Cradle of Life As We Know It
Earth is the only place we know of in the universe that harbors life. Ours is the largest terrestrial planet in the solar system. Our rocky, volcanic world is coated in a thin veneer of liquid water, living things, and translucent atmosphere, whose complicated interactions make Earth's surface into a place of constant change. We humans have only had fifty years of perspective on Earth as a planet, of seeing it as a "pale blue dot" floating in the black vacuum of space.
With that perspective, we know precious and unique our planet is. We know, too, that we are having measurable effects on the complex interactions of ocean, land, life, water, and air, changing our climate. But predicting the future of our climate is hard. Understanding how Earth's systems work by studying the way they operate on other worlds is a major goal of planetary exploration. Mars, Venus, and Titan all have (or had) active geology, hydrology, and weather -- but, as far as we know, they don't have life. Is Earth really that unique? Are we truly alone in the universe? We won't know unless we keep searching.
News from Earth
A pile of Chang'e 3 photos has been released to the Web, and they are much, much better than what I've seen before. They include, for the first time, photos of Earth from the lander.
If there's one thing I've learned after decades of studying the first human voyages to another world, it's that there is always more to discover about Apollo. Case in point: The Apollo 8 Earthrise photo that became one of the iconic images of the 20th century.
Earth's Place in Space
In 2016, The Planetary Society’s LightSail program will take the technology a step further.