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An Earth-grazing fireball seen over the US in 2014


NASA

On a winter evening in southern Australia in 2017 a bright fireball streaked across the sky for a full minute and a half. There was no need to duck and cover though, because after its extended display in our atmosphere, the meteoroid flew back out into deep space.

The so-called Earth-grazing meteor was caught by Australia’s Desert Fireball Network on July 7, 2017, as it scorched a path over southern and western Australia, traveling over 808 miles (1,300 kilometers) through the atmosphere before making its exit to go cool off in interplanetary space. In a new draft of a paper submitted to the Astrophysical Journal, a team of researchers estimate that the fireball weighed about 132 pounds (60 kilograms) with a diameter of around a foot (30 centimeters).

It’s almost as if the small space rock was bouncing off our planet, but not quite. What’s really happening with an Earth-grazer is the meteoroid is entering our atmosphere at a very shallow angle. If it’s moving fast enough and doesn’t get slowed down so much by our atmosphere that Earth’s gravity pulls it down to the surface, it can actually escape back out to space. That is, if it doesn’t totally burn up in the process.

It’s rare to spot such a long-lasting Earth-grazer, but with today’s modern observatories scientists have been able to document and study a handful over the last couple of decades. The July 2017 event was the second longest to be scientifically observed. 

An Earth-grazer thought to be about the size of a truck scorched its way across Canada and the northwestern US in 1972 for almost 100 seconds, but later research found that the original data analysis of the event contained mistakes. That makes the 2017 event, which was captured from multiple spots on the ground by the DFN’s network of over 50 observatories in Australia, perhaps the most significant Earth-grazing meteoroid observed in modern times. 

As for the little space rock that temporarily found itself lit on fire by its trajectory, it’s likely to spend a few hundred thousand years zipping around the solar system and having a number of close encounters with Jupiter before going on to other adventures.

“Eventually the meteoroid will likely be ejected from the solar system or be flung into a trans-Neptunian orbit,” the researchers write.

Sounds a lot more chill than its 90 seconds visiting Earth.