Kepler is NASA's first mission capable of finding habitable planets orbiting other stars in our galaxy. This overview from NASA explains how Kepler works, and why it matters. 

In "NASA's Planet Hunter Needs Money to Continue the Search for Earth's Twins," Alexis Madrigal argues that even though Kepler's funding is in jeopardy, it's our "moral imperative" to continue searching:

Other earths - rocky planets with liquid water and a decent atmosphere - would have the raw materials for life as we know it. Kepler can tell us how many of these earth-like planets there are, bringing us one huge step to answering one of the most profound questions in science: are we alone? If we are, that'll be one stunning answer. If we aren't, that'll be a different kind of stunning answer.

Either way, for my values, there is a moral imperative to answer this question. Finding life outside the earth could reshape the way humanity thinks about itself. The discovery of extraterrestrial life will mark an epoch in a way that even the moonshot did not. When (and it seems like when not if) we find another earth, the real space age will begin.

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