Transcript NATS 1311 From the Cosmos to Earth

NATS1311 From the Cosmos to Earth
Mercury
Property
Earth
Mercury
1
0.4
5.5
5.4
1
0.4
365
88
1
59
23.5°
7°
Inclination of orbit to ecliptic plane
0°
7°
Maximum angle from sun
~
28°
Surface temperature
~
Day: 800°F
~
Night: -280°F
1 atmosphere
10-15 atmosphere
N2, O2
Helium, sodium,
potassium, oxygen
Equatorial Diameter
Density (gm/cm3)
Avg. Distance from Sun (AU)
Orbital Period (days)
Sidereal Rotation Period (days)
Inclination of axis to orbital plane
Atmosphere - pressure
Atmosphere - composition
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
The orbit of Mercury
At an average distance of only 58 million kilometers (36
million miles) from the sun, mercury takes a mere 88 days
to go around its orbit.
As viewed from earth, mercury can be seen only near times
of greatest eastern or western elongation.
At greatest western elongation (when the planet is farthest
west of the sun in the sky), mercury rises about 1 1/2
hours before sunrise.
At greatest eastern elongation (when the planet is farthest
east of the sun in the sky), mercury sets about 1 1/2 hours
after sunset.
NATS1311 From the Cosmos to Earth
NATS1311 From the Cosmos to Earth
Differences between the Moon and Mercury
1. Areas between craters on Mercury smoother than on Moon.
2. Secondary impact craters don't scatter as much on Mercury.
3. Gravitational acceleration on Mercury twice that of moon.
4. Mercury has scarps - lines of cliffs- caused by shrinkage of its
surface.
5. Mercury's atmosphere consists of sodium and potassium
(sputtered form surface by the solar wind), helium and
oxygen.
6. Atmospheric pressure about the same as on the Moon.
NATS 1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth Fig.8.2
Figure 8.2 Surface
views of the terrestrial
worlds. No spacecraft
have landed on Mercury,
so an artist's conception
is shown; all other
images are photos.
NATS 1311 From the Cosmos to Earth
Atmosphere of Earth
Blanket of Gases Surrounding Earth Contains a Mixture of Gases
Composition of Dry Air
Nitrogen
78%
Oxygen
21%
Argon
0.93%
Carbon
Dioxide
0.035%
Water Vapor
< 1%
•Pressure on a surface is weight of air above that surface
•Pressure of 1 atmosphere at Earth’s surface at sea level:
•14.7 Lb. per Square Inch
•76 Cm of Mercury (30 inches of Mercury)
•1034 Grams per Square Centimeter
•Pressure decreases as altitude above Earth’s surface increases
NATS 1311 From the Cosmos to Earth
Regions of the Atmosphere
Region
Upper Boundary
Feature
Names
Altitude
Troposphere
Tropopause
10 Miles
Meteorological
interest
Temperature decreasing
Stratosphere
Stratopause
30 Miles
Temperature increasing
Mesosphere
Mesopause
50 Miles
Temperature decreasing
Temperature increasing
Thermosphere
-
300
Miles
Exosphere
-
-
Gas molecules can
escape from atmosphere
NATS 1311 From the Cosmos to Earth Fig. 8.12
Figure 8.12 The
structure of a generic
planetary atmosphere:
Solar X rays are
absorbed in the
thermosphere,
ultraviolet light is
absorbed in the
stratosphere, and
visible light reaches the
ground. Planets that
lack ultravioletabsorbing molecules
will lack a stratosphere,
and planets with very
little gas will have only
an exosphere.
NATS 1311 From the Cosmos to Earth
Thermal structure of
the atmosphere.
Atmospheric
temperature plotted
as a function of
altitude from ground
level to 110
kilometers.
NATS 1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth Fig. 8.13
Figure 8.13 Atmospheric gases scatter blue light more than they scatter red
light. During most of the day, you therefore see blue photons coming from
most directions in the sky, making the sky look blue. But only the red photons
reach your eyes at sunrise or sunset, when the light must travel a longer path
through the atmosphere to reach you.
NATS 1311 From the Cosmos to Earth Fig. 8.14
Figure 8.14 The greenhouse effect: The troposphere becomes
warmer than it would be if it had no greenhouse gases.
NATS 1311 From the Cosmos to Earth Fig. 8.16
Figure 8.16 A planet's
magnetosphere acts like
a protective bubble that
shields the surface from
charged particles
coming from the solar
wind. Among the
terrestrial planets, only
the Earth has a strong
enough magnetic field to
create a magnetosphere.
The Earth's
magnetosphere allows
charged particles to
strike the atmosphere
only near the poles,
thereby creating the
phenomena of the aurora
borealis and aurora
australis.
NATS 1311 From the Cosmos to Earth
VENUS
Comparison of Venus and Earth
Parameter
Venus
• Distance from Sun (AU)
(million KM)
Earth
.72
108
1.00
150
• Sidereal Period (year) (earth days) 225
365
• Rotation Period (day) (earth days)
-243
1.00
• Direction of rotation
Retrograde
Direct
• Equatorial Diameter
0.96
1.00
• Escape velocity (km/Sec.)
10.3
11.2
• Inclination of axis
3
23.5
• Seasons
No
Yes
NATS 1311 From the Cosmos to Earth
VENUS
• Parameter
Comparison of Venus and Earth
Venus
Earth
• Surface Temperature
480C (900F)
15C (60F)
• Surface atmospheric pressure
90
1
• Atmospheric gases
CO2
N2, O2
• Cloud cover
Total
Partial
• Surface
Solid
3/4 water
• Number of satellites
0
1
(atmospheres)
NATS1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth
VENUS
• Venus clouds:
 3 layers 49 to 65 km in altitude
 haze down to 30 km
 clear below 30km
 composition:
H2so4 droplets and sulfur particles
• Venus surface:
Rock strewn surface
• Temperature: 480c (900f)
NATS 1311 From the Cosmos to Earth
VENUS
Surface:
 Venus:
 No plate tectonics - (movement of surface)
 Radioactive heating
 Vocanoes are scattered over the surface of Venus
 Crustal material is denser than the underlying
magma
 Every 500 million years, the crust breaks up and
sinks, forming a new crust
 Earth:
 1 0 plates - volcanoes found on plate boundaries
NATS 1311 From the Cosmos to Earth
Atmosphere Formation
Original atmospheres were swept away from the terrestrial
planets early in their life.
Present day terrestrial atmospheres are secondary
atmospheres:
Venus:
Formed by outgassing (volcanoes and gas seepage)
from beneath the surface.
Surface too warm for water to condense as a liquid water dissociated into hydrogen and oxygen.
Hydrogen escaped - oxygen combined with surface
materials.
NATS 1311 From the Cosmos to Earth
Atmosphere Formation
Carbon dioxide and nitrogen accumulated in the
atmosphere.
CO2  96%
N2  3-4%
"Runaway" greenhouse effect.
Earth:
Water condensed into liquid form
CO2 dissolved into the water - formed limestone rocks
Nitrogen accumulated in the atmosphere
Oxygen accumulated after life formed in the oceans
NATS 1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth
Differences between Venus and earth
1. Venus rotation rate is very slow and in retrograde direction.
2. Venus surface consists of 1 plate; earth has 9 plates.
3. Venus has little or no magnetic field.
4. Venus' atmosphere pressure is 90 times that of earth.
5. Dominant gas in the Venus atmosphere is carbon dioxide.
6. Venus' surface temperature is 900° F.
7. Venus has very little water vapor in its atmosphere.
8
Venus has a very strong greenhouse effect.
9. There is no water on Venus' surface.
10. Venus has a very dense cloud cover.
NATS 1311 From the Cosmos to Earth Fig. 8.26
Figure 8.26 The surface of Venus is covered with
abundant lava flows and tectonic features, along with a few
large impact craters. Because these images were taken by
the Magellan spacecraft radar, dark and light areas
correspond to how well radio waves are reflected, not
visible light. Nonetheless, geological features stand out
well. In (b), the data have been converted to a threedimensional perspective view; heights are magnified by a
factor of more than 20, so the volcano is not actually as
steep-sided as it appears.
NATS 1311 From the Cosmos to Earth Fig. 8.26
NATS 1311 From the Cosmos to Earth Fig. 8.26
Figure 8.26
(a) Two of Venus's relatively rare impact craters.
(b) Shield volcanoes like this one are common on Venus.
(Height exaggerated to show detail.)
(c) Tectonic forces have fractured and twisted the crust in
the region.
(d) The circular cracks and volcanic bumps make up a
corona, probably caused by the pressure of a mantle
plume below.
NATS 1311 From the Cosmos to Earth
Mars
Comparison of Venus, Earth and Mars
•Parameter
Venus
•Distance from Sun (AU)
(million KM)
Earth
Mars
.72
108
1.00
150
1.52
228
•Sidereal Period (year) (earth days) 225
365
687
•Rotation Period (day) (earth days)
-243
1.00
1.03
•Direction of rotation
Retrograde
Direct
Direct
•Equatorial Diameter
0.96
1.00
0.53
•Escape velocity (km/Sec.)
10.3
11.2
5.0
•Inclination of axis
3
23.5
25.2
•Seasons
No
Yes
Yes
NATS 1311 From the Cosmos to Earth
Mars
Comparison of Venus, Earth and Mars
•Parameter
•Surface Temperature
Venus
Earth
Mars
480C (900F) 15C(60F) -60C(-76F)
•Surface atmospheric pressure 90
1
1/200
(atmospheres)
•Atmospheric gases
CO2
N2, O2
CO2
•Cloud cover
Total
Partial
Rare
•Surface
Solid
3/4 water Solid
•Number of satellites
0
1
2
NATS 1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth
Viking Life Detection Experiments on Mars
Living organisms alter their environment they breathe, eat, grow, and produce waste
Three experiments were designed to detect signs of living
organisms by treating soil samples in a closed
environment (a container):
NATS 1311 From the Cosmos to Earth
Viking Life Detection Experiments on Mars
Gas exchange Looked for changes in the atmosphere
caused by metabolism of organisms in the soil.
Soil sample fed nutrient in a carbon dioxide (co2)
atmosphere.
Organisms eat nutrients and release gases like CO2,
methane, oxygen and hydrogen into the container.
Some gases were found but were thought to be due to
chemical reactions between the nutrient water and
the soil.
NATS 1311 From the Cosmos to Earth
Viking Life Detection Experiments on Mars
Labeled release Looked for co2 breathed into the atmosphere
Soil sample fed radioactive nutrient
Organisms released radioactive CO2 into the
container
Some gases were found but were thought to be
due to the chemical reactions between the
nutrient and the soil
NATS 1311 From the Cosmos to Earth
Viking Life Detection Experiments on Mars
Pyrolytic release Looked for radioactive carbon in soil sample
Soil sample in radioactive CO2 atmosphere
illuminated by ultraviolet light to simulate sun
light
Soil sample then heated to 650°C to decompose
any growth material in the soil
Soil contained some radioactive carbon - did not
represent life
Conclusion:
Some positive results found in each experiment.
However, not sufficient to confirm life as we know it
Explanation - unusual chemical activity
NATS 1311 From the Cosmos to Earth
METEORITES FROM MARS
Meteorites found on antarctic ice
Concentrated in place where ice flows are impeded
and the ice is ablated
Well preserved:
Not exposed to water erosion
Not exposed to industrial contaminants
NATS 1311 From the Cosmos to Earth
METEORITES FROM MARS
Twelve antarctic meteorites came from Mars:
Called SNC meteorites
Age: 4.5 billion years
Ejected from Mars by collision of some large
object (asteroid?) with Mars
Spent several million years in orbit, then
landed on earth
Discovered within the last 20 years
Why from Mars?
Trapped gases in voids in the meteorites
match martian atmosphere
NATS 1311 From the Cosmos to Earth
ALH 84001 METEORITE
Formed 4.5 billion years ago
Ejected from Mars 1 6 million years ago
Arrived on earth 13,000 years ago
Found in 1993
Contains carbonate globules formed 3.6 billion years ago
Found along fractures in meteorite not of earth origin
Formed from CO2 in martian atmosphere
NATS 1311 From the Cosmos to Earth
ANALYSIS OF GLOBULES:
Laser desorption mass spectrometer
Showed presence of polycyclic aromatic
hydrocarbons (PAM) unlike any on earth
These molecules contain many rings of carbon
atoms
APPEARANCE OF GLOBULES:
Transmission electron microscope images
Orange color
Flattened circular disks
Iron rich materials characteristic of fossil
remains
NATS 1311 From the Cosmos to Earth
Scanning electron microscope images
Tubular shaped bodes
Dimensions - less than 100 nanometers
(1000 times smaller than the diameter of
a human hair)
Carbonate globules are the key to biogenic activity on Mars
Globules formed in fractures of rock
Globules are younger than the rock
Globular features resemble earth microorganisms,
earth biogenic carbonate structures and microfossils
Globules contain PAH's
NATS 1311 From the Cosmos to Earth
CONCLUSION:
Alternative explanations exist for each globular
phenomenon taken individually
Collectively, they are evidence for primitive life on
Mars
NATS 1311 From the Cosmos to Earth
NATS 1311 From the Cosmos to Earth FIG. 11.16