Download Defrosting North Polar Dunes

Our Sun is the 5-billion-year-old star that sustains life here on Earth. The connection and interaction between
the Sun and Earth drive the seasons, currents in the oceans, weather and climate. With a core reaching a fiery
16 million degrees Kelvin (nearly 29 million degrees Fahrenheit), the Sun's surface temperature is so hot that
no solid or liquid can exist there. Luckily for humans, Earth is a little less than 150 million kilometers (93 million
miles) away from the Sun. Although its interior has been modified by nuclear reactions, the outer layers of the
Sun are composed of very nearly the same material as the original solar nebula. As the star for nine planets, a
multitude of asteroids, comets and other celestial objects, the Sun contains more than 99 percent of the entire
mass in the solar system.
The surface of Mercury shows the remnant cratering from the Heavy Bombardment period that lasted
over 600 M.Y. Brahms’ Crater, shown here, is 47 miles in diameter. Most of the Phoenix Valley would fit
within this crater!
Venus’ Sapas Mons Volcano is 248 miles across and .9 miles high. Here is evidence of this terrestrial planet
showing similar geologic activity to what we see on Earth.
This satellite image of Antarctica shows the tracking of some huge icebergs. The dynamics of Earth’s geologic
process of glaciation is observed here. About 30 icebergs are currently tracked with some as large as 17 by 109
nautical miles (31 by 202 Km) being identified to help avoid dangers to shipping lanes. This new data is building
a basis for better understanding of the Antarctic Ice Sheet. B10A shown here was first observed in 1999 and was
the size of Rhode Island. It is shown entering the shipping lanes along the Drake Passage.
Valles Marineris is shown on page
13 of your text. This canyon is
2700 Km long, 500 Km wide and 6
Km deep. That is 3.75 miles deep
over 3 times the depth of the
Grand Canyon!
We know that Mars has remnant
cratering from the Heavy
Bombardment, but here in this
canyon, there are no visible
craters. It appears that erosional
processes have erased any signs
of the craters and may have a
rather rapid rate of erosion.
The erosion is believed to be from
wind and gravity working along
steep slopes.
Nigral Vallis is one of a
number of canyons called
valley networks or runoff
channels. Much of the
debate concerning the
origin of these valleys
centers on whether they
were formed by water
flowing across the surface,
or by collapse and upslope
erosion associated with
groundwater processes. At
the resolution of this image,
it is just barely possible to
discern an interwoven
pattern of lines on the
highland surrounding the
valley, but it is not possible
to tell whether this is a
pattern of surficial debris
(sand or dust), as might be
expected with the amount
of crater burial seen, or a
pattern of drainage
channels. New images
with better resolution
should result in a
determination of what
process caused these
features.
The left image was acquired during early northern summer; the right was acquired almost exactly one Mars year
later. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular
band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north
polar cap is roughly 1100 kilometers (680 miles) across.
Close inspection will show that there are differences in the frost cover between the two images (for example, in
the upper center of each image, and on the left edge center). These changes are quite large--the change in frost
covering is equivalent to the amount of frost that would be evaporated or deposited in almost 5 months. What
gives rise to such large changes in the heat budget for the polar caps from one year to the next is not known.
Is it caused by the 11 year solar cycle? Does this suggest that other ice caps in the solar system have
experienced melting that is not attributed to changes in an ozone layer or from pollution?
Olympus Mons is a mountain of
mystery. Taller than three Mount
Everests (that is 29,000 feet X 3 !
We are talking about 16.6 miles.)
It is about as wide as the entire
Hawaiian Island chain, this giant
volcano is nearly as flat as a
pancake. That is, its flanks
typically only slope 2° to 5°.
What are some of the events that
could account for the low slopes?
Could winds have blown debris
away while the volcano formed?
Maybe the material was very fluid
that formed the volcano?
North is to the left. So where is
east positioned?
This image was taken in 1998 and
its location is shown on page 13 of
your text.
April 1999, the Mars Global Surveyor Mars Orbiter Camera (MOC) passed over the Apollinaris Patera
volcano and captured a patch of bright clouds hanging over its summit in the early martian afternoon. This
ancient volcano is located near the equator and--based on observations from the 1970s Viking Orbiters--is
thought to be as much as 5 kilometers (3 miles) high. The caldera--the semi-circular crater at the volcano
summit--is about 80 kilometers (50 miles) across. How do we know that this is not a meteor crater? How
does it compare with meteor craters in the image? ( The image was rotated and North is to the left.)
Utopia Planitia This highresolution color photo of the
surface of Mars was taken by
Viking Lander 2 at its Utopia
Planitia landing site on May 18,
1979, and relayed to Earth by
Orbiter 1 on June 7. It shows a thin
coating of water ice on the rocks
and soil. The time the frost
appeared corresponds almost
exactly with the buildup of frost one
Martian year (23 Earth months)
ago. Then it remained on the
surface for about 100 days.
Scientists believe dust particles in
the atmosphere pick up bits of solid
water. That combination is not
heavy enough to settle to the
ground. But carbon dioxide, which
makes up 95 percent of the Martian
atmosphere, freezes and adheres
to the particles and they become
heavy enough to sink. Warmed by
the Sun, the surface evaporates
the carbon dioxide and returns it to
the atmosphere, leaving behind the
water and dust. The ice seen in this
picture, like that which formed one
Martian year ago, is extremely thin,
perhaps no more than onethousandth of an inch thick.
Late in June 2001, as southern winter transitioned to spring, dust storm activity began to pick up as cold air from
the south polar cap moved northward toward the warmer air at the martian equator. By early July, dust storms had
popped up all over the planet, particularly throughout the southern hemisphere and in the Elysium/Amazonis
regions of the northern hemisphere. Soon, the entire planet--except the south polar cap--was enshrouded in dust.
Similar storms have occurred before. For example, the planet was obscured by dust when the Mariner 9, Mars 2,
and Mars 3 spacecraft reached the planet in late 1971. The MGS MOC images showed the evolution of the 2001
great dust storm period. There was never a time when the entire planet was in the midst of a single storm. Several
large storms would occur at the same time, and dust was kicked high into the atmosphere to cause much of the
rest of the planet to be obscured. The dust storms largely subsided by late September 2001, but the atmosphere
remained hazy into November of that year.
Defrosting North Polar Dunes
Each spring as the sun comes up over the
polar regions, the seasonal frosts that have
accumulated there during winter begin to
sublimate away.
Dunes are among the first features to show
spots and streaks resulting from the
defrosting process. Unknown is whether the
dark spots and streaks are sand (from the
dune) that has been mobilized by wind, or
frost that has become disrupted and coarsegrained (coarse grains of ice can look darker
than fine grains).
This Mars Global Surveyor (MGS) Mars
Orbiter Camera (MOC) image shows north
polar dunes near 76.6°N, 255.9°W in early
spring. The image, acquired in June 2002, is
3 km (1.9 mi) across. Sunlight illuminates the
scene from the lower left.
Here is a natural color image of
Jupiter. Shown to the lower right is
the massive Giant Red Spot or storm
of gasses that constantly rotates
around the planet and is believed to
be 300 years old. This storm is
almost the size of 3 Earths.
It is the largest planet in our solar
system and is the first gaseous planet
as we move from the Sun past Mars.
It has 28 moons of which Io is the
closest to the planet and is tidally torn
constantly having violent volcanic
eruptions. The icy Europa is one of
Jupiter’s moons which shows a thick 2
mile or greater ice covering with liquid
water beneath. It is a possible target
to explore for life in our solar system.
The sixth planet from the Sun,
Saturn, is the second largest
planet in our solar system. Its
intricate ring system has
fascinated astronomers for
centuries.
The rings are made of ice and
rock particles--some as big as
houses--that were probably
pieces of comets or asteroids
that broke up before they
reached the planet.
At least 30 moons orbit Saturn.
The largest, Titan, exceeds the
size of the planets Mercury or
Pluto and wraps itself in a
dense, nitrogen-rich atmosphere
reminiscent of the early Earth's
atmosphere.
Uranus, the third largest
planet in our solar
system, may be the
strangest because it
spins on its side.
That severe tilt to its
rotational axis may
result from a great
collision long ago.
As the seventh planet
from the Sun, Uranus
takes 84 years to
complete an orbit.
It is a "gas giant" with no
solid surface.
It may have a small,
silicate-rich core, but
most of its gas consists
of water, ammonia and
methane. The methane
gas above the cloud
layers gives it a bluegreen color.
Neptune orbits about 30 times as
far from the Sun as Earth does. It
takes about 165 years to
complete each loop.
Most of the time, it is the eighth
planet from the Sun, but because
of Pluto's odd-shaped orbit,
Neptune is actually the farthest
out of the nine planets for about
20 years out of every 248 years.
Like the other three "gas giant"
planets -- Jupiter, Saturn and
Uranus -- Neptune has no solid
surface. Its atmosphere contains
hydrogen and helium with
enough methane to give it a
bluish tint.
Winds on Neptune blow faster
than on any other planet.
The discoveries of Neptune and
its largest moon, Triton, came
less than a month apart in 1846.
Mathematicians had accurately
predicted where Neptune could
be discovered, based on its
gravitational effect on Uranus.
Taking 248 years to orbit the
Sun, Pluto is the smallest
and most distant planet from
the Sun.
Its diameter is only about
two-thirds that of our
Moon's.
Pluto is sometimes
considered a double planet
system because its moon,
Charon, is about half Pluto's
size, making Charon the
largest satellite in the solar
system in proportion to the
size of its planet.
This distant planet is the
only one in our solar system
yet to be visited by
spacecraft, but NASA is
exploring the possibility of
such a mission.