Earth is hit by thousands of meteorites each year, according to a 2020 study published in Geology — but they're small meteorites, not planet-changing asteroids. And with those meteorites come numerous elements that are the key building blocks for life on Earth.
Until now, researchers believed that volatile elements like zinc and water might have come from asteroids that formed near Earth. However, a new study published in the journal Science indicates that these volatile elements may have come from asteroids originating closer to Jupiter, Saturn, and Uranus.
Though these small rocks have made a long journey through space, they've significantly changed our planet. Here is what meteorites bring to Earth.
What Is the Difference Between Asteroids, Meteors, and Meteorites?
If volatile elements come from asteroids, then why do they also arrive on Earth with meteorites? When it comes to space rocks, there can be some confusion between asteroids, meteoroids, meteors, and meteorites — and that's without including comets.
What Is an Asteroid?
According to NASA, asteroids are airless rocks, smaller than planets but larger than the space rocks that typically make their way through Earth's atmosphere. They are likely the leftover pieces from the formation of our solar system. Asteroids are often found in the asteroid belt — a region between Mars and Jupiter — though some are closer to Earth. Some asteroids are large enough to have their own "satellites" or objects in their orbit.
What Is a Meteoroid?
Once in a while, two asteroids may collide, breaking off a small piece of rock or dust, which sails through our solar system. The broken piece is called a meteoroid.
What Is a Meteor?
While meteoroid fragments are small, they can be seen with the naked eye as they turn into meteors that streak across the night sky after entering Earth's atmosphere. When multiple meteors fall to Earth, they form a meteor shower.
What Is a Meteorite?
Meteorites, however, are the space rocks that fall through Earth's atmosphere and actually make it to the ground. And while it may seem that meteor showers produce a lot of meteorites, the opposite is true.
Types of Meteorites Brought to Earth
Meteorites can be rich in elements such as metals and silicate crystals. According to the Natural History Museum in London, there are three types of meteorites: iron, stony, and stony-iron.
Iron meteorites usually contain iron-nickel metal and trace amounts of sulfide and carbide minerals. Experts believe that these meteorites are part of an asteroid core that melted. ted.
Stony Meteorites contain mostly silicate minerals and are the most common type of meteorite found.
The Right Element
As the recent study suggests, meteorites may be responsible for bringing volatile elements like water and zinc to our planet from beyond the asteroid belt.
What Are Volatile Elements?
Volatiles are "elements or compounds that change from solid or liquid state into vapor at relatively low temperatures," according to a press release.
"This contribution of outer solar system material played a vital role in establishing the Earth's inventory of volatile chemicals," says senior study author Mark Rehkämper in a press release. "It looks as though without the contribution of outer solar system material, the Earth would have a much lower amount of volatiles than we know it today – making it drier and potentially unable to nourish and sustain life."
Most Common Earth Elements
Meteorites contain the six most common elements found in living things: oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus. These six elements, combined with other volatiles like water and zinc, may have helped establish life as we know it.
Even though the elements found on meteorites are also found on Earth, the addition of these elements and compounds from our solar system may have helped make our planet livable. Space rocks continue to help scientists better understand the origins of our solar system and how planets are formed. While these meteorites may not have left large impact craters, they have impacted Earth in other ways.
Frequently Asked Questions About Meteors and Meteorites
What Are Meteors Made Of?
Meteors are primarily made up of small fragments from meteoroids, which themselves can be debris from asteroids, planets, or comets. These fragments typically consist of various metals and silicate minerals.
What Does a Meteor Look Like?
A meteor appears as a bright streak of light in the night sky, often referred to as a "shooting star." This streak is caused by the meteoroid fragment burning up due to friction as it enters Earth's atmosphere.
What Are Meteorites Made Of?
Meteorites are composed of materials such as iron-nickel alloys, silicate minerals, and sometimes semi-precious stones like olivine. They are generally classified into three types: iron meteorites from asteroid cores, stony meteorites similar to Earth's crust, and stony-iron meteorites representing a mix of metallic and rocky materials.
How to Identify a Meteorite?
Meteorites are identified by their high metal content, particularly iron-nickel alloys, and their fusion crust, a thin, glassy coating formed as the meteorite's outer surface melts while passing through the atmosphere. Other features include a higher density compared to ordinary rocks and often a magnetic property due to their metal content.
What Is a Meteor Shower?
A meteor shower occurs when the Earth passes through a trail of debris left by a comet or from asteroid fragments, causing numerous meteors to streak across the night sky. These showers are named after the constellation from which the meteors appear to originate.
When Are Meteor Showers?
Meteor showers usually occur annually at predictable times when the Earth crosses specific comet debris trails. The Ursid meteor shower typically peaks around December 21 to 22 each year. Other well-known showers include the Perseids in August and the Leonids in November.
This article was originally published on Feb. 7, 2023 and has since been updated by the Discover staff.