Clemson astrophysicists tell us about asteroids and whether we need to worry 

Earlier this year, a “city killer” asteroid made major headlines for its slim chance of striking Earth in 2032. NASA now says that asteroid poses no threat to our planet (but there’s still a chance it could hit the Moon).

So, what are these looming threats in space? The dinosaurs’ downfall, asteroids are rocky structures left over from the solar system’s formation. In honor of Asteroid Day on June 30, we interviewed two Clemson University Department of Physics and Astronomy faculty members — physics and astronomy Professor Marco Ajello and lecturer Frank Gyngard — to learn more about asteroids.

What are asteroids?

Dust – defined by astronomers as heavy materials found in space, anything bigger than hydrogen and helium — sticks together and eventually becomes rocks. These rocks may continue this process to become an asteroid, which could one day, with enough material, turn into a planet. 

Asteroids typically orbit between Mars and Jupiter (due to Jupiter’s gravitational pull) and come in all shapes and sizes. Typically, asteroids are smaller than moons. Scientists hypothesize that asteroids are leftovers from planets that never formed.

Some asteroids are just groups of rocks held loosely together by gravity. They contain rare-earth elements, critical components of computers, smartphones and other electronic devices that people have considered mining to bring back to Earth. 

Asteroid impacts

Mercury and Mars both have many impact craters, indicating that in the first billion years of our solar system asteroids were more abundant. Planets and moons were continuously bombarded. Signs of bombardment are less visible on Earth due to geological processes, such as plate tectonics, which recycle the Earth’s surface every few million years. As our solar system ages, asteroid impacts have become rarer.

“The asteroid that killed the dinosaurs was around a billion times the energy of the nuclear bombs that we dropped on Japan in World War II,” Gyngard says. It was about 10 miles in diameter when it hit off the coast of what is now Mexico. This asteroid led to the extinction of two-thirds of all species on Earth.

More recent asteroid strikes have left less catastrophic but still impressive marks. Meteor Crater in Arizona remains as evidence of an asteroid strike from approximately 50,000 years ago. In 1908, an asteroid exploded over Siberia and flattened a forest. In 2013, vehicle dash cameras and other surveillance cameras captured asteroids falling from space in Russia. 

Another of note is the Oumuamua asteroid that scientists discovered “wandering through the Milky Way” in 2017, although some scientists believe it was a comet. Oumuamua translates to traveler in Hawaiian. This asteroid is especially fascinating because it is the first known object to enter our solar system that did not originate in it. Oumuamua garnered special interest due to its irregular shape and unorthodox rotation

Monitoring asteroids

One function of NASA is to track the path of asteroids that have the potential to strike Earth.  Even relatively small asteroids could have catastrophic implications if they hit Earth. However, asteroids large enough to cause an extinction-level event are extremely dark, so scientists can’t see them until they come close enough to the sun. 

“It’s very important that scientists monitor asteroids because the earlier we know, the better we can react,” Ajello says.

In 2021, NASA carried out the DART (Double Asteroid Redirection Test) mission, which tested the feasibility of redirecting a threatening asteroid’s path by slamming a spacecraft into it. 

Research on asteroids

Asteroids can give scientists key insights into the formation of our solar system and the Milky Way. They contain materials that predate the formation of our solar system. 

Gyngard does research on dust grains from meteorites —smaller, broken-off pieces of asteroids colliding with each other. He investigates how stars form and evolve from this dust by measuring elements and isotopes. The particles Gyngard studies are usually at least four and a half billion years old. 

The most popular theory among scientists is that the Asteroid Belt should have been one planet. However, the gravitational pull of Jupiter and the competing gravitational pull of the Sun didn’t allow it to accrete into a planet. These rocks are snapshots of the time in space when the Milky Way formed. Unlike lots of planets, they were not exposed to water or heat. 

Most of the meteorites Gyngard studies are those that have fallen to the Earth. Some come from space, where government organizations like NASA send robotic missions to comets or the Asteroid Belt that return with samples for multiple universities.