On Saturday, revelers from Spain and Portugal ventured out into the temperate spring night, hoping for a night to remember. No one expected a visitor from space exploding above their heads.
At 11:46 pm in Portugal, a fireball streaked across the sky, leaving a smoking trail of incandescent graffiti in its wake. Images shared on social media show jaws dropping as the dark night briefly turns to day, glowing in shades of snowy white, otherworldly green and arctic blue.
Rocky asteroids cause sky-high streaks as they self-destruct in Earth’s atmosphere with some frequency. But over the weekend, the projectile plunged toward Earth at a remarkable speed — about 100,000 miles per hour, more than twice that expected from a typical asteroid. Experts say it had a strange trajectory, not matching the type normally followed by nearby space rocks.
That’s because the intruder was not an asteroid. It was a fragment of a comet – an icy object that may have formed in the early 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,” said Meg Schwamb, a planetary astronomer at Queen’s University Belfast.
It is not uncommon for comets to create shooting stars. “We have notable meteor showers throughout the year that are the result of Earth passing through clouds of debris from specific comets,” said Dr. For example, the Perseids, which occur every August, are the result from scanning the debris left behind by comet Swift-Tuttle on our world.
These meteor showers and the single fragment from the weekend light up the sky in a similar way. The air in front of objects is compressed and heated, which cooks, corrodes, cracks and destroys debris. This destructive process releases light – and, if the projectile is large enough, a powerful shock wave as it delivers its immense kinetic energy into the sky.
“The weekend chunk is probably a little bigger than a good fraction of the meteors we see during meteor showers, so it just generated an even bigger light show,” Dr. Schwamb said.
In addition to its showy performance, the comet fragment’s breakup served as a dry run for experts hoping to defend the planet from large, killer asteroids.
A principle of planetary defense is to find space rocks before they find us; that way, the planet’s protectors can try to do something about it. But the fragment about Portugal and Spain was not spied on before its disappearance.
“It would have been great to detect the object before it collided with Earth,” said Juan Luis Cano, a member of the European Space Agency’s Planetary Defense Office.
The concern is that an object slightly larger than Saturday’s missile could again escape detection and explode with lethal effect on an unaware and unsuspecting city. The small 17-meter-high meteor that exploded over the Russian city of Chelyabinsk in 2013, for example, was also not identified before its arrival – and its aerial explosion, equivalent to almost 500,000 tons of TNT, caused widespread damage, which injured at least 1,200 people.
But as technology improves on the ground and in space, the hope is that even tiny, harmless objects from across the solar system (like the weekend’s icy visitor, which experts estimate to be a few meters in diameter) could be spotted, providing practice for planetary defense. researchers scour the skies for ordinary but elusive rocks the size of a football field that could destroy a city.
Fortunately, a number of next-generation observatories are expected to 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, previously unknown asteroids.
For now, the spectacle in Spain and Portugal reminds us that Earth is a participant in the solar system’s never-ending planetary billiards game, and that working to find as many killer space rocks as possible is a task of the utmost importance.
