Chapter 16: Earth and Other Planets

In addition to numerous moons, each of the four Jovian planets has a ___________________________________.

System of rings formed from fragments of ice and rock Saturn: ice crystals separated by larger objects called shepherd satellites Uranus and Neptune: dark carbon-rich material

True or false: Scientists have observed the presence of numerous disks around young stars

TRUE - Hubble Space Telescope - Orion nebulae

Solar system

The Sun, the planets and their moons, and all other objects gravitationally bound to the Sun

Outgassing today

Volcanoes release large amounts of gases from Earth's interior

Scientists estimate that Earth's mass grows by about _______________________ per day by accretion of material falling from space

20 metric tons - Still occurring

The planet with the greatest number of named moons is ___________________________.

Jupiter

Continuously Habitable Zone (CHZ)

The region around a star where the temperature stays in the right range for water to be in its liquid form

The structure of the outer giant planets is _____________________________.

Also layered - Don't have a well-defined solid surface Moving down from space into the planet: 1. Move through progressively denser and denser layers of clouds 2. Pass imperceptibly into a layer where the gases change into liquids - High pressure

Great bombardment

An event following the initial period of planetary formation in which meteorites showered down on planets, adding matter and heat energy - Impacts affected planets' axis of rotation (explains why the rotations of individual planets can be so different)

Comet

An object composed of chunks of materials such as water ice and methane ice embedded with dirt - Usually found outside the orbit of Pluto - May fall toward the Sun if its orbit is disturbed/deflected (creates a display or is captured in an orbit)

A comet's tail is _______________________________.

Blown away from the Sun by the solar wind - Reflects light to us

Humans in environments with lower gravity experience ____________________________.

Bone loss

Objects found by Doppler are categorized as ____________________.

Candidates until they can be confirmed as planets

______________________________ was the first spacecraft to enter orbit around Saturn

Cassini - 2004 - Largest and most complex space probe ever launched - Mainly explores Saturn's moon Titan

Pluto was discovered by ____________________________________.

Clyde Tombaugh - Originally called "Planet X"

The impacts of _______________________________________ may have drastically altered Earth's climate and produced mass extinctions

Comets or asteroids - Strike near Mexico's Yucatán Peninsula may have killed the dinosaurs

Nebular hypothesis: the orbits of the planets

Consequence of the solar system's rapid rotation as the nebular cloud began to contract - The planets formed from a rotating disk of material, and their eventual orbits had to lie close to the disk's plane

The ancestors of modern living things may not have gotten their start until the ___________________________.

End of the bombardment - Otherwise, would have been vaporized - 4.2 and 3.8 billion years ago

Extrasolar planets were predominantly discovered by ____________________________.

Examining the fluctuations in the frequency of light emitted by the star

True or false: hot Jupiters are common

FALSE

The closest gas giant is ____________________________.

Jupiter - Five times the Earth-Sun distance, over 800 million kilometers away

Terrestrial planets have a ________________________ structure.

Layered - Due to differentiation

Another name for a shooting star is a(n) ____________________________

Meteor

Meteor vs. meteorite

Meteor A piece of interplanetary debris that hits Earth's atmosphere and forms a bright streak of light from friction with atmospheric particles: a "shooting star" Meteorite The fragment of a meteor that hits Earth

Opportunities to study the atmosphere of Jupiter

Mid-1990s 1. Comet Shoemaker-Levy - String of objects that collided with Jupiter - Brought gases that normally lie hundreds of miles deep up to the top of the atmosphere 2. Galileo - Orbited Jupiter and launched a probe

The _____________________________ is one of the largest bodies in the solar system.

Moon - Larger than Mercury and almost as large as Mars - Composition almost identical to Earth's mantle

Halley's Comet

Most famous comet to be captured and fall into a regular orbit around the Sun - Seen every 76 years

Plutoid

Planet-like bodies in the Kuiper Belt, including Pluto - Applies to any large planet-like object orbiting farther out than Pluto - Eris is larger than Pluto

Scientists speculate that the existence of solar systems similar to ours, (terrestrial planets moving in near circular orbits about the star) is __________________________________.

Possible, but not typical throughout the universe

The _______________________________ on early Earth can be thought of as the first global pollution event.

Production of oxygen by living things

Scientists believe that ____________________________, may well serve as a laboratory for chemical reactions that took place billions of years ago on Earth

Saturn's moon Titan - Made primarily of rock and water ice, with liquid methane raining down and forming large lakes - Presence of black goo suggests that the chemical reactions that form organic compounds take place on Titan (slowed down by the cold)

Asteroids

Small rocky objects that circle the Sun like miniature planets - Concentrated mostly in an asteroid belt between Mars and Jupiter - Never underwent the process of differentiation, so tend to be rich in minerals

Clues to the origin of our solar system can be found in _____________________________.

The motion of the planets around the Sun

Extrasolar planets

Exoplanets; planets outside the solar system

Nebular hypothesis

1. About 4.5 billion years ago, nebulae collected in the region now occupied by the solar system 2. Under the influence of gravity, the nebula started to collapse on itself 3. The collapse caused the cloud to spin faster and faster 4. The rapid spin caused some of the material in the outer parts of the cloud began to spin out into a flat disk - Analogy: large pancake with a big lump in the middle. 5. The big lump represents the material that will eventually become the Sun - More than 99% of the nebula's original mass 6. The material in the thin, flattened disk will eventually become the planets and the rest of the solar system

As the solar system formed, not all the material in the planetary disk was taken up into the bodies of the planets and moons. The remaining debris comes in two main forms, _________________________________.

1. Asteroids 2. Comets

Composition of Earth

1. Core - Earth's center - Primarily iron and nickel metal - Metallic bonding - High heat - Inner core is kept solid by high pressure, but pressure lessens slightly as you move outward, resulting in a liquid outer core 2. Mantle - Middle layer - High in oxygen, silicon, magnesium, and iron - Minerals with primarily ionic bonds - More dense than surface minerals 3. Crust - Outer layer - Made up of the least dense materials - Varying thickness - Source of almost all the rocks and minerals used by humans

Planetary Atmospheres: Formation

1. During the early formation of the Sun, large amounts of material and radiation were thrown off 2. This flood of materials would have blown off any atmosphere Earth might have accumulated 3. During the period of cooling that followed the great bombardment and melting, large amounts of water vapor, carbon dioxide, and other gases would have been released from deep within Earth's solid interior in a process called outgassing - Gases that formed the ancestor of today's atmosphere were locked into the rocks near Earth's surface or in orbiting debris 4. Initially, Earth's atmosphere was probably too hot for water to condense from a gas to a liquid 5. Eventually the atmospheric temperature dropped and torrential rains began to fill the ocean basins

Formation of the moon

1. Earth underwent differentiation so that the heaver material sank to the core and the lighter material floated up into the mantle 2. At this point, a Mars-sized planet that was competing with Earth for a similar orbit around the Sun smashed into Earth in an immense collision - As a result of the collision, large-scale melting occurred so that Earth's surface re-formed without any crater. 3. This blasted a large amount of Earth's mantle material (but not the dense metal core) into space 4. Some of this material went into orbit around Earth and formed the Moon - Causes the moon's low density

Planetary Atmospheres: Evolution

1. Gravitational escape - The molecules in an atmosphere heated by the Sun may move sufficiently fast so that appreciable fractions of them can escape the gravitational pull of their planet - Ex: The Moon, Mercury, and Mars 2. Effect of living things - Only occurs on Earth - Photosynthetic organisms, etc.

The force of gravity, pulling inward on all of Earth's layers, results in _____________________________________. The highest sustained laboratory pressures available today are obtained by _______________________________________.

1. Immense internal pressures - Exceeds 3 million times the atmospheric pressure at Earth's center 2. Clamping together two tiny pointed anvils of diamond - Samples are squeezed between the diamond-anvil faces and subjected to high pressures

Three important moons of outer planets

1. Io - Jupiter - Has active volcanoes (driven by Jupiter's gravitational forces) 2. Europa - Jupiter's second moon - Newer (no craters) - May have conditions for the development of life - Smooth, ice surface with potential for liquid water underneath (some indications of liquid on surface) - Magnetic field c 3. Enceladus - Saturn - Similar structure to Europa

Why did the terrestrial and Jovian planets form differently?

1. Light energy began to radiate out from the Sun 2. Large temperature differences began to develop in the disk 3. Parts nearest the Sun were heated higher than those farther out 4. Separated by a "frost line" somewhere outside the orbit of Mars, beyond which liquid water did not form. 5. Inner and outer solar systems developed differently Inner planets - Formed from materials that could remain solid at high temperatures - Compounds such as water, methane, and carbon dioxide were in gaseous form Outer planets - Formed from material that condensed and accumulated under the condition of lower temperatures far from the Sun - Same composition as the material concentrated in the original nebula (large amounts of hydrogen and helium) - Theorize have concealed core like a small terrestrial planet (small fraction of total mass) - Compounds such as water, methane, and carbon dioxide are liquids or solids (pressure and temperature)

_______________________________ once had a large ocean. It may have looked much like Earth before ___________________________________.

1. Mars - A substantial quantity of water remains locked in the Martian crust (ex: polar regions) - Microbial life may have existed and may still persist underground 2. It lost its atmosphere to gravitational escape

Planetary Orbits

According to Newton's laws, there are no constraints regarding the orientation of the orbit, and planets could orbit any which way around the Sun. Nevertheless: 1. All planets, and most of their moons, orbit in the same direction around the Sun - Direction is the same as that of the rotation of the Sun 2. All orbits of planets and their larger moons are in more or less the same plane - Ex: Marbles rolling on a plate 3. Almost all planets and moons rotate on their axes in the same direction as the planets orbit the Sun

How does the material in the thin, flattened disk eventually become the planets and the rest of the solar system?

1. Matter is more densely collected in some regions than elsewhere 2. These regions exert a stronger gravitational force than their neighbors, so that nearby matter tends to gravitate to them 3. Leads to the rapid breakup of the disk into small objects called planetesimals 4. Gravity causes planetesimals collide with each other 5. Larger planetesimals swallowed smaller planetessimals - Coalesce into planets 6. Each growing planet gradually swept up most of the debris that lay near its orbit

Gravitational escape and earth

1. Most of the light elements were lost - Ex: hydrogen and helium 2. The heavier gases remained because they were too heavy to escape Earth's gravitational force - Ex: carbon dioxide and water vapor

Potential means to drill through Europa's ice layer

1. Penetrator - Melt surface ice, then heat the resulting water to melt its way down through the thick ice layer - When reached liquid, would release a small submarine that would explore the new environment 2. Lightweight drill - Lowered by a tether until it had penetrated to the ocean

The nebular hypothesis was developed by ______________________________. The nebular hypothesis explains ____________________________________.

1. Pierre Simon Laplace 2. The rotation of the Sun, the orbits of the planets, and the distribution of mass into one large central object and lots of much smaller orbiting bodies

Clues to the origin of the solar system

1. Planetary Orbits 2. The Distribution of Mass

Differentiation of Earth

1. Planetesimals hit the young Earth 2. All the planetesimals' kinetic and potential energy was converted into heat 3. The heat diffused through the planet 4. Earth heated to high enough temperatures so that it was very soft all the way through 5. Heavy, dense materials (like iron and nickel) sank under the force of gravity toward the center of the planet 6. Lighter, less dense materials floated to the top Other inner planets underwent similar differentiation

Terrestrial vs. Jovian planets

1. Relatively small, rocky, high-density worlds - Inner (near the Sun) - Mercury, Venus, Earth, Mars, and (although it isn't really a planet) Earth's Moon 2. Jovian planets - Outer (far from the Sun) - Gas giants - Jupiter, Saturn, Uranus, and Neptune

Pluto

1. Small - Only about 0.3% of Earth's mass 2. Orbit is tilted out of the plane of other planetary orbits - Spends part of each of its "years" inside the orbit of Neptune 3. Circled by a moon which is almost as large as itself - Charon

Two main reservoirs of comets

1. The Oort cloud - Large spherical array - Located far from the solar system 2. Part of the Kuiper Belt

The first extrasolar planet was found because __________________________. Transits are monitored by the __________________________________.

1. The planet was circling a pulsar - Changes in the pulsar's radio emissions were monitored 2. Kepler satellite - Orbits the sun behind Earth

Why are there differences in composition between the various outer planets?

1. Uranus and Neptune formed much closer to the Sun than they are now 2. Formed in a region where much of the hydrogen had been blown away by particles streaming out from the Sun 3. Less of the lighter elements than Jupiter and Saturn 4. Gravitational forces associated with Jupiter and Saturn pushed Uranus and Neptune out to their present orbits

Extrasolar planets are found ______________________________.

1. Using the Doppler effect - Periodic changes in the redshift or blueshift) - Usually "hot Jupiters" (large planets orbiting close to their stars) 2. Transits - The temporary dimming of a star when its planet passes between it and Earth

The Distribution of Mass

1. Virtually all of the material of the solar system is contained within the Sun - Only a small fraction in the planets and other objects in orbit 2. Planets are divided into only two distinct types - Terrestrial planets (inner) - Jovian Planets (outer)

How many moons orbit the planet Mars?

2

Kuiper Belt

A region close to our solar system that contains comets that orbit the Sun; a reservoir of new comets - Rather than a planet, Pluto is the first typical object in the Kuiper Belt (plutoid)