SUNSET: 
Dawn Arrives at Vesta
NASA's spacecraft Dawn entered orbit around Vesta on July 16th and is preparing for a year's observation of the second-largest body in the asteroid belt.
More on Saturn's Thunderstorm
Two studies reveal that the white smear across Saturn's northern face was caused by a deep seated thunder storm that discharged powerful lightning bolts for days on end.
The Truth About Neptune's Spin
By tracking two visible features in Neptune's atmosphere, a University of Arizona astronomer has clocked a new spin rate for the blue planet. But does this mean the Voyager results from 1989 are wrong?
Asteroid Flyby Yields New Thinking
When the little asteroid 2011 MD zipped within 8,000 miles of Earth in late June, dynamicists realized they need to change the way they compute such close flybys.
Two More Moonlets for Jupiter
Astronomers have discovered a pair of tiny satellites traveling far from Jupiter. So which planet — Jupiter or Saturn — now has the most moons?
Saltwater Ocean on Enceladus
Recent findings hint at the possibility of a saltwater ocean beneath Enceladus's icy surface.
Odd Couple: Phobos and Jupiter
Recently two very different bodies made a joint appearance, as viewed by the stereo camera aboard the European orbiter Mars Express.
Messenger Reveals Mercury Anew
Already a fourth of the way through its basic mission, NASA's well-equipped orbiter has found that the "Iron Planet" is far different than planetary scientists expected.
Meteorite Cooks Up Its Organic Brew
A dash of this and a pinch of that — slow cooked with water inside an asteroid — could have yielded a rich and diverse soup of organic matter. That's the remarkable new finding from careful analysis of the super-primitive Tagish Lake meteorite.
Dissecting Saturn's Big Storm
Scientists have combined images from Cassini and big telescopic eyes in Chile to understand Saturn's massive storm in ways never before possible.
Praising Arizona — II
S&T contributing editor Govert Schilling visits observatories in southern Arizona.
Praising Arizona — I
S&T contributing editor Govert Schilling visits observatories in southern Arizona
New Insights on Lunar Swirls
Comet impacts? Magnetic oddities? Crashed alien spaceships? Soon scientists hope to solve the longstanding mystery of bright swirls like Reiner Gamma on the lunar surface.
Messenger: Mercury's New Moon
The fleet-footed planet of the ancients has a new companion — a NASA spacecraft that will now call it home after a convoluted, 6½-year-long, 5-billion-mile interplanetary cruise.
What Makes Iapetus So Weird?
Now that scientists have puzzled out this moon's yin-yang appearance, they're tackling the cause of its out-of-round shape, slow spin, and bizarre equatorial ridge.
Is Water Flowing on Mars?
Spacecraft images are keeping an eye on little surface flows on Mars that show up in midsummer, then fade over time. It's the strongest suggestion yet that the Red Planet can get wet.
Remembering James Elliot, 1943–2011
The co-discoverer of Uranus's rings and Pluto's atmosphere has passed away at age 67.
Game Plan for NASA's Planetary Missions
If you had billions of dollars to spend on interplanetary spacecraft, which ones would you choose and why? After an exhaustive, two-year assessment, a blue-ribbon panel turned over its top picks to NASA.
A New Take on the Spotless Sun
A trio of researchers believe a slow-moving conveyor belt between the Sun's equator and its poles is responsible for the recent years-long absence of sunspots.
Double Whammy on Mars
On January 10th, NASA's Mars Reconnaissance Orbiter spotted twin craters joined at the rim — the consequence of equal-size halves of a single object striking the planet together.
