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One of the balls of fire (highlighted by the red circle) captured in the Northern Territory. Credit: NT Emergency Services
In recent days, two spectacular fireballs have honored the Australian skies.
The first, in the early hours of Monday, May 20, crossed the Northern Territory and was seen from Tennant Creek and Alice Springs, more than 500 km apart.
The second arrived two days later, spanning South Australia and Victoria.
Such fireballs are not uncommon and are another reminder that Earth is sitting in a heavenly shooting room. In addition to their show, they hold the key to understanding the formation and history of the solar system.
Crash, bang, boom!
On any clear night, if you look at the sky long enough, you will see meteors. These flashes of light are the result of objects having an impact on the atmosphere of our planet.
Debris stains evaporate safely in the atmosphere, 80 to 100 km above our head, all the time, about 100 tons per day.
The larger the object, the more spectacular the flash is. When your typical meteor is caused by an object the size of a grain of dust (or, in the case of a particularly shiny grain, a grain of rice), fireballs like those observed this week are caused by much bigger bodies, about the size of a grapefruit, a melon or even a car.
Such impacts are rarer than their tiny siblings because there are many more small objects in the solar system than larger bodies.
By moving to even larger objects, you get some truly spectacular but rare events like the amazing fireball of Chelyabinsk in February 2013.
It was probably the most significant impact on Earth for 100 years and caused many injuries and injuries. This was the result of the explosion of an object of a mass of 10,000 tons, about 20 meters in diameter.
Over longer periods, the biggest impacts are really huge. Some 66 million years ago, a comet or asteroid about 10 km in diameter sank in the current Yucatan Peninsula, Mexico. The result? A crater of some 200 km and a mass extinction including dinosaurs.
Even this is not the greatest impact the Earth has experienced. Back in the youth of our planet, he was the victim of a truly cataclysmic event when he collided with an object the size of Mars.
When dust and debris dissipated, our planet, once alone, was accompanied by the moon.
Fortunately, the impacts that could threaten life on Earth are very rare. While scientists are actively seeking to ensure that no impact on the level of extinction will occur in the near future, this is not really something that should make us lose too much. sleep.
The lower impacts, like those seen earlier this week, are much more common – indeed, images of another fireball have been reported earlier this month on Illinois in the United States. United.
In other words, it is not unusual to have two brilliant fireballs in a few days over a country as vast as Australia.
Immaculate Relics of the Formation of the Planet
These fireballs can be an incredible asset for our understanding of the formation and evolution of the solar system. When an object is large enough, it is possible that fragments (or all) enter the atmosphere intact, delivering a new meteorite to the surface of our planet.
Meteorites are extremely valuable to scientists. They are celestial time capsules – relatively immaculate fragments of asteroids and comets that formed when the solar system was young.
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NASA's record on the place marked in the great Australian bay of one of the fireballs on Australia this week. Credit: NASA
Most of the meteorites we find have been on Earth for long periods before they are discovered. These are called "discoveries" and, although they remain useful, they are often degraded and altered, chemically altered by the hot and humid environment of our planet.
On the other hand, the "falls" (meteorites whose fall has been observed and which were recovered a few hours or days after the event) are much more valuable. When we study their composition, we can be sure to study something old and virgin, rather than worry about seeing the effect of the Earth's influence.
Stalking the fireballs
For this reason, the Australian Desert Fireball Network has set up a huge network of cameras on our vast continent. These cameras are designed to travel the sky all night, every night, watching the appearance of fireballs like those observed earlier this week.
If we can observe such a fireball from several directions, we can triangulate its path, calculate its motion in the atmosphere and determine if it is likely that it has dropped a meteorite. By using these data, we can even determine where to look.
In addition to these cameras, the project can use all the data provided by the people who attended the event. For this reason, the Fireballs team has developed a free app, Fireballs in the Sky.
It contains excellent information on fireballs and meteor showers, and links to experiences related to the national program. More importantly, it also allows its users to submit their own Fireball reports.
With regard to this week's fireball over southern Australia, NASA said it was probably caused by an object the size of a small car. As for the discovery of remains, they are probably now lost in the waters of the Great Australian Bay.
The search for meteorites about to begin
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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What is the cause of the fireballs that illuminated the sky over Australia? (May 24, 2019)
recovered on May 26, 2019
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