Astronomers believe that every star in the galaxy has a planet, one fifth of which might harbor life. Only we haven't seen any of them — yet. Jeremy Kasdin and his team are looking to change that with the design and engineering of an extraordinary piece of equipment: a flower petal-shaped "starshade" that allows a telescope to photograph planets from 50,000 kilometers away. It is, he says, the "coolest possible science."

Ariel Anbar is a biogeochemist interested in the past and future evolution of the Earth as a habitable planet and how this knowledge informs the search for inhabited worlds beyond Earth.

NASA’s Astrobiology Program addresses three fundamental questions: How does life begin and evolve? Is there life beyond Earth and, if so, how can we detect it? What is the future of life on Earth and in the universe? In striving to answer these questions and improve understanding of biological, planetary, and cosmic phenomena and relationships among them, experts in astronomy and astrophysics, Earth and planetary sciences, microbiology and evolutionary biology, cosmochemistry, and other relevant disciplines are participating in astrobiology research and helping to advance the enterprise of space exploration.

Professor Anbar and Dr. Lev Horodyskyj further delve into the subject of habitable worlds on their online course. Could there be intelligent life on other planets? This question has piqued imagination and curiosity for decades. Explore the answer with the Drake Equation — a mathematical formula that calculates the possibility of undiscovered life.

Kepler-22b is the first confirmed planet in the “habitable zone,” the area around a star where a planet could exist with liquid water on its surface, that has been discovered by NASA's Kepler mission.

This article explains a technique scientists used to discover water on a planet 64 light years from Earth. The search for water on other planetary bodies has taken a giant leap forward. In November 2010, NASA announced that it had found substantial quantities of water on the Moon. Also, the Cassini spacecraft obtained data about one of Saturn's moons, Enceladus, that may confirm the presence of sub-surface liquid water.

While these missions scour our solar system for traces of water — a necessary condition for life — a group of scientists is looking beyond, at solar systems light years away. A recent study published in the journal Astrobiology described using infrared spectroscopy to model the dust surrounding young extrasolar stars to try to detect the presence of hydrous minerals called phyllosilicates.

This article discusses why we should consider planets with oceans in our search for extraterrestrial life. Extraterrestrial liquid water, the presence of water in its liquid state, is a subject of wide interest because it is commonly believed to be a prerequisite for extraterrestrial life.

Given the vast number of planets in the universe, many much older than Earth, why haven't we yet seen obvious signs of alien life? The potential answers to this question are numerous and intriguing, alarming and hopeful.

Launched in July, 2006, SESE (pronounced 'see-see') is a bold initiative to combine science and engineering research and education to achieve a better understanding of the universe and, especially, our home world.

For more information, check out The Extrasolar Planets Encyclopaedia.