Transcript ASTR 330: The Solar System Dr Conor Nixon Fall 2006

ASTR 330: The Solar System
Lecture 16 - Quiz
1. Are there canals on Mars? How did the idea start, and how was the
issue resolved?
2. What features were discovered by Mariner 9?
3. What was the greatest accomplishment of the Viking missions?
4. Does Mars have any large impact basins?
5. Describe the main geologic features of the Tharsis uplift. How was
Tharsis produced?
6. Compare Martian volcanoes to terrestrial and Venusian mountains.
7. Are the Valles Marineris on Mars bigger versions of the Earth’s Grand
Canyon?
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Lecture 17:
Mars II
Picture credit: NASA/JPL - MER Mission Team
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Mars: up-close and personal
• In this lesson, the main theme is the in-situ exploration of the Martian
surface.
• We will begin by looking at the landing sites of Viking, continue with
the Sojourner Rover, and finish right up at the present day with the
Spirit and Opportunity Rovers.
• We will consider the detailed information returned by these explorers
regarding rock and soil, sediments and water.
• We will also examine the atmosphere and polar caps.
• Finally, we look at some of the planned missions to Mars in the next
few years.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Viking 1: Chryse
• Chryse Planitia (The Plains of Gold) is a
rock-strewn plain, originally volcanic in
nature like the lunar maria, but modified by
water and wind erosion.
• The rocks appear to be igneous, ejected
from nearby impact craters.
Viking 2: Utopia
• The Utopia, like Chryse, was intended to
be flat landing site, but ended up being
even rockier. Viking 2 ended up with one
leg on a boulder, tilting at 8 degrees.
• Most of the rocks are ejecta from the 90km crater Mie, 200 km away.
Image credit: NASA/JPL and Calvin Hamilton
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Viking: Rock and Soil
• The Viking landers were able to find the cause of Mars’ red
coloring: iron oxides in the surface soil.
• Their chemical analysis showed that the soil was similar to
some iron-rich clays we see on Earth.
• The Vikings were not equipped to analyze rocks, unlike the
later rovers, however they did attempt to search for the
presence of life in the soil using two experiments.
• We will return to these in a later lecture when we discuss the
emerging field of astrobiology and the search for life outside
the Earth.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
View from Orbit: Dunes
• Most of the fine dusty surface material is
light in color.
• After a major dust storm, dark surface
rocks can be covered up by light-colored
wind-blown sand.
• Later on, other winds or dust-devils can
blow the sand away again, re-exposing the
darker surface.
• This is the true explanation for the
observed ‘seasons’ on Mars, the shifting
light and dark coloration originally thought
to be due to vegetation.
• The image (right) is of ‘cemented’ sand dunes in the
Herschel crater of the Terra Cimmeria, taken by MGS/MOC.
Image credit: MSSS/NASA/JPL.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Successes and Failures
• The Viking landers of 1976 were hugely successful: so successful in
fact (in showing the apparent lifelessness of Mars) that NASA neglected
the Red Planet for over a decade.
• From the late 1980s to the present day, the road has been littered with
causalities:
Mission
Phobos 1
Phobos 2
Mars Observer
Mars Global Surveyor
Mars 96
Mars Pathfinder
Nozomi/Planet-B
Mars Climate Orbiter
Mars Polar Lander
Mars Odyssey
Mars Express
Beagle 2
Spirit Rover
Opportunity Rover
Mars Recon Orbiter
Country
USSR
USSR
US
US
Russia
US
Japan
US
US
US
Europe
Europe
US
US
US
Year Outcome
1988
1988
1992
1996
1996
1996
1998
1998
1998
2001
2003
2003
2003
2003
2005
Lost contact en-route
Entered orbit and returned data for brief time
Lost contact before arrival
Successful orbiter - still operating
Launch Failure
Rover lasted for 90+ days
Never entered orbit
Crashed into planet due to units errorMars
Lost contact
Successful orbiter - still operating
Successful orbiter - still operating
Lander - crashed
Successful rover - still operating
Successful rover - still operating
Successful orbiter - still operating
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
What Really Happened?
Mars Climate
Orbiter 1998
Mars Polar
Lander 1998? 
Cartoons: New Orleans Picayune (Handelman), Detroit Free Press (Thompson).
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Successful Surface Explorers
• The surface of Mars has been explored more thoroughly than any
other planet outside the Earth and Moon.
• We have a multitude of information from at least 5 landing craft:
• Viking 1: landed on the Chryse Planitia, July 1976.
• Viking 2: landed on the Utopia Planitia, September 1976.
• Pathfinder/Sojourner: landed on Ares Vallis, July 1997.
• Spirit: landed at Gusev Crater, Jan 4th 2004.
• Opportunity: landed at Terra Meridiani , Jan 24th 2004.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
US Return to Mars 1996-1997: Pathfinder
• After the costly M.O. failure, NASA opted for a scaled-down approach and
had success with the Mars Global Surveyor (MGS) and Pathfinder
missions in 1996 and 1997.
• While MGS orbited the planet, Pathfinder landed and became a weather
station, returning 16,000 images and 8.5 million measurements of
atmospheric pressure, temperature and wind speed.
• The battery, which kept the lander warm at night, was designed to only
recharge about 40 times - to keep costs down. On Day 83 (‘Sol’ 83) after
landing, the lander ceased communicating with the Earth - probably due to
cold nighttime temperatures.
• The lander by that time had been renamed ‘Sagan Memorial Station’
after planetary scientist and writer Carl Sagan who died in 1996.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Pathfinder at Ares Vallis
• Pathfinder landed in the Ares Vallis region - a location where
scientists hoped to find a variety of rocks carried from the southern
highlands to the northern lowlands by floodwaters.
Image credit: NASA/JPL
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Pathfinder Rover: ‘Sojourner’
• The Pathfinder mission included a small rover, Sojourner, which
roamed the surface for 3 months before the lander failed and
communication with the Earth was lost. It was the first ever rover on
another planet.
• Sojourner weighed just 10 kg
and was the size of a microwave
oven. It’s maximum speed was
just 1 cm/s (0.02 mph).
• Sojourner successfully
demonstrated many technologies
used in subsequent missions,
including obstacle avoidance
and airbag landing on Mars, as
well as completing real science.
Picture credits: NASA/NSSDC
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Sojourner Science
• Sojourner’s sole scientific instrument (besides cameras) was an AlphaProton X-Ray Spectrometer (APXS) - an instrument designed to analyze
the elements of rock composition.
• In this image, the Sojourner rover examines a rock nick-named ‘Yogi’.
• The chemical analysis
showed that all the
rocks were igneous,
but surprisingly they
were not the expected
basalts (volcanic), but
rather silicon-bearing
granites, similar to the
continental crust on
Earth created by
tectonics.
Image credit: NASA/JPL
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Mars Rocks on Earth
• Do we have samples of Mars rocks on Earth?
• We have never in fact sent a mission to return samples, however, we do
have around 20 meteorites which have been positively confirmed to be of
Martian origin. How do we know?
• Tiny bubbles of gas trapped in the rocks trapped inside the rocks perfectly
match the atmosphere of Mars, as sampled by Viking.
• However, these rocks are basalts, with solidification ages mostly around
1.3 Gyr. One is as old as 4 Gyr.
• But we just said that Sojourner found only granites, no basalts! This
mystery would have to wait for a new generation of explorers…
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Mars Exploration Rovers 2003-2006
• Pathfinder paved the way for a much more ambitious (and expensive) duo
of rovers: the Mars Exploration Rovers Spirit and Opportunity.
• These are larger,
faster, smarter and
better equipped with
many more scientific
tools than
Pathfinder/Sojourner
(see scale comparison,
right).
• Each rover weighs
185 kilos: 18 times the
little Sojourner Rover.
MER - First Year Movie
Picture credit: JPL/NASA/PDS
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Mars Landing Sites 1976-2003
Map: NASA/JPL/GSFC
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
MER Science Instruments
•
Each Rover is equipped with the following:
1. Panoramic Camera (Pancam): for determining the mineralogy, texture, and
structure of the local terrain.
2. 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.
3. Mössbauer Spectrometer (MB): for close-up investigations of the mineralogy
of iron-bearing rocks and soils.
4. Alpha Particle X-Ray Spectrometer (APXS): for close-up analysis of the
abundances of elements that make up rocks and soils.
5. 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.
6. Microscopic Imager (MI): for obtaining close-up, high-resolution images of
rocks and soils.
7. Rock Abrasion Tool (RAT): for removing dusty and weathered rock surfaces
and exposing fresh material for examination by instruments onboard.
Instrument descriptions from: marsrovers.nasa.gov
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Spirit at Gusev Crater
• Spirit landed as planned
inside a large (150 km) impact
crater named Gusev, which
probably formed 3-4 billion
years ago.
• This area was targeted
because orbital pictures
starting with Viking had shown
Gusev to have been likely
flooded at some point in the
past.
• Note the Ma’adim Vallis to
the south, which looks like a
dry riverbed or water channel.
Image credit: NASA
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Where’s the
water?
• Spirit’s initial science
findings were somewhat
disappointing: nearly all
the rocks investigated
were plain old basalt:
thrown up in the impact
which formed the giant
crater.
• Where were the waterbearing minerals that that
the orbital reconnaissance
had suggested?
Image credit: NASA/JPL/Cornell
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Spirit of Adventure
• Spirit spent much of its travels driving to, and then climbing the
‘Columbia Hills’ - a range of low peaks named for the Columbia Shuttle
Crew.
Image credit: NASA/JPL/Cornell
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Spirit - Sol 986
(6.9 km on odometer)
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Perseverance pays off…
• At last, Spirit hit ‘paydirt’ in the hills. Examination of a rock named ‘Clovis’
showed the signature of a mineral called Goethite, which contains water in
the form of hydroxyl: OH.
• Spirit was at last finding
water, but Gusev crater had
turned out to be much
different to expectations.
• Scientists still believe that
Gusev was flooded in the
past, but the picture is more
complex than anticipated and
the process of unraveling the
clues continues.
Image credit: NASA/JPL/Cornell
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Opportunity at Eagle Crater
• Opportunity had landed in a small crater on the Meridiani Planum,
• The 22-meter depression proved to
be a rich hunting ground for waterdeposited minerals.
• Opportunity used its RAT to grind
away the surface of a rock dubbed
‘El Capitan’. The Mossbauer
spectrometer then showed evidence
for Jarosite: another type of waterbearing rock.
Image credit: NASA/JPL/Cornell
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Munching On
Blueberries
• Much of the terrain inside Eagle
crater was covered in scattered
small spherules (2-4 mm in size),
dubbed ‘blueberries’ by the
science team.
• On analysis, the ‘blueberries’ turned out to
be rich in haematite, an iron-bearing mineral
which often forms in the presence in water.
• Along with the jarosite, the blueberries
were telling a story of a watery past in this
region.
Image credit: NASA/JPL/Cornell
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
‘Martian’ meteorite!
• On Sol 339
Opportunity chanced
upon the last thing
anyone expected: a
object which was clearly
not from Mars!
• The nickel-iron
meteorite is about the
same size as basketball,
and would be a valuable
find on Earth.
• This was the first ever
meteorite found on
another planet.
Image credit: NASA/JPL/Cornell
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Opportunity
(9.0 km on
odometer)
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Victoria Crater
• Opportunity has now
reached the 800m wide
Victoria Crater, much
larger the the Eagle and
Endurance craters
explored to date.
• This photo was taken
from orbit, by the HiRISE
camera system on Mars
Reconnaissance Orbiter,
showing a dune field
inside.
• Animation of Victoria
Crater
Image credit: NASA/JPL/UA
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Victoria Crater
• Opportunity is currently exploring the rim of Victoria Crater, photographing
the terrain and scouting for a way to descend inside.
• The image (below) superimposing a scale image of the rover on an actual
photo to show scale - the rover was actually taking the picture at the time!
• The promontory is called ‘Cape Verde’ and is about 6 m in height,
showing layered terrain.
Image credit: NASA/JPL/Cornall
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Opportunity - spotted!
• Opportunity has even been photographed from orbit! This image was
taken by HiRISE on MRO at the start of October.
Image credit: NASA/JPL/UA
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
MER Rover Status
• Both rovers continue to function, well beyond their designed lifetime:
as Steve Squyres, the Rover PI likes to joke: the are 900 days into their
90-day mission!
• Spirit’s right front wheel ceased working on March 13th 2006: the
drivers thereafter managed to make some progress by alternating
forward motion with reversing the rover and dragging the wheel behind.
• Since April, Spirit has been parked on a south-facing slope to maintain
power through the winter solstice (Aug 8th). The rover is now waiting for
optimum power to be restored before setting off again.
• Spirit will need to stay clear of deeper sand, where it could become
stuck.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Polar Caps
•
Mars possesses two types of polar caps:
1. Seasonal Polar Caps: these are composed of CO2 frost (dry
ice) which condenses and evaporates seasonally. In the south,
these reach to 55° latitude, though only to 65° in the north.
(Southern winters are more severe than northern, due to Mars’
elliptical orbit which brings it closer to the Sun in the northern
winter than the southern one.)
2. Permanent Polar Caps: until several years ago, the residual ice
at both poles in summer was believed to be CO2 ice also,
however it has now been showed to be mainly water ice instead.
The northern and southern permanent polar caps show some
surprising differences.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Permanent South Polar Cap
• The southern residual or
permanent polar cap is only
350 km across, and composed
of two layers:
1. An 8m-thick covering of
CO2 ice.
2. A much deeper layer of
water ice.
• The south polar cap is at a
temperature of 150 K, the freezing
point of CO2 ice, even during the
warm southern summer.
Image credit: NASA/JPL
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Permanent North Polar Cap
• The north polar cap is much larger (1000 km) and also warmer during
summer (200 K) than the southern one. During northern summer, the
the amount of water vapor rises sharply above the cap.
• Therefore most of the cap is water ice: perhaps the main repository on
Mars.
• It is covered in a
much thinner layer of
CO2 ice than the
southern cap: only 1
meter thick.
• This is an effect of the
warmer temperatures.
Image credit: NASA/JPL/MSSS
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Polar differences
• It is somewhat baffling that the southern cap remains colder in
summer (150K) than the northern one (200K), although southern
summers are warmer!
• The explanation may lie with the global dust storms which occur
during southern summer, blanketing the northern cap with dust as it is
forming.
• This in turn makes the northern cap darker, and more able to absorb
sunlight.
• Therefore in the northern summer, the northern cap absorbs a lot of
light and evaporates all its CO2 and some of the water too.
Image credit: NASA/JPL/UA
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
North Polar Laminated Terrain
• This image from a
Viking orbiter shows
laminated, or layered
terrain where the
northern ice has melted.
• This is caused by
successive years of
freezing and melting,
leaving the dust behind
in the summers.
• Each layer is 10 to 50m
thick, showing cyclical
climatic, rather than
annual changes.
Image credit: solarviews.com
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
North Polar Dune Fields
• Yet another northsouth difference is the
existence of large
dunefields, encircling
the north pole for a
distance of 500 km.
• This is another Viking
image, showing two
types of dunes:
transverse at left, and
barchan on the right,
with a transition zone in
the center.
Image credit: solarviews.com
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Atmosphere
• Indirect evidence for an atmosphere on Mars was long ago determined:
including the seasonal ice caps, dust storms, and even clouds. But how
much atmosphere, and of what?
• The Viking landers carried out the first definite test of the atmosphere, and
found:
• 95.4%
• 2.7%
• 1.6%
• 0.13%
• 0.07%
• 0.03%
carbon dioxide
nitrogen
argon
oxygen
carbon monoxide
water
CO2
N2
Ar-40
O2
CO
H 2O
• The first three gases also exist in the atmosphere of Venus, and in almost
the same proportions. But the atmosphere of Mars is much thinner, by
about 10,000 times, at 0.007 bar.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Atmosphere and Temperature
• The minor constituents of Mars’ atmosphere are much different from
Venus however, especially as Argon-40, a radiogenic isotope, is more
prevalent than Ar-36, the original cosmic isotope.
• We also find no sulfur compounds, or acids.
• Mars has a troposphere and stratosphere, similar to Earth and Venus.
The troposphere is about 10-20 km thick and does have convection in the
day, but practically disappears at night.
• The surface temperature reaches a maximum of -30°C – on a summer
afternoon! Night-time temperatures can dip to -100°C.
• The overall air pressure can vary by as much as 20%, due to the seasonal
exchange of CO2 between the atmosphere and the polar caps.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Methane Surprise
• In 2004, scientists using infrared spectroscopy were surprised to
discover small amounts of CH4 in the atmosphere of Mars.
• Methane is destroyed in about 300 years by sunlight, so the presence
of even trace quantities (10 ppb - parts per billion) indicates that the gas
must be being released somewhere at the present day.
• Possible sources include:
• Volcanic activity (as on the Earth)
• Reactions in the soil
• Methane-releasing bacteria.
• Hence, the presence of methane has added to the debate on whether
there is life on Mars. Scientists are currently split, with the majority
espousing a ‘wait and take more data first’ attitude.
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Mars Science Laboratory
• MSL is a new rover currently under development by NASA for probable
launch in 2009. It is twice as long and four times the weight of the MER
rovers. It may be nuclear powered rather than solar powered.
• MSL carry new tools for
scientific investigation,
including:
• a laser for vaporizing the
rock surface
• full soil chemistry and
biology analysis package,
to search fpr organic
material (amino acids etc).
Image credit: NASA/JPL
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Mars Science Laboratorry
Image credit: NASA/JPL
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
What really
happened to
pathfinder?
The source of all the
Mars mishaps? 
Cartoons: Des Moignes Register ‘Duffy’, Richmond Times Dispatch (Brookins).
Dr Conor Nixon Fall 2006
ASTR 330: The Solar System
Lecture 17 - Quiz
8. Are craters on Mars the same as those on the Moon and Mercury? If
not, what differences are there?
9. What differences are there between the northern and southern
hemispheres on Mars?
10. What types of rocks were found on Mars. Is this what we expected?
11. What three types of channels are found on Mars, and what caused
them?
12. Is there liquid water on the surface of Mars today?
13. Compare the Martian atmosphere to that of (i) Venus (ii) the Earth.
14. What missions are currently underway to explore Mars?
Dr Conor Nixon Fall 2006