Nell Greenfieldboyce

Asteroid experts have been simulating a large asteroid heading towards Earth. Friday is the conclusion to the realistic simulation and will reveal how well planetary defense efforts work in this scenario.

A fictitious asteroid is the focus of a realistic exercise, as experts at the Planetary Defense Conference run through how they would respond to news of a looming asteroid strike.

The cells regained a startling amount of function, but the brains didn't have activity linked with consciousness. Ethicists see challenges to assumptions about the irreversible nature of brain death.

The swirling mass around a black hole is called an "event horizon," the point of no return beyond which not even light can escape. Scientists unveiled the first image of this on Wednesday.

On April 1, astronomers will start two huge machines and continue hunting for ripples in space-time. One scientist gets his mom to translate news of each discovery into her native language, Blackfoot.

The Salt Institute spent decades questioning government efforts to limit Americans' sodium intake. Critics say the institute muddied the links between salt and health. Now it has shut its doors.

Female mosquitoes searching for a meal of blood detect people partly by using a special olfactory receptor to home in on our sweat. The finding could lead to new approaches for better repellents.

The first all-female spacewalk was called off for want of the right-sized spacesuit. NASA has long been questioned about how its limited number of suit sizes disproportionately affects women.

The twin sites in the Laser Interferometer Gravitational-Wave Observatory are about to go back online. New hardware should make them able to sense more colliding black holes and other cosmic events.

For years, NASA has had to rely on Russian vehicles to get astronauts to the International Space Station. That could soon change if the flight test of SpaceX's Crew Dragon capsule succeeds.

As the 50th anniversary of the Apollo 11 lunar landing nears, some say the site of the first footprints on the moon should be protected. But historic preservation off our planet is unprecedented.

Martin Luther King Jr. dealt with anger in both his personal life and life's work. He often tried to turn his anger into constructive action, but he did occasionally struggle with that balance.

Sound travels differently through open fields than the woods. When deer eat up bushes, small trees and other forest plants, it affects the transmission of bird calls and other natural sounds.

Physicians have been taught to look for signs of hopelessness, sadness and lack of motivation to help them diagnose depression. But anger as a depression symptom is less often noticed or addressed.

A new study shows that Saturn's rings are only 10 million to 100 million years old, much younger than the planet itself.

Analysis of fossilized dental tartar of a medieval woman buried in a German monastery reveals specks of blue to be lapis lazuli — a luxurious pigment used to create gorgeous illuminated manuscripts.

There's an effort underway to make a new atlas of all the cells in the human body, and to describe each cell type using all the powerful tools of today's genetic technology.

China's space program has landed a wheeled rover on the far side of the moon that's never seen from Earth. It's part of a systematic plan that the country has for space exploration.

Scientists say Ultima Thule, a newly explored world out beyond Pluto, is a relic from our solar system's earliest days.

Minutes after the turn of the new year, NASA's New Horizons probe will fly by a minor planet in the most distant exploration of a world ever attempted.