Life in meteorites

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Life in meteorites the STONE 6 experiment
John Parnell University of Aberdeen STONE 6
Team
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About 300 craters on Earth (Barringer Meteorite
Crater, Arizona)
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• Meteorites at Earth
• Meteorites size range dust (micrometeorites) to
  kilometre-size.
• -up to 1,000,000,000 kg reaches Earth each year.
• -tons micrometeorites reach Earth each day.
• -50,000 bigger than 20g hit Earth each year.

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• Impacts and Life I a problem
• Impacts involve physical damage (a hole!), shock
  waves, extreme heat, vaporization of rocks.
• Life locally affected by heat and shock
• Life globally affected by poisoning of atmosphere
• -Dust obscures sun, hence cold and dark
• -Sulphur and other gases toxic
• Thus impacts followed by mass extinctions
• (global loss of large numbers of species) or
  even sterilization (life ceases)

Mars
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• Impacts and Life II
• the plus side
• BUT meteorites may bring life to a young planet
• 1. Add large amounts of carbon
• -200,000kg/yr today 50 million kg/yr Early Earth
• -feedstock for organic chemistry that creates
  life
• 2. Primitive life from another planet hitches a
  ride (Panspermia)

Meteorite on sands of Mars
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Panspermia (seeds everywhere) Long-held view
that life may have come to Earth from another
planet Ancient Greeks Lord Kelvin (1880s)
onwards Theory meteorites splashed off a planet
by a previous impact carry microbial
life. Microbial life very tolerant of extreme
conditions. Early in Solar System, Mars may be
better for evolution of life than Earth. Possibly
life started on Mars, and transferred to Earth.
A B C DA B C D
A B C D
Comet 81P/Wild 2 (Tichy Moravec
1997) Intercepted by STARDUST mission carrying
organics
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Fossil life in meteorites?
1996 NASA announcement to the world that life
found in Mars meteorite ALH84001. Many rocks on
Earth contain fossil remains (visible,
chemical). If life on early Mars, maybe Mars
meteorites contain evidence. 5 Mars meteorites
reach Earth Would that evidence survive journey
to Earth?
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The Journey. 1 Blast-off Ejection off planet
surface needs BIG impact. High shock pressure
temperatures even some melting. Can organics
survive? Rocks must be very robust Poor homes?
Martian meteorite Nakhla (solid basalt)
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The Journey. 2 Through space Most take millions
of years. Hazards extreme cold desiccation
vacuum asteroid collisions irradiation DNA
breakdown ltlt1 million yrs.
Solar flares emit high energy irradiation
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The Journey. 3 Atmospheric entry Frictional
heating. Melting on outside of meteorites Stress
causes meteorite break-up. Showers of smaller
fragments
Martian meteorite LA 002
Meteorite shower (Leonids 1966)
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The Journey. 4 Landing Large meteorites impact
with huge energy (craters). Meteorites and target
vaporized! Small meteorites remain intact. Thus
fragmentation helpful. So could life or fossil
organic matter survive the journey?
Zagami, Biggest Martian meteorite known (18kg)
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Artificial meteorite experiments Exposure to
atmospheric re-entry STONE experiments organized
by European Space Agency, using Russian
spacecraft
Foton-class spacecraft
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Orcadian laminites (flagstones) record of past
life Finely laminated rocks deposited in lake
380 million years ago. Orkney,
Caithness Includes fish beds Black colour Lots
of fossil organic matter Fish remains, but
mostly algae Analyses Chemical evidence of
algae Evidence of life even if no fish
etc. Extremely hard and robust
A B C DA B C D
A B C D
Cruaday Quarry, Orkney
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Chemical evidence of life
Life is full of organic molecules -allow
chemistry essential to life (e.g. sugars,
proteins, DNA, sterols) Some survive and are
preserved in rocks. Analyses of rocks reveal
molecules that tell us about life.
Organic compounds derived from bacterial cell
walls
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Carbonaceous chondrite (Murchison,
Australia) -contains clay, organic compounds and
water
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• Objectives of STONE 6 experiment
• Is ablation high, as in carbonaceous chondrites?
• Is any carbon preserved when the rock is ablated?
• Do complex organic molecules survive atmospheric
  entry?
• Would microbial life survive atmospheric entry?
• Would this rock, as a meteorite, tell aliens
• there was life on its home planet?

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STONE 6 samples on FOTON M3 capsule. Orcadian
sample position III Launch from Baikonur
Cosmodrome, Kazakhstan 14th September 2007
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Foton-M3 mission profile Launch Friday 14 Sept
2007 Flight duration 284 hours (11.8
days) Orbital altitude260- 310 km Period 90.0
minutes Landing Wednesday 26 Sept -Entry
starts over Namibia at 275 km altitude -Retrorocke
t burns for 38 sec, speed reduced from 7.7 to 7.6
km/sec - Spacecraft sinks slowly down into the
atmosphere - 24 minutes later parachute deployed
over Kazakhstan at 9 km altitude - In those 24
minutes a distance of 10 000 km is covered -
Entry trajectory near-horizontal.
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landing area
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Capsule with experiment presented. Note melt
streaks.
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Preservation of Orcadian sample
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Most of exposed middle section ablated
away. Reflects heating to gt1700 ºC
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Sample coated with green glass
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Sample underside painted with microbial biofilm
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Vesicular glass crust, Orkney laminite
(?), Allende carbonaceous chondrite (?)
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Rock-melt boundary glass quenching and
neoformed minerals
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XRD traces pre- and post-flight. Calcite
roasted to CaO (minimum dissociation temp. 898
ºC), then rehydrated to portlandite
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Preservation of STONE 6 sample Total survival
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Re-entry melt (green, 0.14 carbon) and furnace
melt (yellow, 0.08 carbon) Different levels of
oxidation
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Iron silicides in melt glasses FexSiy
alloys Silicate-metal partitioning Extremely
reducing environment
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Increased structural order of carbon
(graphitization) in post-flight sample
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d13 C
Yield C ng
Temperature

C

• Stepped combustion data for carbon isotopes
• whole, (b) decarbonated
• (courtesy Open University)

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C18
C18
C19
Prior to geological heating
C20
C21
C22
Ph
C23
Oil generation
Control
Beginning Gas generation
time
STONE experiment
time
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Cell membranes of Archaea
Chlorophyll
Fossil organic matter
Phytane
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Hopane preservation
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Hopanes Mass 191 suggests C14H23 and a specific
structure with no non-biological origin.
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Fate of meteorites according to size
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Biofilm well preserved but dead. Cell clusters
arrowed, with Polysaccharides. Just 1mm from
melted rock. (C. Cockell, OU)
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• Objectives of STONE 6 experiment
• Is ablation high, as in carbonaceous chondrites?
• YES. SUBSTANTIAL MASS LOSS
• Is any carbon preserved when the rock is ablated?
• YES. LACK OF OXYGEN ALLOWS SURVIVAL
• Do complex organic molecules survive atmospheric
  entry?
• YES. BIOLOGICAL COMPOUNDS SURVIVE
• Would microbial life survive atmospheric entry?
• UNLIKELY IN SMALL METEORITES

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Evidence of life Morphology 1. Mega-fabric in
fossil organic matter ? 2. Cellular structures in
fossil organic matter 3. Adhering extant
microbial life ? Molecules 4. Organic molecules
with no non-biological origin ? 5. Preferred
formation of complex molecules (implies
biological selection) Isotope Chemistry 6. Large
fractionation organic carbon and carbonate carbon
(suggests possible biological mechanism) ?
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Thanks European Space Agency Emily Baldwin Mark
Burchell Franz Brandstätter Charles Cockell Rene
Demets Barry Fulton Paula Lindgren Dan
Milner David Muirhead Nigel Trewin Frances Westall
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