We have much to learn from asteroids, but researching them is not just theoretical. Although most asteroids are gravitationally corralled by the planets, thousands exist on trajectories that still have potential to intersect with the planets, especially through complex interactions with other asteroids and planets. This leads to occasional collision between asteroids and the planets, and given the high relative speed of objects in space, even a small asteroid can cause devastating destruction.
The cratered face of the Moon reveals a history of impacts, mostly from the first billion years of our Solar System’s history–but since it was proven in the mid-20th century that asteroids are the source of some crater features on Earth we’ve determined that our planet is covered with the pockmarks of ancient impacts. In the 1990s researchers associated one of these impact sites as a probable cause of the extinction of the dinosaurs.
On February 15, 2013 we were viscerally reminded of the threat asteroids can pose to the Earth. Astronomers were preparing for the close flyby of a small Near Earth Asteroi Duende (then designated as 2012 DA14), which slipped between Earth and the Moon on an unprecedented close flyby.
As it did, another asteroid approached from the direction of the Sun, its orbit intersected with the Earth, and it entered the atmosphere over the Russian city of Chelyabinsk. The small rocky asteroid exploded as it heated up as it rammed through the atmosphere, creating a shockwave that shattered windows across the city, with many videos of the event captured on car dashcams.
NASA had been mandated since the 1990s to discover all of the so called “planet killer” asteroids, 1 kilometer in length or bigger, and the decreasing frequency of discoveries suggest a great many of them have been found. But the Chelyabinsk impactor was likely only 20 meters across. Even small bodies can cause citywide, nationwide, or continentwide destruction and create social, humanitarian, and economic impacts that will be felt across the globe.
Scientists continue to explore planetary defense solutions to detect and protect the Earth from such asteroids. In the early 2020s the DART mission successfully tested the ability to change an asteroid orbit with a small impactor. Even slight changes to an asteroid’s orbit years in the future can safely shift them away from impact with Earth.
But the most important step of protecting the Earth is identifying the threats–that means discovering asteroids. I’ve been privileged throughout my career to work on visualizing asteroid data with the B612 Foundation, founded by astronauts Ed Lu and Rusty Schweikart, whose orbital experiences showed them just how fragile our world truly looks from space. Inspired by this, B612 advocates for planetary defense, and in recent years helped develop their ADAM application for asteroid detection, which can comb through images observatories around the world have already taken of the sky and identify undiscovered asteroids within the data and reconstruct their orbits.
Credit: Rubin Obs./NSF/AURA
The Vera Rubin Observatory in Chile is also expected to revolutionize asteroid discovery–taking high resolution images across the sky every night. This observatory has already discovered thousands of asteroids and will provide an unprecedented perspective on the true density of small asteroids that may pose a risk to the Earth.
