Meteorites burn up in Earth’s atmosphere on a regular basis, but a space rock that landed in Canada last year threatens to shake up our entire understanding of the solar system. Scientists traced its origins back to a distant cloud of comets that wasn’t thought to be home to any rocky material.
On February 22, 2021, at 6:23 am local time, a fireball streaked across the skies over Alberta, Canada. The event was simultaneously captured by observatories, doorbell cameras, security systems, GoPros, and many other eyes in the area. It appeared to be about the size of a grapefruit, weighed around 2 kg (4.4 lb), and judging by the way it fragmented and dropped smaller pieces on entry, it was clearly made of rock.
That in itself is hardly unusual – it’s estimated that as many as 17 meteorites fall to Earth every day. But the true significance of this rock was uncovered when scientists worked out where it came from.
Among the cameras that caught the event were some in a network called the Global Fireball Observatory (GFO), which is specifically designed to look for these shooting stars and allow scientists to calculate their trajectories, and a point of origin. This kind of rocky meteorite usually comes from the asteroid belt between Mars and Jupiter, or somewhere even closer to Earth.
But in this case, the team discovered the fireball had made a much longer journey. According to their calculations it had traveled all the way from the Oort cloud, a huge collection of icy objects that surrounds the solar system. This is where long-period comets are thought to originate.
Current models for the Oort cloud’s formation suggest that the material started off much closer to the Sun, as leftovers from the birth of the solar system’s planets. Over time, the gravitational influence of Jupiter and the other giants pushed it all out to its current distance about 2,000 to 200,000 times the distance between the Sun and Earth. However, this model predicts that Oort objects should be made of ice, not rock like this observed fireball.
“This discovery supports an entirely different model of the formation of the solar system, one which backs the idea that significant amounts of rocky material co-exist with icy objects within the Oort cloud,” said Denis Vida, an author of the study. “This result is not explained by the currently favored solar system formation models. It’s a complete game changer.”
Other teams have proposed that the Oort cloud might have different origins than those currently accepted. These alternate hypotheses include that objects in the cloud were captured by the gravity of the Sun and its long-lost binary partner.
The new research was published in the journal Nature Astronomy. The trajectory model can be seen in the video below.
Source: Western University
