Astrobiology

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Astrobiology Wednesday, March 19, 2008 The
Search for Life in the Solar System The Planet
Mars
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The Search For Biosignatures On Mars
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The Search for Biosignatures on Mars
There are three direct methods for investigating
life in the solar system
Methodology

• in-situ investigation
• meteorites
• sample return missions

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Missions to Mars
Launch Date Name Country Result 1960 Oct. 10,
1960 Korabl 4 USSR Failed in Earth orbit Oct. 14,
1960 Korabl 5 USSR Failed in Earth
orbit 1962 Oct. 24, 1962 Korabl 11 USSR Failed to
leave Earth orbit Nov. 1, 1962 Mars 1 USSR Lost
communications Nov. 4, 1962 Korabl
13 USSR Failed in Earth orbit, reentered Nov.
5 1964 Nov. 5, 1964 Mariner 3 USA Launch failure,
entered solar orbit Nov. 28, 1964 Mariner
4 USA Reached Mars July 15, photographs/atmospheri
c measurements Nov. 30, 1964 Zond 2 USSR Lost
communications May 1965 1965 July 18, 1965 Zond
3 USSR Photographed Moon, reached Mars
orbit 1969 Feb. 24, 1969 Mariner 6 USA Flyby July
31 successful mission Mar. 27, 1969 Mariner
7 USA Flyby Aug. 5 successful mission Mar. 27,
1969 none USSR Failed believed launch
failure Apr. 14, 1969 none USA Failed 1971 May 8,
1971 Mariner 8 USA Failed to reach orbit May 10,
1971 Kosmos USSR Failed to leave Earth orbit
reentered May 10 May 19, 1971 Mars 2 USSR Orbited
Mars descent module crashed Nov. 27 May 28,
1971 Mars 3 USSR Orbited Mars descent module
failed upon landing Dec. 2 May 30, 1971 Mariner
9 USA Orbited Mars Nov. 13 successful
mission 1973 July 21, 1973 Mars 4 USSR Failed to
orbit, flew by Feb. 10 July 25, 1973 Mars
5 USSR Entered orbit of Mars Feb. 12 partially
successful mission
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Missions to Mars
Launch Date Name Country Result
1973 Aug. 5, 1973 Mars 6
USSR Flyby descent module communications failed
landing Mar. 12 Aug. 9, 1973 Mars 7
USSR Failed, flew by Mars 1975 Aug. 20,
1975 Viking 1 USA Orbited 1976 June
19 landed July 20 Sept. 5, 1975 Viking 2
USA Orbited 1976 Aug. 7 landed Sept.
3 1988 Aug. 5, 1988 Phobos 1
USSR Lost contact Aug. 31 Aug. 9, 1988 Phobos 2
USSR Orbited Mars 1989 Jan. 29 lost
contact Mar. 27 1992 Sept. 25, 1992 Mars Observer
USA Lost contact Aug. 21, 1993 1996 Nov. 7,
1996 Mars Global USA Arrived Sept,
1997, Prime mission began March, 1999
Surveyor and ended January, 2001. Still
in operation. Nov. 16, 1996 Mars 96
Russia Failed orbit insertion, fell to Earth Nov.
18. Dec. 4, 1996 Mars Pathfinder USA Landed
July 4, 1997, one year mission exceeded
goals. 1998Jul. 4, 1998 Nozomi
Japan Failed to orbit December, 2003 Dec. 11,
1998 Mars Surveyor 98 Mars Climate Orbiter USA
Lost contact September, 1999 1999 Jan. 3,
1999 Mars Surveyor 98 - Mars Polar Lander
USA Lost contact December 3, 1999
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Missions to Mars
Launch Date Name Country Result
2001 April 7, 2001 Mars Odyssey
USA Orbited October 24, 2001, still in
operation. 2003 June 1, 2003 Mars Express
Europe Arrived December 26, 2003
Beagle 2
Contact lost during landing. June 10, 2003 MER
- Spirit USA Landed January 2,
2004. Mission in progress.July 24, 2003 MER -
Opportunity USA Landed January 24, 2004. Mission
in progress. 2005 August 12, 2005 Mars
Reconnaissance Orbiter USA Arrived Mars,
February 3, 2006
See also - http//phoenix.lpl.arizona.edu/timeline
.php
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Future Missions to Mars
2007 to 2009 Phoenix Launched August 2007 -
Small Mars scout lander (NASA) Phobos-Grunt -
October 2009 - Mars orbiter and Phobos sample
return (Russia) Mars Science Laboratory - 2009 -
Mars Rover (NASA) Beagle 2 Evolution - 2009 -
Mars Lander (ESA) 2010s ExoMars - 2011 - Mars
Rover (ESA) Mars 2011 - 2011 - Mars Scout
mission (NASA) Astrobiology Field Laboratory -
2016 - Mars Rover - proposed (NASA) Mars Sample
Return Mission - delayed until at least 2016,
more probably to 2024 - planned mission by ESA
and NASA as part of the Aurora Programme
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Mariner Missions to Mars

• Mariner 4 was the fourth in a series of
  spacecraft used for planetary exploration in a
  flyby mode and in 1965 represented the first
  successful flyby of the planet Mars, returning
  the first pictures of the Martian surface.
  showing a moonlike cratered terrain without any
  signs of vegetation, and measured atmosphere and
  temperatures much less comfortable for most
  creatures on Earth
• the first Mars orbiter, Mariner 9, revived some
  hope for all those considering life on Mars
• Mariner 9 mapped virtually the whole planet and
  found a diversity of forms, including high
  volcanoes, huge canyons, extended chaotic terrain
  and dry river beds indicating the former presence
  of huge quantities of water on ancient young
  planet Mars

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The Search for Biosignatures on Mars
NASA Missions Viking 1 and 2
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The Search for Biosignatures on Mars

• if we wish to search for life on Mars, we will
  need to study actual soil samples from Mars to
  see whether it contains living microbes
• this type of search was first carried out by the
  two NASA Viking landers in 1976

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Landing Sites of NASA Viking 1 and 2
Viking 2
Viking 1
Mars Pathfinder
MER Opportunity
MER Spirit
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Viking 1 and 2
Viking lander
Launch of Viking 1, August, 1975
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The view of Mars from Viking Lander 1. The large
rock is about 2 m across.
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The view of Mars from Viking Lander 2.
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Viking 1 and 2 Primary Mission Objectives

• NASA's Viking Mission to Mars was composed of two
  spacecraft, 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 and 2

• INVESTIGATIONS INSTRUMENTS
• Orbiter imaging Two vidicon
  cameras
• Water vapor mapping Infrared
  spectrometer
• Thermal mapping Infrared
  radiometer
• Entry science
• Ionospheric properties Retarding potential
  analyzer
• Atmospheric composition Mass spectrometer
• Atmospheric structure Pressure, temperature
• Lander imaging Two facsimile cameras
• and acceleration sensors
  
• Biological analyses
• Metabolism Three separate experiments,
• Growth gas exchange, labeled release,
  Photosynthesis and pyrolytic release, were
  included to test different biological
  models.

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Viking 1 and 2 - Background

• from a biological point of view, the Viking
  mission to Mars can be interpreted as a test of
  the Oparin-Haldane hypothesis of chemical
  evolution
• assuming that the early histories of Mars and
  Earth were similar, and that terrestrial life
  appears to have originated on Earth very early
  from materials that could well have been present
  also on Mars - it is not unreasonable to assume
  that chemical evolution, leading to complex
  organic compounds capable of replication, could
  have also occurred on Mars

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Viking 1 and 2 - Background

• further, if replicating systems did appear on
  Mars in an earlier, more benign environment than
  exists today, the question is whether these
  ancient organisms were able to adapt to worsening
  conditions on that planet, as it lost its surface
  water and much of its atmosphere, and cooled to
  its present cold, arid, seemingly hostile
  condition
• the biological experiments aboard the Viking
  spacecraft were intended to probe this possibility

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Viking Biology Experiments

• the two landers conducted four experiments
  intended to detect the presence of
  microbiological life on the Martian surface
• soil samples were retrieved by the landers'
  extendible arms

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Viking 1 2 The Four Experiments

• The Gas Exchange Experiment (GEX)
• The Labeled Release Experiment (LR)
• The Pyrolytic Release Experiment (PR)
• The Gas Chromtaograph - Mass Spectrometry
  Experiment (GCMS)

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1. The Gas Exchange Experiment (GEX)

• measured the production and/or uptake of CO2, N2,
  CH4, H2 and O2 during incubation of a soil sample
• a sample of Martian soil was deposited into a
  reaction chamber
• a solution of organic nutrients in H2O was added
• microorganisms were supposed to grow and produce
  the gases proving metabolism and thus the
  existence of life

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1. GEX - Results

• large quantities of O2 were released that were
  attributed to oxygen-producing chemical reactions
  caused by the addition of water

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2. The Labeled Release Experiment (LR)

• Labeled Release detect metabolic processes
  through radiorespirometry
• a radioactive nutrition solution containing 14C
  was added to a soil sample
• after metabolizing the nutrients, living
  organisms would release radioactively-tagged
  gases such as CO2 and CH4, which would be
  detected by radiation detectors

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2. LR - Results

• after first wetting, a sudden rise in the
  radioactivity level of the gases was found
• but after a second wetting, which should have
  been equally nourishing for the organisms in the
  soil, the radioactivity level did not only fail
  to rise, but actually decreased
• the explanation was that the nutrition solution
  reacted with oxygen-rich compounds in the soil,
  but after the first wetting, the compounds were
  used up

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3. The Pyrolytic Release Experiment (PR)

• Pyrolytic Release (carbon assimilation) to
  detect the photosynthetic or chemical fixation of
  CO2 or CO containing 14C
• a soil sample was placed in a reaction chamber
  containing an atmosphere identical to Mars,
  except that the gases CO and CO2 were replaced by
  radioactive counterparts containing 14C

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3. PR - Results

• radioactive 14C was taken up by the soil sample,
  and after incineration could be detected as
  planned
• a second experiment then heated the soil sample
  for a long time at 175oC, whereby all forms of
  life must have been destroyed, then the
  experiment was repeated by adding radioactive
  gases
• this procedure gave the same results, indicating
  that biology had nothing to do with the
  translocation of 14C from CO and CO2 to other
  compounds

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4. The Gas Chromatograph - Mass Spectrometry
Experiment (GCMS)

• the GCMS also heated a soil sample and revealed
  an unexpected amount of water but failed to
  detect organic compounds
• this absence was so absolute that it seemed there
  must be some mechanism actually destroying carbon
  compounds on the surface

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Viking Biology Experiments

• NASA conclusion "Viking not only found no life
  on Mars, it showed why there is no life there....
  the extreme dryness, the pervasive
  short-wavelength ultraviolet radiation... Viking
  found that Mars is even dryer than had previously
  been thought... The dryness alone would suffice
  to guarantee a lifeless Mars combined with the
  planet's radiation flux, Mars becomes almost
  moon-like in its hostility to life."
• Gilbert Levin, who was the principal investigator
  for the Labeled Release (LR) experiment,
  maintains that "...it is now more than probable
  than not that the LR experiment did in fact
  detect life on Mars."

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Viking Biology Experiments

• a consideration is that all the Viking
  experiments used samples from the uppermost
  Martian surface - but current thinking, from the
  new facts of life in extreme environments on
  Earth, is that it is more likely that life would
  be extant in the deeper subsurface. organisms
  that had migrated or been carried to deeper
  levels would enjoy a measure of protection not
  experienced by surface dwellers..."

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Viking Non-Biological Experiments

• several other instruments aboard the Viking
  landers ultimately made substantial contributions
  to our understanding of the status of extant
  biology on Mars
• these included
• an extremely sensitive gas chromatograph-mass
• spectrometer for elucidating the nature of
  organic compounds that might be present in
  martian surface material, and also for
  determining the composition of the Martian
  atmosphere
• an X-ray fluorescence instrument for analyzing
  the elemental composition of surface samples
• 3. an imaging system capable of surveying the
  local surroundings in black and white and color,
  over the course of the seasons

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Viking Non-Biological Experiments

• Major findings of interest were
• that no organic compounds were detected in
  surface samples
• that the inorganic elemental composition of
  surface samples were consistent with a mixture of
  iron-rich (smectite) clays, magnesium sulfate,
  and iron oxides
• that, in addition to carbon dioxide and carbon
  monoxide, the surface atmosphere contained about
  2.5 nitrogen and 0.15 oxygen
• that no structures uniquely attributable to
  biological entities were present in more than
  4500 images obtained from the two landers

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Viking Experiments

• Qualifications
• the general acceptance of the lack of biological
  activity on Mars is based on the failure of the
  Viking organic analysis instrument (GCMS for
  gas chromatograph mass-spectrometer) to find any
  organic compounds, even though the LR returned a
  positive result, no structures uniquely
  attributable to biological entities were present
  in more than 4500 images obtained from the two
  landers, and the presumed absence of liquid water
  on the surface of the planet

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Martian Meteorites

• Martian meteorites are not the ideal samples
  within which to look for signs of life as they
  represent relatively fresh samples of igneous
  rocks, produced by volcanic activity either at
  high or low levels within the martian crust
• hence from only their primary features, it is
  apparent that they should not record any evidence
  of life
• in the case of Martian rocks, it is the
  subsequent histories of the samples that are
  investigated - secondary events such as
  weathering, hydrothermal activity and atmospheric
  exposure
• in other words, processes that occurred after the
  rocks crystallized and cooled down

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Martian Meteorites

• preservation and recovery of meteorites in the
  Antarctic ice fields

• meteorites are easier to find in Antarctica than
  elsewhere on Earth as it is easy to see black
  meteorites on the white ice. Also, meteorites
  that fall onto the Antarctic ice are frozen and
  preserved much better than they would be anywhere
  else on Earth

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Martian Meteorites

• 19 Martian-meteorites (igneous rocks) have been
  found
• previously classified as Shergotty, Nakhla and
  Chassigny (SNC) meteorites in the 1960s
• petrographic features differ from other
  meteorites leading scientists to believe that the
  SNC group are derived from planets, not asteroids
• ages mostly 150-1300 Ma, corresponding to
  probable periods of volcanic activity on the
  Martian surface, except ALH84001 which is 4.5 Ga
• e.g., the 14N/15N ratios from trapped gasses in
  the SNCs are exactly equivalent to the 14N/15N
  ratios measured by the Viking landers

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The Martian atmosphere was measured, on Mars, by
the Viking lander spacecraft in 1976. The gas in
Martian meteorites are measured in laboratories
on Earth. If the two gas samples were identical,
points on the graph would fall on the straight
line from lower left to upper right. As you
can see, the gas from the Martian meteorite
EETA79001 is identical to the Martian atmosphere.
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Martian Meteorites
Element ratios allow the identification of Mars
meteorites plots of different element ratios
occupy different regions in the diagrams. This
is likely due to variations of the element
abundances with distance from the Sun during
accretion.
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Oxygen Isotope Composition of Martian Meteorites
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Martian Meteorite ALH84001
ALH84001 with intact fusion crust
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History of Martian Meteorite ALH84001

• ALH84001, an igneous rock (magmatic),
  crystallized 4.5 Ga
• 4.0 and 3.8 Ga, shock and fractures from a nearby
  impact event produced the many fissures now seen
  filled with other material

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History of Martian Meteorite ALH84001

• between 4.0 and 3.6 Ga, when Mars was likely
  warmer and wetter, water penetrated fractures in
  the subsurface rock
• 3.5 to 1.39 Ga, carbonates crystallized from
  fluid

• living organisms also may have assisted in the
  formation of the carbonate and were fossilized

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Birthplace of Martian Meteorite ALH84001

• data from the Mars Global Surveyor and Mars
  Odyssey orbiters suggests matches between the
  ALH84001s mineral content and the composition of
  the Eos Chasma branch of the Valles Marineris
  canyon system

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History of Martian Meteorite ALH84001

• 12 - 17 Ma, after one or more nearby impacts
  after the deposition of carbonates, ALH 84001 was
  launched into interplanetary space by a large
  nearby meteor impact on Mars
• this is the only type of natural event that could
  eject a rock from Mars' gravitational field with
  the necessary escape velocity of 5.4 km/sec
• after 15 Ma, a small body struck Mars, ejecting
  a piece of the rock - for millions of years, the
  rock floated through space, falling in Antarctica
  13 Ka as a meteorite

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Event Ages of Martian Meteorite ALH84001

• Phase I primary crystallization age 4.5 Ga a.
  based on 238U and 235U in relation to Pb
• Phase II shock at 4.0 Ga a. based on 40Ar/40K
  clock reset b. possible multiple shock events
  before ejection c. volcanic event,
  probably brought cumulate to surface
• Phase III shock at 15 Ma a. possible ejection
  event b. based on exposure to mineralogical
  changes due to exposure to cosmic
  ray bombardment

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Cosmic Ray Exposure Age of ALH84001

• cosmic ray exposure age is how long a meteorite
  orbited in interplanetary space, exposed to
  cosmic rays from the Sun and the galaxy
• as these cosmic rays (high-energy elementary
  particles) hit a meteorite, they produce some
  characteristic new isotopes (by transmutation) of
  chemical elements, both radioactive and stable
• the longer a meteorite is exposed to cosmic rays,
  the more of these new isotopes are present

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Cosmic Ray Exposure Age of ALH84001

• for ALH 84001, isotopes of the elements 3He,
  21Ne, and 38Ar have been used to calculate a
  cosmic ray exposure age
• most of these ages are between 16 and 17 million
  years, with a few measurements as young as 12
  million years

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Terrestrial Age of ALH84001

• streaking through Earth's 300-km thick atmosphere
  at a minimum speed of 15 km/sec, ALH 84001 melted
  partially on the surface, forming the glassy
  black fusion crust, which later quickly
  identified it as a meteorite

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Terrestrial Age of ALH84001

• the terrestrial age of a meteorite is how long
  ago the meteorite fell to Earth
• radioactive isotopes are formed in a meteorite,
  in space, as it is bombarded by cosmic rays
• after its fall, it was protected from further
  cosmic ray bombardment by Earths shielding
  magnetic field, it is no longer hit by cosmic
  rays, no more of the radioactive isotopes form,
  and the ones already in the rock continue to
  decay
• the more of these isotopes in a meteorite, the
  less time it has spent on Earth

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Terrestrial Age of ALH84001

• terrestrial ages are usually determined from
  isotopes of the elements C (14C), Be (10Be), and
  Cl (36Cl)
• the best measure of ALH84001s terrestrial age
  comes from its abundance of 14C
• the abundance of 14C in ALH 84001 gives a
  terrestrial age of about 13,000 years

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Terrestrial Age of ALH84001

• 13,000 to less than 20 years ago - glacial
  transport

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