Picture the scene: An asteroid is hurtling toward Earth. It’s the size of the Eiffel Tower, shaped like a peanut and potentially dangerous – sounds scary, right?
Take asteroid 2026 JH2. It was first detected on May 10, 2026. And it was scheduled to fly by Earth eight days later – less than a quarter of the distance between Earth and our moon. There is still very little chance of it hitting Earth. But media coverage was everywhere.
Scary discovery stories come out all the time.
In 2024, it was due to be Asteroid 2024 ON – it missed us because it was never supposed to hit.
“Publications need these ‘cliffhangers’ for the tour,” said Juan Luis Cano of the European Space Agency’s Planetary Defense Office. “But on a daily basis we encounter many objects.”
In fact, about 100 tons of space material hits Earth every day. Fortunately, the mass is spread across many smaller rocks rather than one large destroyer.
Large Destroyers: Near Earth Objects in Brief
The United Nations Office for Outer Space Affairs defines near-Earth objects (NEOs) as any object An asteroid or comet that passes close to Earth’s orbit.
In more technical terms, NEOs are objects with perihelion – their closest orbital distance to the Sun – of less than 195 million kilometers (121 million miles).
Given that Earth orbits the Sun at a distance of about 150 million kilometers, NEOs are well within our solar neighborhood.
Scientists like Cano know of about 34,000 NEOs, but no large NEOs are currently on a collision course with Earth.
What is the probability of an asteroid impact on Earth?
While smaller NEOs strike Earth every day, larger NEOs strike much less frequently. Asteroids of the size of 2024 ON may hit Earth once every 10,000 years.
Asteroids larger than a kilometer in diameter, such as the Chicxulub asteroid that sent dinosaurs to extinction 66 million years ago, may collide within the next 260 million years.
“We estimate that there are about a thousand objects larger than a kilometer and we have discovered 95% of them,” Cano said. “These are the ones that could cause global disaster.”
But small ones also have destructive potential. Depending on the speed and angle of entry into Earth’s atmosphere, the 40-metre-wide (131 ft) rock could level an entire city. Thousands of such smaller NEOs still remain to be cataloged.
“We have discovered about 3,000 near-Earth asteroids [NEAs] Every year,” Cano said. “[But] is needed […] To find them quickly.”
Finding near-Earth objects is a ‘difficult’ task
A handful of space-based telescopes have been tasked with finding NEOs.
First, there was NEOWISE, which documented over 158,000 NEOs. NEOWISE was launched in 2009 and is retired in 2024 after a mission of more than 10 years.
Second, there is a successful mission called Near-Earth Object Surveyor.
And Canada’s NEOSSat tracks asteroids and comets as well as space debris and exoplanets.
NEO Surveyor is scheduled to begin operation in 2027. Its goal will be to find the remaining potentially hazardous asteroids (PHAs) within 50 million kilometers of Earth’s orbit. But it is difficult to find dangerous objects in space.
“One of the hardest things to do in astronomy is to tell how far away something is,” said Amy Mainzer, a planetary scientist at UCLA who led the NEOWISE mission and will lead the NEO surveyor.
“You would think, ‘Well, we see objects at the edge of space, why don’t we know what’s right next to us near Earth? Don’t we know everything?’ And the answer is, ‘No, it’s really, really hard.'”
It’s important to keep track of the objects we observe and communicate those findings, Mentzer said.
To do this, astronomers also use ground- and space-based telescopes to monitor NEOs and PHAs. One of the latest is the Vera Rubin Observatory, currently under construction in Chile, which will spend a decade creating a time-lapse map of the universe.
“This is going to revolutionize the number of asteroids we discover,” Cano said.
ESA is also preparing four small “FlyEye” multi-lens telescopes to make wide-field observations of the night sky.
How NEO tracking helps protect our planet
No known asteroid is likely to hit Earth for at least the next century. We know that thanks to our planetary defense systems. Tracking NEO is a part of that.
Once an object is identified, researchers like Mainzer and Cano take repeated observations to quickly but accurately plot the NEO’s trajectory. This could help ease concerns about NEOs and is part of what scientists call planetary defense.
Take Apophis for example. When it was first identified in 2004, the 340-meter-wide Apophis was considered one of the most potentially dangerous objects ever discovered. It was thought that it could hit Earth in 2029, 2036, or 2068.
Later calculations rejected this. At the end of this decade it will come within 30,000 km of the planet, which is closer than the Moon and within the range of geostationary satellites. But according to current estimates it will not hit the Earth.
But what if a new, rogue NEO is spotted on a collision course with Earth? Given enough warning, engineers can attempt to divert it off target.
In 2022, NASA’s Double Asteroid Redirect Test (DART) mission successfully crashes a spacecraft into an asteroid named Dimorphos. It demonstrated that a collision-based mission could change the direction of a celestial body and protect our planet.
Edited by: Zulfikar Abbani
This article was originally published on Asteroid 2024 ON’s flyby of Earth on October 4, 2024. This was updated on May 15, 2026, ahead of the expected flyby of asteroid 2026 JH2.