Meteorites

Introduction:

Humanity has been observing meteors for thousands of years. Many civilizations looked to the sky to see the “shooting stars” and believed that they were messages of doom from their gods.

These objects exist in all different sizes and shapes, from the tiniest grains of dust to the size of small asteroids.

Those that exist in orbit are called meteoroids. Scientists like to think of them as a kind of “space rock” and when they get too close to our Earth they are caught with gravity and most burn up in Earth’s atmosphere.

Once they enter the atmosphere, the objects are called meteors. However, anything that survives the hot burning trip and actually lands on Earth’s (or another planet’s) surface is called a meteorite.

The meteorites that have been found are usually from asteroids that have been shattered in collisions.

While this is the majority, there are some small pieces that scientists believe arrived from Venus or Mercury, but they haven’t been confirmed.

Meteorite Statistics:

When meteors enter Earth’s atmosphere they can burn so brightly that they are brighter than the planet Venus. Scientists have estimated that around 48.5 tons/44,000 kg of meteoritic debris fall on our Earth every day.

Meteors travel at tens of thousands of miles per hour and those that are smaller than a football field will be broken apart and burn up in the atmosphere of Earth.

Those that survive the atmosphere leave less than 5% of the original size as it hits the surface. They are often the size of a pebble to the size of a fist and is the reason why they are so difficult to find.

The origins of meteorites can be estimated by scientists based on a few guidelines.

The first is estimating where a meteorite has fallen so that they can calculate its orbit and reverse calculate its path back to the asteroid belt. Scientists also compare what the meteorite is made up of to see what classification it falls into and possibly its age.

How are Meteorites Named:

The Meteoritical Society is an organization that assists in all knowledge regarding meteors and meteorites. They established a method of naming meteorites by using the name of the place that it was found. If more than one meteorite was found in a single location, each would have a designation number.

Formation:

Meteorites are thought to be a key to how the planets and our solar system was formed many billions of years ago. The materials that they are made up of give scientists information about processes and conditions involved in the history of our solar system.

The materials that the meteorites are made from are part of the inside and surfaces of asteroids and are the building blocks of the planets.

Structure and Types:

Meteorite hunters are probably the best experts at finding these illusive items, and yet even the best of them often have difficulties distinguishing a meteorite from a regular Earth rock.

There are some locations such as the deserts and the frozen ice and snow areas of the Earth that make it easier to find meteorites.

Although meteorites may look like rocks from Earth, their exterior is usually burned so badly that they have a kind of shiny appearance.

This exterior is called a “fusion crust” and is formed as the outside of the meteorite melts due to the intense heat of entering Earth’s atmosphere.

There are three types of meteorites:
Iron Meteorites:
The iron meteorites are the leftovers of the core of a destroyed planet or asteroid. They are thought to originate between Jupiter and Mars in the Asteroid Belt.

This type of meteorite is the densest and you would be able to detect an iron meteorite because it’s so incredibly heavy.

The iron meteorites are also very magnetic, and most of the specimens have iron as 90-95% of their content with the rest being made up of nickel and trace elements.

Stone Meteorites:

The largest number of meteorites found fall into the stone meteorite category. These were once a part of the exterior crust of an asteroid or planet.

If they are newly fallen to the Earth the meteorite will have a black crust, but those that have been on the planet for a longer period of time look a lot like Earth rocks. Most stone meteorites contain enough iron so that they are magnetic.

Some of the stone meteorites have small, colorful granular inclusions. These small grains were part of the solar nebula before our solar system was created. The stone meteorites are considered to be some of the oldest matter that we can study to learn more about our solar system and the universe.

The stone meteorites that contain the “chondrule” grains are called “chondrites” and they contain space volcanic rock that melted from being blasted from a parent body and then cooled.

These are more difficult to find because they contain almost no iron, however, one clue is that they are often very glossy in appearance.

Stony-Iron Meteorites:

Less than 2% of all meteorites found are stony-iron meteorites. These are made up of about equal percentages of stone and nickel-iron and are believed to have formed at the mantle or core of their parent body. Stony-iron meteorites fall into two groups:

Pallasites are the most attractive of all of the meteorites because they contain nickel-iron that is surrounded by olivine crystals. The more pure the crystal, the more it is closer to an emerald-green color.

This type of olivine is also a gemstone on Earth known as peridot. When these meteorites are cut and polished the crystals become translucent.

Mesosiderites are smaller than Pallasites and have both silicates and nickel-iron, however, they also contain black and silver tones that give them an incredible beauty when they are cut and polished.

Exploration:

Our exploration missions to Mars has given us an incredible volume of information about the rocks and surface of Mars. Thanks to the scientific experiments that the Mars Rovers accomplished, we learned about the gasses trapped in Martian rocks.

Other space missions that had led to knowledge about space rocks have included the visits to the moon where astronauts brought back moon rocks.

As we find various meteorites we can compare them to the information that we already have and continue to collect to try to figure out where they came from.

NASA has established the NASA All Sky Fireball Network which consists of 17 cameras that observe, monitor, and track the various fireballs in the sky that are brighter than Venus. The network calculates both speed and trajectory of the objects.

The Canadian Meteor Orbit Radar (CMOR) is set up to detect meteoroids that are 0.04 in/1 mm across or bigger. The radar system detects speed, direction, and location.

Another location for monitoring these sky objects is Canada’s Southern Ontario Meteor Network. This is a similar setup as NASA, with 17 cameras. This automatic network updates each morning with the information taken the night before.

The International Space Station has an experiment that is called Meteor Composition Determination. The Meteor research studies what all of the meteors are made of that enter the atmosphere of Earth.

It involves high-resolution video and images and has a software program that searches for the meteor bright spots. Another part of the experiment is that it involves studying the chemistry of meteoroid dust.

Interesting Information:

So far, people have found over 50,000 meteorites on Earth.

One meteorite that has the designation of Northwest Africa (NWA) 7034 is also called “Black Beauty.” This meteorite originated from Mars and weighs 11 oz/320 grams.

Of the 50,000 meteorites found, 99.8% of them originate from asteroids. The 0.2% of the meteorites that are left come from Mars and the moon.

We have discovered 60 meteorites that have been confirmed to have come from Mars and wer blasted away due to a meteoroid impact.

Of all of the meteorites found, there are 80 that are confirmed lunar meteorites. They have similar composition to the moon rocks that were brought back by the Apollo space mission.

Due to some of the differences they are believed to come from other areas of the moon.

Important Events:

65 million years ago a huge asteroid impacted the Earth and is thought to have been the main reason for the destruction of 75% of the land and marine animals on the planet, including the dinosaurs.

The impact created a crater that is 180 mi/300 km wide and the Chicxulub Crater is at the Yucatan Peninsula. The devastation was so great that the impact through up dust and debris that encircled the globe and when it finally fell it left a layer that is now identified as the “KT Boundary.”

The Barringer Meteor Crater in Arizona is one of the few impact craters that we can see today that hasn’t been destroyed by erosion or weather.

The 0.6 mi/1 km across crater was due to a piece of iron-nickel metal meteor that was around 164 ft/50 m in diameter and struck the Earth 50,000 years ago.

Although meteorites hit the Earth all the time, it is rare for them to cause a death or injury. The first reported case occurred in 1954 when a lady in Alabama was badly bruised when an 8 lb/3.6 kg stony meteorite crashed through her roof.

In 1908, the local tribes in Tunguska, Siberia Russia reported seeing a light so bright that it looked like daylight and then an explosion. No crater was ever found and scientists believe that this meteor exploded in the air just a few miles up.

This report was the first reported firsthand sighting and the explosion was so intense that it destroyed the land and trees as far as hundreds of miles wide. Based on the studies, scientists think that the meteor was around 120 ft/37 m across and weighed nearing 220 million lbs/100 million kg.

In 2013 a fireball streaked across the Chelyabinsk sky in Russia. The meteoroid was about the size of a house and hit the atmosphere at a speed of 11 mi/18 km per second.

It exploded 14 mi/23 km above the ground and the shock wave damaged buildings and blew out windows for 200 sq mi/518 sq km. Most of the 1,600 people injured was due to glass that had been broken. Scientists believe that the explosion was comparable to 440,000 tons of TNT.

Facts about Meteorites for Kids:

• If you live in South Africa, it’s against the law to buy or sell meteorites or meteorite pieces.
• When a meteorite is seen in the sky and detected for a landing it is called a “falls.” Those people that discover the meteorite later are called “finds.”
• The odds are that every 180 years a meteorite will hit a human being. This is based on a 1985 study done by Nature.
• A meteoroid that hits the Earth’s atmosphere can travel at 130,000 mph/209,215 kmh.

Pop Culture:

There have been quite a few meteorite-based stories that have entered our society.

The 1979 movie “Meteor” was star-studded, including Sean Connery and Natalie Wood. Although the movie itself was pretty much a flop.

Part of the disaster movies of the 1970s, the world tries to fend off the impending five mile wide meteor that was going to hit Earth.

One of the most notable was the 1998 movie “Deep Impact.” As you can guess, it was one of the disaster-style films. In this case, there was a killer comet that was set to hit the Earth.

When people made the decision to try to blow it up with nuclear weapons, it split into two pieces with one piece being obliterated and the other hitting the Earth and causing a tsunami that was cataclysmic.

https://solarsystem.nasa.gov/asteroids-comets-and-meteors/meteors-and-meteorites/overview/

https://geology.com/meteorites/meteorite-types-and-classification.shtml

https://en.wikipedia.org/wiki/Meteorite

https://theplanets.org/meteorites/