55 Music Concourse Dr.
Golden Gate Park
San Francisco CA
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9:30 am – 5:00 pm


11:00 am – 5:00 pm
Members' Hours:


8:30 – 9:30 am


10:00 – 11:00 am

The Academy will be closed on Thanksgiving and Christmas Day.

Planetarium will be closed Sep. 22, 23, 24

Extreme Life 

Extreme Life on Earth

Smoker Pompeii Worm Ice Worm Brine Pool Eel Prismatic Lake Living Mat
Filament Bacteria Lake Vostok Arcobacter Basalt Eaters Mono Lake Snottites

Astrobiologists – scientists interested in the understanding the prospects for life beyond Earth – study life in some of Earth’s most “extreme” environments in order to understand the full range of life’s capabilities and limitations.  By comparing these findings to the range of environmental conditions presented by other bodies in the solar system, they identify potentially “habitable” environments beyond Earth. 

Deep–Sea Hydrothermal Vents

Recently discovered in 1977, hydrothermal vents, also known as "black smokers", revolutionized our understanding of life. Until the discovery of these vent systems, all known ecosystems on Earth had photosynthetic organisms at the base of their food chain.

However, this particular type of ecosystem is dependent on chemosynthetic bacteria that generate energy from hydrogen sulfide, the chemical responsible for the smell of rotten eggs.

These chemotrophic (chemical eating) bacteria exist in symbiotic relationships with other members of the ecosystem including mussels and 8 foot long tubeworms. These tubeworms have no mouth, gut or anus. Instead, they have a giant organ in the center of their body called a "trophosome". It is filled with symbiotic bacteria that take on all the digestive and excretory functions of the worms.

Photo Courtesy of NOAA

Pompeii worms, like the one pictured below, are also found close to these vents. These worms are the most heat-tolerant complex life form on Earth. They are able to thrive in 176°F water, whereas the Sahara Desert ant, the runner-up, can only survive in temperatures up to 136°F.

The bluish "hair" covering Pompeii worms is actually made up of bacteria that produce heat resistant enzymes. Researchers believe these enzymes could have a variety of applications, including pharmaceutical production and food processing.

In addition to supporting a variety of worms, hydrothermal vents also support crabs, shrimp and fish.

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Methane Seeps

Methane seep ecosystems are based on methane hydrate, a crystallized form of methane. Although it looks remarkably similar to ice, if you hold a match to methane hydrate, it will burn—thus its nickname "fire ice". It has a much higher melting point than water and it is a poor conductor of heat. Even though it is frozen, it doesn't feel cold when you touch it.

Ice Worm Photo courtesy of NASA JPL

In 1997, ice worms were discovered living on the surface of methane hydrate, their principle source of food being methane eating bacteria.

Other organisms have also been found subsisting on the methane including mussels, clams and 100 year old tubeworms. The mussels and clams have developed a symbiotic relationship with methane eating bacteria. Without these bacteria to metabolize energy for them, the mussels and clams would not survive.

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Ocean Floor Brine Pools

Underground salt deposits fill depressions in the ocean floor. These deep ocean brine pools are five times saltier than the surrounding ocean water and can kill creatures that accidentally swim into them.

Not only do these pools have highly concentrated salt solutions, they also have methane. This methane supports methane eating bacteria, which work in a symbiotic relationship (in this case, mutually beneficial) with mussels that gather on the "shores" of these pools.

A submarine floats above a brine pool below. Mussels line the dark brine pool to the left.

Photo Courtesy of NOAA

Tube worms and pink polychaete worms also line the brine pool's edge, which in turn lure more complex life forms such as eels and fish. These pools are oases of life on the desolate ocean floor.

Image Courtesy NOAA

Pink polychaete worms, mussels and an eel show the diversity of life that can flourish near brine pools.

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Hot Springs

Hot springs are often surrounded by a wide variety of rocks that influence their water chemistry. Because of this, they can support large numbers of poly-extremophiles. These organisms are adapted to living under multiple combinations of hostile conditions, including hot and acidic, hot and sulfidic, hot and alkaline, or hot and filled with toxic heavy metals.

Yellowstone's Grand Prismatic Basin is a beautiful example of a hot spring. It is 300 feet across and its blue center is the product of uncommonly pure water bubbling up into the pool's center. All of the other colors are the product of photosynthetic, thermophilic (heat loving) bacteria flourishing in the boiling water. These bacteria survive temperatures ranging from 147°F (64°C) to 225°F (107°C).

To provide a sense of scale, the grey line on the left hand side of the picture above is a walkway, with the people appearing on the path as tiny dots that are barely visible.

This vast bacterial mat is found in regions around hot springs such as the Grand Prismatic Springs. There are more bacteria alive in one inch of this bacterial mat than there are humans in existence.

Microbes at the top of the mat use sunlight to produce chemical byproducts. Deeper microbes use this chemical energy, then recycle nutrients back to the top.

The thin pink strands in the picture above are chemotrophic bacteria that derive their energy from the chemicals they eat. These bacteria feed on sulfides in the hot spring water, in much the same way as the bacteria that thrive near deep–sea hydrothermal vents.

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Polar Regions

The coldest temperature recorded on Earth was recorded at Vostok Station in Russia. With the help of radar, in 1996, a vast sub-glacial lake was discovered nearby.

In 1998, Russian researchers attempted to drill down to Lake Vostok. After removing an ice core more than two miles in length, the scientists stopped 492 feet short of the lake to keep from contaminating the water with the freon and aviation fuel they had been using to keep their hole from freezing over.

The ice core samples have proven valuable, and have resulted in the discovery of new bacteria that are 400,000 years old. The bacteria have not been reanimated.

Several interesting features of Lake Vostok make it a unique testing ground. It is one of the 15 largest lakes in the world, and is untouched by humans. It is also covered by a sheet of ice that is 2.3 miles thick. This makes it an ideal candidate for testing the kind of exploration that would take place on Jupiter's ice moon Europa.

Perhaps the strangest feature of Lake Vostok is that it has oxygen levels that are 50 times higher than those commonly found in freshwater lakes. If life exists in the lake, it would have to have a protective mechanism that would enable it to survive the corrosive stresses of living in such a highly oxygenated environment. Whether or not life is able to do so remains to be seen, but as you have seen, life thrives in places we would never expect.

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Sub Sea Floor

Photo courtesy of Craig Taylor & Carl Wirsen, WHOI

In 1991, this species of Arcobacter was discovered in the underwater dust plume that resulted from a volcanic explosion on the Earth's floor. These strange bacteria, which live in warm sediments well below the ocean floor, were stirred up by the huge volcanic explosion. They use the energy of the Earth’s core to flourish and are probably very similar to the first life forms that evolved on this planet.

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Bacteria are happy to exploit the crooks and crevasses of rocks. However, some bacteria don't just live inside these cracks, they live inside the actual rocks. They exist as the only organisms on the planet that are completely independent of any oxygen produced by photosynthesis.
These bacteria are particularly exciting to astrobiologists because if life were to exist on Mars, it would have to be in the subsurface, with no access to light or oxygen. The types of rocks that support these rock eaters on Earth are also found on Mars.

Basalt Eaters

Basalt eaters, like those pictured above, are evidenced by the tunnels they create in rock. Although they exist independently of oxygen produced by photosynthesis, they do use oxidation as their source of power.

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Supersaturated Saltwater Lakes

Mono Lake is three times saltier than the ocean. Because of its high density, swimmers can float in it with little or no effort. It is highly alkaline, with a ph of 10. This is comparable in strength to a strong detergent. The bacteria that thrive in this environment are polyextremophiles, because they overcome at least two hostile barriers to life.
Mono Lake is an important environment for astrobiologists to study because the last water on Mars probably existed in salty lakes. As water evaporated off the planet, it would have left behind bodies of water with an increasingly higher salt content. The evidence found by the Mars rover, thus far, supports this notion.

The strange structures pictured above, called "tufa", were only revealed a few decades ago when tributaries to Mono Lake were diverted to supply water to Los Angeles. These delicate structures were formed by the interaction of underwater springs with calcium carbonate (the main component of seashells), and are now rapidly disappearing because of exposure to the elements.

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Snottites, also known as snotties, win the prize for the microbe with the coolest name. These colonies of single-celled bacteria hang from the walls and ceilings of caves. They are similar to small stalactites, but have the consistency of "snot," or mucous.
They feed on the sulfur-rich water that seeps into caves, and they live ensconced in a biofilm that protects them from the sulfuric acid in their environment. This acid is as strong as the acid found in car batteries!

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No Sunlight Required


Video courtesy of Ferran Garcia-Pichel.

This unique ecosystem was discovered in 1977. Chemical energy, not sunlight, sustains it. The white froth behind the strange fish is a seething cloud shrimp. Mussels are also visible.