Download Written by David L

Written by David L. Coleman and
Sarah Kennedy for Jensan
Scientifics
The Surface of Mars
Information Packet
Copyright © 2001 Jensan Scientifics
For thousands of years, we on Earth have watched the planet Mars move across the night skies. Its
blood-red color, the way it appears first dim, then bright as a burning ember, and its strange back—
and-forth movement in the sky at certain times gave Mars an air mystery from the start. It was-one of
the five planets known to ancient observers who discovered that these objects did not remain fixed in
position, as the stars were, but moved across the sky night-by-night. The study of this motion in the
case of Mars led the German astronomer and mathematician, Johannes Kepler, to the discovery of the
fundamental laws of planetary motion in 1605.
By1610, Galileo Galilei had become the first person to examine Mars with his new telescope. The
view he had was no t very good, but as the design of telescopes continued to improve over the next 200
years or so, astronomers began to get tantalizing glimpses of some of the details of the Martian surface.
They noted specific dark patches on the surface,
and the presence of white patches at the north and
south poles. They were able to measure the rate of
rotation of Mars, finding it to be nearly the same
as that of the Earth; 24 hours and 37 minutes.
Things became even more curious when the tilt of
Mars' axis was measured to also be very close to
that of Earth: 25.2 degrees for Mars, 23.5 degrees
for Earth. This meant that Mars experienced
seasons, as Earth does. The white patches at the
poles were eventually discovered to be icecaps,
apparently again like on Earth, that were observed
to grow and shrink as the temperatures changed
during the Martian summers and winters.
So, for most of the early 20th century, Mars remained a mysterious neighbor to Earth, alike in certain
ways that made us wonder if there could actually be life there. Many science fiction writers and some
in the astronomical sciences were convinced that there was a real population of Martians, at though
there was disagreement about what form this life might take.
Now, at the end of the 20th century, the situation is a bit different Not only have we studied Mars
through the finest f telescopes, but have sent robotic explorers to take pictures from orbit and from on
the surface. WB have scratched, measured, and analyzed the rocks and soil. We have measured the air
temperature, the atmospheric pressure, and wind speed. Ws even recognize familiar types of desert
scenery and rock types there.
Fig 1. Shown Is the rock dubbed Barnacle Bill. This
rock is thought to be a silica-rich basaltic andesite.
The bright soil is common on Mars, and the "wind
tail’ behind Barnacle Bill is indicative of the winds
that pound the Martian terrain. The reddened
spectrum for this soil type indicates that it contains
oxidized ferric (iron) minerals.
The surface of Mars has become for us a place: a real,
recognizable terrain that we can imagine traveling to
and exploring In person. As you examine the
samples presented in this set, imagine yourself there
on Mars, safety space-suited, exploring with rock hammer and camera in hand, picking up Martian rocks of
similar formation, and containing many of the same minerals as those you see in this set.
Fig 2. Types of rock and soil: (A) Dark rock and bright soil. Shown is the dark rock Barnacle Bill. It's spectra is typical of a
fresh basaltic andesite. These rocks are typically the small boulders at the Pathfinder site. The bright soil is very common,
and here comprises Barnacle Bill's wind tail and surrounding soil area. This soil's spectrum is indicative of oxidized ferric
(iron) minerals.(B) Bright rock type: Shown is the bright rock Wedge, whose spectrum is typical of weathered basalt. These
rocks are typically larger than 1 meter in diameter and many display characteristics indicating flood deposition. (C) Pink
rock type: Shown is the pink rock Scooby Doo. This material may be a chemically cemented hardpan that underlies much
of the Pathfinder site. (D) Dark soil type: Dark soil is typically found on the windward side of rocks or in rock-free areas
where the bright soil has been stripped away by the wind: (E) Disturbed soil type: The darkening of disturbed soil relative
to it's parent material is a result of movement of the Rover. (F) Lamb-like soil: This soil type shows spectral characteristics
intermediate between the bright and dark soils, with a weak spectral absorption near 900 nanometers (infrared) not seen in
either the bright or dark soils.
Sample Guide to the Surface of Mars Study Set:
1. Basalt (breccia) A breccia is composed of
broken and re-cemented rock fragments. The
fragments may be all of one type, or of many rock
types. Breccias are formed on a planetary surface
that has been broken and cratered by impacting
asteroid fragments, as on the Moon and Mars.
Volcanic breccias are the result of explosive
activity. On Earth they are found in active tectonic
regions where angular rock fragments can occur
due to rock stress and fracturing.
On Mars, meteoritic impact can be the cause of the
breccias found at the Pathfinder site. The
composition of the Mars' surface could be mixed
with that of the meteorites' and with the application of the pressure from the blast on the surface, cause
a third material to form, such as breccia.
Basalt is a common volcanic rock on both Earth and Mars.
2-Andesite- This is another volcanic rock, different
from basalt in the higher silicon content. Many of
the rocks analyzed at the Pathfinder site appear to be
a form of andesite.
3. Chert Breccia - This type of breccia is a sedimentary
rock composed of many different size clasts or rock/grain
fragments. Angular fragments of rock and grains in
"clasts" can be clayey, siliceous, (containing silica)
calcareous (containing calcium) , or sometimes even
limonitic (containing iron oxide). Chert is a type of
quartz, and quartz is made out of silicon dioxide. Silicon
and oxygen were found on Mars, as well as calcium
(calcareous rock) in the form of calcium phosphate from
the Pathfinder APXS chemical analysis of Barnacle Bill
and Yogi.
4. Conglomerate – This sample is a sedimentary rock. It
is composed of quartz grains and various mineral
fragments. The fragments vary in size and composition,
but quartz is its main component. This material may
contain quartz, calcite, clay minerals, and iron oxide which colors it red.
Conglomerates are the result of erosional features.
Bedding is absent or poorly developed. They are
generally associated with fluvial (river action) deposits,
and the source rock usually comes from a different
location. Running water can round pebbles and cobbles
and cement them into a sand/ day matrix. At the
Pathfinder site, scientists saw what appears to be
rocks and pebbles resembling conglomerates.
5. Tephra--The red dust of Mars is closely matched in
spectroscopic qualities by this unique Earth material.
This special palagonitic tephra is volcanic in origin and
is found on the slopes of a certain volcano in the
Hawaiian islands. At the Pathfinder site, the iron-rich
dust that gives Mars its red appearance is magnetic. On
Earth, magnetic sands and dusts are very unusual.
6. Sulfur- Sulfur has been discovered on
Mars in fairly high concentrations in the soil.
Sulfur compounds can also be an indicator for
the presence of living organisms. Many
diverse marine organisms have been found
thriving on percolated elements from oceanic
vent systems on Earth. Sulfur is one of many
elements they have been found subsisting on.
Even though Earth's oceans systems offer
extreme environments of both high pressures
and the absence of sunlight, life manages to exist. Because of the tenacity of life on Earth, there is a
possibility for life on Mars also, perhaps as we know it- perhaps not.
7.Hematite-- Hematite is an iron mineral that has a distinctive dark red color. Hematite forms in a
variety of ways which often includes the presence of water. A 300-mile-wide mineral deposit of
hematite was discovered by the Mars Global
Surveyor. It is thought by scientists that the
presence of large amounts of iron minerals are
responsible forgiving Mars its red appearance.
8. Stromatolite - A stromatolite is the fossilized
remains of a simple bacteria colony, sometimes
known as blue-green algae. Organisms such as
these have been found on Earth living in very
harsh environments, leading some scientists to
believe that IF the remains of any Martian life
were eventually found, this may be the most likely
form.
Vesicular basalt--Basaltic lava showing a spongy
appearance is called vesicular basalt. The holes are
formed when gases dissolved in the molten lava
are released as the lava comes to the surface. The
rust colored specimen is the same kind of rock as
the dark specimen on the left. Iron in the basalt
weathers to iron oxide and produces the rust
colored dust and soil so abundant on Mars.
Fig. 4 Many Martian rocks and
boulders are shown in this
picture from the Viking site.
Fig 5
Rocks and boulders are strewn across the
landscape, all of varying size. Remember
that there is a layer of Martian dust
present.
Fig. 6 This is one of many pictures of the now famous
meteorite specimen, ALH84001. This is a stony
meteorite, which belongs to a class of meteorites that
came from Mars. This picture seems to show evidence
of life...suspiciously like we know it here on Earth. The
controversy rages about whether these are indeed
organisms.... and if so, did they arrive with the
meteorite or did they become a part of the meteorite
after its arrival on our planet.
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