused by human input of carbon dioxide and other greenhouse gases into the atmosphere

changes in reflectivity

an increase in a planet's reflectivity -- for example, from increased cloud cover, or particles released from volcanoes -- means a decrease in the amount of sunlight it absorbs, and vice versa

convection cell

an individual small region of convecting material

The core, mantle, and crust of a planet are defined by differences in their

composition

precipitation

condensed atmospheric gases that fall to the surface in the form of rain, snow, or hail

seismic waves

earthquake-induced vibrations that propagate through a planet

greenhouse gases

gases, such as carbon dioxide, water vapor, and methane, that are particularly good absorbers of infrared light but are transparent to visible light

The terrestrial planet cores contain mostly metal because

metals sank to the center during a time when the interiors were molten throughout.

changes in greenhouse gas abundance

more greenhouse gases tend to make a planet warmer, and less make it cooler

snowball earth

name given to a hypothesis suggesting that, some 600-700 million years ago, earth experienced a period in which it became cold enough for glaciers to exist worldwide, even in equatorial regions

seafloor spreading

on earth, the creation of new seafloor crust at mid-ocean ridges

seafloor crust

on earth, the thin, dense crust of basalt created by seafloor spreading

ice ages

periods of global cooling during which the polar caps, glaciers, and snow cover extend closer to the equator

feedback processes

processes in which a small change in some property (such as temperature) leads to changes in other properties that either amplify or diminish the original small change

geological activity

processes that change a planet's surface long after formation, such as volcanism, tectonics, and erosion

Which internal energy source is the most important in continuing to heat the terrestrial planets today?

radioactivity

mantle

rocky material of moderate density -- mostly minerals that contain silicon, oxygen, and other elements -- forms a thick mantle that surrounds the core

Coriolis effect

the effect due to rotation that causes air or objects on a rotating surface or planet to deviate from straight-line trajectories

weather

the ever-varying combination of winds, clouds, temperature, pressure in a planet's troposphere

planetary geology

the extension of the study of Earth's surface and interior to apply to other solid bodies in the solar system, such as terrestrial planets and Jovian planet moons

WHAT FACTORS CAN CAUSE LONG-TERM CLIMATE CHANGE?

the four factors that cause climate change are solar brightening (noticeable only over many millions of years), changes in axis tilt, changes in reflectivity, and changes in greenhouse gas abundance.

plate tectonics

the geological process in which plates are moved around by stresses in a planet's mantle

core

the highest-density material, consisting primarily of metals such as nickel and iron, resides in a central core

climate

the long-term average of weather

troposphere

the lowest atmospheric layer, in which convection and weather occur

crust

the lowest-density rock, such as granite and basalt (a common form of volcanic rock), forms a thin crust, essentially representing the world's outer skin

What is differentiation in planetary geology?

the process by which gravity separates materials according to density

differentiation

the process by which gravity separates materials according to density, with high-density materials sinking and low-density materials rising

greenhouse effect

the process by which greenhouse gases in an atmosphere make a planet's surface temperature warmer than it would be in the absence of an atmosphere

carbon dioxide cycle (CO2 cycle)

the process that cycles carbon dioxide between earth's atmosphere and surface rocks

magnetic field

the region surrounding a magnet in which it can affect other magnets or charged particles

magnetosphere

the region surrounding a planet in which charged particles are trapped by the planet's magnetic field

lunar maria

the regions of the moon that look smooth from earth and actually are impact basins

bar

the standard unit of pressure, approximately equal to earth's atmospheric pressure at sea level

solar brightening

the sun has grown gradually brighter with time, increasing the amount of solar energy reaching the planets

atmospheric pressure

the surface pressure resulting from the overlying weight of a atmosphere

changes in axis tilt

the tilt of a planet's axis may change over long periods of time

radiation

this radiation (light) carries energy away and therefore cools an object. Planets lose heat to space through radiation; because of their relatively low temperatures, planets radiate primarily in the infrared.

charged particle belts

zones in which ions and electrons accumulate and encircle a planet