Astrobiology
Astrobiology
Current research in astrobiology
Astrobiology is the area of life science that investigates the origin of life, how the biological components interact to create environment, and what makes planets habitable. It also searches for life on other planets. Astrobiologists are scientists from many areas of science, including biologists (molecular biologists, microbiologists, ecologists, geneticists), chemists, oceanographers, climatologists, archeologists, paleontologists, geologists, and astronomers. The foundations of astrobiology were laid in 1920s by Russian scientist A. I. Oparin, with his theory of development of organic matter from inorganic components under the conditions resembling early Earth’s atmosphere. It took, however, over half a century before studies into evolution of life on Earth and extraterrestrial life became an independent branch of life science. Astrobiology was created thanks to NASA’s administrator Dan Goldin in the mid-1990s. Coordination of the global effort in astrobiology rests now with the NASA Astrobiology Institute (NAI), created in 1998 and based at Ames in California, and includes over 700 scientists from numerous research institutes in the U.S. affiliate organizations were also created in Europe and Australia.
Aims of astrobiology
The NAI identified three main goals of astrobiology. Primary among these goals is the investigation of the evolution of life principally on Earth. This is achieved by understanding how organic matter became organized into living organisms and how life and environment co-evolved with Earth. NAI’s second aim is to find extraterrestrial life by identifying habitable planets. This will require identifying conditions essential for life to develop and searching for life signatures on planets of the solar system and beyond. The third goal is to determine the future of life on
Earth and in outer space. This area is addressed by studying the response of terrestrial organisms to reduced gravity conditions and investigating how environmental changes affect life on Earth.
Current research in astrobiology
Studying the Earth’s history revealed that life appeared on our planet after its surface had adequately cooled down, around 3.8 billion years ago. Fossil evidence indicated that the first organisms were unicellular (one-celled) and anaerobic (non-oxygen requiring). By studying extreme environments such as thermal vents, the freezing waters of the Antarctic, and anoxic marine sediments, scientists are able to determine mechanisms of microbial evolution and reconstruct the early history of life on Earth.
The evolution of life on Earth is closely linked to extraterrestrial intervention in form of asteroids, comets, and meteors. These objects falling onto Earth were likely to bring inorganic and organic compounds used later to create proteins and DNA, the basis of life, as it is known today. Analysis of space dust from our galaxy and beyond revealed the presence of ammonia and organic compounds such as glycine, vinyl alcohol, benzene, polycyclic aromatic hydrocarbons, and formaldehyde.
The crushing of large objects onto the Earth’s surface not only brought new molecules to Earth,
but also often had catastrophic consequences leading to sudden climate changes and mass extinctions (for example, possibly the disappearance of the dinosaurs). Events from Earth’s past were described by scientists studying fossils, rocks, and more recently, Greenland’s and the Antarctic’s ice sheets.
Meteors that land on Earth are analyzed for signs of life. For example, a 2002 study of meteors originating on Mars (blown off that planet by meteor impacts and then coming to Earth by chance over millions of years) claimed that tiny crystals in the rocks were best explained as products of life. However, most scientists have not agreed that the Martian meteorites show unambiguous evidence of life activity.
Clues to the possible existence of extraterrestrial life are also provided by studies of the chemistry and geology of the surface of planets and moons. The presence of hydrated salts and formations similar to ice fields of the Antarctic have been identified on Jupiter’s moons Callisto, Europa, and Ganymede. Thanks to the Galileo space probe that orbited the planet from 1995 to 2003, we now there are subsurface oceans of liquid on Callisto and Europa. These oceans are considered prime locations for possible extraterrestrial life, but it has not yet been possible to examine them directly.
Beside searching for life in and beyond our solar system, astrobiology is involved in studying the response of Earth life-forms to weightlessness in orbit and possible space travel. Space shuttle missions have investigated the effects of lack of gravity on the physiology of human and animal bodies and their immune systems, plant growth in space, and fertilization. Early twenty-first century planned research includes flying worms into space and studying gene expression in their multiple generations to see if weightlessness affects them similarly to vertebrates.
KEY TERMS
Anoxic —Deprived of oxygen
Astrobiology —The study of living organisms on planets beyond Earth and in space.
Evolution —in biology, inheritable changes occurring over a time span greater than one generation.
Extraterrestrial —Beyond Earth
So far, the main problems encountered with prolonged stay in space are muscle atrophy (shrinkage), loss of bone mass, and radiation exposure, especially during walks outside the shuttle.
Future of astrobiology
New challenges for astrobiology include developing methods to test newly discovered extrasolar planets for life signs. Strong evidence of life would be the existence of large quantities of molecular oxygen, which exists in the Earth’s atmosphere only because plants put it there. As of 2006, it was not yet possible to detect small, Earthlike planets in suitable orbits around distant stars, or to examine their spectra for the presence of oxygen, but such observations may become feasible in the near future.
See also Astronomy; Biosphere; Chemical evolution; Extrasolar planets; Life history.
Resources
BOOKS
Dick, Steven J., and James E. Strick. The Living Universe NASA and the Development of Astrobiology. Piscataway, NJ: Rutgers University Press, 2004.
Gilmour, Iain, and Mark A. Sephton, editors. An Introduction to Astrobiology. Cambridge, UK: Cambridge University Press, 2004.
PERIODICALS
Hogan, Jenny. “Astrobiology: Life at the Cutting Edge.” Nature. 437 (2005): 1080-1082.
Cooper, John F., et al. “Space Physics, Mars, and Life.” Astrobiology. 6 (2006): 437-438.
OTHER
“The Astrobiology Web. Your Online Guide to the Living Universe” <http://www.astrobiology.com> (accessed October 17, 2006).
Hobish, Mitchell K., and Keith Cowing. “Astrobiology 101: Exploring the Living Universe.” Astrobiology Web. 1999 <http://www.astrobiology.com/adastra/astrobiology.101.html> (accessed October 17, 2006).
NASA Astrobiology Institute, Ames Research Center, Moffett Field, CA 94035 (accessed October 17, 2006). <http://astrobiology.arc.nasa.gov>.
Agnieszka Lichanska