Does a massive, extremely distant planet orbit the Sun? A new analysis of distant solar-system orbits argues that it should exist.
Are enigmatic gullies seen on many steep Martian slopes caused by liquid water or instead by episodic coatings of frozen carbon dioxide?
A mechanical problem in the spacecraft's seismometer can't be fixed before the planned launch date, so NASA managers have postponed the mission until 2018.
Scientists and engineers gathered together to figure out what would make a good Martian landing site and what hurdles they’ll have to overcome for a 2035 launch.
Following a wildly popular contest, the International Astronomical Union has named 14 stars and 31 planets that orbit them.
Results from NASA's Dawn spacecraft hint that the stark brightenings in and near scores of craters on Ceres might result from salty brines seeping onto the surface.
Engineers executed an innovative contingency plan to save the Akatsuki spacecraft and place it in orbit around our sister planet.
Dynamicists predict that the larger of Mars's two moons will shatter to create a ring, slam into the planet — or both — in 20 to 40 million years.
An ultra-deep survey has turned up a sizable object situated nearly 10 billion miles from the Sun — more distant than any known solar-system object.
As ESA's comet orbiter enters its final year of operations, mission managers are deciding its fate.
Four months after New Horizons' historic flyby, mission scientists have been amazed by unexpected discoveries — and by how some preconceptions about Pluto were flat-out wrong.
NASA’s Mars orbiter MAVEN has painted a detailed picture of how the solar wind robs the Red Planet of its atmosphere.
WT1190F will burn up over the Indian Ocean on November 13th, giving researchers an unprecedented opportunity to follow its path — and figure out where it came from.
Astronomers can't decide whether the sizable object known as 2015 TB145, which is cruising past Earth today, is a renegade asteroid or a dead comet.
On October 28th, the Cassini spacecraft took its deepest dive through the water plume spewing from the south pole of Saturn’s moon Enceladus. It passed only 30 miles (50 kilometers) above the icy surface.
New Horizons' principal investigator describes the most amazing discoveries made when NASA's New Horizons spacecraft flew past Pluto last July.
The recently discovered asteroid 2015 TB145 won't come especially close to Earth on October 31st, but it's big enough to be seen in medium-size backyard telescopes.
Forget the high-octane press releases. NASA's New Horizons team has detailed the mission's early results in today's issue of Science.
A Hubble legacy program has returned high-res pictures of Jupiter, revealing changes to the Great Red Spot and mysterious new wisps in the North Equatorial Band.
Comet 67P’s nucleus was born when two became one.
A fresh batch of high-resolution images from NASA's New Horizons spacecraft shows that Charon, Pluto's largest moon, has endured a lot.
Planetary scientist Alan Stern continues his exclusive series of blogs with details of what awaits the New Horizons spacecraft when it reaches its next objective.
Thanks to the Rosetta spacecraft, researchers can follow the cycle of water escaping from the nucleus of Comet 67P/Churyumov-Gerasimenko.
New maps from NASA’s Dawn spacecraft reveal more about both the landscape and composition of the largest asteroid.
Scientists have confirmed that water-soaked salts likely create dark seasonal lines on Mars.