Chapter 7

What do we conclude if a planet has few impact craters of any size?

geological processes have erased craters.

Where is most of the CO2 that has outgassed from Earth's volcanoes?

it is locked up in rocks

How many of the five terrestrial worlds are considered "geologically dead?"

only two

New photographs reveal sand dunes on Mercury.

False, Our current observations of Mercury show it covered by craters, and absolutely barren of water or an atmosphere. Since sand dunes are built up by erosion cause either by winds of an atmosphere or of currents in water, we therefore wouldn't expect to see sand dunes since we see neither water nor air on Mercury.

What is outgassing, and how did it lead to the existence of Earth's atmosphere and oceans?

Outgassing - the release of pressure expelling trapped gasses from molten rock. The gas that made the Earth's atmosphere and the water vapor that formed the Earth's oceans came from outgassing.

What is the carbon-dioxide cycle and why is it so crucial to life on Earth?

Plants use carbon dioxide to react with water in photosynthesis to make starch and sugar and oxygen. Without carbon dioxide, there would be no plants, no animals. Carbon dioxide traps heat from the sun in the atmosphere. Without it, the world would be a lot colder.

What do we mean by a runaway greenhouse effect? Explain why this process occurred on Venus but not on Earth?

Runaway greenhouse effect refers to the fact that the co2 concentration increases exponentially, and when this happens light is scattered, but heat doesn't escape our atmosphere It happens in Venus because they have no plant life, but also because it can't dissolve in water (there isn't any). Our earth had a high co2 concentration, but over time, it solidified and was absorbed in water.

Describe the basic geology of Venus. Why is it surprising that Venus lacks plate tectonics? We might explain this lack?

Venus's surface shows evidence of major volcanic and tectonic activity in the past billion years, as expected for a planet nearly as large as Earth. This activity explains the relative lack of craters. Erosion is only a minor process despite the thick atmosphere, because of the high temperature (no rainfall) and slow rotation (little wind).Venus almost certainly remains geologically active today. Either Venus has a weaker mantle convection or that its lithosphere resists fracturing

Describe 4 ways in which Earth is unique among the terrestrial worlds, and how each is important to life.

1. Surface liquid water, made possible by earth's moderate temperature. 2. Atmospheric oxygen, a product of photosynthetic life. 3. Plate tectonics, driven by internal heat. 4. Climate stability a result of the carbon dioxide cycle, which in turn requires plate tectonics.

In general, what kind of terrestrial planet would you expect to have the thickest lithosphere?

A small planet

Explain why liquid water is not stable on Mars today, but why we nonetheless think it flowed there in the distant past.

Current surface conditions do not allow liquid water to remain stable on Mars. In most places and at most times, Mars is so cold that any liquid would immediately freeze into ice. The air pressure is so low that liquid water would quickly evaporate. Mars must once have had very different surface conditions- conditions such as warmer temperatures and greater air pressure that would have allowed water to flow and rain to fall.

Why did the terrestrial worlds undergo differentiation? Why have larger worlds retained more internal heat than smaller ones?

Differentiation- the process by which gravity separates materials according to density, with high-density materials sinking and low-density materials rising. Because larger planets have more insulation.

Describe the conveyor-like action of plate tectonics, and how it changes the arrangements of the continents with time.

Earth's geology as a result of the slow motion of plates that essentially "float" over the mantle, gradually moving over, under, and around each other as convection moves earth's interior rock. Earth's lithosphere is broken into more than a dozen plates. Subduction occurs at ocean trenches, where dense seafloor crust pushes under less dense continental crust, thereby returning seafloor crust to the mantle. The subducting seafloor crust may partially melt, with low-density material melting first and erupting from volcanoes as new continental crust. New seafloor crust is created by eruptions at mid ocean ridges, where plates spread apart. The entire seafloor is replaced every 200 million years.

We find a planet in another solar system that has an Earth-like atmosphere with plentiful oxygen but no life of any kind.

False, Oxygen is highly reactive and in presence in at atmosphere suggests replenishment by a living organism of some sort

A new orbital photographs of Mars shows a crater bottom filled with a lake of liquid water.

It could be possible due to how there was water on Mars in the past, if the photo were real it wouldn't exactly be a lake more maybe like a puddle.

Which describes our understanding of flowing water on Mars?

Once important but no longer is

Describe the leading hypothesis for how Mars lost much of its atmosphere some 3 billion years ago, and identify the role played by Mar's size.

The hypothesis is that after Mars lost it's magnetic field solar wind particles stripped away the atmosphere. The size of the planet it important for explaining why the magnetic field was lost. The magnetic field would have been sustained by the movement of molten metal in the core. However, a small planet like Mars cools more quickly, so the metal stops moving and the magnetic field weakens.

A new orbiter observes a volcanic eruption on Venus.

True, Venus has more volcanoes than any other planet in the solar system

Radiometric dating of rocks brought back from one lunar crater shows it formed only 10mill years ago

True, With no atmosphere, asteroids have collided with the moon and created craters since it was formed 4 billion years ago and will continue to do so as long as it exists.

Which terrestrial world has the most atmospheric gas?

Venus

Which of the following is a strong greenhouse gas?

carbon dioxide

Define the four major geological processes, giving examples of features on Earth shaped by each process.

1. Impact cratering- the excavation of bowl-shaped depressions (impact craters) by asteroids or comets striking a planet's surface (Scarred faces of the moon and mercury). 2.Volcanism- the eruption of molten rock, or lava, from a planet's interior onto its surface (Mount Hood on Earth). 3. Tectonics-the disruptions of a planet's surface by internal stresses (New Mexico's Rio Grande Valley). 4. Erosion-the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather (glaciers, craving of canyons, rivers, shifting of sand dunes).

Why does Earth have a global magnetic field? -What is the magnetosphere?

Because it meets the three basic requirements 1. An interior region of electrically conducting fluid (liquid or gas) such as molten metal 2. Convection in that layer of fluid 3. At least moderately rapid rotation. -Magnetosphere means the region surrounding the earth or another astronomical body in which its magnetic field is the predominant effective magnetic field.

Which of the planet's fundamental properties has the greatest effect on its level of volcanic and tectonic activity?

Its size

Briefly summarize the geological histories of the Moon and Mercury. How did the lunar maria form? How are Mercury's great cliffs thought to have formed?

Mercury: Same as the moon basically. Heavy bombardment, then lava covered up some of the craters, it has more huge impact craters. They formed when tectonic forces compressed the crust, causing the surface to crumple. the lunar maria formed when lava filled in large craters

Describe the key ways in which the atmosphere affects Earth. What is the greenhouse effect, and how does it work?

The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. D uring the day, the Sun shines through the atmosphere. Earth's surface warms up in the sunlight. At night, Earth's surface cools, releasing the heat back into the air.

How do crater counts tell us the age of a surface? Explain why the Moon has so many more craters than Earth?

The more craters a planet or moon has the older it is. There are more craters on the Moon because: the moon's surface must have stayed virtually unchanged for billions of years. And our surface we see very few craters, so we must be looking at a younger surface, one on which the scars of ancient impacts have been erased over time by other geological processes such as volcanic eruptions or erosions.

The oxygen in Earth's atmosphere was released by....

life