To What Extent Does Terrestrial To What Extent Does Terrestrial Life ‘Follow The Water’?Life ‘Follow The Water’?

Eriita JonesEriita JonesSupervisor: Dr Charles LineweaverSupervisor: Dr Charles Lineweaver

Research School of Astronomy and Astrophysics, Australian National UniversityResearch School of Astronomy and Astrophysics, Australian National University

ContentsContents•Motivation•Constructing the model•Model: Phase representation of Earth•Quantifying Earth’s biosphere•Applying the model to Mars

ConceptConcept

ConceptConcept

Constructing the modelConstructing the model

Constructing the modelConstructing the model

~ 75 km~ 75 km

440 440 CC

~ 4 % of the volume ~ 4 % of the volume of the Earth has liquid of the Earth has liquid

waterwater

Earth occupies 78 % Earth occupies 78 % of the phase space of of the phase space of

liquid water.liquid water.

75 km6380 km

The terrestrial biosphereThe terrestrial biosphere Maximum temperature of life: 122 C (Kashefi & Lovley, 2003; Takai et al., 2008) Minimum temperature of active life: -20 C (Junge et al., 2004) Maximum depth/pressure of life: 5.2 km in crust; 1.5 x 103 bar (Szewzyk & Szewzyk, 1994)

The terrestrial biosphereThe terrestrial biosphere

Coldest possible Coldest possible terrestrial water (-89 terrestrial water (-89 ooC)C)

Where are there liquid water Where are there liquid water environments that may not support life?environments that may not support life?

Have not been Have not been searched for life.searched for life.

Thermal vents are being searched Thermal vents are being searched for life > 121 for life > 121 C. Several groups C. Several groups have suggestive evidence of life have suggestive evidence of life around 250 around 250 C. C.

Permafrost/ice core environments are being Permafrost/ice core environments are being searched for life < -20 searched for life < -20 C. Terrestrial brines C. Terrestrial brines persist to at least – 30 persist to at least – 30 C , thin films persist C , thin films persist to -100 to -100 C. Unclear how much liquid is C. Unclear how much liquid is present at these temperatures.present at these temperatures.

??

Only Only dormant dormant life found life found

at high at high altitudes.altitudes.

Where are there liquid water Where are there liquid water environments that may not support life?environments that may not support life?

NO EVIDENCE FOR NO EVIDENCE FOR A HIGH PRESSURE A HIGH PRESSURE LIMIT TO LIFELIMIT TO LIFE

LIFE MAY BE LIMITED BY LIFE MAY BE LIMITED BY HIGH TEMPERATURES. HIGH TEMPERATURES.

LOW TEMPERATURE AS A LOW TEMPERATURE AS A LIMIT FOR LIFE IS POSSIBLE LIMIT FOR LIFE IS POSSIBLE BUT UNLIKELY.BUT UNLIKELY.AT LOW TEMPERATURES AT LOW TEMPERATURES LIFE MAY INSTEAD BE LIFE MAY INSTEAD BE LIMITED BY LOW WATER LIMITED BY LOW WATER ACTIVITY.ACTIVITY.

??

LOW ALTITUDE LIFE MAY BE LOW ALTITUDE LIFE MAY BE RESTRICTED BY LITTLE AVAILABLE RESTRICTED BY LITTLE AVAILABLE

LIQUID WATER OR NUTRIENTS.LIQUID WATER OR NUTRIENTS.

Quantifying the terrestrial biosphereQuantifying the terrestrial biosphere~ volume of the Earth ~~ volume of the Earth ~

Volume of Earth with active life(life 5.28km crust, 10.3km ocean)

Depth life in volume of Earth with liquid water (liquid water 75km; life 5.3km crust; 10.3km ocean)

Max. depth 122C in volume of Earth with liquid water (liquid water 75km; 122 C at 32km)

Constructing the Martian modelConstructing the Martian model

Potential Martian biospherePotential Martian biosphere

~ 9 m~ 9 m

Conditions for terrestrial Conditions for terrestrial life reached in shallow life reached in shallow subsurface, if liquid water subsurface, if liquid water is present.is present.

~ 10 m~ 10 m

~ 20 km~ 20 km

Conditions for terrestrial life and liquid water between 10 m – Conditions for terrestrial life and liquid water between 10 m – 20 km beneath the surface. Ice likely present at these depths.20 km beneath the surface. Ice likely present at these depths.

ConclusionsConclusions

• The potential Martian biosphere must be between 10m – 20km beneath the surface, if liquid water is present.

• ~12% of the volume of the Earth where liquid water exists is known to host life. Thus, according to our current state of exploration, 88% of the volume of the Earth where liquid water exists, is not known to harbour life.

• Biosphere occupies < 1% of the volume of the Earth. Thus, after 4 billion years of evolution, the terrestrial biosphere has been unable to extend into ~99% of the volume of the Earth.

• 65% of the phase space of terrestrial water and 88% of the volume of the Earth containing water, is not known to harbor life. Thus, we have shown that there are many liquid water environments on Earth that, as far as we know, do not host life.

Coldest liquid waterColdest liquid water• Water activity below 0.6 thought to be a biological limit (Grant, 2004)•Thin films below –20 oC have a low activity & are only nanometres thick (Möhlmann, 2005; Jakosky et al., 2003)•Several common brines (eg. NaBr) have eutectics around -30 oC and activity above 0.6• Candidate brines can provide a test of whether water activity or low temperature is a real limit for life.

Quantifying the terrestrial biosphereQuantifying the terrestrial biosphere~ maximum extent ~~ maximum extent ~

Volume of EarthVolume of Earth(100 %)(100 %)

250 250 ooC (3 %)C (3 %)

122 122 ooC (1.5 %)C (1.5 %)

Volume of Earth with Volume of Earth with liquid water (100 %)liquid water (100 %)

250 250 ooC (95 %)C (95 %)

122 122 ooC (43 %)C (43 %)

Quantifying the terrestrial biosphereQuantifying the terrestrial biosphere~ volume of liquid water ~~ volume of liquid water ~

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