Download Earth - Astro UC

Introduction to
Astronomy
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AST0111-3 (Astronomía)
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Semester
2014B
Prof. Thomas H. Puzia
Venus
Venus
The atmosphere of Venus is very dense
and an opaque layer of clouds covers the
planet, such that we cannot see the surface
directly and it can only be mapped by radar.
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For this reason, it was very difficult to
determine the duration of rotation of the
planet. The 243 d rotation period was
measured by radar from Earth.
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This rotation is retrograde, however,
probably due to a collision when the planet
was forming.
The atmospheric clouds are not composed of water vapor, but sulfuric acid. Due to
its atmosphere, the surface conditions are extreme: the temperature (735K) and
pressure (93 bar vs 1 bar on Earth’s surface) are quite high.
Venus
Venus is the planet closest to the Earth,
orbiting at about 0.7 AU from the Sun.
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Many properties of the planet are quite
similar to our own. For example, its size
and interior structure are very similar to
that of the Earth.
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However, there are some important
differences: Venus has no magnetic field
like Earth because its rotation is so slow,
and its atmosphere is about 100 times
denser than ours.
The high atmospheric density has led Venus to undergo a runaway
greenhouse effect. All of the greenhouse gases like CO2 and H2O have
ended up in the atmosphere, causing extreme greenhouse conditions.
What does the lack of a strong magnetic field mean for planets like Venus?
A.
B.
C.
D.
They have no north and south.
They have no aurorae.
They can be more directly affected by the solar wind.
They can be more directly affected by high-energy particles called
cosmic rays, which travel large distances throughout our Galaxy.
E. More than one of the above.
Magellan Probe
In the 1990s, the Magellan spacecraft took detailed images of the surface of Venus
using radar that can pass easily through the clouds.
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The Magellan radar images revealed a complex terrain, including volcanoes,
volcanic domes, valleys, canyons, and many pristine impact craters. The latter
implies the volcanoes are largely inactive now and there is little large scale erosion.
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There are two elevated regions or “continents”, Ishtar Terra in the north and the
landmass of Aphrodite in the equatorial zone. The highest mountains are the
Maxwell Montes, which are higher than Mount Everest.
Venera Probes
The only spacecraft to land on the surface successfully were the Russian spacecraft
Venera 9 and 10 in 1975 and then Venera 13, 14, 17 and 18.
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The Venera photos show a rocky soil that is eroded, with sharp-edged flat rocks.
Some rocks are basalt, volcanic, and others appear to be granite, probably from the
old planetary crust.
Venera Probes
The Venera probes landed in some highland regions called Beta Regio.
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These ships only survived for an hour before succumbing to the pressures and
extremely high temperatures of the corrosive atmosphere. That was enough to
make and broadcast some images of the surface. The real color of the surface
and the air would be ochre, with lighting that looks like a very cloudy day on Earth.
Venera Probes
Earth
Internal Structure
Geologically active planet
Surface:
oceans and
continents
Atmosphere
Greenhouse effect
Life
Magnetic Field
Earth and Moon images taken from Mars!
Earth and Moon as seen from Mars (at a distance of 139 million km) from the
MGS spacecraft in 2003.
Earth and Moon as seen from Mars (at a distance of 139 million km) from the
MGS spacecraft in 2003.
Earth
The Earth has 6 principle regions, from inner to outer:
1. The core
2. The mantle
3. The crust
4. The hydrosphere
5. The atmosphere
6. The magnetosphere
Geological Activity
The Earth is a geologically active planet,
its land is always being renewed,
although on time scales very slow
compared to human life.
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We find abundant evidence of geologic
activity, volcanism, earthquakes, plate
tectonics.
Earthquakes, Volcanoes, and Plates
The interior of the Earth is a furnace. Pressure builds and needs to be
released from time to time.
Earthquakes, Volcanoes, and Plates
Earthquakes as probes of the interior structure!
The Surface
The surface of the Earth has extreme variety.
With the view from orbit, we lose the magnificent scenery.
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Life, including humans, are adapted to different ground conditions.
Antarctica and Atacama desert are two of the most extreme places in
the world.
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The Hydrosphere
More than 70% of the Earth's
surface is covered with water.
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The highest concentration of water
is in the southern hemisphere.
The Hydrosphere
The largest reserve of fresh water on the planet is in Antarctica.
• Superficial Temperature
• Superficial Temperature
Grand Canyon,
Arizona
Vegetation
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Impact cratering, volcanism, tectonics, erosion, life all modify surface!
Emisiones Humanas
We also have some direct impacts on Earth’s appearance
South America at night
Emisiones Humanas
We also have some direct impacts on Earth’s appearance
South America at night
The Atmosphere
100 km
RT=6300 km
The Atmosphere
The Earth has a fairly dense atmosphere.
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Atmosphere contains water vapor clouds and sometimes rain, snow or ice.
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Winds are generally moderate, although giant storms form in the equatorial
sea with winds of over 150km / h.
The Atmosphere
The atmosphere is divided into layers, with the densest being lowest.
NOTE: logarithmic scale!
The Atmosphere (Earth’s Energy Budget)
What happens to
sunlight?
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Greenhouse effect...
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How do these
processes affect our
“appearance” from
space?
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Now imagine this
process on other
planets, with
different surface and
air compositions...
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we can learn a lot!
Evolution of the terrestrial atmosphere
The original atmosphere of Earth was lost early on in its history.
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The current “second” atmosphere is due largely to volcanism and comets.
The oceans also ...
J. Kasting 2004
Evolution of the terrestrial atmosphere
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The atmosphere changes as a consequence of life on Earth
today
original
J. Kasting 2004
Evolution of the terrestrial atmosphere
This begs a few questions:
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Will the chemical composition of our atmosphere continue to evolve?
On what timescales?
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How can we differentiate changes in the atmosphere due to human
activity and those due to evolution?
Magnetosphere
Earth acts a crude/chaotic dynamo
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The magnetosphere protects the
Earth's surface (including atmosphere)
from solar wind particles.
Magnetosphere
auroras
Magnetosphere
auroras
The
Moon
The mass of the moon is so small that
it lacks an atmosphere.
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It also does NOT have a magnetic
field like Earth.
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It is a geologically dead
planet, with no volcanism,
although occasionally
it has “moonquakes”.
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It is covered with
impact craters
and "seas"
(darker
regions
caused by
ancient
lava flows).
The Moon
Formation of Craters
Cratering process.
The morphologies of the craters depend on:
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1.
2.
3.
4.
Meteor mass
Meteor velocity
Impact angle
Terrain features
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We can learn about the Moon’s (and by
extension the solar system’s) history via careful
crater counting and studying the size distribution
of craters.
History of Craters
a) Period of intense bombardment (“craterization”)
b) Period of intense volcanism
c) Cooling and formation of more craters
Moon
Effects of the Moon on the Earth
– Eclipses
– Tides (mareas)
Formation of the Moon
The formation of the Moon is currently thought to
be due to a collision with an object the size of
Mars
From its formation, the Moon does not possess a
large nucleus with heavy fundamental elements
(Fe, Ni) like the Earth or Mercury.
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Moon
Before landing for the first
time, many orbiting
spacecraft photographed
the Moon in detail.
As the rotation period of the Moon is equal to the period of travel
around the Earth, the Moon always shows the same face to Earth.
Rest assured, the dark side of the Moon is morphologically similar to
the visible face.
• Various spacecrafts
have allowed us now
to image the entire
surface of the Moon
in fine detail.
Moon
Due to its relative proximity, the moon is
the most studied extraterrestrial body by
humans. Different spacecraft have
explored the planet.
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It is rather uninteresting, however, in
terms of sustaining life or mining.
Moon
The Moon is the only
object outside the Earth
where we have set foot.
Astronaut Aldrin "walking"
on the moon.
Astronauts
Astronauts
on the Moon
on the Moon
There is no atmosphere,
yet the sky is black due to
contrast.
The force of gravity is
very low, equivalent to
1 / 6 that of Earth.
North Pole of the Moon
Although the Moon would be very
useful for space development and
exploration of the solar system
because of its low gravity, the
main difficulty of having a moon
base is the lack of water. Various
probes have found evidence of
water ice in craters at the lunar
poles. However, direct evidence
has yet to be confirmed.
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It will be important to establish
permanent lunar bases as a
“relay” station if we ever seriously
consider future plans for
colonizing the Solar System.
What do we conclude if a planet has few impact craters of any size?
A.
B.
C.
D.
The planet was never bombarded by asteroids or comets
Its atmosphere stopped impactors of all sizes.
Other geological processes have erased evidence of craters.
Bruce Willis saved it from all the impactors.