chap 10 & 11 Flashcards
Why is it hard for us to view Venus’ surface?
Because it is surrounded by a layer of cloud which never clears.
What are our 3 main sources of information about Venus?
Venus Express, Magellan + USSR mission
Why does Venus rotate clockwise (opposite to most other planets)?
Venus rotates clockwise (retrograde) and it is likely it rotated counterclockwise initially, but it got knocked about by a large impact toward the end of its growth period which caused it to flip its axis 180 degrees. This situation may also be controlled by the gravitational force between the Earth and Venus.
- Which is longer, a year or a day on Venus?
A day is longer than a year on Venus due to the slow retrograde rotation of 243 Earth days and the direct revolution around the Sun of 225 days (a year), combines to give a Venusian day of 117 Earth days.
What is the composition of the cloud layer? What is the main component of the
atmosphere? How do these things affect the climate?
The cloud layer that covers Venus is composed mainly of droplets of liquid/solid sulfur and droplets of sulfuric acid.
The main component of the atmosphere is carbon dioxide (96.5%), nitrogen (3.5%), and trace amounts of water vapour, sulfur dioxide and free oxygen.
The carbon dioxide rich atmosphere affects the climate.
Has there ever been water on Venus? What is the evidence? What happened to it?
There was water on Venus before which since then broke down into atomic form. We know water existed b/c Venus had a similar formation as Earth and was bombarded with comets that delivered quantities of water. However, without an ozone layer to protect the Venusian atmosphere from ultraviolet radiation, the atmospheric water was broken up and much of the hydrogen was lost to space.
Earth and Venus have similar amounts of carbon – so why doesn’t Earth have the same runaway greenhouse effect as Venus?
Earth avoided the runaway greenhouse effect that made the surface of Venus so hot because it was farther from the Sun and cooler. Thus, it could form and preserve liquid-water oceans to absorb the carbon dioxide, which left a nitrogen atmosphere.
Why are their fewer impact craters (and fewer small craters) on Venus compared to
Moon and Mercury?
This is a result of the planet’s dense atmosphere - the small objects just burn up through friction with the atmosphere
What is the evidence that the surface of Venus is young?
Crater counts help estimate relative age of a Solar System body, and Venus has fewer craters of any size relative to the Moon, Mercury and Mars
Crater analysis says the surface is about 500 million years old but we know the planet is about the same age as Earth: close to 4.5 billion years old
What volcanic features exist on the surface of Venus?
Volcanic features include very small volcanic domes on fairly level lava fields, immense volcanoes, and immense blocky rides and valleys bounded by faults.
What causes a global volcanic event? What is the evidence that this has occurred?
A global volcanic event is caused by plate tectonics on Earth, but on Venus there are no plate tectonics, so it could build up tremendous heat and eventually cause volcanic eruptions that resurface the whole planet.
There is visual evidence of the breakdown of surface rock.
Why do rocks erode faster on Earth than on Venus?
Earth has water as an agent of weathering and erosion, and as well, winds on Earth are much faster than those on Venus.
What causes erosion on Venus?
wind.
What causes the weak magnetic field on Venus (how does this differ from the cause of
the magnetic field on Earth)?
The weak magnetic field on Venus comes from the interaction between the solar wind and the atoms/molecules of the upper atmosphere, creating a very weak magnetosphere. On Earth, the magnetic field is generated by the speed differential between an inner solid metal core and an outer liquid metal core. On Venus, there is no such zonation - the core is completely liquid metal.
What is the proposed geological history of Venus – how does this compare to the stages of formation of the other rocky planets you have read about so far?
While Earth, the Moon, and Mercury all passed through the same four stages of history: differentiation (separation of material according to density), cratering (by violent comet impacts), flooding (by lava flows), and slow surface evolution, Venus is different as its formation is not thoroughly understood.
