Earth Sciences 1086F/G Study Guide - Final Guide: Martian Meteorite, Near-Earth Object, Geology Of Mars

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Earth Sciences – Final Exam, Chapters 10-19
Tuesday, April 12 at 7pm in AH201
Chapter 10 – Venus
1. Introduction
Named after the Roman goddess of love and beauty
Often called the ‘evening star’ or ‘morning star’ as you normally see it 3 hours before or
after sunrise/sunset
oIs brighter than any other object in the sky other than the moon at these times
Difficult to see with a telescope, as it has a large layer of clouds which never clears
Used to be known as “Earth’s twin” – this is no longer true
oUsed to think this because: Nearly the same size and similar density
oNow know: its drier that Earth
Russia (USSR) won the space race to Venus
Magellan space probe collected data for the USA
oEntered Venus’s atmosphere in 1994
Venus Express
olaunched in 2005
oCollected data that caused us to rethink some of our previous theories
oMission ended in December 2014
oExciting discovery: the observation of young lava flows, which means that Venus
may well be geologically active today
2. Planet Facts
Apparent retrograde
Very slow rotation
Very hot 462°C
No satellites
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2.1. Orbit and Rotation
0.72 AU (second planet from the sun)
Orbit takes 225 days
Venus rotates in a clockwise or retrograde motion
oDoes so very slowly (you could walk faster than the planet rotates)
Surface rotates very slowly, clouds rotate quicker
Every time Venus is close to Earth, we see the same side of the planet (may be due to
the gravitational forces between Earth and Venus)
3. Atmosphere
Venus is completely covered in a thick blanket of clouds made of liquid sulfur and
droplets of sulfuric acid
Atmosphere on Mars: CO2, nitrogen, water vapor, sulfur dioxide, free oxygen
At one time Venus had an abundant source of water, but has since lost it
There is an equal amount of CO2 on Venus as Earth, but most of our CO2 is in the rocks
and oceans
Atmospheric pressure is 90x greater on Venus than Earth
Large volumes of the atmosphere on Venus is escaping
The stream of electrons coming from the Sun collides with particles in the upper
atmosphere of Venus, energizes them, and blasts them off into space. Scientists are still
working to determine the replacement process from the planet surface.
Greenhouse
Has a greenhouse effect that is fearsome
Carbon dioxide is transparent to in-coming light energy and opaque to out-going
infrared energy
greenhouse effect begins with incoming short
wavelength light energy from the Sun warming a
planet’s surface, but ends up with a surface or near-
surface growth of heat because of the inability of the
long wavelength infrared energy to escape a CO2-
rich atmosphere and get back out to space
the wavelengths of radiated energy that CO2 does
allow to escape back into space from a planet
surface are exactly blocked by water and sulfur
dioxide
there is not a large amount of this on Venus, but it is
enough to strengthen the greenhouse effect very, very substantially
End result: temperature surface of Venus is 462 °C (hotter than Mercury)
Water on Venus
There was quite a bit of water on Venus
When ultra-violet radiation strikes a water molecule (H2O) it breaks it up into
hydrogen and OH
Hydrogen has two stable isotopes: normal hydrogen and heavy hydrogen
(deuterium)
The gravity of both Earth and Venus is such that hydrogen atoms can escape, but
obviously the lighter atoms escape more readily than the heavy ones (the
deuterium)
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Discoveries mean that Venus once had an abundance of liquid water that since
broke down to atomic form
o150 times more deuterium per atom of light hydrogen in the Venus
atmosphere
odetected OH (the other breakdown product of the water molecule) in the
Venus atmosphere
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.
The released oxygen presumably formed oxides in the soil.
Thus, Venus is now a deadly dry world with only enough water in the atmosphere to
make an ocean 0.3 meters
Surface temperature increased, oceans evaporated, so Venus losy its ability to
cleanse its atmosphere of CO2
high temperature baked even more CO2 out of the surface, and the atmosphere
became even less transparent to infrared radiation (making temperature rise
further)
Earth avoided this as we are farther away from the Sun
Remember: If all of the carbon dioxide in Earth's rocks was put back into the
atmosphere, our air would be as dense as that of Venus, and we would suffer from a
severe greenhouse effect.
Even though there are clouds covering Venus, the lower atmosphere is clear/has
visibility
Venus has gentle winds (about 13km/hr)
Atmospheric circulation on Venus is not broken up into small cyclonic storms over
most of the planet, but instead is organized as a single, planet-wide wind pattern.
But not so at the poles: Figure 10.8 is a collage of infrared light images taken
recently by
4. Geology
4.1. The Surface of Venus
Has relatively few large impact craters
oMajority of impact craters are medium to large
Is a result of the planet’s dense atmosphere
oThe small objects burn up through friction with the atmosphere
We can age planets based off of the number/size of craters
oVenus would therefore be quite young – this is not the case
oVenus is about the same age as Earth, so there must have been some sort of
global resurfacing about 500 million years ago
4.2. Volcanic Features
Surface is variable there are: clusters of volcanic domes sitting on fairly level lava
fields, immense volcanoes, ridges and valleys
Surface is dominated by volcanic features
Coronae: a huge dome surrounded by concentric fractures (figure )
oFormed by mantle plumes that bring magma right up under the crust and
then partially subside
Pancake volcanoes
oVolcanoes less than 20 km in diameter that may appear as flattened domes
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