Exploring the Solar System
Lecture 8:
The Terrestrial Planets: Mars
Professor Paul Sellin
Department of Physics
University of Surrey
Guildford UK
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Lecture 8
Paul Sellin
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Introduction
 Physical data for Mars
 Earth-based observations
 First missions to Mars:
 Craters and topography
 Surface water on Mars
 Polar ice caps
 The Martian atmosphere:
 Models for atmospheric development
 Dust storms
 Exploration of Mars:
 Mars Exploration rovers
 Mars Global Surveyor
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Mars – the red planet
High quality image of Mars
viewed from Earth using the
Hubble Space Telescope
Early observations by
astronomers claimed to see
evidence for ‘canals’ on Mars,
perhaps evidence for life on the
planet
Recent missions have shown no
sign of water on Mars, but much
evidence that it once existed
Ancient flood channels prove that
water once existed, and may
have sustained oceans and lakes
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Physical Data
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Earth-based observations of Mars
The best Earth-based views of Mars are obtained when Mars is simultaneously at opposition and near
perihelion
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Mars is a relatively small planet, just over half the diameter of the Eaeth.
However it is the easiest planet to observe with a telescope – it can be seen high
in the night sky when it is at opposition. Mars has a thin almost cloudless
atmosphere that allows the surface to be clearly seen.
Opposition is when Mars is close to the Earth and appears high in our night sky,
giving the best views of the planet. Due to the elliptical orbit of Mars some
oppositions are better than others. The favourable opposition is when Mars is
simultaneously at its perihelion, and the Earth-Mars distance is only 0.37 AU (56
million km). At this point the angular diameter of Mars is 25.1 arcsec (the same
diameter as a person’s head at 1 mile!).
The favourable opposition in August 2003 was one of the best for several 1000
years. At this time Mars is a brilliant red object 3.5 times brighter than the
brightest star Sirius.
The time between favourable oppositions is approximately 15 years. The next
unfavourable opposition is in 2012 when Mars is near aphelion. The Earth-Mars
distance will be 0.68 AU (101 million km) and Mars will appear as a featureless
red dot.
Lecture 8
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Earth-based Observations
A solar day on Mars is nearly the same length as on Earth – the period of rotation is 37 minutes
longer than Earth
The average surface temperature is 220K (-53°C) and the pressure is 0.0063 atm: water cannot
exist as a liquid in this low pressure
Mars has polar caps that expand and shrink with the seasons: but these cannot be water ice since
the atmosphere contains hardly any water vapour
25cm telescope
HST
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Early signs of intelligent life on Mars?
Some early astronomers reported a network of linear
features called ‘canals’ – from the Italian for ‘channels;
Giovanni Schiaparelli observed canals during the
favourable opposition of 1877 – claiming 40 criss-cross
lines across the surface
The American millionaire Percival Lowell financed a
major new observatory in Flagstaff, Arizona, to study
Mars
The claims of canals fuelled speculation about life on
Mars, particularly linked to the perceived water at the
polar caps
Some much earlier observations were more accurate:
 Cassini measured the Martian day in 1666
 Cassini also first observed polar caps – more than a
century later Herschel suggested these might be ice or
snow
 Herschel found that the axis of rotation is tilted from
the perpendicular of the orbital plane by 25° - very close
to the Earth’s tilt of 23.5 °
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Because Mars takes nearly twice as long as Earth to go around the Sun (1.88
years or 687 days), the Martian seasons last nearly twice as long as on Earth.
During a Martian spring and summer the polar cap shrinks and the dark surface
markings become prominent. These can appear greenish in colour, prompting
early speculation that there was vegetation on Mars. Likewise in winter the dark
markings fade and the polar cap grows.
Lecture 8
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First missions to Mars
Three Mariner spacecraft flew past Mars
during 1964-1969 sending back the first
close-up pictures
There was no evidence of canals nor of
vegetation – the dark markings were just
different coloured surface terrain
The main surprise was that the Martian
surface has numerous craters - the
number and magnitude suggesting that the
surface, at least in part, was very old
Martian craters are obscured from Earth by
the thin Martian atmosphere
Mariner spacecraft also showed several
huge volcanoes, a vast rift valley the the
Valles Marineris, and dried-up riverbeds
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The early Mariner missions showed that Mars’ surface contained a lot of crater
impacts. These show that at least part of the Martian surface is very old (>3
billion years). This data was surprising since craters had not been observed from
Earth due to the Martian atmosphere – event the HST could not resolve crater
structures. The pictures from Mariner changed our perception of Mars – no
longer seen as a similar to Earth but rather a larger version of the barren moon.
The Mariner spacecraft only imaged 10% of the surface of Mars. Three orbiting
spacecraft reached Mars in 1971:
• NASA’s Mariner 9 which mapped the planet for a year
• Soviet Mars 2 and Mars 3
During a 4 year period starting in 1976 NASA’s 2 Viking Orbiters took images
of Mars, and most recently Mars Global Surveyor and Mars Odyssey since
1997 and 2001 respectively.
The ESA mission Mars Express entered Mars orbit in 2003.
Missions which have successfully landed on Mars include:
• Viking Lander 1 and Viking Lander 2 (1976)
• Mars Pathfinder (1997) containing the Sojourner Rover
• Mars Explorer (2004) containing 2 Rovers, Spirit and Odyssey
Lecture 8
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Martian Craters
For reasons that are not understood, the chemical composition of ancient Martian lava is
different from that of more recent lava
Mars has no planet wide magnetic field at present but may have had one in the ancient past
HST image
Viking Orbiter composite image
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The left image was taken by the HST during the opposition of 2003, showing
regions which are seen from orbiting space craft to be rich in craters. . The
massive Hellas Planitia feature was created by a massive single impact.
The right image is a mosaic of pictures from Viking Orbiter of the Sinus Sabeus
region just south of the Martican equator, containing numerous flat-bottomed
craters.
Lecture 8
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Topography of Mars
The northern and southern hemispheres are very different. The heavily cratered southern
highlands are older and about 5 km higher in elevation than the smooth northern lowlands.
The northern lowlands are smooth and contain few craters, hence the surface must be
relatively new compared to the southern hemisphere. This difference between the two Martian
hemispheres is called the crustal dichotomy – it is not completely understood.
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The images shows the landing sites marked with a cross for:
• Viking Landers 1 & 2 (VL1, VL2)
• Mars Pathfinder (MP)
• Mars Exploration Rovers (Spirit and Opportunity)
• Beagle 2 (B2)
Various suggestions have been made for the crustal dichotomy:
-impact of a massive object onto the northern hemisphere relatively late in the
planet’s history. This type of impact would excavate the crust down to several km
and erased older craters. This is similar to the impacts that formed the lunar
maria. A smaller, but still cataclysmic, impact of this type would have created
Hellas Planitia, a massive basin 2300km across and 6km deep. However the
boundary between north and south regions is too irregular to be the edge of an
impact crater.
- Mars may have shown plate tectonics, like Earth, early in its history before it
cooled down. The younger northern lowlands could have been formed by ‘crustal
spreading’ as seen along the Mid-Atlantic Ridge on Earth. We know from Earth
that the crust is thinner under the oceans than on land. Measurements by Mars
Global Surveyor showed that the northern crust was about 40km thick compared
to 70km for the southern uplands. However the boundary line between regions of
thin and thick crust did not match the observed topographic boundary.
Lecture 8
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Olympus Mons
Olympus Mons is a massive volcano on Mars – the largest in the solar system. 24km high and
600km high – 3 times higher than Earth’s largest volcano Mauna Loa in Hawaii.
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The crustal dichotomy could be the result of various factors, with the northen
lowlands resurfaced due to volcanic activity. Such resurfacing has occurred on
Venus, where crater features have been covered over.
The first evidence of volcanic activity on Mars came from images taken by
Mariner 9, which showed very large volcanoes.
This perspective view of Olympus Mons was created from several images
acquired by Viking Orbiter spacecraft. The scarps around the edge are up to 6km
high in places, with the caldera (volcanic crater) 70km across.
Olympus Mons and the other Martian volcanoes were probably formed by hotspot volcanism in which magma wells up from a hot spot in the planet’s mantle,
lifting up the overlying surface and producing a volcano. The huge size of
Olympus Mons is evidence of a lack of plate tectonics on Mars, with a single vent
possibly pumping magma up over millions of years. A similar process probably
led to Maxwell Montes and the other large volcanoes on Venus.
Hot spot volcanoes, although very large tend to have relatively sloping sides and
so cast only small shadows. This is one of the reasons that these features were not
observed from Earth.
Lecture 8
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Valles Marineris
Valles Marineris (Latin for Mariner Valley) was named by the NASA Mariner 9 spacecraft team
whose unmanned probe returned the first close-up views of the Martian surface in 1971.
Valles Marineris looking east
This is how the Valles Marineris canyons may appear shortly after sunrise from an altitude of 35 miles. The view is
from a position over the center of the trough system looking east. In the right foreground is the Ius Chasma, and above
it toward the Sun is the Melas Chasma, and on the left nearer to the horizon is the West Candor Chasma. The horizon
itself spans about 300 miles. This rendering is based upon elevation data from NASA's Mars Orbiter Laser Altimeter.
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Valles Marineris, or Mariner Valley, is a vast canyon system that runs along the
Martian equator just east of the Tharsis region. Valles Marineris is 4000 km
(2500 mi) long and reaches depths of up to 7 km. For comparison, the Grand
Canyon in Arizona is about 800 km long and 1.6 km deep. In fact, the extent of
Valles Marineris is as long as the United States and it spans about 20 percent
(1/5) of the entire distance around Mars!
The canyon extends from the Noctis Labyrinthus region in the west to the chaotic
terrain in the east. Most researchers agree that Valles Marineris is a large tectonic
"crack" in the Martian crust, forming as the planet cooled, affected by the rising
crust in the Tharsis region to the west, and subsequently widened by erosional
forces. However, near the eastern flanks of the rift there appear to be some
channels that may have been formed by water.
Lecture 8
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The great canyon system of Valles Marineris stretches 4000 kilometers across
Mars. This figure shows part of Ius Chasma, the southwestern part of the Valles
Marineris. The region shown here is 600 kilometers across.
Ref: www.lpi.usra.edu/expmars/activities/valmar.html
Lecture 8
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Surface water features on Mars
Flash-flood features and dried riverbeds on the Martian surface indicate that water has flowed
on Mars at least occasionally. These features are particularly seen on the older southern
uplands. No liquid water can exist on the Martian surface today
Teardrop-shaped islands from an Martian channel
called Ares Valles – signs of ancient floods
Networks of dried river beds in the cratered
southern highlands
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There is no evidence for rainfall or water on Mars today, and this is expected by
the low atmospheric pressure. The average surface temperature is 220K (-53°C)
and a pressure of 0.0063 atm.Under these conditions water can only exist as solid
or vapour, with transfer between these states by sublimation and freezing.
However there are many dried-up river and channel features, especially in the
southern highlands. It is likely that large amounts of water flowed across the
Martian surface in the distant past. Images show evidence for both flash floods
and sustained water flow, eg. canyons evolved by sustained flows. This implies
that Mars’ atmosphere must have been both warmer and of higher pressure in the
past.
Lecture 8
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Sustained water flow on Mars
2.5km wide canyon in southern uplands, with
terraces resembling Earth riverbed structures
Martian ‘mud splash’ – young Martian craters show
mud flow patterns, indicating a subsurface ice layer
that melted on impact. This is not seem on the Moon
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Polar Ice Caps
Mars’s polar caps
contain frozen water, a
layer of permafrost may
exist below the Martian
regolith, and there may
be liquid water beneath
the surface
The Martian polar caps
expand in winter as a
thin layer of frozen
carbon dioxide (dry
ice) is deposited from
the atmosphere
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Where is the Martian water now? It is not in the atmosphere, which is 95.3% CO2
and only contains trace amounts of water.
The polar caps may contain the planet’s water as ice, but they cannot be made by
ice alone. The polar temperatures are -140°C which is below the freezing
temperature of CO2 – hence solid CO2 must be form a part of the polar caps.
During the Martian spring the caps recede rapidly, consistent with a thin layer of
CO2 frost melting rapidly in the sunlight. As summer develops the rate of
recession slows abruptly, perhaps indicating that thicker and less easily
evaporated layer of water ice has been exposed. Consequently the residual polar
caps – the parts which remain during the summer – are expected to contain large
quantities of frozen water.
Lecture 8
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Neutron imaging of water
Map of water abundance under the surface, from Mars Odyssey. The image shows the
intensity of fast neutrons emitted from the near surface (1m deep) region, produced by cosmic
ray interactions. If water is present, the neutrons are preferentially absorbed by the hydrogen.
The image confirms a large amount of water under the surface at the poles. however there is
also subsurface water in regions around the equator. These frozen surface layers are similar
to tundra on Earth
The total amount of water on Mars is not known. However it is possible that there was enough
to once form oceans and lakes.
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Mars has strong winter and summer seasons in which carbon dioxide (and some
water) is exchanges between the surface and the Martian atmosphere. Condensed
CO2 accumulates at both northern and southern poles during each winter period,
and sublimes back to the atmosphere during spring exposing the residual ice caps
at the poles.
Generally the Martian ice caps are a mixture of CO2 and water ice. During Spring
the ice caps sublime and withdraw towards the poles, exposing the surface layer
of the planet. There is very little water in the atmosphere, however the nearsurface layer of the planet does appear to contain a large amount of water ice in
even awat from the poles. This water-rich surface later is the Martian equivalent
to permafrost.
Lecture 8
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Imaging of epithermal neutrons from Mars’ surface
Seasonal variation of average fluxes of epithermal neutrons measured from Mars for latitudes in the
northern hemisphere
Epithermal neutrons are produced in
the near surface region due to
interactions with cosmic rays:
 The energetic charged particles
produce fast neutrons, which are
moderated (slow down) by light nuclei
such as hydrogen
 Slow, or epithermal, neutrons then
emit from the surface and are
detected by the spacecraft
 An enhanced epithermal neutron
signal indicated the presence of
hydrogen, either as hydrated minerals
or as water/ice
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Mars Odyssey spacecraft revealed new details about the dynamic character of the
frozen layers that dominate the high northern latitudes of Mars. Odyssey contains
neutron and gamma ray sensors that were used to track seasonal changes in the
polar “ice cap”: layers of dry ice (carbon-dioxide frost or snow) accumulated
during northern Mars' winter and then dissipated in the spring, exposing a soil
layer rich in water ice.
The data show an enhanced epithermal neutron signal in Mars’ winter, which is
more pronounced close to the poles. This is direct evidence of increased thickness
of the ice cap in the winter.
Lecture 8
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Epithermal neutron maps of the North pole of Mars
Polar maps of the epithermal neutron flux from the northern hemisphere of
Mars as measured during northern winter and summer.
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The maps show are derived from a combination of high energy neutron flux
(from the high-energy neutron detector HEND on Mars Odyssey) combined with
direct measurements of the thickness of condensed carbon dioxide by the Mars
Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor. These maps confirm
the data obtained from epithermal neutrons, that there is a latitudinal dependence
of northern winter deposition of carbon dioxide. The observations are also
consistent with a shallow substrate consisting of a layer with water ice overlain
by a layer of drier soil. The lower ice-rich layer contains between 50 and 75
weight % water, indicating that the shallow subsurface at northern polar latitudes
on Mars is even more water rich than that in the south.
The maps have a pixel resolution of 1° by 1° (60 km by 60 km) and have been
smoothed with linear averaging in 5° by 5° cells. The count rate of the neutron
flux has been normalized by its maximum value, which is observed in the
equatorial Solis Planum region at 270°E, 25°S. The neutron flux is superposed on
a shaded relief map of the Mars topography (25).
Mitrofanov et al, Science, 27 June 2003, 2081-2084
Lecture 8
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The Martian atmosphere
 Mars’s primordial atmosphere may have been thicker and warmer than the present-day atmosphere
 It is unclear whether it contained enough carbon dioxide and water vapor to support a greenhouse
effect that would permit liquid water to exist on the planet’s surface
 The present Martian atmosphere is
95.3% CO2, 2.7% N2, with small amounts
or Ar, CO, O2, H2O
 Martian clouds are made up of tiny
crystals of water ice (similar to Earth) and
CO2 ice
 On most Martian afternoons blueishwhite clouds form on the tops of Olympus
Mons and the other large volcanoes of the
Tharsis highlands
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Both CO2 and H2O vapour contribute to a planet’s greenhouse effect. Both the
atmospheres of Earth and Mars are transparent to sunlight, so they are indirectly
heated from IR radiation off the planet’s surface. The atmospheric gases trap the
IR from the planet and cause heating of the atmosphere. Without the greenhouse
effect the average temperature on Earth would be ~40°C lower than it is now, and
water would be permanently frozen. On Mars the thin atmosphere is much less
efficient at retaining the IR radiation, and the greenhouse effect only accounts for
a ~5°C temperature rise.
It is likely that the Martian atmosphere was thicker in the past, and the
greenhouse effect would have been stronger. This combination of higher
temperature and pressure would allow liquid water to exist. This ancient Martian
atmosphere could have been created by the planet’s volcanoes, causing
significant amounts of out gassing of CO2 and H2O into the Martian atmosphere
~4 billion years ago.
Lecture 8
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Earth’s Atmosphere
The diagram shows the evolution of the earth’s atmosphere which is strongly influenced by the
planet’s active geology
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On Earth most of the water is in the oceans. N2 which is not very reactive mainly
remains in the atmosphere. CO2 however dissolves in the rain and enters the
geology, ultimately as carbonate rocks such as limestone. As a result there is very
little CO2 left in the atmosphere. The cycle of CO2 on Earth is sustained partly by
plate tectonics, which cause carbonate rocks to pass through volcanoes and so
emit CO2 back into the atmosphere. Without volcanic activity our atmosphere
would be empty of CO2 in just a few thousand years.
The unique aspect of earth’s atmosphere is the presence of O2 which is formed by
biological activity, primarily by photosynthesis.
Lecture 8
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Mars’ Atmosphere
In contrast to the Earth, the geology of Mars is relatively inactive, with CO2 not recycled back into
the atmosphere
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If Mars once had a thick atmosphere, the CO2 would have originally been emitted
into the atmosphere by volcanic activity. The CO2 would be returned by rainfall
to form carbonate rocks, in the same was as on Earth. However as Mars cooled
any tectonic activity stopped and the CO2 remained locked in the rocks. The
depletion of CO2 from the Martian atmosphere would become permanent.
With a reduction in atmospheric CO2 the greenhouse effect weakens, the
temperature drops, and the water vapour in the atmosphere condenses faster. A
negative greenhouse (‘icehouse’) effect builds up, with the atmosphere eventually
becoming very thin. The surface temperature would stabalise at its current low
level.
With as thin atmosphere, UV from sunlight will penetrate further and cause the
various gas molecules to dissociate (eg. N2, H2O, CO2), with the N, H, O, C
atoms free to escape from the atmosphere into space. Some O atoms combined
with iron-bearing compounds to form iron-oxide which gives Mars its
characteristic red colour.
Lecture 8
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Dust storms on Mars
Great dust storms sometimes blanket Mars - Fine-grained dust in its atmosphere gives the Martian
sky a pinkish-orange tint
Seasonal winds blow dust across the face of Mars, covering and uncovering the underlying surface
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material and causing seasonal color changes
Lecture 8
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Afternoon dust devils help to transport dust from place to place
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Paul Sellin
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Winter Frost
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Landers have explored the surface of Mars
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Mars exploration rovers
NASA's twin Mars Exploration Rovers launched toward Mars on June 10 and July 7, 2003 to
investigate the history of water on Mars. They landed on Mars January 3 and January 24 PST
(January 4 and January 25 UTC).
After the airbag-protected
landing craft settle onto the
surface and open, the
rovers rolled out to take
panoramic images. These
give scientists the
information they need to
select promising geological
targets that tell part of the
story of water in Mars' past.
Then, the rovers drive to
those locations to perform
on-site scientific
investigations.
marsprogram.jpl.nasa.gov/
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These are the primary science instruments to be carried by the rovers:
Panoramic Camera (Pancam): for determining the mineralogy, texture, and
structure of the local terrain.
Miniature Thermal Emission Spectrometer (Mini-TES): for identifying
promising rocks and soils for closer examination and for determining the
processes that formed Martian rocks. The instrument will also look skyward to
provide temperature profiles of the Martian atmosphere.
Mössbauer Spectrometer (MB): for close-up investigations of the mineralogy
of iron-bearing rocks and soils.
Alpha Particle X-Ray Spectrometer (APXS): for close-up analysis of the
abundances of elements that make up rocks and soils.
Magnets: for collecting magnetic dust particles. The Mössbauer Spectrometer
and the Alpha Particle X-ray Spectrometer will analyze the particles collected
and help determine the ratio of magnetic particles to non-magnetic particles.
They will also analyze the composition of magnetic minerals in airborne dust and
rocks that have been ground by the Rock Abrasion Tool.
Microscopic Imager (MI): for obtaining close-up, high-resolution images of
rocks and soils.
Rock Abrasion Tool (RAT): for removing dusty and weathered rock surfaces
and exposing fresh material for examination by instruments onboard.
Ref: http://marsrovers.nasa.gov/overview/
Lecture 8
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Mars Explorer Rovers
The mission's main scientific goal is to search for and characterize a wide range of rocks and soils
that hold clues to past water activity on Mars. The spacecraft are targeted to sites on opposite
sides of Mars that appear to have been affected by liquid water in the past.
The landing sites are at Gusev Crater, a
possible former lake in a giant impact crater,
and Meridiani Planum, where mineral
deposits (hematite) suggest Mars had a wet
past.
The Mars Odyssy orbiter spacecraft acts as
the communication relay for the Mars Explorer
Rovers
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Selection of landing sites for the two Mars Exploration Rovers required more
than two years of intensive study. More than 100 scientists and engineers
participated in evalu-ating sites both on the basis of favorable criteria for safe
landings and on the prospects for outstanding science opportunities after the
rovers reach the ground.
To qualify for consideration, candidate sites had to be near Mars‘ equator, not
too rugged, not too rocky, not too dusty, and low enough in elevation so the
spacecraft would pass through enough atmosphere to slow down sufficiently. In
all, 155 potential sites met the initial safety constraints. Detailed observations by
two active orbital spacecraft, Mars Global Surveyor and Mars Odyssey, provided
an unprecedented amount of information for evaluating finalist candidate sites.
Lecture 8
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Gusev Crater - Spirit
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The first Mars Exploration Rover, Spirit, is flying to Gusev Crater, a bowl bigger
than Connecticut that appears to have held a lake long ago. Scientists will use the
robot's instruments to seek and analyze geological evidence about past
environmental conditions in the crater. If sedimentary rocks lie on the surface,
they may yield telltale clues to whether the crater ever did hold a wet
environment that might have been suitable for sustaining life.
An asteroid or comet impact perhaps as much as 4 billion years ago dug Gusev
Crater. Many smaller, younger impact craters pock Gusev's 150-kilometerdiameter (95-mile) floor. One of the largest branching valleys on Mars, likely
carved by flowing water more than 2 billion years ago, leads directly into Gusev
Crater through a breach in the crater's southern rim. Gusev sits at 15 degrees
latitude south of Mars' equator at longitude 184.7 degrees west, in a transition
zone between the ancient highlands on the southern part of the planet and
smoother plains to the north. The valley, called Ma'adim Vallis, snakes northward
Nile-like about 900 kilometers (550 miles) from the highlands to Gusev. In
places, it gapes more than 25 kilometers (16 miles) wide and 2 kilometers (1.2
miles) deep.
Water flowing down the valley would have pooled in Gusev Crater, dropping
sediments there before exiting through a gap in the crater's northern rim.
Comparable crater lakes, such as Lake Bosumtwi in Ghana, exist on Earth.
Gusev's lake, if indeed it did exist, is now gone. But the floor of Gusev Crater
may hold water-laid sediments that preserve records of the lake environment, of
the sediments' highlands origins and of the sediments' river trip.
Lecture 8
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Meridiani Planum - Opportunity
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The second Mars Exploration Rover, Opportunity, is targeted for Meridiani
Planum, a smooth plain near the equator halfway around the planet from Gusev
Crater. Intense scientific interest in the site results not from the shape of the
terrain, as at Gusev, but from an unusual mineral deposit found by a Marsorbiting spacecraft.
Scientists using an instrument called the thermal emission spectrometer on
NASA's Mars Global Surveyor have discovered that Meridiani Planum is rich in
grey hematite, a type of iron oxide mineral. On Earth, grey hematite usually - but
not always -forms in association with liquid water. Some environmental
conditions that can produce grey hematite, such as a lake or hot springs, could be
quite hospitable to life. Others, such as hot lava, would not.
The grey hematite covers an estimated 15 to 20 percent of the surface in the
vicinity of the planned landing site. It appears as a dark cap layer atop a brighter
layer that is exposed at many places within the ellipse-shaped landing target.
Lecture 8
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Where are the Rovers now?
Spirit reached Sol 1055 in Dec 2006:
As of sol 1054 (Dec. 20, 2006), Spirit's total
odometry was 6,886.80 meters (4.28 miles).
Spirit is ‘stalled’ by May 2010:
Currently at "Troy" on the west side of Home
Plate – no communication has been received
since March
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SPIRIT UPDATE: Winter Solstice Two Weeks Away - sols 2240-2247, April
22-29, 2010:
Spirit remains silent at her location called "Troy" on the west side of Home Plate.
No communication has been received from the rover since Sol 2210 (March 22,
2010).
It is likely that Spirit has experienced a low-power fault and has turned off all
sub-systems, including communication. The rover will use the available solar
array energy to recharge her batteries. When the batteries recover to a sufficient
state of charge, Spirit will wake up and begin to communicate. When that does
happen, Spirit will also trip an up-loss timer fault. This fault response will allow
the rover to communicate over Ultra-High Frequency (UHF), as well as X-band.
It is not known when the rover will wake up, so the project has been listening for
any X-band signal from Spirit through the Deep Space Network every day. The
Mars Odyssey orbiter is also listening over any scheduled UHF relay passes. The
winter solstice is about two weeks away.
Total odometry is unchanged at 7,730.50 meters (4.80 miles).
Lecture 8
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Where are the Rovers now? (2)
Opportunity's traverse through Sol 1039
By Dec. 2006 Opportunity's had covered 9.8
km (6.1 miles).
By May 2010 Opportunity reached Sol 2020
By Dec. 22006 Opportunitys had covered 20.60
km (12.8 miles)
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OPPORTUNITY UPDATE: Opportunity's Balancing Act - sols 2219-2226,
April 21-28, 2010:
Opportunity drove twice in the last week. The rover took time in between drives
to recharge her batteries and performed a soil campaign with the instrument
deployment device (IDD).
The drives took place on Sols 2220 (April 22, 2010), and 2226 (April 28, 2010).
The drive on Sol 2220 (April 22, 2010) halted after about 10 meters (33 feet)
when a slip check failed while traversing the soft side of a sand dune. Post drive
analysis determined that this slip-check failure was of the type that is expected
occasionally from driving in this terrain and did not indicate a fundamental
change in hazard level. Therefore, following the completion of the IDD soil
campaign, a drive was planned for Sol 2226 (April 28, 2010), which executed
nominally and added approximately 33 meters (108 feet) of progress.
A complicating factor for Opportunity during this winter period is that she has to
balance her recharge efforts against the need to stay warm. That is, if she doesn't
expend a minimum amount of energy into the electronics during a given sol, she
risks thermostatic heaters coming on that will consume even greater amounts of
energy. At this point, this balancing act is primarily an impact on driving as
Opportunity can at anytime park herself on a sunny northerly slope to satisfy
survival requirements.
Lecture 8
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Mars Global Surveyor
NASA's Mars Global Surveyor (MGS)
orbiter is the oldest Mars spacecraft
currently in operation, studying the planet
for nearly a decade.
MGS arrived at Mars on September 11,
1997 and has since returned more
scientific data about the evolution of the
red planet than all other Mars missions
combined.
MGS circles in a polar orbit once every two
hours collecting global "snapshots" from
400 kilometers (249 miles) above the
martian surface.
MGS has not communicated with Earth
since Nov 2nd 2006.
Mars Exploration rover Opportunity failed
to detect any signal from MGS on Nov 22
2006, indicating the end of this mission
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Lecture 8
Paul Sellin
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Recent evidence for water on Mars
NASA photographs from MGS have revealed bright new deposits seen in two gullies on Mars
that suggest water carried sediment through them sometime during the past seven years.
This set of images shows a comparison of the gully site as it appeared on Dec. 22, 2001 (left),
with a mosaic of two images acquired after the change occurred (the two images are from
Aug. 26, 2005, and Sept. 25, 2005).
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December 6th, 2006
Paul Sellin
Liquid water, as opposed to the water ice and water vapor known to exist at Mars,
is considered necessary for life. The new findings heighten intrigue about the
potential for microbial life on Mars. The Mars Orbiter Camera on NASA's Mars
Global Surveyor provided the new evidence of the deposits in images taken in
2004 and 2005.
"The shapes of these deposits are what you would expect to see if the material
were carried by flowing water," said Dr. Michael Malin of Malin Space Science
Systems, San Diego. "They have finger-like branches at the downhill end and are
easily diverted around small obstacles." Malin is principal investigator for the
camera and lead author of a report about the findings published in the journal
Science.
The atmosphere of Mars is so thin and the temperature so cold that liquid water
cannot persist at the surface. It would rapidly evaporate or freeze. Researchers
propose that water could remain liquid long enough, after breaking out from an
underground source, to carry debris downslope before totally freezing. The two
fresh deposits are each several hundred meters, or yards, long.
Ref: http://marsprogram.jpl.nasa.gov/mgs/newsroom/20061206a.html
Lecture 8
Page 34
Delta structures on Mars
Structures like river deltas were observed by
MGS on Mars
The images show eroded ancient deposits of
transported sediment long since hardened into
interweaving, curved ridges of layered rock.
Scientists interpret some of the curves as
traces of ancient meanders made in a
sedimentary fan as flowing water changed its
course over time.
The shape of the fan and the pattern of inverted
channels in it suggest it may have been a real
delta, a deposit made where a river enters a
body of water," he said. "If so, it would be the
strongest indicator yet Mars once had lakes."
Ref:
http://marsprogram.jpl.nasa.gov/newsroom/pres
sreleases/20031113a.html
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marsprogram.jpl.nasa.gov/
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Lecture 8
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