Lecture Notes:
Lecture #24 April 15
-
MARS:
Over almost all of its surface, the low atmospheric pressure (.006 that
of
the earth) means that open water would rapidly evaporate. Only in its
deepest valleys near the equator, may there be pools of open water
occasionally. The large temperature range of -200F to +81F is the result
of its very thin atmosphere.
-
EARTH:
While 96% of the atmosphere of Mars is carbon dioxide, only .03% of
the
earth's atmosphere is carbon dioxide. The vast difference is due to the
influence of life. We owe an immense debt of gratitude to those wonderful
plants which convert carbon dioxide to oxygen. Think of that next time
you
hear of a forest being clear-cut!
The coupling between the atmosphere, ocean, and surface of the earth
establishes negative feedback processes that stabilize the amount of
carbon dioxide in the atmosphere. If we pour too much carbon dioxide in
to
the atmosphere such that the negative feed back is converted into positive
feedback, the earth might become life Venus. Venus stands like a warning
in the sky against misuse of our planet.
Venus, Mars, and Earth have been mightily transformed since their birth,
due to positive feedback and plant life (in the case of the earth).
-
JUPITER:
In contrast the giant ball of gas known as Jupiter has changed little
since the solar system began. Hydrogen was and remains the most abundant
constituent. Its mass of 318 times that of the earth and its distance from
the sun have mean that it has gravitationally retained practically all
of
its original gas. At certain depths in its immense atmosphere, conditions
are ripe for the formation of life: elements of hydrogen, carbon, oxygen,
nitrogen; presence of water; energy in the form of heat, winds, and
lightning discharges. Because of the rapid rotation of Jupiter (9 hr 55
min) winds have speeds up to 28,000 miles/hr. In the form of ballasted
gas
bags, alien life may be floating in its atmosphere.
-
GALILEAN SATELLITES AND LIFE
Is there life on Io? Probably not; it is almost as hot and hostile as
Venus. Because it is in the heart of Jupiter's Van Allen belt, the
electrons and protons raining down on its surface would kill any
unprotected human being within minutes. No space craft that we can design
now could last more than a few house on its surface.
It is the most volcanically active object in the solar system
ejecting some 10000 tons of matter per second, such that the matter
falling back on the surface collects at the rate of 10 meters per year
over the entire surface of the moon. The magnetic field of Jupiter sweeps
past and generates an electric current of 5 million amps which connects
to
the polar regions of Jupiter to produce immense auroral storms.
Tidal flexing of Io inject some 80 million megatwatts of energy
into the moon resulting in its molten interior and the resulting
volcanism. This energy comes from the rotational energy of Jupiter, which
is slowing down due to the tidal effects of Io and Europa.
There are pools of lava on its surface which are the size of the
island of Hawaii. There is a thin crust of solid rock; pressures building
up beneath the cruse can blow off chunks of the crust revealing violently
bubbling pools of sulfur, initially at a temperature of 1200K. As the
sulfur cools, it changes its color enabling us to estimate the
temperatures of parts of its surface. At a temperature of 500K sulfur is
black, and the black lakes such as LOKI which is 200 km wide and which
has
"ice" bergs floating on its surface must have that temperature.
At 470K
sulfur turns red and very liquid; the extensive lava flows down the sides
of its volcanoes must be produced by such flowing hot sulfur. At 400K and
cooler it turns to yellow orange, which is predominate color.
The volcanic explosions have no atmosphere to slow them down and
reach to 280 km above the planet and may be 1000 km wide.
Course Home Page | More
Lectures