Amphibians are disappearing in the United States at an unexpectedly brisk pace. More disturbing,  according to a report this week from the U.S. Geological Survey, the more rare the species of toad, frog or salamander, the higher the risk of decline.

The author's sobering conclusion: “This analysis suggests that amphibian declines may be more widespread and severe than previously realized.”

The study found that on average, populations of amphibians vanished at a rate of 3.7 percent each year. At that rate, those species would disappear from half their current habitats in about 20...

Wearing an ear-to-ear smile and her hair slightly frizzy from her helmet, Caltech junior Curie Ahn craned her neck up toward the sky, her eyes still wide from the adrenaline.

“I was actually pretty terrified,” the biology major said. “I’m a little bit afraid of heights.”

Afraid or not, Ahn didn’t have much of a choice when the senior class gave her the task of rappelling about 60 feet down the side of one of the school’s buildings Friday. It was “Ditch Day” at Caltech, and overcoming the senior class obstacles is tradition.

Caltech...

Looks can be deceiving, especially when it comes to nebulae.

From here on Earth, the well-studied Ring Nebula looks like a fiery, slightly misshapen ring with fuzzy edges and a hole in its center.

But using data collected from the Hubble Telescope, and land-based observations, astronomers have revealed that the shape of the Ring Nebula is more complex than previously thought.

PHOTOS: Amazing images from space

It turns out that what looks like an empty space in the center of the nebula is actually filled with low-density material that stretches toward Earth and away from us.

If we could rotate...

Need more blood donors? Economists have a suggestion: Pay them.

For nearly 40 years, efforts to compensate people for donating blood have been discouraged by the World Health Organization. In the United States, the American Red Cross says “all blood collected for transfusion in the United States must be from volunteer donors.”

But the authors of an essaypublished in Friday’s edition of Science challenge the rationale for such policies, which presume that the highest-quality blood comes from altruistic donors. The types of people who would donate blood only if offered...

Federal wildlife officials on Friday for the first time agreed not to prosecute a developer if an endangered California condor is struck and killed by turbine blades at its proposed wind farm in the Tehachapi Mountains, about 100 miles north of Los Angeles.

In granting a right-of-way, the U.S. Bureau of Land Management, with approval of the U.S. Fish and Wildlife Service, will shield Alta Windpower Development from prosecution if a condor is fatally injured at its 2,300-acre site near the high-desert town of Mojave during the projected 30-year lifetime of the project.

The Fish and Wildlife...

At the beginning of this week, the wind's fury was unleashed on the Oklahoma city of Moore. As the extent of the devastation has unfolded over the past several days, it's a bit of an understatement to say that Moore has been unlucky.

The tornado was estimated to have followed a path nearly 20 miles long, remaining on the ground for about 50 minutes. Most tornadoes end within 10 minutes.

LIVE VIDEO DISCUSSION: Join us at 11 a.m. Pacific time

Meteorologists in the National Weather Service's forecast office in Norman upgraded Monday's storm to the highest severity a tornado can achieve on the...

NASA Administrator Charles Bolden dropped by JPL on Thursday to outline the agency's plans to capture an asteroid, and to look at a model of a powerful new ion thruster that has enough strength to drag a space rock into orbit around the moon.

NASA unveiled a multistep plan to rendezvous with a smallish asteroid, put it in what looks like a giant reflective garbage bag, and bring it into lunar orbit, earlier this year.

Once the space rock is in a stable orbit around the moon, astronauts could land on it and bring small chunks of it back to Earth.

"This is the first chance humanity has to...

It’s common knowledge that Americans don’t get enough exercise – young Americans too. And the Institute of Medicine issued a report on Thursday calling on schools and government at all levels to make sure that all students get an hour a day of “vigorous or moderate-intensity” physical activity.

That would be a big change in schools all over the country.

The surgeon general has urged all school systems to require 150 minutes per week of physical education; as of 2006, only 3.8% of elementary schools had done so. The report notes that estimates suggest that only...

The leading cause of death during Superstorm Sandy last fall was drowning, according to a new report released by the Centers for Disease Control and Prevention.

The report, which analyzed 117 storm-related deaths, comes amid a National Oceanic and Atmospheric Administration warning that this year's hurricane season stands a good chance of being more active than usual. In its annual Atlantic hurricane season outlook, NOAA forecasters said Thursday that there was a 70% likelihood of three to six major hurricanes occurring this year. The seasonal average for such major storms is three.

In its...

Scientists are gaining a better understanding of the H7N9 bird flu that has sickened more than 130 people -- and killed more than 30 -- in China and Taiwan since February.

The latest research into the virus, which before this year had never been detected in humans, was published Thursday (subscription required for full text) in the online edition of the journal Science. 

Working with ferrets, an animal that is often studied to gain insight into flu transmissibility in people, scientists in China, Canada and the U.S. found that H7N9 could spread from one ferret to another -- suggesting that it...

Three astronauts who recently returned to Earth after living aboard the International Space Station will answer questions from the public in a live Google Hangout on Thursday.

The online chat starts at noon PDT, and you can watch it live right here.

(The video stream above will switch to the hangout at noon.)

If you've been wondering what it feels like to sweat through a heated reentry to Earth in the Soyuz capsule, or how foreboding a normal flight of stairs looks after months spent in zero gravity, now is your chance to ask three men with first-hand experience.

T...