SUNSET: 
Mercury, Messenger, and Observers
As the first images are released from Messenger's flyby of the innermost planet, previous ground-based observations are proving to be surprisingly accurate.
A Bird's-Eye View of the Sun
What's it like to coast high over our star? The European-built spacecraft Ulysses is doing that right now — for its third and likely final time.
Reunion with Mercury
For the first time in nearly 33 years, mission controllers have guided a spacecraft past Mercury, a fire-and-ice world that may hold many keys to the solar system's formation.
Mars Dodges a Bullet
Fortified with two months of telescopic tracking, dynamicists say there's now virtually no chance that a small asteroid will strike Mars later this month.
Martian Crater Named for “Chick” Capen
A crater on Mars has been officially named for the American scientist Charles F. Capen.
A New Cycle is Dawning
It's nothing more than an inconspicuous blemish in the Sun's northern hemisphere, but a new sunspot has heralded the start of the next 11-year-long cycle of solar activity.
Cassini's Popularity Contest
After a month-long contest, the Cassini Imaging Central Laboratory for Operations (CICLOPS) has announced which images of Saturn are fan favorites.
Odds of Mars Strike Now 1-in-25
Astronomers have been watching a small asteroid that, they now say, has a 4% chance of colliding with Mars on January 30th.
Mars in the Crosshairs?
Astronomers are waiting to see what becomes of a skyscraper-size asteroid that has a 1-in-75 chance of hitting Mars in late January.
Tunguska's Blast: Less is More
Aided by high-def supercomputer simulations, two researchers now argue that small asteroids striking Earth — like what happened over Siberia in 1908 — may pose greater danger than previously believed.
David Levy's Binary Asteroid
An otherwise run-of-the-mill, main-belt asteroid named 3673 Levy just got a lot more interesting: It has a tiny moon!
Earth's Magnetosphere: On the Ropes
A constellation of five identical orbiting probes has detected skirmishes with the solar wind along Earth's magnetospheric front lines.
Deep Impact's New Assignments
Put to sleep after its smash success in 2005, one of NASA's interplanetary craft is getting a chance to search for extrasolar Earths and to visit a second comet.
Saturn's Sci-Fi Moons
Just when you thought you'd seen everything the ringed planet has to offer, the Cassini orbiter glimpses bizarre little moons shaped like flying saucers.
My Kind of Beauty Contest!
What's the most beautiful image taken by the Cassini spacecraft since it arrived at Saturn? Vote for your favorite today!
Lightning on Venus
The world next door seemed hellish enough with an atmosphere 90 times the sea-level pressure on Earth and surface temperature of 900°. Now, scientists say, there's lots of lightning — and what little water it has seems to be escaping to space.
Call for Images of Venus
Venus Express project scientists are inviting amateur and professional astronomers to contribute Earth-based images of the planet made at infrared, visible, and ultraviolet wavelengths.
Meteor Showers on Mars
Scientists now know what meteor showers occur in the rarefied atmosphere above Mars. So how come NASA's intrepid rovers can't see them?
Automated Lunar Impacts
NASA is watching the Moon to see how often it gets hit by meteoroids.
Pluto's New Family Portrait
Years of painstaking observation with some of the world's most powerful telescopes are finally showing us a glimpse of what awaits New Horizons when it reaches Pluto in 2015.