Extraterrestrial Life

1. Extraterrestrial Life By aylahenson

2. definition • From Latin words extra("beyond", or "not of“) and terrestris ("of or belonging to Earth“) • Defined as life that does not originate from Earth. It is often also referred to as alien life, or simply aliens (or space aliens, to differentiate from other definitions of alien or aliens)

3. Background • These hypothetical forms of life range from simple bacteria-like organisms to beings far more complex than humans. The possibility that viruses might also exist extraterrestrially has been proposed.[ • According to scientists such as Carl Sagan and Steven Hawking, it is improbable that such life forms do not exist elsewhere in the universe. • Copernican Principle: Earth does not occupy a unique place in the universe. • Mediocrity Principal: Life on Earth is nothing special.

4. Americans think extraterrestrial life exists? • According to a poll done by Huffington Post, 50% of Americans believe life on other planets exists while only 17% believes that it does not. 33% of Americans polled reported say that they are not sure. • In the same poll, a 1/4 of Americans said that they think aliens have visited Earth, while a 1/3 said they have not—the rest of the respondents weren't sure. • Among those who said that life exists on other planets, 45% said that aliens have visited Earth.

5. Ways extraterrestrial life is thought to have existed • Biochemistry • Evolution and morphology

6. Biochemistry • All life on Earth is based upon 26 chemicals. • 95% of life is built upon only six of the twenty-six chemicals • Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur (CHNOPS). • Life on Earth requires water as a solvent where biochemical actions take place. • Suggestions have been made that self-replicating reactions of some fort could occur within the plasma of a star. • Several preconceived ideas about life outside of Earth have been questioned. • NASA scientist suggested that the photosynthesizing pigments of extrasolar planets may not be green.

7. Science fiction Depictions • Science fiction has often depicted extraterrestrial life with humanoid or reptilian forms. • Aliens have often been depicted as having light green or grey skin, a large head, as well as four limbs—human-like. • Other representations have been comparable to felines, insects, blobs, etc.

8. Planetary habitability within our solar system

9. Planetary habitability in the solar system • Venus • Mars • Ceres • Jupiter • Europa • Saturn • Titan • Enceladus

10. Venus • Carl Sagan, David Grinspoon, Geoffrey Landis, and Dirk Schulze-Makuch have put forward a hypothesis that microbes could exist in the stable cloud layers 31 miles above the surface of Venus. • This hypothesis is based on the premises of hospitable climates and chemical disequilibrium.

11. Mars • Life on Mars has been long speculated. • Liquid water is widely thought to have existed on Mars • It is still thought that there may still be liquid water beneath the surface. • On January 24, 2014, NASA reported that current studies on the planet Mars by the Curiousityand Opportunity rovers will now be searching for evidence of ancient life. • Including a biosphere as well as ancient water that may have been habitable.

12. Ceres • Ceres is a dwarf planet. • It has been confirmed by the Herschel Space Observatory to have water vapor in its atmosphere. • Frost on the surface may also have been detected. • The presence of water and the temperature on Ceres has led to speculation that life may be possible there. • A space probe by the name of Dawn is scheduled to enter orbit around Ceres in the spring of 2015.

13. Jupiter • Scientists in the 1960’s and 1970’s computed conditions for hypothetical amino acid-based macroscopic life in the atmosphere of Jupiter. • However, the conditions do not appear to permit the type of encapsulation thought necessary for molecular biochemistry, so life on Jupiter is thought to be unlikely.

14. Europa • Europa is one of Jupiter’s moons. • Europa has been speculated to have life due to the possibility of liquid water below the ice layer on the surface. • Hydrothermal vents on the bottom of the ocean, if they exist, may warm the ice and could be capable of supporting multicellular microorganisms. • In 2011, the possibility of life on Europa was immensely increased because it was discovered that vast lakes exist within Europa’s thick, icy shell. • On December 11, 2013, NASA reported the detection of clay-like minerals on the icy crust of Europa. Subsurface oceans such as this one pictured on Europa could possibly harbor life.

15. Saturn • Although it has been determined by astronomers that Saturn is inhabitable, its natural satellites Titan and Enceladus have been speculated to be possible sites for habitable conditions.

16. Titan • Titan is the largest moon of Saturn. • It is the only known moon with a significant atmosphere. • The existence of liquid hydrocarbon lakes in the polar regions of Titan have been demonstrated. • These are the first stable bodies of surface liquid discovered outside of Earth. • Hypotheses have been formally proposed that microorganisms could have left Earth when it suffered a massive asteroid or comet impact. • These microorganisms would have survived a journey through space to land on Titan.

17. Enceladus • Enceladus is another moon of Saturn. • It has some conditions such as geothermal activity and water vapor as well as under-ice oceans heated by tidal effects. • The Cassini probe detected carbon, hydrogen, nitrogen and oxygen on the moon which are all key elements to supporting life.

18. Small solar system bodies

19. Small solar system bodies • These bodies have been suggested as habitats for extremophiles. • Fred Hoyle has proposed that microbial life might exist on comets. • Live bacteria were found on the camera of the Surveyor 3 probe that had stayed on the moon for two and a half years. • This finding was later considered doubtful as sterile procedures may not have been fully followed.

20. The drake equation

21. The Drake equation • In 1961, Dr. Frank Drake devised the Drake equation. • The controversial equation multiplied estimates of the following terms together. • The rate of formation of suitable stars. • The fraction of those stars which are orbited by planets. • The number of Earth-like worlds per planetary system. • The fraction of planets where intelligent life develops. • The fraction of possible communicative planets. • The “lifetime” of possible communicative civilizations. • This equation was originally formulated merely as an agenda for discussion at the Green Bank Conference. • Drake used the equation to estimate that there are approximately 10,000 planets in the Milky Way containing intelligent life with the possibility of communicating with Earth.