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Astrobiology: Its Origins and Development

    By G. Scott Hubbard

    For thousands of years humans have gazed at the night sky and wondered about the presence of life elsewhere, whether in our solar system or on some other blue planet or body around another star. Such thoughts have found their expression in fiction, scientific missions and religions worldwide. Philosophers and ordinary people have pondered the rise of life on our planet. Creation myths are fundamental to every civilization and culture, and reflect the profound resonance of the question of our origins. Today, astronomers have pushed back our understanding of the origins of the universe to within tiny fractions of microseconds of the big bang. However, science cannot, as yet, offer any complete definition of life, nor yet point to the exact time, conditions and mechanisms when organic matter first went from nonliving to living. Just 50 years ago, humans began to extend their presence into space, first with robots and then with humans. As this tentative expansion of our species into other worlds continues, basic questions remain unanswered about the long-term adaptation of living organisms to other environments. For example, we do not know what the effect will be of living for years on Mars, where the pull of gravity is about one-third that of Earth. Astrobiology addresses all these compelling mysteries by embracing the study of the origin, evolution, distribution and future of life in the universe.

    Dr. Harold “Chuck” Klein, father of NASA’s life sciences program.

    Dr. Harold “Chuck” Klein, father of NASA’s life sciences program.

    NASA’s current astrobiology program addresses three fundamental questions: How does life begin and evolve? Is there life beyond Earth and, if so, how can we detect it? What is the future of life on Earth and in the universe? While questions of our origins have been discussed for millennia, NASA took a new direction in 1995 by defining a science program that also was a novel experiment in research that bridges and connects many disciplines. Politics, science, personalities and serendipity all contributed to the creation and success of what is now called astrobiology as a field of inquiry.

    HISTORICAL ANTECEDENTS

    In 1953, University of Chicago researchers Stanley Miller and Harold Urey conducted a now-famous experiment in which they succeeded in forming some of the compounds that scientists consider life’s building blocks. The new U.S. space program embraced this field of study of life in the universe (dubbed “exobiology”). NASA funded its first exobiology project in 1959: an instrument designed to detect microbial life in extraterrestrial environments. Led by people such as the late Dr. Harold "Chuck" Klein, NASA established a life sciences program that included exobiology as part of its purview. When roles and responsibilities for the new agency were defined, the former Ames Aeronautical Laboratory was renamed the Ames Research Center (ARC) and assigned two space exploration roles: management of the Pioneer series of spacecraft and space life sciences. This home at ARC and research sponsored by NASA’s exobiology program laid the groundwork for the broader approach to studying life in the universe that would eventually become astrobiology.

    Purdue President France Córdova, former NASA chief scientist. Photo credit-Purdue News Service/David Umberger.

    Purdue President France Córdova, former NASA chief scientist.
    Photo credit: Purdue News Service/David Umberger

    In the 1970s, NASA attempted to answer the question of life’s uniqueness in the solar system in a single mission with the Viking landers’ (developed and managed by the Langley Research Center) search for signs of microbial life on the surface of Mars. These life detection experiments were designed to “culture” (grow) microbes and detect the signs of their metabolic activity using samples from the top few centimeters of Martian soil. The experiments failed to produce evidence of extraterrestrial life. Scientists determined that chemistry and radiation at the surface of Mars made that environment hostile to life as we know it. In addition, scientists now know that fewer than one percent of microbes on Earth can be cultured in a laboratory. As a consequence of this perceived scientific failure NASA sidelined exobiological experiments for space missions, especially to Mars, for many years. The scientific community proceeded to rethink its approach to the detection of biosignatures, or signs of life. Out of this redirection eventually came the concept of searching for habitable environments rather than the direct detection of organisms.

    A Mars meteorite (ALH940001) discovered in Antarctica in 1984 being studied by NASA for potential fossil evidence that primitive life may have existed on Mars more than 3.6 billion years ago.

    A Mars meteorite (ALH940001) discovered in Antarctica in 1984 being studied by NASA for potential fossil evidence that primitive life may have existed on Mars more than 3.6 billion years ago.

    NASA continued its small exobiology grants program, funding a wide variety of investigations into key questions about life in the universe. Significant scientific developments fostered by NASA exobiology research include the identification of a new class of organisms, archaea, and the subsequent redrawing of the tree of life and the new field of study of extremophiles, organisms that thrive in environments deadly to familiar forms of life.

    While exobiology moved forward, researchers in astrophysics, planetary science, and other areas of space science were making progress as well. By 1995, advances in science coupled with changes in the national political landscape made the study of life in the universe attractive once again, and NASA’s astrobiology program was born.

    In The World of Politics and Science

    An electron microscope image of tubular structures that are possible microscopic fossils of bacteria-like organisms that may have existed in Mars ancient past. A two-year investigation by a NASA research team found organic molecules, mineral features characteristic of biological activity and possible microscopic fossils such as these inside the famous Martian rock discovered in Antarctica in 1996.

    An electron microscope image of tubular structures that are possible microscopic fossils of bacteria-like organisms that may have existed in Mars ancient past. A two-year investigation by a NASA research team found organic molecules, mineral features characteristic of biological activity and possible microscopic fossils such as these inside the famous Martian rock discovered in Antarctica in 1996.

    In the early 1990s NASA Ames had a thriving scientific organization with world-class research in Earth science, space science and space life science. One special aspect of this enterprise was the interdisciplinary interactions it fostered among the researchers. Ames scientists such as Jim Pollack routinely published in both Earth science and space science journals. Similarly, some scientists such as Chuck Klein worked both in the field of exobiology and in space life sciences. This cross-disciplinary work was not well-recognized, and in one of the periodic “roles and missions” exercises that sweep through NASA centers, Ames was challenged to justify its approach to space science.

    A coalition at NASA Headquarters began to form, dedicated to saving the extraordinarily high quality scientific capability at Ames. Three figures were key: then-Chief Scientist France Córdova, (now the president of Purdue University); Wesley Huntress, then-associate administrator for Space Science; and Charles Kennel of UCSD, then-associate administrator for NASA’s Mission to Planet Earth. In March of 1995, Huntress suggested that NASA use the term “astrobiology” to describe the expanding study of life in the universe. On May 19, 1995, NASA Administrator Dan Goldin held a press conference at Ames, officially declaring it NASA’s lead center for the new field of astrobiology.

    Throughout the 1990s, space missions produced a stream of scientific findings that fueled the interest in astrobiology. The Hubble Space Telescope announced many space science firsts, ranging from evidence for black holes to the existence of brown dwarf stars. In 1994 the Human Genome Project stated it had met its five-year goal of constructing a detailed, comprehensive human genetic map, one year ahead of schedule. In December of 1995, a truly startling discovery was the first confirmed detection of an extrasolar planet orbiting a sun-like star.

    Students at the NASA Ames Research Center’s first Astrobiology Academy.

    Students at the NASA Ames Research Center’s first Astrobiology Academy.

    In August 1996, a group of researchers including NASA scientist Dr. David McKay published a controversial article in Science about possible signs of life in a Martian meteorite. The Martian meteorite showed evidence of something that could be interpreted as microscopic fossils of primitive, bacteria-like organisms, authors of the paper claimed. While the broad science community has yet to accept these claims, the paper provoked for the first time a scientific discussion about the size limits of a living organism. At almost the same time, NASA’s Galileo spacecraft began returning intriguing images of the Jovian moon Europa. The images of Europa held compelling evidence of ice rafts floating on what might be a liquid ocean. These revelations across a broad spectrum of scientific endeavor provided the material for an interdisciplinary focus. In September 1996, the first NASA Astrobiology Workshop was held at Ames, attended by over 250 scientists from a broad range of Earth, space, and life science fields. Ideas for a new effort to understand life in the universe across all three disciplines began to coalesce, and the workshop produced an ambitious roadmap defining the three essential questions and driving the field.

    NASA Astrobiology Institute

    The advocacy work of Córdova, Huntress and Kennel led to the creation of a new platform for the broad multidisciplinary study that was astrobiology. A virtual institute, a common forum for like minds to share insights and leverage one another’s work, would be created. The NASA Astrobiology Institute (NAI) was born. An institute freed of the expense of traditional bricks and mortar had been discussed previously, but the concept had never been truly put to the test.

    In October 1997, NASA solicited astrobiology science proposals as the first step. That solicitation described the NAI as an experiment in interdisciplinary research and virtual collaboration. While the competitive selection process was under way, the methods of leading and managing an interdisciplinary virtual institute were not yet created or in place.

    In May of 1998, Huntress’ deputy, the late Earl Huckins, visited Ames with the direction to establish the management approach for the institute. At Huntress’ direction I was asked to be interim director and was tasked with creating a virtual institute from the teams selected through the NASA announcement. The NAI was up and successfully running within six months, a major effort for an untried concept. It was during this initial phase that the tools and techniques of research portfolio management and inter-group communications were created. In addition, the original charter for astrobiology research was defined and extended, embracing not only basic science but also instrumentation and field campaigns aimed at understanding the limits of Earth-based life.

    Icy Europa - Two images of Jupiter’s ice-covered moon Europa taken by the Galileo spacecraft on Sept. 7, 1996. The left image shows the moon’s approximate natural color appearance, and the right image presents a false-color version combining infrared images to enhance color differences in the moon’s predominant water-ice crust with coarse-grained ice (dark blue) distinguished from fine-grained ice (light blue).

    Icy Europa - Two images of Jupiter’s ice-covered moon Europa taken by the Galileo spacecraft on Sept. 7, 1996. The left image shows the moon’s approximate natural color appearance, and the right image presents a false-color version combining infrared images to enhance color differences in the moon’s predominant water-ice crust with coarse-grained ice (dark blue) distinguished from fine-grained ice (light blue).

    While I continued in office for another year, functioning as the founding director, Goldin issued a requirement to recruit an institute director who was a “King Kong” biologist. The charge was fulfilled in May 1999 by the appointment of Baruch Blumberg, a Nobel Prize-winning biologist and physician, as the first NAI director. Subsequent directors have included UCLA professor Bruce Runnegar and, most recently, Carl Pilcher, an astronomer and former NASA Headquarters astrobiology senior scientist.

    More than 50 U.S. research institutions responded to the first NASA solicitation, and the field of astrobiology soon had a home. The proposed projects were investigator-initiated basic science within the strategic constraints imposed by NASA, including an emphasis on cross-disciplinary collaborative investigation. That first year, 11 teams were chosen and, along with a single foreign associated institution in Spain, constituted the NAI. Each of the 11 teams was designated by the name of the institution of the principal investigator. Members of each of the teams were from the lead institution and from co-institutions. This pattern continues today.

    Big ocean beneath - An artist’s drawings depict two proposed models of Europa’s subsurface structure based on findings of the Galileo spacecraft. In the top scenario, Europan features may be explained by the existence of a warm, convecting icy layer, located several miles below a cold, brittle surface ice crust. In the second scenario, Europa has a 60-mile-deep ocean (10 times deeper than any ocean on Earth) below a 10-mile-thick ice crust.

    Big ocean beneath? - An artist’s drawings depict two proposed models of Europa’s subsurface structure based on findings of the Galileo spacecraft. In the top scenario, Europan features may be explained by the existence of a warm, convecting icy layer, located several miles below a cold, brittle surface ice crust. In the second scenario, Europa has a 60-mile-deep ocean (10 times deeper than any ocean on Earth) below a 10-mile-thick ice crust.

    Three more competitions have been held since the initial selection, resulting in changes in the institutional mix. During this process the number of investigators and lead institution has grown from 11 to 16 teams, with five international associates and affiliates, and thousands of scientists and students worldwide. Complete information on the NAI, including its history, both programmatic and scientific, is available at the NAI Web site, http://nai.arc.nasa.gov.

    The scientific progress and impact of the NAI has been substantial in a broad array of research, including the study and definition of habitable environments, understanding the limits of life, biosignature research, Earth’s early biosphere, and the origins of life. In 2003, the National Research Council conducted a review of U.S. and international programs in astrobiology and applauded the progress in this new science.

    As noted earlier, the NAI also was an experiment in virtual collaboration. To achieve this goal the NAI staff, director and investigators used advanced collaborative tools, including video conferencing, internet-linked “smart boards” that allowed for simultaneous data sharing across many networked users, and the then-modern tools available in the cutting-edge “Collaborative Engineering Environment.” Readily accessible server sites, initially developed and hosted at Ames but now available commercially, fostered easy yet secure exchange of documents and other information. Webcams streamed video from laboratory to laboratory, linking researchers. Such Internet-based collaborations are now taken for granted, but were considered pioneering a decade ago.

    ASTID, ASTEP and The Astrobiology Program Portfolio

    Extreme Earth organisms - Principal Investigator Kimberley Warren-Rhodes surveys the desert floor for cyanobacteria in Xinjiang, China.

    Extreme Earth organisms - Principal Investigator Kimberley Warren-Rhodes surveys the desert floor for cyanobacteria in Xinjiang, China.

    While the principal new programmatic element of astrobiology was embodied in the multi-institution, highly cross-disciplinary NAI, NASA officials recognized from the beginning that there was a need to maintain a portfolio of research that included the individual investigator. The principal investigator-based element of the astrobiology program is now called the Exobiology and Evolutionary Biology Program, and it currently funds about 150 individual researchers.

    An additional early goal of NASA’s astrobiology initiative was to create instrumentation, tools and techniques to explore for the “fingerprints of life” in extreme environments here on Earth and on missions to other worlds. To meet these goals, NASA created two new initiatives for the astrobiology program: the Astrobiology Science, Technology and Instrument Development program (ASTID), in 1998; and the Astrobiology Science, Technology for Exploring Planets (ASTEP) program, in 2001.

    Astrobiology investigations require the development of miniaturized instrumentation capable of extensive, autonomous operations on planetary surfaces. NASA’s ASTEP program sponsors investigations to explore the Earth’s extreme environments in order to develop a sound technical and scientific basis to search for life on other planets. A unique and central feature of the ASTEP program is the use of terrestrial field campaigns to further science and technology. For example, in 2007, ASTEP field campaigns were conducted in Mexico and Chile, on Svalbard Island north of the Arctic Circle, and in the north Atlantic and Arctic oceans. Through the ASTID program, a miniaturized X-ray diffraction instrument was selected as the first astrobiology funded space flight experiment to fly on the Mars Science Laboratory. As noted in various reviews and assessments, investments in biosignature detection sensors are critical to achieving the goals of flight missions in the Mars Exploration Program.

    Education and Outreach

    Big ocean beneath - An artist’s drawings depict two proposed models of Europa’s subsurface structure based on findings of the Galileo spacecraft. In the top scenario, Europan features may be explained by the existence of a warm, convecting icy layer, located several miles below a cold, brittle surface ice crust. In the second scenario, Europa has a 60-mile-deep ocean (10 times deeper than any ocean on Earth) below a 10-mile-thick ice crust.

    Next stop Red Planet -Artist's concept of NASA’s Mars Science Laboratory, slated for a 2009 launch, will land near the Red Planet’s northern hemisphere and investigate soil and rock samples to determine the past and present ability of Mars to support life.

    Communicating the discoveries and excitement of astrobiology has also been understood as a fundamental requirement since the early development of the field. Meeting this objective has taken various forms. One element was a common forum, embodied in the Astrobiology Science Conference held biennially that today attracts over 800 scientists from over 30 fields. With meetings in 2000, 2002, 2004 and 2006 that have continued to grow in attendance, the conference remains a forum where scientists are encouraged to push the boundaries.

    Another measure of the maturity of a field of research is the presence of peer-reviewed professional journals reporting on scientific progress. Two such journals have emerged: Astrobiology, published by Mary Ann Liebert, Inc., and the International Journal of Astrobiology, published by Cambridge University Press. Both are now several years into their publication and routinely receive very high quality papers.

    From the beginning of astrobiology, the field has made a concerted effort to emphasize the importance of education, both to train the next generation of researchers and explorers and to keep the public aware of the many breakthroughs. Ten years ago virtually no universities had dedicated degree programs in astrobiology and very few even offered a course in the field. Today, virtually every major university in the country has at least a course in astrobiology and many have degree programs. Courses have been designed, curricula developed, textbooks written, movies made, and workshops and training classes developed for teachers and students both.

    The Future

    The first decade of astrobiology has laid significant groundwork for the understanding of the genesis and evolution of life in the universe. Fieldwork has provided fossils, organisms, and ecosystems that have all led to significant insight into the early Earth, possible models for origins and a huge expansion of the recognized environmental limits of life. Laboratory work, coupled with astronomical observation, has added another significant piece of the puzzle and continues to provide clues and refine models. Missions are just beginning to take astrobiology to entire new levels of understanding. Given the timeless fascination with questions of the origins and prevalence of life, astrobiology will endure long into the future.