Astronomy Test Chpt8-9

How do scientists determine the ages of very old rocks?

1) Scientists determine the ages of very old rocks through radiometric dating where : the ratio of unstable radioactive elements to stable radioactive elements signals the age of the rock as the older the rock is----> the more the stable radioactive elements---> and the fewer the unstable radioactive elements-if any. 2) The number of craters indicates the surface's age ----> More craters means an older surface and minimal geologic activity ---> Tectonism and erosion can erase craters.

What planets have relatively few craters? Why?

Earth and Venus have relatively few craters because they have thicker atmospheres that act as shields to meteoroids.

Erosion

Erosion via many variables such as water hitting against rock

If the Moon isn't a planet, why do we include it when comparing/contrasting the terrestrial planets?

Even though the Moon is not a planet, it is included in the comparing/contrasting of terrestrial planets because: it has many of the same traits as terrestrial planets and can therefore be used as reference point in the comparing/contrasting process.

Why do geologists think there was once a lot of liquid water on the surface of Mars?

Geologists think that there was once a lot of liquid water on the surface of Mars because: 1) the impact craters on Mars look as though they are surrounded by liquid-like material; 2) this suggests that there must have been ice on Mars that, 3) when impacted by the meteorite, was so affected by the heat of the impact that the ice liquefied and mixed with the surface [of Mars] then eventually dried, leaving the appearance of a past existence of water on Mars.

If crater A formed inside crater B, what does this tell us about their ages?

If crater A formed inside crater B, this tells us that crater B is older than crater A as crater B has clearly existed long enough to be impacted again. ]

Volcanism

Igneous activity, magma/lava

Four Processes that have shaped the Earth

Impact cratering, Tectonism, Volcanism, Erosion

Jovian Planets

Jovian Planets are large, made primarily of gases, and are found farther than the Sun.

Jovian Planets

Jupiter, Saturn, Uranus, Neptune

Impact Cratering

Material falling from space onto planet's surface. Impact cratering, tectonism, and volcanism create features whereas erosion tears down features.

What planets are covered with craters? Why?

Mercury and the Moon are covered with craters b/c they have weak, if any, atmospheres that fail to act as shields to meteorites

Terrestrial Planets

Mercury, Venus, Earth, Mars

Tectonism

Modifications of the Crust (b/c movement of tectonic plates)

What is plate tectonics?

Plate tectonics is the concept that the Earth's lithosphere -its outer shell- is made up of many geographical 'plates' that are constantly in motion and are therefore responsible for much of the Earth's geography.

Secondary Craters

Secondary craters are created as result of ejecta from an impact cratering

Comparative Planetology

Studying planets by comparing them to each other

Terrestrial Planets

Terrestrial Planets are small, rocky, and near the Sun

What planets are affected by Impact Cratering?

The Moon and other terrestrial planets are affected by impact cratering. Large impacts can melt and vaporize rock.

Is the rate of impact cratering constant, or has the rate of impacts changed over time?

The rate of impact cratering can not be steadily determined due to the processes of terrestrial planets: tectonism, volcanism, and erosion- which constantly create, alter and rid of geographical features such as crater impacts