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AstrobiologyA Science in Search of its

Second Data Point

Or

A Cautionary Tale

Outline

• What it is (and what it is not!)• Search for life on Mars

– Then– Now– Future

• Search for life elsewhere in the Solar System

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Astrobiology – What?

• What is it?– Is it the search for extraterrestrial

intelligence (ET)?– Why or why not?

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Astrobiology

• Based upon on our one data point - Earth– Earth forms 4.5 billion years ago– 700 million years (0.7 billion years) after that

evidence for prokaryotic life– 1.5 billion years later (2.2 billion years after Earth forms)

evidence for eukaryotic life– “Intelligent” life < 10 million years ago

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Astrobiology• In other words

– Life forms same time Earth forms– But ½ of that time is spent at the prokaryotic

only stage (simple one celled life)

Astrobiology

• Currently (as of 10:00 am)– 763 known planets in orbit around other stars– Many multiple planetary systems

(twins up to quintuplets)

• If one of these planets had life on it what kind of life would you expect to find?

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The Drake Equation

• N = Rs fp ne fL fi fc L

N = Number of civilizations that we could contact

RS = Solar type star formation rate per yearfp = Fraction of Stars that have planetsne = Number of “Earth-Like” planets per starfL = Fraction of planets on which life occursfi = Fraction which become technologically

advancedfc = Fraction willing and able to communicate L = Lifetime of technologically advanced

civilization

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The Drake Equation

• We know the value of only two of these variables– Rs about 10 per year– fp ½ About half of all stars are binary (two stars orbiting

each other) so assume that all of the other stars have planets

• The rest ???– ne based upon our on solar system 3– fL based upon our on solar system 0.333– fi based upon our on solar system 1– fc based upon our on solar system 1– L based upon our on solar system 100 years

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The Drake Equation

• And the answer is… 500 (maybe)

• Change the numbers so only looking for life– ne based upon our on solar system 3– fL based upon our on solar system 0.333– L based upon our on solar system 3.8 billion years– And the answer is… – 19,000,000,000

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Astrobiology – What?• Astrobiology is the scientific study of the:

– Origin– Evolution– Distribution– Future of life in the universe

• The study of astrobiology brings together scientists from many different areas such as:Microbiology Ecology ChemistryGeology Paleontology Astronomy

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Astrobiology – Why?

• Intellectual curiosity? – Just nice to know with no practical benefits?

• Spiritual curiosity?– Are we alone in the universe?

• Spin-offs?

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Search for Life

• NASA has had one (1) search for life on another planet (a second data point)

• It occurred before you were born… (sigh)

• Mars Viking Mission– Twin orbiters & landers– Launched in 1975, arrived in 1976– All four spacecraft were successful

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Mars Fact Sheet

• Gravity 1/3 of Earth • Day 24.6 hours• Surface pressure 1/100 of Earth

95% CO2, 2.7% N2, 1.6% Ar, O2 0.13%

• Average temperature range -20 to -60ºCFull range -140ºC to 20ºC

• Polar caps of frozen H2O and CO2

• Cold and dry now but liquid H2O was present in the past

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Weight about 600 kg, science payload 91 kg, 2.2 m wide, 1 m high, 70 W of power

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Mars Viking Mission Biology Search

• Four experiments focused on biology, or evidence for life:– Gas Chromatograph/Mass Spectrometer (GCMS)– Gas exchange (GEX)– Pyrolytic release (PR)– Labeled release (LR)

• Use the robot arm to scoop up Martian soil and dump it into the spacecraft where the four experiments could use it

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Mars Viking Mission Biology Search

• Gas Chromatograph/Mass Spectrometer (GCMS)– Could detect molecules with carbon in them, chemists

call all molecules with carbon in them organic molecules– If I took you (or any living thing on the Earth) apart

molecule by molecule would I find a lot of carbon containing molecules

– BUT not all carbon containing molecules come from life– Really two experiments

• Gas chromatograph • Mass Spectrometer

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Mars Viking Mission Biology Search

• Gas exchange (GEX), Pyrolytic release (PR), &Labeled release (LR)

• Looking for microscopic plants or animals

• Variation upon a theme• Add water and food to Martian Soil Sample• Look for CO2 and O2 being given off

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MARS Viking Mission Biology Search

• Gas exchange (GEX)– A sample was sealed and purged by He– Then a mixture of He, Kr, and CO2 was introduced as an

initial incubation atmosphere. – Nutrient solution added– Sample incubated. – At certain intervals, samples of the atmosphere were

removed and analyzed by a gas chromatograph with a thermal conductivity detector.

– Measured the production and/or uptake of CO2, N2, CH4, H2, and O2 during incubation of a soil sample.

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MARS Viking Mission Biology Search

• Pyrolytic release (PR)– A sample was incubated for several days in the presence of

radioactive CO2 or CO (containing 14C). – Some samples with simulated sunlight and some without.– Each sample was heated to 120 C to remove unreacted

CO2 and CO. – The soil was pyrolized at 650 C and any organic products

were collected in an organic vapor trap (OVT). – Finally, the trap was heated to combust the organic

material to CO2 and any evolved radioactive gas was measured.

– Sought to detect the photosynthetic or chemical fixation of CO2 or CO

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MARS Viking Mission Biology Search

• Labeled release (LR)– 14C-labeled nutrient medium added to sample– Sample incubated at approximately 10º C– Evolution of radiolabeled gas was monitored by a beta

detector in a chamber connected to the test cell – Measured the production of CO2, CO, or CH4 during

incubation of a soil sample.

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Then they had a problem…

Or

Is it Chemistry?

Is it Alive?

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• At great budgetary expense SDU has procured 8 Martian soil samples– Two are sterile– Two have “interesting chemistry”– Two have life– Two have both life and “interesting chemistry”

• You have the following supplies to determine which is which:– Warm water– Warm nutrient solution (Water + C12H22O11)– Only observations of gas (or not) being given off – But no digging in the dirt! (same as original experiment)– Your intelligence– Other groups samples

• Why use water?

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• Step 1– Come up with a procedure– Come up with criteria that will enable you to decide is it

alive or not?

• Step 2– Do your experiment– Communicate your observations

• Step 3– Decide is your sample sterile, contains life, or has

interesting chemistry– Decide if you want to revise your life vs. chemistry criteria

in step 1

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Split into your project groups, get a worksheet and a soil sample

and have at it.

SAMPLES ARE HETEROGENOUS!

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Results – 1

• Gas Chromatograph/Mass Spectrometer (GCMS)– Zip, Zilch, Nada (Maybe)– Did detect H2O– Not sensitive enough?

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Results – 2• Gas exchange (GEX)

– After addition of nutrient and incubation saw O2 being given off

– O2 definitely coming from soil• Biology?• Chemistry? Presence of peroxides, H2O2, on Martian soil?

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Results – 3• Pyrolytic release (PR)

– Seven of the nine pyrolytic-release tests executed on Mars gave positive results.

– The amount of radioactive carbon dioxide obtained by the experiment was small enough to furnish organic matter for between 100 and 1000 bacterial cells.

– So small....that it could not have been detected by the gas chromatograph-mass spectrometer

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Results – 4• Labeled release (LR)

– Like the gas-exchange experiment, this experiment added a small amount of nutrient to the soil sample.

– It also produced a large amount of gas after that injection. – Shortly after the addition of the nutrient, the radiation

counts rose sharply, leveling off at about 10,000 counts per minute.

– Careful examination of the radiation curve showed• No evidence of any doubling of cells • No growth appeared to be taking place • But curve did not seem to behave would have expected it to for

chemical reactions

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Results – Summary

• “Informed Opinion” is that Viking discovered interesting chemistry on the surface of Mars

• Dr. Gilbert V. Levin, principal investigator for the Labeled release experiment argues that Viking diddiscover life on Mars

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Results – Summary

• Would it matter if NASA said yes, we have found life on Mars, but it is bacterial?

• What if the bacteria:– Was DNA based life?– Was NOT DNA based life?

• NASA gave up looking for life on Mars and focused on looking for water

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Events Since Then

• Martian meteorite ALH84001

• Extremophiles: Bacteria than can live under extreme conditions

• Discovery of Methane (CH4) in the atmosphere of Mars

• Evidence for “recent” H2O on the surface of Mars

• Current Mars Missions

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Martian meteorite ALH84001

• The original igneous rock solidified within Mars about 100 million years after the formation of the planet.

• Between 3.6 and 4 billion years ago the rock was fractured, presumably by meteorite impacts. Water then permeated the cracks, depositing carbonate minerals

• 16 million years ago, a large meteorite struck Mars, dislodging a large chunk of this rock and ejecting it into space.

• 13,000 years ago, the meteorite landed in Antarctica

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Martian meteorite ALH84001

• Three indications of life all discovered within the meteorite close to each other– Abundant polycyclic aromatic hydrocarbons (PAHs)– Carbonate mineral "globules" – Presence of tiny "ovoids"

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Martian meteorite ALH84001 • PAHs are a type of molecule with carbon in them

– Mixture of PAHs found on ALH84001 suggestive of a biological origin

• Carbonate mineral "globules" – Some have cores containing manganese and rings of iron

carbonate and iron sulfides, along with magnetite and pyrrhotite.

– These minerals bear strong resemblance to mineral alterations caused by primitive bacteria on Earth.

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Martian meteorite ALH84001 • Presence of tiny "ovoids“

– May actually be fossil remnants of tiny (20 to 100 nanometer) bacteria

– But if so, they are 100 times smaller than any bacteria microfossils found on Earth • Virus 70 nanometers• Bacteria 1 micrometer = 1000 nanometers• Animal cell 25 micrometers

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Digging in the Ice (on Earth)

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Extremophiles

• Coldest -15°C – Crypotendoliths (Antarctica)

• Most acidic pH 0.0 – These bacteria grow in caves

• Saltiest 30% salt– By comparison seawater and human blood are about 3.5%

salt.

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Extremophiles

• Longest in space 6 years – Bacillus subtilis– Lived in an orbiting NASA satellite that exposed test

organisms to the extreme conditions of outer space– Are we Martians then?

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Recent Water on Mars?

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Mars Missions• Notable failures:

– Mars Climate Orbiter burned up in atmosphere in 1998 because of unit conversion error

– Mars Polar Lander less than a month later failed most likely due to software\hardware problems

• Mars Global Surveyor lasted a long time 1997 – 2006, death due to software error

• Mars Odssey orbiter 2001 - current• Mars Exploration Rovers 2003 - current• Mars Express (ESA mission) 2003 - current• Mars Reconnaissance Orbiter 2005 - current• Mars Phoenix Lander - 2008

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Mars Phoenix Lander• 25 May 2008 Lands at 68 N latitude on Mars• Science instrument packages

– Cameras– Thermal and Evolved Gas Analyzer– Microscopy, Electrochemistry, and Conductivity– Wet Chemistry

• Results – Confirms presence of subsoil water– Identifies oxidizing agent perchlorate in soil– Detects evidence for Calcium Carbonate in soil (forms

in presence of liquid water)

• Mission over due to deteriorating weather 45

Mars Science Laboratory - Rover

• Instruments– Mast camera– Hand lens imager– Alpha Particle X-Ray Spectrometer– Laser-Induced Remote Sensing for Chemistry and

Micro-Imaging– Chemistry & Mineralogy X-Ray Diffraction– Sample Analysis at Mars Instrument Suite– Radiation Assessment Detector– Detector of Albedo Neutrons– Rover Environmental Monitoring Station (REMS)

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Mars Science Laboratory• Cost >= $2 Billion (initial estimate $650 million)

Launched 26 November 2011Arrive 6 August 2012

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Results – Summary

• ????

• When does chemistry end and life begin?

• Have we found life on Mars and just don’t realize it?

• Are Extremophiles possible candidates for Martian life?

Search for life elsewhere in the Solar System

• Back to looking for water

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