An asteroid recently flew closer to Earth than the ISS

An asteroid recently made the second closest pass to Earth ever observed on October 1st. And astronomers only found it after it had already completed its closest approach. That offers another lesson in how difficult it is to find small objects coming close to our planet in the vast dark ocean of space.

To be clear, the asteroid, now known as Asteroid 2025 TF, didn’t pose any sort of danger. It is likely only 1–3 m across, and would have created a pretty spectacular fireball if it had entered Earth’s atmosphere—but most likely no one would have been there to see it as it flew over Antarctica in the beginning of their spring. There was a possibility it would have burned down to a meteorite that could have one day been discovered though.

Alas, that didn’t happen as the asteroid made a pass around 428 km above the southern continent at around 1 AM UTC on October 1st. For comparison, that’s around the same height as the International Space Station’s orbit, which can vary from between 370 and 460 km. It would have been a very bad day if those two had found each other, but luckily the orbital space that far above the planet is vast, and even something as large as the ISS is easy to miss in that vastness.

Astronomers from the Kitt Peak National Observatory in Arizona first detected the asteroid only a few hours after its closest approach using the Bott Telescope. Additional observations came from the Catalina Sky Survey and the European Space Agency’s Planetary Defense Office, who utilized the Las Cumbres Observatory in Siding Spring, Australia.

2025 TF marks the second closest approach of any known asteroid, behind only 2020 VT4, a slightly larger asteroid estimated to be about 5–10 m across that passed about 386 km above the Pacific Ocean in November 2020. It, too, was found after its closest approach—about 15 hours later compared to the six hours that it took astronomers to discover 2025 TF.

While these relatively small asteroids don’t pose any danger to the planet themselves, they do pose a threat to the increasing constellation of orbital infrastructure present, especially in low Earth orbit. An impact of one of these rocks, which likely occurs relatively frequently, could be the start of a chain reaction that leads to Kessler Syndrome or a similar dismal fate for our orbital infrastructure.

Unfortunately, we still don’t have the means to protect against these kinds of incursions into our planet’s personal space. To do so would require a massive effort with a combination of more ground-based telescopes linked up with space-based observatories specifically designed to track these small, dark, fast-moving objects. Given the current state of international cooperation and funding in space, that seems unlikely for now.

Until we get to that point, we just have to hope that, when we see a fireball in the sky, it’s not one of these asteroids taking out a piece of valuable orbital infrastructure. Or, if it is, then maybe that would provide enough impetus to the powers that be to do something about what could be an impending disaster that locks us on our world for decades.