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Thermophile Research in Yellowstone Helps Guide the Search for Extraterrestrial Life

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Yellowstone's Grand Prismatic Spring. The vivid colors of this hot spring's mineral-rich edges are produced by pigmented bacteria living in microbial mats. NPS photo.

Studying heat-loving microbes living under extreme conditions in hydrothermal sites at Yellowstone National Park might help answer some of the most important questions that scientists have ever asked about life as we know or can imagine it. That includes the question of whether there might be life on planets and moons elsewhere in the universe. If you haven't yet heard about the research that astrobiologists are conducting in Yellowstone, it's time you knew.

Astrobiology: An Emerging Area of Scientific Inquiry

Astrobiology -- the study of the origin, evolution, distribution, and future of life in the universe -- is one of the most fascinating scientific disciplines to emerge in the modern era. Drawing on the knowledge, technology, and perspectives of many different disciplines, including (but not limited to) biology, chemistry, physics, ecology, geology, geography, astronomy, planetary science, and even philosophy, astrobiology addresses three fundamental questions:

* How did life begin and evolve?

* Is there life elsewhere in the universe?

* What is the future of life on Earth and beyond?

This field of scientific inquiry is sometimes called exobiology, which is more narrowly defined as the branch of biology that deals with the search for extraterrestrial life and the effects of extraterrestrial surroundings on living organisms. It remains that research into the origin, early evolution and diversity of life on Earth provides information vital to the search for other habitable environments in our solar system and on planets and moons around other stars.

NASA's Astrobiology Program

The National Aeronautics and Space Administration (NASA) has been in the forefront of astrobiological research since the early days of the U.S. Space Program. In fact, NASA recently (October 14, 2010) celebrated the 50th anniversary of its exobiology/astrobiology program with a Seeking Signs of Life symposium held in Arlington, Virginia. To learn more about the symposium and NASA's exobiology/astrobiology program, visit NASA's astrobiology website.

The Exobiology and Evolutionary Biology Program that NASA founded in 1960 remains an important element of the agency's multifaceted Astrobiology Program, which now also includes the Astrobiology Science and Technology Instrument Development (ASTID) Program, the Astrobiology Science and Technology for Exploring Planets (ASTEP) Program, and the NASA Astrobiology Institute.

The NASA Astrobiology Institute

The NASA Astrobiology Institute (NAI) is a key component of NASA's broadly-based Astrobiology Program. Established in 1998 to develop the field of astrobiology, provide guidance for space flight missions, and address related needs, the NAI is an interdisciplinary research and training organization employing the resources of many different scientific research institutions and universities. At present it consists of teams of researchers located at NASA's Goddard Space Flight Center, the Massachusetts Institute of Technology, and a dozen other universities and science centers throughout the United States. A list of all 14 teams and additional information can be found at this site.

The Institute also has six international partners, including the Russian Astrobiology Center.

The Case for Extraterrestrial Life

Whether we should be searching for extraterrestrial life at all is not the fiercely debated topic that it was half a century ago. Although many people dismiss the possibility of life elsewhere in the universe because of their religious beliefs, scientific evidence indicates that extraterrestrial life may exist in breathtaking profusion.

The case for extraterrestrial life has many facets, but rests on two primary observations: (1) Life can exist under a very wide range of conditions, and; (2) The number of stars that might have habitable planets or moons associated with them is so large that it staggers the imagination. Among people with this knowledge, it now takes a very strong act of faith to believe that life in some form or another cannot exist outside Earth's biosphere.

We have known for quite some time now that environments far too extreme for "normal" life forms can harbor life of some sort. Living organisms have been found -- sometimes to our astonishment -- in mine shafts miles below the Earth surface, near volcanic vents on the dark ocean floor, in supercooled brine under Antarctic ice, and in water so hot, acidic, or toxic that you'd think nothing could possibly live there. Scientists have long believed that habitability requires an energy source, liquid water, and a source of carbon. The discovery of these highly unusual life forms (extremophiles) has not changed this thinking, but has widened the search for places in which life can form and develop.

Advances in astronomy have recently made us aware that the universe is much larger and more diverse than we had ever suspected. While no one knows how many solar systems there may be, we now know that to say "there are more stars than there are grains of sand on all the world's beaches" (a common analogy) is to greatly understate the case. Our sun is one of about 200 to 400 billion stars in the Milky Way galaxy, and there appear to be at least 100 billion other galaxies of various sizes. One calculation places the total number of stars at around 10,000,000,000,000,000,000,000 (ten billion trillion) -- a number equivalent to more than a trillion stars for every human being alive today. Other estimates vary with the underlying assumptions, and there is still no way to estimate how many planets and moons there might be in the "right neighborhoods" of distant solar systems. Be that as it may, it's clear that places that could harbor life might be exceedingly abundant in the universe at large.

First, Know the Limits of Life

Astrobiologists want to ensure that the search for extraterrestrial life is focused in the right places, uses the correct technology, and employs the right chemical signatures. Understanding the origin, evolution, and limits of life right here in Earth's biosphere, a great end in itself, is absolutely vital to this effort. Knowing which environmental conditions can develop and sustain life on our own planet affords a basis for identifying other planets and moons where life might exist.

Yellowstone's Thermophiles May Hold Important Clues

To help unlock the remaining secrets of life's origin, evolution and limits, teams of scientists are studying extremophiles in a wide variety of places. Yellowstone National Park is considered among the most promising of these places because the park's roughly 10,000 geothermal sites, representing Earth's largest and most diverse collection of hot springs, mudpots, fumaroles, geysers, and related hydrothermal features, include areas with conditions thought to resemble those of the early Earth and the surface of other planets and moons.

In collaboration with other scientists, NASA Astrobiology Institute scientists from Montana State University are studying Yellowstone's thermophiles -- microbes that thrive in the high-temperature environments of many hydrothermal sites. These exceptionally hardy single-celled organisms can be found in hot springs and other hydrothermal features, some of which are at near-boiling temperatures and have sulfuric water nearly as acidic as battery acid. There are many kinds of thermophiles in a typical hydrothermal feature, each adapted to local conditions and existing in harmony with other thermophiles and the non-living environment.

Yellowstone's sulfuric pools are thought to closely resemble the Earth environment of about 3.5 billion years ago, a time when Earth was much hotter than today. Earth's surface temperature back then was 131 to 185°F, which is the temperature range preferred by many of Yellowstone's heat-loving thermophiles.

Studying the chemistry of the pools, especially iron- and sulfur-containing compounds, could reveal important clues about the conditions under which non-living chemicals can be energized and combined to produce amino acids (the protein building block of life) and living organisms. Knowing how the precursors for life are assembled here on earth, scientists can deduce how life might be formed on other planets and develop the chemical signatures needed to detect it.

A Handy Booklet

A recently-published pamphlet, Science Of The Springs: Guidebook To Yellowstone Astrobiology. provides additional information about this fascinating research, including the key attributes and portent of individual research sites such as Mammoth Hot Springs, Grand Prismatic, Old Faithful, and Norris. You can obtain printed copies of the full-color, pocket-sized booklet (16 pp.) from the Montana State University Astrobiology Biogeocatalysis Research Center, but you might prefer to just go online and access the pdf version (4.7MB).

If you have a Web-enabled phone with a camera and QR Reader software (installed on many phones or free to download), you can use the QR codes in the booklet to unlock extra videos and content from the Internet. Web links are also provided.

Postscript: Information gained from thermophile research has already been used in biotechnology applications that have yielded major benefits to society. One application that uses the Thermus aquaticus microbe simplifies the polymerase chain reaction (PCR) that makes it possible to copy genes, diagnose and treat genetic diseases, and perform DNA analyses faster and more affordably. Another application uses "environmentally friendly" heat-stable enzymes to replace some of the dangerous chemicals now used in high-temperature industrial processes such as those used to remove sulfur from coal, process food, convert corn to ethanol, clean up oil spills, leach gold from ore, and decompose hazardous wastes. Many other applications are in use or in development.

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