ASTR 330: The Solar System

1
ASTR 330 The Solar System

• Lecture 16 - Quiz

• Are there canals on Mars? How did the idea start,
  and how was the issue resolved?
• What features were discovered by Mariner 9?
• What was the greatest accomplishment of the
  Viking missions?
• Does Mars have any large impact basins?
• Describe the main geologic features of the
  Tharsis uplift. How was Tharsis produced?
• Compare Martian volcanoes to terrestrial and
  Venusian mountains.
• Are the Valles Marineris on Mars bigger versions
  of the Earths Grand Canyon?

Dr Conor Nixon Fall 2006
2
ASTR 330 The Solar System

• Lecture 17
• Mars II

Dr Conor Nixon Fall 2006
Picture credit NASA/JPL - MER Mission Team
3
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
4
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 90-km
  crater Mie, 200 km away.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL and Calvin Hamilton
5
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
6
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
7
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

Dr Conor Nixon Fall 2006
8
ASTR 330 The Solar System

• What Really Happened?

?Mars Climate Orbiter 1998
Mars Polar Lander 1998? ?
Dr Conor Nixon Fall 2006
Cartoons New Orleans Picayune (Handelman),
Detroit Free Press (Thompson).
9
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
10
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
11
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL
12
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. Its 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.

Dr Conor Nixon Fall 2006
Picture credits NASA/NSSDC
13
ASTR 330 The Solar System

• Sojourner Science

• Sojourners sole scientific instrument (besides
  cameras) was an Alpha-Proton 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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL
14
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
15
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
Dr Conor Nixon Fall 2006
Picture credit JPL/NASA/PDS
16
ASTR 330 The Solar System

• Mars Landing Sites 1976-2003

Dr Conor Nixon Fall 2006
Map NASA/JPL/GSFC
17
ASTR 330 The Solar System

• MER Science Instruments

• Each Rover is equipped with the following
• 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.
• 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.

Dr Conor Nixon Fall 2006
Instrument descriptions from marsrovers.nasa.gov
18
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 Maadim Vallis to the south, which
  looks like a dry riverbed or water channel.

Dr Conor Nixon Fall 2006
Image credit NASA
19
ASTR 330 The Solar System

• Wheres the water?

• Spirits 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 water-bearing minerals that that
  the orbital reconnaissance had suggested?

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornell
20
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornell
21
ASTR 330 The Solar System

• Spirit - Sol 986
• (6.9 km on odometer)

Dr Conor Nixon Fall 2006
22
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornell
23
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 water-deposited 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 water-bearing rock.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornell
24
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornell
25
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornell
26
ASTR 330 The Solar System

• Opportunity
• (9.0 km on odometer)

Dr Conor Nixon Fall 2006
27
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

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/UA
28
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/Cornall
29
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/UA
30
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!
• Spirits 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
31
ASTR 330 The Solar System

• Polar Caps

• Mars possesses two types of polar caps
• 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.)
• 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
32
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
• An 8m-thick covering of CO2 ice.
• 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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL
33
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/MSSS
34
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.

Dr Conor Nixon Fall 2006
Image credit NASA/JPL/UA
35
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.

Dr Conor Nixon Fall 2006
Image credit solarviews.com
36
ASTR 330 The Solar System

• North Polar Dune Fields

• Yet another north-south 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.

Dr Conor Nixon Fall 2006
Image credit solarviews.com
37
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 carbon dioxide CO2
• 2.7 nitrogen N2
• 1.6 argon Ar-40
• 0.13 oxygen O2
• 0.07 carbon monoxide CO
• 0.03 water H2O
• 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
38
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
  -30C on a summer afternoon! Night-time
  temperatures can dip to -100C.
• 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
39
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
40
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).

Dr Conor Nixon Fall 2006
Image credit NASA/JPL
41
ASTR 330 The Solar System

• Mars Science Laboratorry

Dr Conor Nixon Fall 2006
Image credit NASA/JPL
42
ASTR 330 The Solar System
?What really happened to pathfinder?
The source of all the Mars mishaps? ?
Dr Conor Nixon Fall 2006
Cartoons Des Moignes Register Duffy, Richmond
Times Dispatch (Brookins).
43
ASTR 330 The Solar System

• Lecture 17 - Quiz

• Are craters on Mars the same as those on the Moon
  and Mercury? If not, what differences are there?
• What differences are there between the northern
  and southern hemispheres on Mars?
• What types of rocks were found on Mars. Is this
  what we expected?
• What three types of channels are found on Mars,
  and what caused them?
• Is there liquid water on the surface of Mars
  today?
• Compare the Martian atmosphere to that of (i)
  Venus (ii) the Earth.
• What missions are currently underway to explore
  Mars?

Dr Conor Nixon Fall 2006