Astrobiology, and the related field of exobiology, is an interdisciplinary scientific field that studies the origins, early evolution, distribution, and future of life in the universe. Astrobiology is the multidisciplinary field that investigates the deterministic conditions and contingent events with which life arises, distributes, and evolves in the universe. It considers the question of whether extraterrestrial life exists, and if it does, how humans can detect it.
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.
Extraterrestrial life, sometimes colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might range from simple forms comparable to prokaryotes, to intelligent beings, possibly bringing forth civilizations that might be far more advanced than humankind. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life in all its forms is known as astrobiology, the multidisciplinary field that investigates the deterministic conditions and contingent events with which life arises, distributes, and evolves in the universe.
The Fermi paradox is the conflict between the lack of clear, obvious evidence for extraterrestrial life and various high estimates for their existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."
Anthem is a dystopian fiction novella by Russian-American writer Ayn Rand, written in 1937 and first published in 1938 in the United Kingdom. The story takes place at an unspecified future date when mankind has entered another Dark Age. Technological advancement is now carefully planned and the concept of individuality has been eliminated. A young man known as Equality 7-2521 rebels by doing secret scientific research. When his activity is discovered, he flees into the wilderness with the girl he loves. Together they plan to establish a new society based on rediscovered individualism.
Harlow Shapley was an American scientist, head of the Harvard College Observatory (1921–1952), and political activist during the latter New Deal and Fair Deal.
In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth required an improbable combination of astrophysical and geological events and circumstances.
In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure. The bounds of the CHZ are based on Earth's position in the Solar System and the amount of radiant energy it receives from the Sun. Due to the importance of liquid water to Earth's biosphere, the nature of the CHZ and the objects within it may be instrumental in determining the scope and distribution of planets capable of supporting Earth-like extraterrestrial life and intelligence.
Archie Fairly Carr, Jr. was an American herpetologist, ecologist, and conservationist. He was a Professor of Zoology at the University of Florida. In 1987 the Ecological Society of America awarded him the Eminent Ecologist Award. He brought attention to the world's declining sea turtle populations due to over-exploitation and habitat loss.
Human extinction is the hypothetical end of the human species due to either natural causes such as population decline due to sub-replacement fertility, an asteroid impact or large-scale volcanism, or anthropogenic (human) causes, also known as omnicide. For the latter, some of the many possible contributors include climate change, global nuclear annihilation, biological warfare and ecological collapse. Other scenarios center on emerging technologies, such as advanced artificial intelligence, biotechnology, or self-replicating nanobots. The scientific consensus is that there is a relatively low risk of near-term human extinction due to natural causes. The likelihood of human extinction through its own activities, however, is a current area of research and debate.
Planetary habitability is the measure of a planet's or a natural satellite's potential to develop and maintain environments hospitable to life. Life may be generated directly on a planet or satellite endogenously or be transferred to it from another body, through a hypothetical process known as panspermia. Environments do not need to contain life to be considered habitable nor are accepted habitable zones ("HZ"s) the only areas in which life might arise.
The habitability of natural satellites is a measure of their potential to sustain life in favorable circumstances. Habitable environments do not necessarily harbor life. Natural satellite habitability is a new area that is significant to astrobiology for various reasons, the most important of which being that natural satellites are expected to outnumber planets by a large margin, and it is projected that habitability parameters will be comparable to those of planets. There are, nevertheless, significant environmental variables that affect moons as prospective alien life locations. The strongest candidates for natural satellite habitability are currently icy satellites such as those of Jupiter and Saturn—Europa and Enceladus respectively, although if life exists in either place, it would probably be confined to subsurface habitats. Historically, life on Earth was thought to be strictly a surface phenomenon, but recent studies have shown that up to half of Earth's biomass could live below the surface. Europa and Enceladus exist outside the circumstellar habitable zone which has historically defined the limits of life within the Solar System as the zone in which water can exist as liquid at the surface. In the Solar System's habitable zone, there are only three natural satellites—the Moon, and Mars's moons Phobos and Deimos —none of which sustain an atmosphere or water in liquid form. Tidal forces are likely to play as significant a role providing heat as stellar radiation in the potential habitability of natural satellites.
The RAND Corporation is an American nonprofit global policy think tank created in 1948 by Douglas Aircraft Company to offer research and analysis to the United States Armed Forces. It is financed by the U.S. government and private endowment, corporations, universities and private individuals.
Caleb Asa Scharf is a British-born astronomer and the director of the multidisciplinary Columbia Astrobiology Center at Columbia University, New York. He received a B.Sc. in Physics from Durham University and a PhD in Astronomy from the University of Cambridge; he did postdoctoral work in X-ray astronomy and observational cosmology at the NASA Goddard Space Flight Center and the Space Telescope Science Institute in Maryland.
Kepler-22b is an exoplanet orbiting within the habitable zone of the Sunlike star Kepler-22. It is located about 600 light-years from Earth in the constellation of Cygnus. It was discovered by NASA's Kepler Space Telescope in December 2011 and was the first known transiting planet to orbit within the habitable zone of a Sun-like star, where liquid water could exist on the planet's surface. Kepler-22 is too dim to be seen with the naked eye.
In astrobiology and planetary astrophysics, the galactic habitable zone is the region of a galaxy in which life might most likely develop. The concept of a galactic habitable zone analyzes various factors, such as metallicity and the rate and density of major catastrophes such as supernovae, and uses these to calculate which regions of a galaxy are more likely to form terrestrial planets, initially develop simple life, and provide a suitable environment for this life to evolve and advance. According to research published in August 2015, very large galaxies may favor the birth and development of habitable planets more than smaller galaxies such as the Milky Way. In the case of the Milky Way, its galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs (33,000 ly) and an inner radius close to the Galactic Center.
The habitability of red dwarf systems is presumed to be determined by a large number of factors from a variety of sources. Modern evidence indicates that planets in red dwarf systems are unlikely to be habitable, due to their low stellar flux, high probability of tidal locking, small circumstellar habitable zones and the high stellar variation experienced by planets of red dwarf stars, impeding their planetary habitability. However, the ubiquity and longevity of red dwarfs are factors which could provide ample opportunity for any possibility of habitability to be realized. As red dwarf stars are by far the most common type of star in the universe, astronomers study how each of the many factors, and the interactions among them, could affect their habitability to learn more about the frequency and most likely locations of extraterrestrial life and intelligence.
Su-Shu Huang was a Chinese-born American astrophysicist. A graduate of the University of Chicago, Huang began his career with the study of the continuous absorption coefficients of two-electron systems, but eventually his research focus turned to the study of stellar atmospheres, radiative transfer, and binary and multiple star systems. In subsequent years, Huang began to cover the topic of life on extrasolar planets and the prerequisites thereof, coining the term "habitable zone" to refer to the region around a star where planets could support liquid water at their surfaces at a 1959 conference of the Astronomical Society of the Pacific.
The Nexus for Exoplanet System Science (NExSS) initiative is a National Aeronautics and Space Administration (NASA) virtual institute designed to foster interdisciplinary collaboration in the search for life on exoplanets. Led by the Ames Research Center, the NASA Exoplanet Science Institute, and the Goddard Institute for Space Studies, NExSS will help organize the search for life on exoplanets from participating research teams and acquire new knowledge about exoplanets and extrasolar planetary systems.
