Which asteroids pose the greatest danger, what is the likelihood of a collision, and how devastating would an impact with Earth be? Below are 6 large asteroids that NASA is closely monitoring.
The Most Dangerous Asteroids for Earth
Approximately 66 million years ago, Earth was struck by an asteroid the size of a city. This collision released energy equivalent to the explosion of 72 trillion tons of TNT, creating a scar over 180 km wide in what is now the Yucatán Peninsula in Mexico.
The most infamous impact from this asteroid, named the Chicxulub impactor, led to the extinction of non-avian dinosaurs along with about 75% of life on Earth in an event known as the Cretaceous-Paleogene extinction.
In an effort to prevent similar catastrophic collisions, NASA’s Center for Near-Earth Object Studies (CNEOS) operates the Sentry impact monitoring system, which continuously conducts long-term analyses of the potential future orbits of potentially hazardous asteroids.
1. Asteroid Bennu
- Size: 0.49 km
- Mass: 74 million tons
Asteroid Bennu, observed on January 6, 2019, by NASA’s OSIRIS-REx spacecraft. (Photo: NASA/Goddard/University of Arizona).
Discovered in September 1999 and officially designated as “101955 Bennu (1999 RQ36)”, this near-Earth asteroid currently poses the greatest impact risk to our planet – but fortunately, not for some time.
NASA scientists estimate that when Bennu approaches Earth on September 24, 2182, there is a 0.037% chance – or 1 in 2,700 – that this asteroid will strike our planet.
To prepare for this, scientists are learning as much as possible about this carbon-rich asteroid, believed to have separated from a larger asteroid between 2 billion and 700 million years ago. On September 24, 2023, NASA’s OSIRIS-REx spacecraft returned a sample from Bennu, which has since been analyzed by research teams worldwide.
Initial results indicate that Bennu contains the building blocks of life, including simple glycine amino acids, as well as various water-containing minerals. This suggests that Bennu’s parent body experienced multiple water-related phases before breaking apart, as reported previously by Live Science.
If Bennu were to collide with Earth, it would release energy equivalent to the explosion of 1.4 billion tons of TNT, causing devastation in the vicinity but unlikely to result in global destruction. If it impacted a densely populated area, Bennu could potentially result in millions of casualties.
2. Asteroid 29075 (1950 DA)
- Size: 1.3 km
- Mass: 78 million tons
The orbit of asteroid 29075 (1950 DA), showing where it intersects with Earth’s orbit. (Photo: NASA / JPL).
The second most dangerous object is asteroid 29075 (1950 DA), which went missing after its initial discovery in February 1950 and was rediscovered 50 years later. 1950 DA is thought to be an iron-nickel-rich asteroid. Currently, it has a 0.0029% chance – or 1 in 34,500 – of impacting Earth on March 16, 2880.
If 1950 DA were to collide with Earth, it would release energy equivalent to 75 billion tons of TNT – enough to cause a global disaster capable of wiping out humanity.
3. Asteroid 2023 TL4
- Size: 0.33 km
- Mass: 47 million tons
Asteroid 2023 TL4, discovered in 2023, represents a newly identified space object that could immediately become one of the most hazardous asteroids. From observations gathered between October 8-19, 2023, astronomers calculate that 2023 TL4 has a 0.00055% chance – or 1 in 181,000 – of striking Earth on October 10, 2119. If such an impact were to occur, 2023 TL4 would release energy equivalent to the explosion of 7.5 billion tons of TNT.
4. Asteroid FT3 2007
- Size: 0.34 km
- Mass: 54 million tons
Asteroid 2007 FT3 is classified as a “lost asteroid” because astronomers have not observed it since 2007. Its orbit is currently not well constrained, but NASA predicts that this asteroid has a 0.0000096% – or 1 in 10 million – chance of colliding with us on March 3, 2030. It has a slightly lower probability of 0.0000087% – or 1 in 11.5 million – of impacting Earth on October 5, 2024.
If such an impact were to occur in 2024 or 2030, FT3 would release energy equivalent to the explosion of 2.6 billion tons of TNT – enough to cause significant regional damage but not a global disaster.
5. Asteroid 1979 XB
- Size: 0.66 km
- Mass: 390 million tons
The orbit of asteroid 1979 XB, showing where it intersects with Earth’s orbit. (Photo: NASA / JPL).
Another lost asteroid, 1979 XB, has not been observed for about 40 years and thus has an unclear orbit. According to what CNEOS scientists understand, this asteroid, first observed on December 11, 1979, has a 0.000055% – or 1 in 1.8 million – chance of impacting Earth on December 14, 2113. Such a collision would release energy similar to the explosion of 30 billion tons of TNT.
6. Asteroid 99942 Apophis
- Size: 0.34 km
- Mass: 27 million tons
It is difficult to discuss risky asteroids without mentioning 99942 Apophis. This asteroid – with a suitably apocalyptic name referencing Apep the Uncreator, the enemy of the ancient Egyptian sun god Ra – has sat on the risk asteroid table for nearly two decades.
Discovered in June 2004, Apophis was quickly identified as one of the most dangerous asteroids that could impact Earth. However, that changed in 2021 when a radar observation campaign better constrained the asteroid’s orbit. This led astronomers to conclude that Apophis, 1,100 feet (340 m) wide, poses no threat to Earth for at least the next 100 years. It is now categorized in the “cleared objects” section of the Sentry Risk table.
This means that sky watchers will be able to observe Apophis during its close approach in 2029 when it passes within 32,000 km – closer than some satellites – using binoculars and telescopes without fearing that its return in 2036 and 2068 will threaten our planet.
