A steaming pool of water might not seem particularly hospitable to life, but some organisms thrive in such environments. Extremophile microbes live in many hot springs, like Grand Prismatic spring in Yellowstone National Park, U.S.A. (shown here). Different strains of thermophiles give this pool its range of hues; extreme heat-lovers dwell in the hottest central portions of the pool, while the cooler edges are inhabited by other, different-colored species. Click on image for full size (114 Kb) Image courtesy of the U.S. Natl. Park Service, photograph by Al Mebane.

Some environments are inhospitable to most "normal" living creatures. However, these extreme environments are not necessarily lifeless. Certain types of organisms, known collectively as "extremophiles", have adapted to survive or even thrive in various types of extreme environments. Philia is the Greek word for "love", so extremophiles are organisms that "love" extreme environments.

Most, though not all, extremophiles are microbes. In the last few decades, scientists have discovered many types of organisms that can survive in difficult environments that were previously thought sterile. Extremophiles have been found in very hot and in very cold environments; in exceptionally dry deserts; in environments that are very acidic or alkaline or doused in other harsh chemicals; and even in places exposed to high levels of radiation. These discoveries have generated lots of interest in life in extreme environments in recent years.

Early in our planet's history, most environments on Earth were extreme by modern standards. Likewise, environments on alien worlds within our Solar System and beyond are often marginally habitable if at all. The study of extremophiles may shed light on the origins and early evolution of life on Earth. Likewise, our knowledge of extremophiles may help us gage the likelihood of life arising in various extreme environments on planets and moons in our Solar System and beyond. The relatively new science of astrobiology is concerned with the study of such organisms.

Scientists have special names for extremophiles that thrive in specific types of challenging environments. Thermophiles live in hot environments (60-80° C, or 140-176° F); hyperthermophiles live in really hot places (80-122° C, or 176-252° F). Acidophiles like acidic conditions, with a pH of 3 or lower. Halophiles live in salty environments, cryophiles (or psychrophiles) like the cold, and xerophiles thrive in very dry deserts. Some organisms live in environments that are extreme in multiple ways; certain microbes that dwell in acidic hot springs are thus both thermophiles and acidophiles.

Though not technically extremophiles, numerous larger organisms are also adapted to survive in environments that would be lethal to most creatures. Camels are famously capable of going for long periods without water in the deserts in which they live. Emperor penguins somehow manage to make it through bitter Antarctic winters. Extreme plants, such as the many species of cactus, cope with the heat and dryness of desert environments as well. Bizarre tube worms grow in the superheated and chemically exotic niches around deep sea hydrothermal vents.

Most life wouldn't last long in the high temperatures of a hot spring like this one. However, some kinds of microbes really like the heat. Creatures that live in extreme environments like this are called "extremophiles". Different kinds of microbes have different colors. The colored microbes make this spring look like a rainbow! Click on image for full size (114 Kb) Image courtesy of the U.S. Natl. Park Service, photograph by Al Mebane.

Some environments are not good homes for most "normal" kinds of life. Places like that are called extreme environments. That doesn't mean that there isn't any life in extreme environments. Certain creatures can live and grow in extreme environments. Scientists have a special name for creatures that live in extreme environments. They are called "extremophiles". The "-phile" in extremophile comes from a Greek word that means "love". Extremophiles are creatures that love extreme environments

Most extremophiles are microbes. There are also a few types of larger creatures, like special types of shrimp and insects, which are also extremophiles. In the last few decades scientists have found extremophiles in places where they used to think life couldn't survive. Some extremophiles live in very hot or very cold environments. Others live in environments that have acids or radiation in them.

When Earth was young, most environments on our planet were extreme compared to today. Environments on many other planets and moons within our Solar System and beyond are also extreme. Scientists hope that studying extremophiles will help us learn about early life on Earth and about evolution. They also hope we can learn about the chances for life on other planets by studying extremophiles. Scientists who study these sorts of things are called astrobiologists.

Scientists use special names for extremophiles that live in different environments. Thermophiles live in hot places. Acidophiles can put up with strong acids. Xerophiles live in deserts and other dry places. Halophiles like it salty, while cryophiles (or psychrophiles) love the cold. Some creatures are extreme in more than one way. Microbes that live in acidic hot springs are both thermophiles and acidophiles.

A few big big animals and plants also survive in really extreme environments. While they aren't exactly extremophiles, some of them do live in places that would kill most normal creatures. Camels can go for long periods without water in the dry deserts where they live. Emperor penguins somehow make it through cold Antarctic winters. Extreme plants, such as many types of cactus, also live in the heat and dryness of deserts. Strange tube worms grow in boiling hot water filled with strange chemicals near deep sea hydrothermal vents.

Most life wouldn't last long in the high temperatures of a hot spring like this one. However, some kinds of microbes really like the heat. Creatures that live in extreme environments like this are called "extremophiles". Different kinds of microbes have different colors. The colored microbes make this spring look like a rainbow! Click on image for full size (114 Kb) Image courtesy of the U.S. Natl. Park Service, photograph by Al Mebane.

It is easy for living creatures to survive and grow in some places. Other places make it tough for life to get by. Scientists call places that are hard on life "extreme environments". There is a special name for creatures that can live in extreme environments. They are called "extremophiles".

Most extremophiles are tiny microbes. There are also a few types of slightly larger creatures which are extremophiles. Some kinds of shrimp and insects are extremophiles, for example. In recent years scientists have found extremophiles living in places where they used to think life was impossible. Some extremophiles live in very hot or very cold environments. Others live in environments that have acids or radiation in them.

When Earth was young, most places on our planet were extreme environments. Environments on many other planets and moons are also extreme. Scientists hope that studying extremophiles will help us learn about early life on Earth and about evolution. They also hope we can learn about the chances for life on other planets by studying extremophiles. Scientists who study these sorts of things are called astrobiologists.

Scientists use special names for extremophiles that live in special places. Thermophiles live in hot places. Acidophiles can put up with strong acids. Xerophiles live in deserts and other dry places. Halophiles like it salty. Cryophiles (also called psychrophiles) love the cold. Some creatures are extreme in more than one way. Microbes that live in acidic hot springs are both thermophiles and acidophiles.

A few big big animals and plants also survive in really extreme environments. While they aren't exactly extremophiles, some of them do live in places that would kill most normal creatures. Camels can go for long periods without water in the dry deserts where they live. Emperor penguins somehow make it through cold Antarctic winters. Extreme plants, such as many types of cactus, also live in the heat and dryness of deserts. Strange tube worms grow in boiling hot water filled with strange chemicals near deep sea hydrothermal vents.