On Saturday, revelers across Spain and Portugal ventured out into the temperate spring evening, hoping for an evening to remember. No one expected a visitor from space to explode over their heads.
At 11:46 p.m., a fireball shot through the sky in Portugal, leaving a smoldering trail of glowing graffiti. Images shared on social media leave jaws dropping as the dark night briefly turns into day, radiant in shades of snow white, otherworldly green and arctic blue.
Rocky asteroids create sky-high streaks as they self-destruct with some frequency in Earth’s atmosphere. But this weekend, the projectile crashed toward Earth at a remarkable speed: about 100,000 miles per hour, more than twice that expected by a typical asteroid. Experts say it took a strange trajectory, which does not match the trajectory normally followed by nearby space rocks.
That’s because the invader wasn’t an asteroid. It was a fragment of a comet – an icy object that may have formed at the beginning of the solar system – that lost the battle with our planet’s atmosphere 60 kilometers above the Atlantic Ocean. It is likely that none of the objects reached the ground, the European Space Agency said.
“It’s an unexpected interplanetary fireworks show,” says Meg Schwamb, a planetary astronomer at Queen’s University Belfast.
It is not uncommon for comets to create shooting stars. “We have remarkable meteor showers throughout the year, which result from Earth crossing debris clouds from specific comets,” said Dr. Schwamb. For example, the Perseids, which occur every August, are the result of the litter left behind in our world by Comet Swift-Tuttle.
These meteor showers and the weekend’s only shard will light up the sky in a similar way. Air in front of the objects compresses and heats, causing the dirt to boil, erode, crack open and obliterate. That destructive process releases light – and, if the projectile is large enough, a powerful shock wave as it releases its immense kinetic energy into the sky.
“This weekend’s portion is probably a little bit larger than a good portion of the meteors we see during meteor showers, so this just made for a bigger light show,” said Dr. Schwamb.
In addition to the flashy performance, the breakup of the comet fragment also served as a test run for experts looking to defend the planet from large killer asteroids.
One principle of planetary defense is finding space rocks before they find us; that way, the planet’s protectors can try to do something about it. But the shard over Portugal and Spain was not spied upon before its demise.
“It would have been great to detect the object before it collided with Earth,” said Juan Luis Cano, member of the European Space Agency’s Planetary Defense Office.
The concern is that an object slightly larger than Saturday’s rocket could again escape detection and explode with deadly effect over an unaware, unwarned city. For example, the paltry 17-meter-tall meteor that exploded over the Russian city of Chelyabinsk in 2013 was also unidentified before its arrival – and its aerial explosion, equivalent to nearly 500,000 tons of TNT, caused widespread damage, injuring people. at least 1,200 people.
But with improved technology on the ground and in space, the hope is that even small, harmless objects from across the solar system (like the weekend’s icy visitor, which experts say was a few meters wide) can be spotted, providing practice for the defense of the planet. researchers search the skies for the common but elusive football field-sized rocks that could destroy a city.
Fortunately, a series of next-generation observatories will come online in the coming years, including one named after an American astronomer, the Vera C. Rubin Observatory in Chile, which will detect millions of faint and previously undiscovered asteroids.
For now, the spectacle in Spain and Portugal reminds us that Earth is participating in the solar system’s endless game of planetary billiards, and that finding as many deadly space rocks as possible is a task of paramount importance.