[dropcap]The[/dropcap] question of whether extraterrestrial (ET) life exists (and in particular “intelligent” ET life) is arguably one of the most intriguing questions today. Not just scientists but people in general realize that the discovery of ET life would constitute a revolution rivaling the Copernican revolution in magnitude.
Here is a brief status report on where the quest for ET life is standing.
The endeavors take the form of a three-pronged attack. First, the searches within our own solar system can be performed using probes that either orbit or land on the target planets or satellites. The Curiosity rover on Mars, which has the ability to directly test for the existence of past (or present) life, is currently conducting one such search (Fig. 1 shows a photo taken by the rover). Future missions may explore the possibility of life on satellites of the giant planets, such as Europa (a moon of Jupiter), or Titan and Enceladus (two moons of Saturn).
Second, in the searches for life in other solar systems, most astronomers take the patient, step-by-step route. That is, observations with ground- and space-based telescopes (in particular the Kepler observatory) have discovered (and will continue to discover) thousands of extrasolar planets (or planet candidates). In particular, astronomers are interested in those extrasolar planets that are in the “habitable zone” around their parent star. The habitable zone encompasses the relatively narrow range of distances from the star that allows for liquid water to exist on the planet’s surface. The thinking is that the presence of a potent solvent facilitates the emergence of life by allowing molecules to come into contact with one another, thus creating the long chains that form the building blocks for life. The upcoming James Webb Space Telescope (to be launched in 2018) will even allow astronomerstoidentify those extrasolar planets that