The Search for Extraterrestrial Life
The universe is vast and filled with mystery. With an estimated seventy sextillion planets in the observable universe, many wonder if other forms of life exist beyond our own planet. To answer this question, scientists have dedicated years of research and innovation to the search for extraterrestrial life (SETI) in our universe.
What is SETI?
SETI stands for the Search for Extraterrestrial Intelligence, a term coined in the 1800s. This search involves efforts to detect evidence of intelligent life outside of our own Earthly societies. SETI is the most common use of the term, although the search for extraterrestrial life includes both intelligent and non-intelligent lifeforms.
The History of SETI
The idea of searching for intelligent life beyond Earth originated with scholars in the 1800s. Astronomer Sir William Herschel suggested in 1796 that there could be heavy civilizations living on other planets. This thought was expanded upon by Percival Lowell, an amateur astronomer whose search for life on Mars began in the late 1800s.
In 1959, Cornell physicist Giuseppe Cocconi and Caltech physicist Philip Morrison discussed the potential of searching for emission of radio emissions from space as a way to detect life beyond our own planet. This strategy remains popular today, with many SETI projects focusing on scanning the sky for radio emission.
Projects and Programs for SETI
The primary tools for the search for extraterrestrial life today are radio astronomy and spectroscopy. Spectroscopy looks for specialized gas molecules in the atmosphere of other planets, while radio astronomy looks for radio waves transmitted from space.
One of the major SETI projects is the Allen Telescope Array, which consists of 42 radio nodes in California. It looks for microwave radio signals that could be emitted from an extraterrestrial civilization. The array also has the capacity to detect signals from advanced lasers in space.
Another major project is SETI@Home, which was developed by one of the largest scientific computing organizations in the world, the Berkeley Open Infrastructure for Network Computing (BOINC). It enables anyone to contribute their computer processor to analyze data collected from the SETI@Home program.
The SETI Institute, headquartered in California, is home to the largest multi-disciplinary program dedicated to the search for extraterrestrial life. Its mission is to explore and understand the occurrence and nature of life in the universe via interdisciplinary research, education and public outreach.
The Search for Life on Mars
Mars is one of the primary targets for the search of extraterrestrial life. While it is technically still a part of our own Solar System, life forms on Mars (if any) are believed to have evolved independently from us.
NASA’s rover Curiosity is currently scouring the surface of Mars for evidence of ancient microbial life and environmental changes. The rover is equipped with precisely-calibrated studies that can search for organic molecules, carbonates, sulfates and clay deposits, all of which can help determine the conditions that once supported life.
The ESA’s ExoMars mission focuses on why Mars is now a barren desert and how methane released from the surface of Mars evolved over time. It is expected to launch in 2022 and will contain a robotic orbiter, a lander, and an additional rover more advanced than Curiosity.
Breakthrough Starshot and Other Interests
The Breakthrough Starshot initiative is a unique search for extraterrestrial life program, part of Breakthrough Initiatives funded by Yuri and Julia Milner. This mission proposes launching micro-probes attached to a light sail propelled by a powerful laser towards Alpha Centauri— the closest star to our own Solar System.
The hope is that the probes will reach their destination in about twenty years. All of the probes will carry micro-cameras, sensors, GPS and communication devices. On arrival, they will be able to photograph the exoplanets and beam data back to Earth, as well as search for signs of extraterrestrial life.
The Possibility of Intelligent Extraterrestrial Life
Scientists remain divided on the possibility of intelligent life beyond our own planet. While the prospect of one day discovering another living species amongst the stars remains exciting, there is still no solid evidence of their existence.
However, there are certain considerations when estimating the chance of intelligent life existing elsewhere in the universe. One of the most influential studies is the Drake Equation, which states that the number of civilizations that could exist in our universe is determined by a number of probabilities.
The Drake Equation
This equation helps to estimate the probability of intelligent extraterrestrial life existing. It is an equation formulated by astronomer Frank Drake in 1961. It states that: N = R* x fp x ne x fl x fi x fc x L.
The equation factors in several variables for determining the number of intelligent civilizations that could exist in our universe. These include the rate of formation of stars capable of harboring life (R); the fraction of those stars that have planets (fp); the number of those planets that lie in the habitable zone of their host star (ne); the fraction of those planets that develop life (fl); the fraction of life forms that become intelligent (fi); and the fraction that develop technologies capable of signaling their existence (fc).
While we may never find evidence of extraterrestrial life in our universe, SETI continues to explore the possibilities. From pioneering new technologies and missions to collaborating internationally, these efforts explore what’s possible in our vast universe and help us learn more about our place in the universe.
