Editing Galileo project (section)

===Remote detection of life on Earth===
Carl Sagan, pondering the question of whether [[detecting Earth from distant star-based systems|life on Earth could be easily detected from space]], devised a set of experiments in the late 1980s using ''Galileo''{{'s}} remote sensing instruments during the mission's first Earth flyby in December 1990. After data acquisition and processing, Sagan published a paper in ''[[Nature (journal)|Nature]]'' in 1993 detailing the results of the experiment. ''Galileo'' had indeed found what are now referred to as the "Sagan criteria for life". These included strong absorption of light at the red end of the visible spectrum (especially over [[continents]]) by chlorophyll in photosynthesizing plants; absorption bands of molecular oxygen as a result of plant activity; infrared bands caused by the approximately 1 micromole per [[mole (unit)|mole]] of methane (a gas which must be replenished by volcanic or biological activity) in the atmosphere; and modulated narrowband radio wave transmissions uncharacteristic of any known natural source. ''Galileo''{{'s}} experiments were thus the first [[scientific control]]s in the newborn science of [[astrobiological]] remote sensing.{{sfn|Sagan et al.|1993|pp=715–721}}