Finding planets and life among the stars: For the first time in history, mankind has the tools to look for other planets and whether these might host life.

Abstract

Are we alone in the universe? How can we find out? What would happen if we made contact with extraterrestrial life forms, intelligent or otherwise? These questions have fascinated humans ever since we understood that there is a universe beyond our pale blue dot. As the British physicist and author Arthur C Clarke put it: “Two possibilities exist: either we are alone in the universe or we are not. Both are equally frightening”. > Two possibilities exist: either we are alone in the universe or we are not. Both are equally frightening Speculation about the existence and nature of extraterrestrial life—and how humans might find and interact with it—has gone on for several millennia, but we live in the first age where the tools are available to collect, analyze and understand the potential evidence. The fundamental question “Are we alone?” drives the field of astrobiology, whose researchers tackle everything from microbes that thrive in extreme environments, to the origin of Earth's moon and oceans, to the potential for ecosystems under the icy surfaces of Mars and Jupiter's moon Europa. Momentum is also gathering for the search for habitable Earth‐like worlds orbiting other stars. However, the detection of “exo‐Earths”, and the discovery of any life signs thereupon, is one of the most technically and scientifically challenging feats ever attempted by astronomers. The journey begins with an understanding of our own home. To the Apollo astronauts, the Earth looked like a shiny glass marble suspended above a moonscape of gray and black. In December 1972, the Apollo 17 crew captured on film a view of Earth that can only be seen from a spaceship aligned between the Earth and the sun: in its fully illuminated glory, suspended in endless black space (Fig 1). This so‐called Blue Marble image went on to become one …