Destination Mars

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Module 12 Mars - the Red Planet
Activity 1 Destination Mars
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Summary
In this Activity, we will investigate (a) Mars
vital statistics, and (b) Missions to Mars
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(a) Mars Vital Statistics

• Now well look at the bulk properties of our
  other planetary neighbour, Mars, and compare them
  to those of Earth and Venus.

Again, structurally all three have much in common
4
Mars
Earth
Venus
5

• As Mars has two natural satellites, Phobos and
  Diemos (see later), the mass of Mars can be
  calculated by observing their orbits and using
  Keplers Third Law.

As well as being much smaller than Earth (only
53 ofEarths diameter), Mars turns out to have
a much lower density than does Earth - so its
interior must be significantlydifferent. In
particular, its core must be smaller and probably
less dense too.
6
Earth
Venus
Mars
Av. Distancefrom Sun
1 AU
1.52 AU
0.72 AU
Mars is half as far again from the Sun as is
Earth, whichmeans that it receives less than
half as much sunlight (i.e. half as many photons
per unit area per unit time).We will see that
the distances between the planets quickly
increase as we move out from the Sun.
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Earth
Venus
Mars
Av. Distancefrom Sun
1 AU
1.52 AU
0.72 AU
Length of Year
1 y ?
0.62 y ?
1.88 y ?
A year on Mars takes almost twice as long as a
year on Earth.
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Earth
Venus
Mars
Av. Distancefrom Sun
1 AU
1.52 AU
0.72 AU
Length of Year
1 y ?
0.62 y ?
1.88 y ?
Length of solar day
117 d? retrograde
1 d?
1.03 d?
Surprisingly, a day on Mars is almost the same
lengthas one on Earth.
Like the Earth, the difference between a solar
day (time between successive noons) and
sidereal day (rotation period with respect to
background stars) is only a few minutes.
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Earth
Venus
Mars
Av. Distancefrom Sun
1 AU
1.52 AU
0.72 AU
Length of Year
1 y ?
0.62 y ?
1.88 y ?
Length of solar day
117 d? retrograde
1 d?
1.03 d?
Inclinationof axis
177
23.5
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Another convenient coincidence? Almost identical
axis tiltsgive the Earth and Mars similar
seasonal patterns - exceptthat seasons on Mars
last almost twice as long.
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Earth
Venus
Mars
Av. Distancefrom Sun
1 AU
1.52 AU
0.72 AU
Length of Year
1 y ?
0.62 y ?
1.88 y ?
Length of solar day
117 d? retrograde
1 d?
1.03 d?
Inclinationof axis
177
23.5
25
Accelerationdue to gravity
1 g?
0.38g?
0.90g?
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• Objects weigh only about 40 of their terrestrial
  weight when on Mars.
• Settlers on Mars would need to make adjustments
  to cope with the reduced gravity.

12

• The main reasons why we are not likely to plan
  settlements on Venus involved the atmosphere and
  surface temperature.
• Lets look at the bulk properties of the
  atmosphere and surface temperature on Mars

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Earth
Venus
Mars
av. albedo
0.39
0.16
0.76(cloud tops)
The rusty orange-red, cloudless surface of Mars
is much less reflective than cloud-covered Venus
or even Earth.
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Earth
Venus
Mars
av. albedo
0.39
0.16
0.76(cloud tops)
atmosphere
96 CO2 3.5 N2 0.2 H2O acids
78 N2 20 O2 0.03 CO2 2 H2O
95 CO2 2.3 N2 trace O2 H2O
Like Venus (and the primeval Earth), Mars has an
atmosphere composed mostly of carbon dioxide.
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Earth
Venus
Mars
av. albedo
0.39
0.16
0.76(cloud tops)
atmosphere
96 CO2 3.5 N2 0.2 H2O acids
78 N2 20 O2 0.03 CO2 2 H2O
95 CO2 2.3 N2 trace O2 H2O
av. surface pressure
90 patm
1 patm
0.01 patm
Unlike Venus, the atmosphere that Mars has
managed to retain is very thin indeed, as you
would expect given the low acceleration due to
gravity.
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• Atmospheric pressures on Earth only become as low
  as 0.01 patm at an altitude of 40km.

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Earth
Venus
Mars
av. albedo
0.39
0.16
0.76(cloud tops)
atmosphere
96 CO2 3.5 N2 0.2 H2O acids
78 N2 21 O2 0.03 CO2 2 H2O
95 CO2 2.3 N2 trace O2 H2O
av. surface pressure
90 patm
1 patm
0.01 patm
surface temperature
472C
- 50C ? 50C
- 140C ? 20C
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• Average temperatures on Mars are cooler than on
  Earth, as you would expect for a planet 50
  further from the Sun.

With almost no appreciable atmosphere to insulate
it, temperature changes on Mars can be quite
severe - up to 100K between night and day at
the equator in summer.
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(b) Missions to Mars

• Although Mars is not our closest planetary
  neighbour, it is the most accessible one. Its
  history appears to be similar enough to that of
  Earth to make the study of Mars important for our
  understanding of our own planet too.

In the long term, Mars is the most likely site if
humans ever attempt to colonize and terraform
a planet other than our own.
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There have been several space missions to Mars,
with mixed results. Although Mars does not have
the formidableatmospheric conditions of Venus,
its distance from Earth plus its distance from
the Sun (and relatively low supplyof solar
energy) create problems for mission planners.
As we will see, several of the past Mars missions
were spectacularly unsuccessful. Since then,
NASA has been rethinking its recent low cost
missions approach, despite its early spectacular
success with the Mars Pathfinder Mission.
Here well give a very brief summary of each of
the recent missions.
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• Mariner 9

The Mariner Mars 7 mission originally consisted
of two spacecrafts on complementary missions,
but Mariner 8 failed to launch properly. Mariner
9 then combined the mission objectives of both.
The spacecraft was turned off in October 1972.
The Mariner 9 mission resulted in a global
mapping of the surface of Mars, including the
first detailed views of the volcanoes, Valles
Marineris, the polar caps, global dust storms
and the satellites Phobos and Deimos.
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• Viking Mission to Mars

NASAs Viking Mission was composed of Viking 1
and Viking 2, each consisting of an orbiter and a
lander. The primary mission objectives were to
obtain high resolution images of the Martian
surface, characterize the structure and
composition of the atmosphere and surface, and
search for evidence of life.
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• Viking 1 was launched in August 1975 and arrived
  at Mars in June 1976. One month later the Viking
  1 Lander separated from the Orbiter and touched
  down at Chryse Planitia. Viking 2 was launched
  in September 1975 and entered Mars orbit in
  August 1976. The Viking 2 Lander touched down at
  Utopia Planitia a month later.

The Viking 1 orbiter
The Orbiters imaged the entire surface of Mars at
a resolution of 150 to 300 metres, and selected
areas at 8 metres. NASA powered down the Viking
2 Orbiter in 1978 and the Viking 1 Orbiter in
1980.
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• The Viking Landers sent back images of the
  surface, took surface samples and analyzed them
  to determine their composition and look for signs
  of life, studied the composition of the
  atmosphere and Martian meteorology, and deployed
  seismometers.

The Viking 1 lander
The Viking 2 Lander stopped sending signals to
Earth in April 1980, and the Viking 1 Lander
stopped in November 1982, after transmitting
over 1400 images of the two sites.
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• The Phobos Project

The USSR launched two missionsto Phobos, one of
the naturalsatellites of Mars, in July 1988.
The mission plan intended the twospacecraft,
Phobos 1 and Phobos 2, to be placed intoMars
orbit so that they would be in an almost fixed
position50 m above the surface of Phobos - and
aim laser andion beams at Phobos in order to
determine its chemicalmakeup.
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Phobos 1 failed 2 September 1988 due to a
software error.Phobos 2 operated normally,
gathering data on the Sun, interplanetary
medium, Mars, and Phobos.
Shortly before the final phase of the mission,
during which the spacecraft was to approach
within 50 m of Phobos surface and release two
landers (a mobile hopper and a stationary
platform), contact with Phobos 2 was lost due to
a malfunction of the on-board computer. The
mission officially ended 27 March 1989.
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• The Mars Observer

Launched in September 1992, Mars Observer, the
first of the planned Observer series of
planetary missions, was designed to study the
geoscience and climate of Mars.
To quote NASA, Contact with Mars Observer was
lost in August 1993, three days before scheduled
orbit insertion, for unknown reasons and has not
been re-established. It is not known whether the
spacecraft was able to follow its automatic
programming and go into Mars orbit or if it flew
by Marsand is now in a heliocentric orbit.
Although none of the primary objectives of the
mission were achieved, cruise mode data were
collected up to loss of contact.
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An independent board, headed by Timothy Coffey
(research director of Naval Research Laboratory,
Washington, D.C ) was set up to report on the
failure of the Mars Observer.
The final report of the board stated that After
conducting extensive analyses, the board reported
that the most probable cause of the loss of
communications with the spacecraft was a rupture
of the fuel (monomethyl hydrazine (MMH))
pressurization side of the spacecraft's
propulsion system, resulting in a pressurized
leak of both helium gas and liquid MMH under the
spacecraft's thermal blanket. The gas and liquid
would most likely have leaked out from under the
blanket in an unsymmetrical manner, resulting in
a net spin rate. This high spin rate would cause
the spacecraft to enter into the "contingency
mode," which interrupted the stored command
sequence and thus, did not turn the transmitter
on.
For the full report, seehttp//www.msss.com/mars
/observer/project/mo_loss/nasa_mo_loss.txt
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• Mars Pathfinder

The Mars Pathfinder, the second of NASAs
low-cost planetary Discovery missions, landed
successfully on Mars in July 1997. The mission
consistedof a stationary lander and a surface
rover, with the primary objective of
demonstrating the feasibility of low-cost
landings on and exploration of the Martian
surface.
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• Pathfinder directly entered the planets
  atmosphere and landed by bouncing on inflated
  airbags. The lander operated nearly three times
  its design lifetime of 30 days, while the rover
  operated 12 times its design lifetime of seven
  days. The mission officially ended in November
  1997.

As we will see in a later Activity, the
Pathfinder provided strong evidence that its
landing site underwent massive flooding by water
two billion years ago. It also provided
unexpected evidence which is still being
analysed that the rocks at its landing site,
while basaltic in nature, were rather different
to what was expected on the basis of similar
geology on Earth and from the study of meteorites
believed to have originated on Mars.
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• Mars Global Surveyor

The Mars Global Surveyor (MGS) mission is the
replacement for the Mars Observer mission. To
quote NASA, The science objectives involve high
resolution imaging of the surface, studies of the
topography and gravity, the role of water and
dust on the surface and in the atmosphere of
Mars, the weather and climate of Mars, the
composition of the surface and atmosphere, and
the existence and evolution of the Martian
magnetic field.
32
The spacecraft began its Mars orbit insertion in
September 1997. The primary mapping mission
began about March, 1999. The spacecraft was
placed into a sun-synchronous orbit so that
each image can be taken with the Sun at the same
mid-afternoon azimuth, for a planned period of
one Martian year.
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The picture below is a flat map generated by the
Mars Orbiter Laser Altimeter (MOLA) aboard the
Mars Global Surveyor.
Each elevation point is known to an accuracy of
at least 13 metres, with large areas of the flat
northern hemisphere known to better than two
metres, which is more accurate than our knowledge
of the topography of many of the continental
regions on Earth.
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The Mars Global Surveyor was also designed to be
used to relay data to Earth from further U.S. and
international missions. Mars Global Surveyor was
the first spacecraft in a decade-long exploration
of Mars by NASA, with launches planned every 26
months, to take advantage of the times when Earth
and Mars are closest to each other in their
orbits around the Sun.
These planned missions involve sending orbiters,
landers, rovers, and probes to Mars.
Mars Global Surveyor completed its primary
mission on January 31, 2001 (having studied the
entire Martian surface, atmosphere, and interior)
and is now in an extended mission phase.
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• Mars Climate Orbiter and Polar Lander

The Mars Surveyor 1998 program was made up of two
spacecraft launched separately, the Mars Climate
Orbiter and the Mars Polar Lander. The two
missions were designed to study Martian weather
and climate, and water and carbon dioxide levels.
The Mars Climate Orbiter was launched
successfully in December 1998, but contact was
lost as it was about to go into orbit around Mars.
36
The resulting enquiry found that the Climate
Orbiter had in fact approached Mars much more
directly than planned, due almost certainly to a
programming error, where data originally
calculated in Imperial units was mistakenly and
disastrously interpreted as being in metric
units!
As a result, the Climate Orbiter apparently
attempted to go into orbit only 57 km above the
surface of Mars, instead of a planned altitude of
about 140 150 km. Although the Martian
atmosphere is very thin, the initial speed of the
Orbiter would have resulted in the spacecraft
being destroyed by atmospheric stresses and
friction at this low altitude. The findings of
the NASA Failure Review Board can be found on the
Internet at http//nssdc.gsfc.nasa.gov/planetary/t
ext/mco_pr_19991110.txt
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The Mars Polar Lander was a particularly
interesting mission, from a scientific point of
view, as the plan was to land it less than 1000
km from the Martian south pole, near the edge of
the carbon dioxide ice cap in Mars late southern
spring. The terrain appears to be composed of
alternating layers of clean and dust-laden ice,
and may represent a long-term record of the
climate, as well as a likely source of volatile
compounds such as water and carbon dioxide.
The failure of the Climate Orbiter happened while
the Polar Lander was already en-route to Mars.
Mars Polar Lander
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Atmospheric entry calculations were redone, in
order to avoid the unit conversion problems which
had caused the crash of the Climate Orbiter.
However, contact was permanently lost with the
Polar Lander on 3 December 1999, just prior to
the time calculated for atmospheric entry.
The Review Board report into the mission failure
is at http//nssdc.gsfc.nasa.gov/planetary/text/na
sa_pr_20000328.txt. The report concluded that
the most probable cause of the failure was the
generation of spurious signals when the lander
legs were deployed during descent. The spurious
signals gave a false indication that the
spacecraft had landed, resulting in a premature
shutdown of the engines and the destruction of
the lander when it crashed on Mars. To find out
more about the Mars Polar Lander, visit
http//nssdc.gsfc.nasa.gov/nmc/tmp/1999-001A.html
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There were reports in March 2001 that the US
National Imagery and Mapping Agency (NIMA), a
combat support agency of the US Department of
Defence, had analysed high resolution imagery
from the Global Surveyor and found features in
several images that could be indicative of the
lander and its protective aeroshell.
It was clear from the initial NASA press releases
that NASA and NIMA had rather different
interpretations of the imagery, and there has
been little mention of these reports since (and
in fact the original NASA press release is not
longer available!). For interesting commentaries
on the release see http//www.spacedaily.com/news
/mars-polar99-01a.html http//www.space.com/missio
nlaunches/missions/mpl_new_matter_010322.html
40

• Nozomi

Nozomi (Japanese for hope) was to be the first
Japanese Mars orbiting mission, designed to study
the martian upper atmosphere and its interaction
with the solar wind and to develop technologies
for use in future planetary missions. The mission
was also to relay images of Mars surface.
Nozomi was launched in July 1998, but a series
of unfortunately mishaps prevented it from ever
reaching its destination. After more than 5
years in space, it became clear that Nozomi would
run out of fuel before reaching Mars. In later
2003, the spacecraft was put in a heliocentric
orbit to avoid any possible collision with Mars.
For mission details, seehttp//solarsystem.nasa.g
ov/missions/profile.cfm?MCodeNozomi
41

• 2001 Mars Odyssey

The 2001 Mars Odyssey orbiter mission was
launched from Cape Canaveral on April 7 2001, and
reached Mars on 24 October 2001 and began mapping
the red planets surface.
The main scientific objectives for this mission
are the analysis of the Martian radiation
environment, the mapping of surface chemical
elements and minerals, and the search for water.
It has been conducting this mission since January
2002 and completed its 10,000th Mars orbit in May
2004. The primary mission continues until August
2004.
It also provides communication support for other
missions, including the Mars Exploration Rovers.
42
There are three instruments aboard Odyssey

• THEMIS the Thermal Emission Imaging System
  is a visible and infrared camera used to study
  Martian geology, mapping the mineral
  distribution of the surface.
• GRS the Gamma Ray Spectrometer observes
  gamma radiation coming from the surface of
  Mars (due to cosmic rays) which tells of the
  abundance of 20 primary elements. The GRS also
  detects neutrons which indicate the presence
  of water.
• MARIE the Martian Radiation Experiment
  measures the high energy radiation environment
  of Mars coming from sources such a cosmic
  rays.
• For more details about these three instruments
  and how they work, see http//mars.jpl.nasa.gov/o
  dyssey/technology/

43

• Mars Express

The European Space Agency mission Mars Express
was launched in June 2003 and aims to study the
Martian atmosphere and surface from a polar orbit.
Arriving at its destination on December 2003, the
probe delivered the Beagle 2 lander on Christmas
day that was to perform exobiology and chemistry
research.
Unfortunately after its separation from the probe
and descent onto the Martian surface, contact
with the lander was lost.
44

• Mars Express carries a number of instruments, one
  of which is the High Resolution Stereo Camera
  (HRSC). HRSC is designed to image the entire
  surface of Mars in full colour and 3D with a
  resolution of 10 m, and as low as 2 m in some
  selected areas.
• Other onboard instruments include
• OMEGA a visible and infrared mineralogical
  mapping spectrometer, is used to map the
  surface composition
• SPICAM an ultraviolet and infrared
  atmospheric spectrometer for determining
  the atmospheric composition
• ASPERA an energetic neutral atoms analyser,
  for determining how much of the Martian
  atmosphere is eroding by solar wind and
• MARSIS a sub-surface sounding radar altimeter
  to map below the Martian surface to a depth of
  a few kilometres.

Computer-generated image of a portion of the
Grand Canyon of Mars, based on original Mars
Express data.
45
One of the primary objectives of the Mars Express
mission is to search for water in its various
chemical forms (i.e. water ice, water vapour and
liquid water).
The various instruments are able to search for
underground liquid water, water vapour escaping
from the atmosphere, and, by mapping the surface
composition, search for water ice which it has
already successfully detected! (For details see
the next Activity.)
To find out more about Mars Express, visit
http//www.esa.int/science/marsexpress
46

• Mars Exploration Rovers

Launched in 2003, the Mars Exploration Rovers
Spirit and Opportunity successfully landed on
opposite sides of Mars in January 2004.
The rovers were designed to explore the surface
of Mars for 90 days. At the time of writing, they
have been active for more that twice this time.
The rovers have greater mobility then the
Pathfinder rover and carry a more advanced
scientific payload. With a set of sophisticated
instruments the rovers mission focuses on
determining whether there was liquid water
present on Mars in the past.
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Spirits landing site Gusev Crater
Interesting features
A. Columbia Hills Complex
B. Airbag bounce mark
Interesting feature
C. Rock outcropping
48
While there is no liquid water on the surface of
Mars today, the twin rovers will look signs of
past flowing water and geological features that
form only in the presence of water.
The two rover landing sites were specifically
chosen as potential sites of past water on Mars.
The Gusev Crater, a giant impact crater, may have
been a former lake, and Meridiani contains a lot
of the mineral hematite which can form in various
ways but usually requires water.
After evaluating the composition of soil and
rocks from the recorded images and spectra,
scientists hope to be able to establish whether
life could have been sustained on Mars in the
past.
To find out more about Mars Exploration Rovers
Mission, visit http//marsrovers.jpl.nasa.gov/
49
Follow this link to see a list of Internet sites
containing more information about all these Mars
missions!
50

• Although space missions to Mars have had mixed
  success, some have achieved and even surpassed
  their initial aims.
• In the next Activity we will go on to look at
  what these space missions have told us about the
  atmosphere and surface of Mars.

51
Image Credits
NASA Venus globehttp//nssdc.gsfc.nasa.gov/imag
e/planetary/venus/venusglobe.jpg Earth
globehttp//pds.jpl.nasa.gov/planets/welcome/eart
h.htm Mars globehttp//pds.jpl.nasa.gov/planets/w
elcome/thumb/marglobe.gif Mars - Valles
Marinerishttp//nssdc.gsfc.nasa.gov/image/planeta
ry/mars/marsglobe1.jpg Mars Polar
Landerhttp//nssdc.gsfc.nasa.gov/thumbnail/spacec
raft/mars_polar_lander.gif Nozomi
http//nssdc.gsfc.nasa.gov/thumbnail/spacecraft/p
lanet_b.gif MOLA flat map of Marshttp//mars.jpl
.nasa.gov/mgs/sci/mola/mola-may99.htmlViking 1
orbiter http//nssdc.gsfc.nasa.gov/planetary/thum
bnail/viking_spacecraft.gif
52
Image Credits
NASA Viking 1 lander http//nssdc.gsfc.nasa.gov
/thumbnail/spacecraft/viking_lander_model.gif Phob
os Missionhttp//nssdc.gsfc.nasa.gov/thumbnail/sp
acecraft/phobos_mars.gif Mars Pathfinder
http//nssdc.gsfc.nasa.gov/planetary/thumbnail/ma
rspath_sol65.gif Mars Global Surveyorhttp//nssdc
.gsfc.nasa.gov/planetary/banner/mgs_orbit_pic.gif
Mars Observerhttp//nssdc.gsfc.nasa.gov/thumbnail
/spacecraft/mars_observer.gif Mars Climate
Orbiterhttp//nssdc.gsfc.nasa.gov/thumbnail/space
craft/mars98orb.gif 2001 Mars Odysseyhttp//mars.
jpl.nasa.gov/odyssey/
53
Image Credits
ISAS New Nozomi orbithttp//www.planet-b.isas.ac
.jp/index-e.html Artists impression of Mars
Express - ESA http//marsprogram.jpl.nasa.gov/expr
ess/gallery/artwork/images/35699_br.jpg Portion
of Grand Canyon of Mars in 3D perspective -
ESA/DLR/FU Berlin (G. Neukum) http//www.esa.int/e
xport/externals/images/3D_large2.jpg Mars
Exploration Rover - NASA http//marsrovers.jpl.nas
a.gov/gallery/artwork/images/rover1_400.jpg Gusev
Crater - NASA http//marsrovers.jpl.nasa.gov/galle
ry/landingsites/images/Gusev-plain_br.jpg Meridian
i Planum - NASA http//marsrovers.jpl.nasa.gov/gal
lery/landingsites/images/Meridiani-plain_br.jpg Sp
irit Mars Exploration Rover Panorama -
NASA http//marsrovers.jpl.nasa.gov/gallery/press/
spirit/20040112a/mspan_2X_final-A10R1_br.jpg Oppor
tunity Mars Exploration Rover Panorama -
NASA http//marsrovers.jpl.nasa.gov/gallery/press/
opportunity/20040202a/MSPan_B1_2x-B009R1_br.jpg
54

• Now return to the Module 12 home page, and read
  more about space missions to Mars in the Textbook
  Readings.

Hit the Esc key (escape) to return to the Module
12 Home Page
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More information can be obtained about these Mars
missions on the Internet at the following
sites The Viking Mission, http//nssdc.gsfc.n
asa.gov/planetary/viking.html The Phobos
Project, http//nssdc.gsfc.nasa.gov/planetary/ph
obos.html Mars Observer, http//nssdc.gsfc.nasa.
gov/nmc/tmp/1992-063A.html Mars Pathfinder,
http//nssdc.gsfc.nasa.gov/planetary/mesur.html Ma
rs Global Surveyor, http//mpfwww.jpl.nasa.gov/m
gs/index.html Nozomi, http//nssdc.gsfc.nasa.go
v/nmc/tmp/1998-041A.html Mars Climate Orbiter
http//nssdc.gsfc.nasa.gov/nmc/tmp/1998-073A.html
Mars Polar Lander http//nssdc.gsfc.nasa.gov/nmc
/tmp/1999-001A.html
57
More information can be obtained about these Mars
missions on the Internet at the following
sites 2001 Mars Odyssey http//marsprogram.jp
l.nasa.gov/odyssey/ Mars Express
http//www.esa.int/science/marsexpress Mars
Exploration Rovers Mission http//marsrovers.jpl
.nasa.gov/home/
Details of past and future planned Mars missions
can be found onthe Internet at NASAs Mars home
page http//nssdc.gsfc.nasa.gov/planetary/planet
s/marspage.html together with a very useful
timeline of all attempted and future Mars
missions at http//nssdc.gsfc.nasa.gov/planetary
/chronology_mars.html
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• Back to the Activity!

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