Transcript To What Extent Does Terrestrial Life "Follow The Water"?

To What Extent Does Terrestrial
Life ‘Follow The Water’?
Eriita Jones
Supervisor: Dr Charles Lineweaver
Research School of Astronomy and Astrophysics, Australian National University
Contents
•Motivation
•Constructing the model
•Model: Phase representation of Earth
•Quantifying Earth’s biosphere
•Applying the model to Mars
Concept
Concept
Constructing the model
Constructing the model
Earth occupies 78 %
of the phase space of
liquid water.
~ 4 % of the volume
of the Earth has liquid
water
6380 km
~ 75 km
440 C
75 km
The 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 biosphere
Coldest possible
terrestrial water (-89 oC)
Where are there liquid water environments
that may not support life?
Only
dormant
life found
at high
altitudes.
Permafrost/ice core environments are being
searched for life < -20 C. Terrestrial brines
persist to at least – 30 C , thin films persist
to -100 C. Unclear how much liquid is
present at these temperatures.
?
Have not been
searched for life.
Thermal vents are being searched
for life > 121 C. Several groups
have suggestive evidence of life
around 250 C.
Where are there liquid water environments
that may not support life?
LOW ALTITUDE LIFE MAY BE
RESTRICTED
BY LITTLE AVAILABLE
LOW TEMPERATURE
AS A
LIQUID
ORISNUTRIENTS.
LIMITWATER
FOR LIFE
POSSIBLE
BUT UNLIKELY.
AT LOW TEMPERATURES LIFE
MAY INSTEAD BE LIMITED BY
LOW WATER ACTIVITY.
?
NO EVIDENCE FOR
A HIGH PRESSURE
LIMIT TO LIFE
LIFE MAY BE LIMITED BY
HIGH TEMPERATURES.
Quantifying the terrestrial biosphere
~ volume of theActive
Earth
~
life (0.5 %)
Volume of Earth with active life
(life 5.28km crust, 10.3km ocean)
Liquid water with life
(12 %)
Depth life in volume of Earth with liquid water
(liquid water 75km; life 5.3km crust; 10.3km ocean)
Liquid water too hot for
life 122 C (57 % )
Max. depth 122C in volume of Earth with liquid
water (liquid water 75km; 122 C at 32km)
Volume of Earth (100 %)
Constructing the Martian model
Potential Martian biosphere
~9m
Conditions for terrestrial
life reached in shallow
subsurface, if liquid water
is present.
~ 10 m
~ 20 km
Conditions for terrestrial life and liquid water between 10 m –
20 km beneath the surface. Ice likely present at these depths.
Conclusions
• 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.
• ~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.
• 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.
• The potential Martian biosphere must be between 10m – 20km
beneath the surface, if liquid water is present.
Coldest 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 biosphere
~ maximum extent ~
Volume of Earth
(100 %)
Volume of Earth with
liquid water (100 %)
250 oC (95 %)
122 oC (1.5 %)
250 oC (3 %)
122 oC (43 %)
Quantifying the terrestrial biosphere
~ volume of liquid water ~
Liquid water too hot for
life (1.1 %)
Liquid water with active
life (< 98.9 %)
Volume of liquid
water (100 %)
12/20