Life at the Extreme
What types of life should we expect?
ASTR 1420
Lecture 10
Sections 5.5
Extremophiles
To peek into the possible forms of life in the Universe, we start by studying Earth life at
extreme conditions.
Extremophile = love of the extreme
= an organism that thrives under “extreme” conditions.
“Extremity” is relative to human
 for example, low-oxygen environ is harsh and extreme for humans, but for
many organisms, oxygen is poisonous.
Thermophiles : Deep Sea Vent
• The first extremophile to have its genome sequenced was Methanococcus
jannaschii, a microbe that lives near hydrothermal vents 2,600 meters
below sea level, where temperatures approach the boiling point of water
and the pressure is sufficient to crush an ordinary submarine
Thermophile
• Strain 121 : a single-cell
microbe able to survive and
reproduce at 121 °C (250 °F)
•  can even tolerate 130 °C!
• first discovered by Thomas D. Brock in 1969,
in hot springs in Yellowstone National Park.
Since then, more than fifty species have been
discovered
• Different colors represent different groups of
themorphiles
Deinococcus
radiodurans
• The most radiation-resistant organism known
• Discovered decades ago in canned food that
was sterilized using radiation. Red patches
appeared in the cans – colonies of the
bacterium – setting off questions as to how it
could have survived.
• Flourishing in radioactive wastes
• Withstand 3,000 times more radiation than
human can survive
• Also endure dehydration and low
temperature  found at the South Pole
• effectively repair DNA damages by radiation
(about 100 times better than human).
Owens Lake
Halophiles
• Some hypersaline lakes (e.g., Great Salt Lake,
Mono lake, Owens Lake, etc.) have high salt
concentrations as well as a significant
amount of sulfate. The same could be said
for the evaporates discovered on the
Meridiani Planum plains of Mars, a
hypothesized salt lake.
• halophiles can remain dormant for long
periods of time  good possibility of finding
life in salt crystals from the red planet
Endoliths
• Antarctica dry valley: microbes live in
pores b/w mineral grains
Microbes are frozen and dormant for
most of the year
Live in summers, 500 hours per year (3%
of the year)
endure low humidity and low
temperature
Examples of extremophiles
Environmental
parameter
temperature
Type
hyperthermophile
thermophile
mesophile
psychrophile
Definition
Growth > 80C
Growth 60-80C
15-60C
< 15C
radiation
pressure
Examples
Pyrolobus fumarii, 113C
Synechococcus lividis
Human
Psychrobacter, some insects
Deinococcus radiodurans
piezophile
vacuum
Pressure loving
Microbe at 1,300 bar
Tolerates vacuum
Tardigrades, insects, seeds,
microbes
desiccation
xerophile
anhydrobiotic
Artemia salina, fungi, lichens
salinity
halophile
Salt loving
halobacteriacea
pH
alkaliphile
acidophile
pH > 9
Low pH loving
Natronobacterium (pH>10.5)
Ferroplasma sp. (pH=0)
oxygen
anaerobe
microaerophile
aerobe
Cannot tolerate O2
Tolerates some O2
Requires O2
Methanococcus jannaschii
Clostrifium
Human
…New discoveries pour in…
Asphalt Lake
Gene sequences from
these creatures show
that they are single
celled organisms such as
archea and bacteria.
They thrive in an oxygenfree environment with
very little water, eating
hydrocarbons and
respiring with metals.
2010, Washington State Univ.
(Dr. Schulze-Makuch)
Microbial life lives in the liquid asphalt lake
Pitch Lake (in Trinidad).
Extremophiles inhabit the asphalt lake in
populations ranging between 106 to 107
cells/gram.
Hypergravity :
1g
E. coli and Paracoccus denitrificans
@400,000 g
• Well trained fighter pilots can endure ~9g with a g-suit
• About a minute exposure at 15g will kill human
• bacteria were cultivated while being rotated in an ultracentrifuge at high
speeds corresponding to 403,627 g (super-novae, black-holes?)
• experiment carried in Japan recently (2010).
Relevance of Life in Icy Worlds
• Snowball Earth has happened (many times!)
• Arctic/Antarctic provide a guidance
• Other icy worlds in solar system
o
o
o
o
Snowball Earth + polar icy ocean
Mars: polar ice, permafrost
Snowball Jovian Moons
Planets around other stars
Arctic Sea Ice
(cryophile)
• Ice core with an algae band…
New Harbor, Antarctic
Flourishing Ecosystem under Ice
Krill grazing bottom of ice
Fish & Diatoms
Life below the Ice
• Not all extremophiles are
primitive!
Tardigrades
Tardi-grade : “slow walker”
As big as 1.5mm
Can be found nearly
everywhere on (and under)
the Earth!
Tardigrades “Water Bears”
• Water bears are
fundamentally aquatic
animals, using their eight
legs to walk in liquid.
• They can survive at
extremely low temperature
(-272C), high temperature
(151C), endure 1000 times
more radiation than any
animals, endure 6,000
atmospheric pressure,
nearly a decade without
water, and even in vacuum.
Tardigrades “Water Bears”
• Some tardigrades eat microscopic animals, while others consume algae (Credit: NASA Ames)
• Tardigrades are not primitive!
• In 2007 September, A group of tardigrades were sent to the space to study their survival
capability in open vacuum and solar radiation. They stayed in the vacuum for 10 days and
returned to the ground. Nearly all of them survived!
Water bears …
• More than 1,000 different species known!
• are very small (typically 0.3 to 0.5 mm) but not
primitive
• have a precise muscle control and move like higher
animals
• resemble little bears; some have claws like cats
• have a mouth, head, brain, legs, eyes, nerves,
muscles …
• live next door to you (for sure)
• are thought to be extraterrestrials by some authors
• have strange eggs which look like miniature artwork
• can transform into a dry state which can return to life
after years
• in dry state need only a drop of water to revive
• in dry state survive acid and solvent attack
• in dry state survive very high and very low
temperatures
• in dry state survive high pressure and radioactive
radiation
• have been found under 5 m layers of ice
• have been found in oceans 6000 m below the surface
• have been found on mountains, 6000 m high
What about non-terrestrial Life?
• Life can take place in a wide variety of environments very different from
Earth  their life forms can be quite different from us, in harmony with
their local conditions.
Because of our limited perception, we may be quite biased as
… a person in a small local Chinese village may convince that only the Chinese
language exists in the world (since it is the only one spoken by all the people
around!)…
Non-chemical Life?
• “Black cloud”
In the science fiction written by a British
astronomer, Fred Hoyle…
Giant interstellar cloud
 Can think and move
 Networks of molecules  brain
 Indefinite lifetime
 Thoughts  radio message from one part to
another
 Starlight = energy source
approached to Earth to replenish its
energy…discovered human and make a
communication!
? Very low density and very low temperature 
very slow chemical reaction  really long time
for evolution…
Life on Neutron Stars
Non-chemical Life?
Frank Drake… • Strong force based life…
• Surface temperature ~ 1million degrees,
enormous gravity…  no molecules (not
even atom) can survive.
• Nuclei would last for only 10-15 second,
however this is equivalent to a year!
evolution (or change in life) happens faster
Entire civilizations could rise and fall a
million times while a human eye can wink.
If true, no meaningful way to communicate
with them.
•Human (170cm) with a speed of about 1m/sec with 70 years of lifetime  1 billion
times of its body size…
•Nuclei of size 10-13 cm with speed of 1000 km/sec and lifetime of 10-15 second 
travel distance = 10-15 sec*1000 km/sec = 10-12 km = 1 million times of its body size!
• Entire galaxy as a living organism
Non-chemical Life?
• Life based on gravitational force
• Stars are the subunit as atoms in our body
• Stars interact on a time scale of many
millions of years.
• If we think that a life can emerge from
repeated interactions among stars…
 millions of such interactions are needed for
life to begin at the molecular level.
 Universe is far too young to have such life
forms!
Alternative
Chemical Life
• Life in ammonia, Life in hydrocarbons, Silicate
life
within our Solar System
1. Earth : in interior magma, or within
specialized niches on the surface
2. Mars : if life is present, it is probably based
on Carbon and Water
3. Jupiter : many possibilities
4. Europa : underground water life.
5. Io, Venus : life in liquid sulfur
6. Titan : ammonia- or hydrocarbon-based.
In summary…
Important Concepts
Important Terms
• Some remarkably resilient species
• Good guidance to search for life
beyond Earth
• Remarkable tardigrades!
• Extremophile
• Predestinists
• Carbaquists
Chapter/sections covered in this lecture : 5.5