The amazing advances in all realms of science that began in the seventeenth century and accelerated to tremendous heights in the past few years have finally enabled scientists to meaningfully explore issues surrounding the beginnings of life on Earth. Astrobiology combines all of the natural sciences in an effort to understand the formation, evolution, and future of life here and throughout the cosmos. As we will explore shortly, efforts to replicate the conditions under which life formed on Earth have been carried out since the 1950s. The discovery of strong evidence that liquid water, essential for life as we know it, exists in several worlds in the solar system has added fuel to the astrobiology effort.

Astrobiology as a unified discipline received a big boost in 1996, when a meteorite from Mars, labeled ALH84001, was opened to reveal organic-looking structures that could have been formed by life on Mars. This possibility sparked the interest of many people, including those who fund NASA and other organizations worldwide. Thousands of scientists now work in this field.

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Finding other potential homes for life in the solar system is one facet of astrobiology. Finding homes beyond the solar system is another. The number of known exoplanets has passed 1700. Although most are Jupiterlike (that is, hydrogen-rich bodies), Earthlike planets such as Gliese 581d and HD85512b are now being discovered. Some exoplanets are known to have atmospheres. Some of these planets may have liquid water on their surfaces.

The search for advanced civilizations is also underway. It began on Earth, in the form of people who believe they have seen aliens or, more commonly, their UFO spacecraft. Beliefs are one thing; scientific evidence is something else. Despite all of the alleged UFO sightings and personal encounters that have been reported, no one has produced a single piece of physical evidence to convince scientists that an intelligent, extraterrestrial life-form has ever visited Earth. Furthermore, despite all of the wonderful science-fiction books, movies, and TV shows, there is no known way for spacecraft to travel faster than the speed of light. Therefore, unless they come from planets around the few stars within a few light-years of Earth, aliens would have to travel for centuries, or even millenia, to span the void of space between their worlds and ours. After all that travel time, it would seem illogical for space visitors not to communicate with us and eventually land here.

Searches for extraterrestrial intelligence (SETI) in space began in 1960, when the American astronomer Frank Drake carried out Project Ozma (named after the ruler of the fictional land of Oz in L. Frank Baum’s series of books). Drake used a radio telescope at the National Radio Astronomy Observatory in West Virginia to “listen” for radio signals from civilizations that might have existed around two Sunlike stars: τ (tau) Ceti and ϵ (epsilon) Eridani. He heard nothing.