Most asteroids and comets don't pass anywhere near Earth. Most.
After a seven-year trip, the Cassini spacecraft arrived at Saturn in July 2004.
To what lengths do scientists have to go to snare a gravitational wave?
Water once flowed on Mars—perhaps enough to harbor life.
Two technologies to find and describe faraway planets.
The Universe's oldest light is cosmologists' newest window to the past.
Earth is increasingly vulnerable to the power of solar storms.