Astrobiology is a scientific field within the life and environmental sciences that studies the origins, early evolution, distribution, and future of life in the universe by investigating its deterministic conditions and contingent events. As a discipline, astrobiology is founded on the premise that life may exist beyond Earth.
The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.
Extraterrestrial life, or alien life, is life which does not originate from Earth. No extraterrestrial life has yet been scientifically conclusively detected. Such life might range from simple forms such as prokaryotes to intelligent beings, possibly bringing forth civilizations that might be far more advanced than humans. The Drake equation speculates about the existence of sapient life elsewhere in the universe. The science of extraterrestrial life is known as astrobiology.
In astronomy and astrobiology, the habitable zone (HZ), or more precisely the circumstellar habitable zone (CHZ), 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 HZ 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 HZ 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.
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) the only areas in which life might arise.
Sara Seager is a Canadian-American astronomer and planetary scientist. She is a professor at the Massachusetts Institute of Technology and is known for her work on extrasolar planets and their atmospheres. She is the author of two textbooks on these topics, and has been recognized for her research by Popular Science, Discover Magazine, Nature, and TIME Magazine. Seager was awarded a MacArthur Fellowship in 2013 citing her theoretical work on detecting chemical signatures on exoplanet atmospheres and developing low-cost space observatories to observe planetary transits.
The possibility of life on Venus is a subject of interest in astrobiology due to Venus' proximity and similarities to Earth. To date, no definitive evidence has been found of past or present life there. In the early 1960s, studies conducted via spacecraft demonstrated that the current Venusian environment is extreme compared to Earth's. Studies continue to question whether life could have existed on the planet's surface before a runaway greenhouse effect took hold, and whether a relict biosphere could persist high in the modern Venusian atmosphere.
Kepler-16b is a Saturn-mass exoplanet consisting of half gas and half rock and ice. It orbits a binary star, Kepler-16, with a period of 229 days. "[It] is the first confirmed, unambiguous example of a circumbinary planet – a planet orbiting not one, but two stars," said Josh Carter of the Center for Astrophysics | Harvard & Smithsonian, one of the discovery team.
Kepler-22b is an exoplanet orbiting within the habitable zone of the Sun-like star Kepler-22. It is located about 640 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.
Kepler-62e is a super-Earth exoplanet discovered orbiting within the habitable zone of Kepler-62, the second outermost of five such planets discovered by NASA's Kepler spacecraft. Kepler-62e is located about 990 light-years from Earth in the constellation of Lyra. The exoplanet was found using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. Kepler-62e may be a terrestrial or ocean-covered planet; it lies in the inner part of its host star's habitable zone.
Kepler-62f is a super-Earth exoplanet orbiting within the habitable zone of the star Kepler-62, the outermost of five such planets discovered around the star by NASA's Kepler space telescope. It is located about 982 light-years from Earth in the constellation of Lyra.
Kepler-442b is a confirmed near-Earth-sized exoplanet, likely rocky, orbiting within the habitable zone of the K-type main-sequence star Kepler-442, about 1,206 light-years (370 pc) from Earth in the constellation of Lyra.
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.
The Virtual Planetary Laboratory (VPL) is a virtual institute based at the University of Washington that studies how to detect exoplanetary habitability and their potential biosignatures. First formed in 2001, the VPL is part of the NASA Astrobiology Institute (NAI) and connects more than fifty researchers at twenty institutions together in an interdisciplinary effort. VPL is also part of the Nexus for Exoplanet System Science (NExSS) network, with principal investigator Victoria Meadows leading the NExSS VPL team.
Kepler-452b is a super-Earth exoplanet orbiting within the inner edge of the habitable zone of the sun-like star Kepler-452 and is the only planet in the system discovered by the Kepler space telescope. It is located about 1,400 light-years (430 pc) from Earth in the constellation of Cygnus.
Elisa Victoria Quintana is a scientist working in the field of astronomy and planetary science at NASA Goddard Space Flight Center. Her research focuses the detection and characterization of exoplanets in addition to studying how they form. She is best known for the detection of Kepler 186f, the first Earth-sized planet found in the habitable zone of a star other than the Sun.
Shawn D. Domagal-Goldman is a research space scientist at NASA Goddard Space Flight Center, who specializes in exoplanets, Archean geochemistry, planetary atmospheres, and astrobiology.
Aomawa L. Shields is an associate professor of physics and astronomy at UC Irvine. Her research is focused on exploring the climate and habitability of small exoplanets, using data from observatories including NASA's Kepler space telescope. Shields was a 2015 TED Fellow, and is active in science communication and outreach. She develops interactive workshops to encourage self-esteem and teach about astronomy, combines her training in theater and her career in astronomy.
Habitability of G V stars of G V stars systems defines the suitability for life of exoplanets belonging to yellow dwarf stars. These systems are the object of study among the scientific community because they are considered the most suitable for harboring living organisms, together with those belonging to K-type stars.
Cynthia B. Phillips is an American planetary geologist who works for NASA at the Jet Propulsion Laboratory. A focus of her research has been Europa, one of the moons of Jupiter, and she is project staff scientist and project science communications lead for the Europa Clipper spacecraft mission. An expert on processing images from space missions to the planets and their moons, and on the geological processes operating within moons, she has studied the effects of asteroid impacts on the surface of Europa, and definitions of non-earth-based life that could apply on places like Europa that are outside the circumstellar habitable zone.
