Here's what we don't see very often: a grazing meteorite.
On September 22, 2020, a small space rock jumped through the Earth's atmosphere and bounced back into space. The meteorite was discovered by a camera of the Global Meteor Network, which could be seen in the sky over northern Germany and the Netherlands. It reached an altitude of 91 km – well below any orbiting satellites – before jumping back into space.
Dennis Vida, a physics postdoctoral fellow from Western University in Ontario, Canada who heads the GMN, said they put the rock back into a Jupiter family orbit, but a search for potential parent bodies did not find conclusive matches.
As the ESA explains, a meteorite is typically a fragment of a comet or asteroid that becomes a meteor – a bright light that streaks through the sky – when it enters the atmosphere. Most of them disintegrate, possibly with pieces reaching the ground as meteorites.
Scientists estimate that grazing meteoroids occur only a few times a year. But hundreds of tons of tiny interplanetary objects enter the earth's atmosphere every day. The most common effect these small objects create when interacting with the Earth's atmosphere are meteors – commonly called falling stars. A small percentage of the largest rocks hit the ground as meteorites.
Not an estimate of the size of the September 22nd Earthgrazer, but it was probably quite small. And while tens of thousands of meteorites have been found on Earth, only about 40 can be traced back to a parent asteroid or asteroid source.
In order for a stone to "bounce" off the earth's atmosphere, it has to enter the atmosphere at a relatively flat angle. And like a stone “jumping” from a lake, the meteorite also briefly enters the atmosphere before exiting again.
This image shows the two areas where most asteroids are located in the solar system: the asteroid belt between Mars and Jupiter and the Trojans, two groups of asteroids that move in front of Jupiter in its orbit around the Sun and follow it.
The Global Meteor Network – whose slogan is "No Meteor Unobserved" – is working to cover the globe with meteor cameras to provide the public with real-time alarms and to create an image of the meteorite environment around the earth.
"The network is basically a decentralized scientific tool made up of amateur astronomers and citizen scientists around the world, each with their own camera systems," said Vida, who founded the initiative. "We are making all data such as meteorite orbits and orbits available to the public and science with the aim of observing rare meteorite eruptions, increasing the number of observed meteorite falls, and understanding the release mechanisms of meteorites to earth."
The station operators of the GMN, whose data is shown in the main animation, are Paul Roggemans, Jürgen Dörr, Martin Breukers, Erwin Harkink, Klaas Jobse and Kees Habraken.