精品东京热,精品动漫无码,精品动漫一区,精品动漫一区二区,精品动漫一区二区三区,精品二三四区,精品福利导航,精品福利導航。

Lately,??????? ???? ????? ????? research scientist Maria Valdes has had to remind folks that size doesn't matter, but she understands why the public is enthralled by her team's new space discovery.

On an Antarctic expedition in late December, she and three other scientists stumbled upon a 17-pound meteorite, heavier than most bowling balls and Halloween pumpkins. Only about one out of every 450 or so meteorites found on the frigid continent are this size or larger, according to an announcement by the Field Museum in Chicago where Valdes works.

Meteorites typically range between the size of a pebble and a fist, according to NASA.

"Even tiny micrometeorites can be incredibly scientifically valuable," Valdes said in a statement, "but of course, finding a big meteorite like this one is rare, and really exciting."

This Tweet is currently unavailable. It might be loading or has been removed.

Scientists estimate about 48.5 tons of billions-of-years-old meteor material rain down on the planet daily, much of which vaporizes in Earth's atmosphere or falls into the ocean, which covers over 70 percent of the planet.

More than 60,000 meteorites have been discovered on Earth. The vast majority come from asteroids, but a small sliver, about 0.2 percent, come from Mars or the moon, according to NASA. At least 175 have been identified as originating from the Red Planet.

The majority of space rocks are found in Antarctica because they're relatively easier to spot on the vast frozen plains. The dark lumps stand out against the snowy-white landscape, and even when meteorites sink into the ice, the glaciers churning beneath help to resurface the rocks on blue ice fields.

Want more scienceand tech news delivered straight to your inbox? Sign up for Mashable's Top Stories newslettertoday.

But the conditions for explorers can be brutal. The team spent days riding snowmobiles and trudging through ice, only to retreat into tents for the night. At least the trips weren't directionless, though: For the first time, this Antarctic meteorite-hunting team used satellite images as a treasure map to help identify potential new space rock sites.

Meteorites are divided into three main categories: the "irons," the "stonys," and the "stony-irons." Most meteorites that fall to Earth are stony, though the space rubble that scientists find long after landing are generally irons: they're heavier and easier to distinguish from everyday terrestrial rocks.

• A meteorite punched a hole in a dog house. Now it's a collector's item.
• The space station sprung a leak. NASA and Russia just revealed why.
• A colossal meteorite struck Mars. Then NASA made an even bigger discovery.
• Boom! NASA just slammed into an asteroid and filmed the crash
• Vigilant amateur asteroid hunters keep watch for menacing space rocks

Ryoga Maeda, one of the researchers, said the rock likely came from the main asteroid belt and crashed into Antarctica tens of thousands of years ago. He called it an "ordinary chondrite," according to an announcement from the Vrije Universiteit Brussel, meaning it's thought to be among the most common form of stony meteorite.

Scientists will need to analyze the big rock, as well as four others found on the trip, in a lab before anything conclusive can be said about its type or origin. The Royal Belgian Institute of Natural Sciences will perform the studies.

The individual researchers also will take back sediment samples to their home institutions to see if they contain tiny meteorite debris.

"Studying meteorites helps us better understand our place in the universe," Valdes said in a statement. "The bigger a sample size we have of meteorites, the better we can understand our solar system, and the better we can understand ourselves."