About
Astrobiology — the study of the potential for life in the universe — addresses one of the most profound questions in science: are we alone? The Drake Equation (Frank Drake, 1961) attempted to estimate the number of communicative civilizations in the Milky Way by multiplying factors (rate of star formation; fraction with planets; fraction habitable; fraction with life; fraction with intelligence; fraction communicating; lifespan of civilization). Current estimates suggest there could be thousands to billions of civilizations — making the Fermi Paradox (where are they?) the central unsolved puzzle.
Current evidence and search: Mars (evidence of past liquid water; methane detected in atmosphere; organic compounds found by Perseverance rover); Europa (liquid water ocean under 10-30km of ice, possibly 100km deep — the most promising extraterrestrial ocean); Enceladus (Saturn's moon, water jets from subsurface ocean containing hydrogen and complex organic compounds); Titan (methane lakes, complex organic chemistry); exoplanets (5,000+ known; TRAPPIST-1 system has 3 potentially habitable planets at 40 light-years). SETI (Search for Extraterrestrial Intelligence) has been searching for radio signals since 1960; the Wow! Signal (1977) remains the most promising candidate detection.
# Top 10 astrobiology facts
- 1Drake Equation (1961)
- 2Fermi Paradox ('where are they?')
- 3habitable zone
- 4Europa subsurface ocean
- 5Enceladus water jets
- 6TRAPPIST-1 (3 habitable planets at 40 light-years)
- 7Mars methane
- 8Wow! Signal (1977, unconfirmed)
- 9biosignatures (oxygen, methane, phosphine in atmosphere)
- 10Great Filter hypothesis
Fascinating Facts
- ◆The Wow! Signal (August 15, 1977) — detected by Ohio State University's Big Ear radio telescope — was so unusual and matched so precisely what a signal from extraterrestrial intelligence would look like that astronomer Jerry Ehman circled it on the printout and wrote 'Wow!' in the margin; it has never been detected again despite decades of follow-up observation
- ◆Europa (Jupiter's moon) may have more liquid water than all of Earth's oceans combined — its subsurface ocean is estimated at 100 km depth beneath a 10-30 km ice shell — and with hydrothermal vents potentially heating the ocean floor, it has all the conditions that hosted life's origin on Earth
- ◆The 'Great Filter' hypothesis (Robin Hanson, 1998) proposes that there is some step in the development of civilizations so unlikely that virtually no civilization survives it — the alarming implication is that finding complex life on Mars would be terrible news: it would suggest the Great Filter is still ahead of us, meaning our extinction is likely
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