SUNSET: 
Mars and Moon: Not Dead Yet?
The Martian and lunar surfaces were thought to be geologically dead. But twitches of recent activity are turning up in extreme closeups from orbiting spacecraft.
New Evidence for Ancient Martian Ocean
For decades planetary scientists have speculated about whether a huge depression that dominates the northern hemisphere of Mars was once flooded with water eons ago. Now radar soundings are showing that the answer might be "yes".
Wanted: Meteorites from Mercury
Dynamical oddsmakers insist that several samples of the innermost planet, blasted into space from fresh craters such as Mena, should be lying somewhere on Earth. So where are they?
GRAIL's Twins Safely Reach the Moon
Braking rockets fired on cue yesterday and today, placing twin spacecraft in lunar orbit. In the coming months, they will exploit the Moon's own gravity to revolutionize what we know about the lunar interior.
Pseudo-moons Orbit Earth
Temporary satellites are frequently caught from Earth's neighborhood and may make regular passes at being moonlets. But the objects only stick around long enough to orbit a few times before the Moon kicks them back out into the cold.
Comet Lovejoy: A Solar Survivor
The odds were stacked against it, but a comet discovered just two weeks ago has passed just 116,000 miles from the Sun's surface and — like a celestial phoenix — reemerged into view. Here's the latest on what veteran observer John Bortle calls "one of the most extraordinary events in cometary history."
Asteroids, Planets, and Moons, Oh My
This week’s meeting of the American Geophysical Union brought together a variety of interesting science results, from water on Mars to the Sun’s effect on the Moon’s surface. Here’s a selection of curiosities for your perusing pleasure.
Voyagers Detect Missing Signal
The Voyager spacecraft have observed long-sought emission from the Milky Way while traveling through the outermost reaches of the Sun’s influence.
Europa's Subsurface Lakes
Extensive lens-shaped lakes beneath the surface of Jupiter's moon Europa may explain strange features spread across the satellite's ice shell.
Hi-and-Bye Asteroid Creates a Buzz
The asteroid 2005 YU55 flew by last night exactly on track, capturing the attention of professional astronomers around the world and delighting well-prepared backyard observers.
Sunspot Points at Earth
A huge solar blemish mars the Sun’s disk, in perfect view for Earth-based observers.
Eris and Pluto: Does Size Matter?
It's been nearly a year since the dwarf planet Eris passed directly in front of a star and, in doing so, gave observers the measurements they needed to deduce its diameter. It turns out that Eris and Pluto are almost exactly the same size — and yet different in many ways.
Taking the Temperature of Ancient Mars
The famous (and infamous) Martian meteorite called ALH 84001 has revealed that the Red Planet had a warmer and wetter past — at least here and there on its surface.
Is Mercury Alive After All?
The Messenger spacecraft has discovered unusual hollow formations on Mercury's surface. No one knows what causes them, but volatile-spewing volcanoes are candidates.
Comet Water for a Parched Earth
Recent observations of comet Hartley 2 shed light on one of the oldest mysteries: where did Earth's water come from?
First Science Results from Dawn
Closer observations shed light on the history of Vesta's cratered surface, its mineral composition, and its inner iron core.
Mercury Shows Its True Colors
After six months of studying the innermost planet with NASA's Messenger spacecraft, planetary scientists are discovering unexpected surface compositions and are finally zeroing in on how the innermost planet came to be.
WISE's Survey of Near-Earth Asteroids
A heat-sensing NASA spacecraft finds that there aren't nearly as many large and midsize asteroids hovering near Earth as astronomers thought. Now we can all sleep a little easier.
One Image, Five Moons
A quintet of Saturn's moons come together in the Cassini orbiter's field of view for a group portrait.
GRAIL Heads for the Moon
By this time next year, the twin spacecraft of NASA's Gravity Recovery and Interior Laboratory mission should have given geophysicists an unprecedented peek at the lunar interior from crust to core.
