Meteors and meteorites provide important clues to understand the history of the solar system, the formation of stars and planets, and the origins of life on Earth. Their study has evolved along with many aspects of astronomy: changes in our concept of the Universe and our place in it, the knowledge of different types of astronomical objects, and attitudes about how science is made and who can participate in it.
The Science of Meteoritics
Meteoritics is the branch of science that deals with meteoroids, meteors, and meteorites. Meteoroids are objects travelling in space that range from tiny dust particles to small asteroids. A meteor is a meteoroid that enters the Earth’s atmosphere and burns up due to friction, producing a shooting star or a fireball (as in the artistic rendition shown here). The rocky and metallic fragments that hit the Earth’s surface are called meteorites. The understanding of these phenomena took centuries to evolve, and counted on our intrinsic human curiosity about the sky above and how we are connected with it.
Oddities From Above
This illustration from a 16th-century treatise on celestial wonders shows townsfolk contemplating what was possibly a shooting star or fireball, or maybe a comet. The trumpet highlights that these celestial events were often regarded as omens or messages from the heavens. Their meaning generated great curiosity and debate, but it look long before their origins and physical causes could be satisfactorily understood.
A Sky that Does not Change
This 17th century engraving illustrates the way the Ancient Greek philosopher, Aristotle, conceptualized the cosmos. The immobile Earth is surrounded by moving spheres that carry the Moon, the Sun, the planets, and the stars. According to Aristotle, below the Moon’s sphere everything is made out of four elements: earth, water, air, and fire. The heavens beyond are made of a fifth element, the ether, and are perfect and immutable. In this conception, it was inconceivable that phenomena such as meteors, fireballs, or comets could actually originate in space, therefore they were regarded as atmospheric events.
Stones do Fall From the Sky
These artistic illustrations show fireballs observed in the late 19th century. Reports of fireballs accompanied by the fall of iron or stony objects go back to ancient times, and some of those objects were kept and thought of as sacred. But by the 18th century, scholars remained generally dismissive of popular accounts of such events, deeming them fanciful and as expressions of superstition and ignorance. By the turn of the 19th century, with a growing number of reports on fireballs accompanied by falling stones from various parts of the world, they started to change their minds.
Collecting Space Rocks
This photograph shows visitors looking at a meteorite in the Adler Planetarium, which is home to a small but significant collection of meteorites. Meteorite collections started to be assembled by scholars and amateurs from the late 18th century onwards. These collections allow for the systematic and comparative study of meteorites of different types and origins. By the turn of the 19th century, the comparative analysis of the various meteorite samples led scientists to accept that they could have an originated outside of the Earth.
Where do Space Rocks Come From?
This 19th-century print illustrates the conception of the Universe supported by Isaac Newton and his followers: stars including the Sun (at the center) are evenly distributed in space, each possibly surrounded by its own planetary system. But space is otherwise empty. Where do meteorites come from then? Constrained by this conception, some scholars suggested, in the way of Aristotle, that meteorites actually form in the atmosphere. Others suggested that all meteorites are pieces of the Moon (some actually are, but only a small fraction). New astronomical discoveries in the 19th century led to different explanations.
The Origins of Meteorites
The solar system is shown in this 19th-century illustration with the few asteroids that were known to exist by the mid-1850s. The first one was discovered in 1801; by the end of the 19th-century, more than 500 had been found, and the number kept on growing (the count is now over 800,000). The illustration also shows the orbit of a comet. During the 1800s, a consensus developed around the idea that meteorites originated from different parent bodies, and that most of them came from asteroids, comets, or interstellar space.
The Leonids meteor storm of 12-13 November 1833 was seen throughout the United States and proved important in setting the scenes for modern meteor science. “Leonids” refers to the fact that the meteors seem to radiate from a point in the constellation of Leo, the Lion. The 1833 event is shown here with artistic license, resembling a fireworks display. The storm generated great popular interest and triggered debates about its theological implications. The press took advantage of this popular interest, and dramatic but misleading images such as the one shown here increased the hype around this kind of phenomenon.
The Link Between Comets and Meteor Showers
Meteor showers such as the Perseids (in which meteors radiate from the constellation of Perseus) and the Leonids happen every year, in August and November respectively. The number of observed meteors per hour varies from year to year. In the 1860s, the Italian astronomer Giovanni Schiaparelli found a connection between the orbits of comets and meteor showers, concluding that these events take place when the Earth crosses the trail of dust and particles left by a certain comet in its passage through the inner solar system. Those particles burn up when they enter the Earth’s atmosphere, resulting in swarms of meteors. Schiaparelli ascribed the Perseids to the comet Swift-Tuttle, and the Leonids to the comet Tempel-Tuttle.
All Eyes on the Sky
With Paris in the background, two observers contemplate the Andromedids of Nov. 27, 1872, a meteor shower that caused an impression in that year, but which is now quite modest. Meteor science is one of the few research fields to which amateur observers can contribute just by using their eyes to watch the skies attentively for meteors and fireballs. Organizations such as the American Meteor Society, founded in 1911, or the International Meteor Organization, in operation since 1988, play a crucial role in mobilizing hundreds of amateurs around the world and gathering their observations.
Making an Impact
Amateurs have also played an important role in advancing our knowledge about meteorites and their influence on Earth’s history. Such was the case of Harvey H. Nininger, a self-taught meteorite researcher and collector. Nininger was a keen promoter of the idea that what is now known as the Meteor Crater in Arizona, shown here, resulted from a meteoritic impact. The idea was initially met with resistance, but it is now accepted that the crater resulted from an impact of a 40- to 50-meter iron-nickel asteroid some 50,000 years ago. Nininger’s large meteorite collection is now split by a few institutions, including the Adler Planetarium, which houses roughly 70 meteorites that were originally gathered by this amateur researcher.
Will the Sky Fall on Our Heads?
The rock shown here on display at the Adler Planetarium is a fragment of a car-sized meteoroid that flashed through the sky over Chicago’s south suburbs and exploded on March 26, 2003. The fragment crashed through the kitchen ceiling of a couple’s home in Olympia Fields at over 200 miles (322 kilometers) per hour, before ending up in a pile of laundry in the basement. While such chunks of rock and metal fall into the Earth’s atmosphere fairly frequently, most burn up during entry, and observed impacts in populated areas are very rare.
Messengers from Other Worlds
Adler’s meteorite collection includes meteorites from asteroids, the Moon, and even Mars. Studying the composition of meteorites like these gives astronomers information about how objects in our solar system formed and evolved. For example, one of our Martian meteorites is about 200 million years old and is composed of rock that formed from cooling magma, which gives clues to the history of geologic activity on the red planet. Some meteorites contain chondrules, small pieces of material that date back to the formation of our solar system 4.56 billion years ago. Getting to hold a piece of this history in your hands, whether it’s a rock from the moon, from Mars, or from our early solar system, is an exciting opportunity for scientists and Adler guests alike.
Searching for Meteorites in Lake Michigan
The Aquarius Project engages teen explorers from Chicago with the search for fragments of a meteorite nearly the size of a minivan that crashed into Lake Michigan on February 6, 2017. Not only are these teens keen participants in the research conducted by the project, they actively share their stories about it through a podcast and a blog titled “The Aquarius Project: The First Student-Driven Underwater Meteorite Hunt." By using modern media to address their adventures and achievements as well as their setbacks and lessons learned, they inspire fellow young explorers to embrace the joys and challenges of scientific research.
Thank you to the staff of the Adler Planetarium for their assistance in creating this exhibition.
Special thanks to our generous supporters:
Amy and Steve Louis Foundation
Roderick and Marjorie Webster Fund at The Chicago Community Trust