Life at the ExtremeWhat types of life should we expect?

ASTR 1420

Lecture 10

Sections 5.5

ExtremophilesTo 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• 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

• Strain 121 : a single-cell microbe able to survive and reproduce at 121 °C (250 °F)

• can even tolerate 130 °C!

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 grainsMicrobes are frozen and dormant for

most of the yearLive in summers, 500 hours per year (3%

of the year)endure low humidity and low

temperature

Examples of extremophilesEnvironmental

parameter Type Definition Examples

temperature hyperthermophilethermophilemesophilepsychrophile

Growth > 80CGrowth 60-80C15-60C< 15C

Pyrolobus fumarii, 113CSynechococcus lividisHumanPsychrobacter, some insects

radiation Deinococcus radiodurans

pressure piezophile Pressure loving Microbe at 1,300 bar

vacuum Tolerates vacuum Tardigrades, insects, seeds, microbes

desiccation xerophile anhydrobiotic Artemia salina, fungi, lichens

salinity halophile Salt loving halobacteriacea

pH alkaliphileacidophile

pH > 9Low pH loving

Natronobacterium (pH>10.5)Ferroplasma sp. (pH=0)

oxygen anaerobemicroaerophileaerobe

Cannot tolerate O2Tolerates some O2Requires O2

Methanococcus jannaschiiClostrifiumHuman

…New discoveries pour in…

Asphalt LakeMicrobial 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.Gene sequences from

these creatures show that they are single celled organisms such as archea and bacteria. They thrive in an oxygen-free environment with very little water, eating hydrocarbons and respiring with metals.

2010, Washington State Univ. (Dr. Schulze-Makuch)

Hypergravity :

• 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).

1 g @400,000 g

E. coli and Paracoccus denitrificans

Relevance of Life in Icy Worlds• Snowball Earth has happened (many times!)• Arctic/Antarctic provide a guidance• Other icy worlds in solar systemo Snowball Earth + polar icy oceano Mars: polar ice, permafrosto Snowball Jovian Moonso 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…

Non-chemical Life?Life on Neutron Stars

• 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 fasterEntire civilizations could rise and fall a million

times while a human eye can wink.

If true, no meaningful way to communicate with them.

Frank Drake…

• 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!

Non-chemical Life?• Entire galaxy as a living organism

• 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 System1. Earth : in interior magma, or within

specialized niches on the surface2. Mars : if life is present, it is probably based

on Carbon and Water3. Jupiter : many possibilities4. Europa : underground water life.5. Io, Venus : life in liquid sulfur6. Titan : ammonia- or hydrocarbon-based.

In summary…

Important Concepts• Some remarkably resilient species• Good guidance to search for life

beyond Earth• Remarkable tardigrades!

Important Terms• Extremophile• Predestinists• Carbaquists

Chapter/sections covered in this lecture : 5.5