What do meteorites tell us

All groups of carbonaceous chondrites are marked with a two- or three-letter code starting with C. Carbonaceous chondrites are often named after the first specimen of that type recovered.

The CI group, for instance, is named after the Ivuna meteorite, which crashed into Tanzania in CI meteorites have a high amount of carbon, as well as clay s. Carbonaceous chondrites can also be named after the place where the first specimen of the type was found.

The CV group is named after a meteorite that crashed near the city of Vigarano, Italy, in The Allende meteorite has thousands of tiny chondrules made of the mineral olivine. The Allende meteorite also has grains of a special kind of carbon—diamonds. These diamonds are actually older than the solar system, and astronomers think they were produced as blast material from a nearby, ancient supernova. Achondrite s do not contain the lava droplets chondrules present in chondrites.

They are very rare, making up about 3 percent of all known meteorites. There are many classifications of achondrites. Lunar meteorites are achondrites that crashed to Earth from the Moon, while Martian achondrites crashed to Earth from our neighbor planet, Mars. Very few meteorites, only about 0.

Large meteorites hit the surface of Mars and the Moon, blasting off bits of rock. Iron meteorite s are mostly made of iron and nickel. They come from the core s of asteroids and account for about 5 percent of meteorites on Earth.

Iron meteorites are the most massive meteorites ever discovered. Stony-iron meteorite s have nearly equal amounts of silicate minerals chemicals that contain the elements silicon and oxygen and metals iron and nickel. One group of stony-iron meteorites, the pallasite s, contains yellow-green olivine crystals encased in shiny metal.

The largest meteorites leave enormous holes in the ground called impact craters. The best-preserved impact crater in the world is the Barringer Meteorite Crater, near Winslow, Arizona. There, more than 50, years ago, a meteorite weighing about , metric tons , tons slammed into the Earth with the force of 2.

The impact blasted a hole 1 kilometer. The fragment s left of the space rock show that it was an iron meteorite. More than a hundred impact craters have been identified on Earth.

Perhaps the most famous is the Chicxulub Crater, in Yucatan, Mexico. The Chicxulub Crater can be identified on land, beneath dozens of meters of sediment , although about half of the feature is submerge d in the Gulf of Mexico.

It is one of the larges impact craters ever discovered on Earth. Despite its size, the Chicxulub Craber is famous for another reason. Many scientists think the large meteorite that created the Chicxulub Crater—measuring roughly 10 kilometers 6 miles wide— trigger ed the extinction of the dinosaur s and other animal and plant life 65 million years ago. Deserts, such as Saudi Arabia above and Antarctica, are excellent places to search for meteorites.

Photograph by Thomas J. Abercrombie, National Geographic. Natural Hazards. Most meteorites fall to Earth harmlessly. Sometimes, however, they can cause great damage. The extinction of most life on Earth 65 million years ago is a good example of that. A less catastrophic impact hit a driveway in Peekskill, New York, in Although no one was harmed, the meteorite slammed through the trunk of a parked Chevrolet Malibu, barely missing the gas tank, before creating a small impact crater beneath the car.

The Chevy is nicknamed the "Peekskill Meteorite Car. Ablation Blackening. Thermal ablation, the process that burns off the surface layer of a meteorite and causes it to appear blackened, is the same process that blackens the outside of returning spacecraft, such as tiles on the space shuttle. Mars and the Moon. The meteorites in the Antarctic collection inspire and direct these new space missions, as well as help scientists analyze the material that comes back.

With each new meteorite collected and studied, scientists answer and ask new questions about the early stages of our solar system. You can find her at erinmalsbury. Smithsonian Voices From the Smithsonian Museums. A meteorite in the process of being recovered by volunteers in the Antarctic Search for Meteorites program. The shiny fusion crust on this meteorite suggests it may be an achondrite. ANSMET In mid-January of , a group of men lugged hundreds of pounds of supplies through fierce Antarctic winds, biting cold and dangerous crevasses for over a thousand miles.

Why Antarctica? Gaelen Marsden The team also faces psychological challenges. The meteorites stay inside a nitrogen-filled container, even while scientists work with them. What can meteorites tell us? Chondrite meteorites are made up of smaller chondrules that scientists use to study the origins of the rock. Asteroids are rocky bodies, less than kilometers across, that orbit our Sun. Asteroids occur in the asteroid belt between Mars and Jupiter.

Comets are masses of ice and dust, less than 10 kilometers across, that usually stay in the cold outer reaches of our solar system. Meteoroids are small pieces of asteroids or comets. Where Do Meteorites Come From? Most meteorites appear to come from asteroids. This is based on a comparison of the composition of meteorites with our understanding of the composition of asteroids, based on remote sensing. It also is based on a comparison of the orbits of asteroids and the orbits of meteoroids, calculated from photographs of the meteoroids as they approached Earth.

A few meteorites are from the Moon and Mars. These are pieces of the planets that were broken off and knocked into orbit when asteroids struck the planets. Meteorites from the Moon are similar to the samples collected by the Apollo astronauts. The Mars meteorites include sealed pockets of gas that scientists discovered contain the same gases as occur in the atmosphere of Mars.

Comets as Meteoroid Sources Rarely, meteorites may also come from comets. Most comets are found at the outer edge of the solar system — beyond the orbit of Pluto — in a region called the Kuiper belt.

Some comets reside even farther away in a large spherical cloud around our solar system called the Oort cloud. Comets are so far away from the Sun that they remain frozen; they are important relics from the earliest times of our solar system. Some comets do orbit our Sun in periodic, elliptical paths. Comets are nearly invisible except when they get close to the Sun. Heat from the Sun vaporizes the ice on the comet's surface causing gas and dust to flow away and form the cloud of the coma.

The solar wind — the flow of particles out from the Sun — sweeps the coma away into a long tail. The tail always points away from the Sun because of the solar wind, no matter what direction the comet is moving in its orbit. The tail actually has twin pieces, a gas tail and a dust tail , that can extend for millions of kilometers from the comet nucleus as it travels around the Sun.

As the comet gets very close to the Sun, small pieces of dust, rock grains, and ice are left behind as a trail of meteoroids. Meteor showers occur when Earth passes through the trail of dust and gas left by a comet.

What are Meteorites Made Of? Scientists classify meteorites into three groups: stony meteorites, iron meteorites, and stony iron meteorites. What Do Meteorites Tell Us? Meteorites provide us with information about the processes and materials in our early solar system. The early solar system did not consist of a sun and planets. It was a spinning cloud of dust and hydrogen gas that was hotter in the center and cooler toward the edges. As the gas and dust began to come together, chondrules — tiny spheres of minerals containing silica — condensed.

These tiny spheres and dust gradually grew as other particles collided with them and became attached — a process called accretion.

Some of the particles grew to the point that they were large enough to gravitationally attract other particles, and they accreted all the material in their path as they orbited the young Sun — some of these became our planets. Other particles remained small, space rocks left behind after the planets formed. Accretion is a hot process; when a particle slams into another particle, its motion is converted to heat.

The planets and some of the space rocks became so hot that they began to change, in some cases melting. Melting allowed the bodies to differentiate, with the heavier metals of iron and nickel sinking into a central core, and the lighter materials making a mantle and outer crust. Not much when it is in space. Actually, it is the air in front of the meteoroid that heats up.