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.
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.
Read More: 4 Facts About Asteroids You May Not Have Known
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.
According to the Jet Propulsion Laboratory of the California Institute of Technology, meteoroids can also be debris from planets and comets.
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.
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.
Elements Meteorites Bring 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.
Stony Meteorites contain mostly silicate minerals and are the most common type of meteorite found.
Stony-iron meteorites typically consist of equal parts iron-nickel and silicate minerals — which can include semi-precious gemstones like olivine.
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. 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."
These 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.
Read More: Here’s What Meteors Streaking Toward Earth Look Like From Space