In the mid-1980s, as a group of American archaeologists pored over satellite images showing Mexico’s Yucatan Peninsula, they did not know what to make of one unexpected pattern: a near-perfect ring, about 200km across.Cenotes, the blue water sinkholes that are a staple of Yucatan tourist brochures, dot this arid landscape, opening up seemingly at random as you trek across the vast flatlands of the Yucatan, a dogleg of low, dry forest on Mexico’s eastern edge. But seen from space, they cluster together to form a pattern: an arc, articulating nearly half a circle, as if a drawing compass had been stuck into the map on the shores of the Gulf of Mexico and spun around until running out of land.
View image of Mexico’s Yucatan Peninsula is famous for its cenotes, blue water sinkholes that dot the arid landscape (Credit: Credit: Simon Dannhauer/Alamy)
You may also be interested in:• The cliff that revealed Earth’s history• The island that forever changed science• The clock that changed the meaning of timeThe archaeologists had discovered the pattern, which encircles the Yucatecan capital, Merida, and port towns of Sisal and Progreso, while trying to understand what had become of the Mayan civilisation that had once ruled over the peninsula. The indigenous Maya had depended on the cenotes for drinking water, but the uncanny circular arrangement of the holes perplexed the researchers as they presented their findings to fellow satellite specialists at a scientific conference Selper in Acapulco, Mexico, in 1988.For one scientist in the audience, Adriana Ocampo, then a young planetary geologist at Nasa, the circular formation sounded a klaxon she had been trained to anticipate.Ocampo, now 63, explains that she saw not just a ring, but a bullseye. This is something amazing “As soon as I saw the slides that was my ‘Aha!’ moment. I thought ‘This is something amazing’. ‘This could be it’,” said Ocampo, now director of Nasa’s Lucy programme, which will send a spacecraft into Jupiter’s orbit in 2021. “I was really excited inside but I kept cool because obviously you don’t know until you have more evidence.”Approaching the scientists, heart pounding, Ocampo asked if they had considered an asteroid impact – one giant and violent enough to have scarred the planet in ways still being revealed 66 million years on.“They didn’t even know what I was talking about!” she laughed, three decades later.
View image of Yucatan’s cenotes form a near-perfect ring, about 200km across (Credit: Credit: NASA Image Collection/Alamy)
Ocampos chance encounter was the beginning of a scientific correspondence that would establish the foundations for what most scientists believe today: that this ring corresponds to the edge of the crater caused by an asteroid 12km wide, which struck the Yucatan and exploded with unimaginable force that turned rock to liquid.Since the early ‘90s, teams of scientists from the Americas, Europe and Asia have worked to fill in the remaining blanks. They now believe the impact instantly created a crater 30km deep, causing the Earth to act like a pond after a pebble is dropped, rebounding up in the centre to create a mountain – just for a moment – reaching twice the height of Mt Everest, before crashing down. In the years that followed the cataclysmic impact, the world would have changed beyond recognition, with the plume of ash blocking the sky and creating perpetual night-time for more than a year, plunging temperatures below freezing, and killing off about 75% of all life on Earth – including almost all the dinosaurs.Today, that centre point, the place where that imaginary compass stuck and the mountain once rose, is a buried a kilometre below a tiny town called Chicxulub Puerto.
View image of Scientists believe that the Chicxulub Crater corresponds with an asteroid impact that occurred 66 million years ago (Credit: Credit: Science History Images/Alamy)
When I visited that settlement of a few thousand people, low-rise houses painted yellow, white, orange and ochre surrounded a type of modest town square that makes up the area’s many photogenic but unremarkable Yucatecan villages. The town has had so little publicity that the few dinosaur-lovers who do try to make their way in pilgrimage along the Yucatans long, twisty roads between prickly scrubland forest often end up lost in another nearby town called Chicxulub Pueblo, half an hour’s drive inland. Without that impact, humanity might well have never existed Even if they reach the correct town, located 7km east along white-sand coastline from the popular holiday resort of Progreso, there are few indications that this was the scene of one of the most consequential and disastrous acts of the last 100 million years of Earths history. Stroll around the main square and youll catch sight of paintings of dinosaurs by local children. There is a playground nearby where climbing frames and slides are topped with hard plastic sauropods in primary colours. The only monument, in front of the church on the main square, takes the form of a cartoonish bone, made from concrete, laid in front of an altar like plinth depicting dinosaur species.Until Ocampos findings were published in 1991, this area of the Yucatan had been the subject of little international interest. Today, there is a museum, opened in September 2018 between Chicxulub Puerto and the Yucatan capital Merida, 45km to the south). The Museum of Science of the Chicxulub Crater, a joint project by the Mexican Government and the countrys biggest university, National Autonomous University of Mexico (UNAM), aims to take people back to the moment, 66 million years ago, when the 12km asteroid changed world history, ending the reign of the giant beasts that had lasted hundreds of thousands of years. And by boosting local awareness of the cataclysmic events that took place here, the museum hopes to begin the process of bringing tourists to explore the Yucatan’s prehistoric past, which overlaps with popular Mayan historical destinations like Chichen Itza and the party city of Cancun.
View image of The asteroid impact would have wiped out 75% of all life on Earth, including almost all of the dinosaurs (Credit: Credit: Science Photo Library/Alamy)
Chicxulub Puerto and its surrounds deserve to be better known worldwide, says Ocampo, who was born in Colombia but moved as a child to Argentina, arriving in the US at age 15. The asteroid, although bringing unimaginable violence to this area, benefitted one species above all others: humans, who, millions of years later, would evolve into the ecological gap created by the destruction of the worlds biggest predators.Without that impact, humanity might well have never existed.“It gave us a leg up to be able to compete, to be able to flourish, as we eventually did,” she said.Ocampos discovery came at the end of a decade-long quest for the location of the asteroid impact. The key to her ‘Aha! moment’ had been an intuition she’d picked up after working with a legendary figure in space science, Eugene Shoemaker. Shoemaker – the pioneering American geologist who is credited as one of the founders of the field of planetary science and remains, 21 years after his death, the only person whose ashes are buried on the Moon – had instructed her that near perfect circles were unlikely to have been caused by other terrestrial forces, and could provide clues to Earth’s geological development.
View image of The small coastal town of Chicxulub Puerto is believed to be the centre of the impact crater (Credit: Credit: Adamcastforth/Wikimedia Commons)
The idea that a giant asteroid had wiped out the dinosaurs was proposed by Californian father-son duo Luis and Walter Alvarez in the early 1980s. “But, then, it was extremely controversial,” Ocampo said. What she did was to place one of the final connecting jigsaw pieces that began linking scattered ideas between scientists who were working independently with fragments of information, often on overlapping investigations. Without that impact, humanity might well have never existed For example, as early as 1978, geophysicist Glen Penfield, working alongside Antonio Camargo-Zanoguera for Mexico’s national oil company Pemex, had flown out over the Caribbean waters that lap the shore at Chicxulub Puerto. Using a magnetometer, he scanned the waters looking for signs of oil, instead finding the underwater half of the huge crater. But that evidence belonged to Pemex, so was not made available to the scientific community.In fact, the first person to connect the Yucatan ring with the Alvarez asteroid theory was a Texan journalist named Carlos Byars who wrote an article for the Houston Chronicle in 1981 asking if the two were linked. Byars later shared his theory with a grad student named Alan Hildebrand, who then approached Penfield after examining a rock layer in Haiti, and it was the two of them who determined that the crater wasn’t a volcano, but an asteroid impact. “[Byars] gets the credit for being the first to put the pieces together – a newspaperman!” Ocampo said. “It’s an amazing story when you put all the pieces together.”
View image of Texan journalist Carlos Byars was the first to connect the Chicxulub Crater with the asteroid theory (Credit: Credit: Graham Prentice/Alamy)
But the story is not simply one of history, it could also give us insight into life beyond Earth. Lessons learned in the asteroid crater have informed research by Nasa’s Curiosity rover, which touched down on Mars in 2012 and has spent the last six years investigating the Martian environment and geology.Debris discovered from asteroid impacts on Mars compared with ejecta from the Chicxulub Crater shows similarities that indicate that Mars must once have had much thicker an atmosphere than it does now – one closer to the atmosphere that supports life on Earth. “It’s important for us to know what happened in the past to be prepared for the future,” Ocampo said. “It provides a really good insight into what has happened in the geological evolution of Mars.”
View image of The Chicxulub Crater has been nominated for recognition as a Unesco World Heritage site (Credit: Credit: Reinhard Dirscherl/Alamy)
But, in the Chicxulub Crater, much of the incredible knowledge remains buried below ground, rarely recognised by visitors or locals despite the opening of the museum and Mexico’s application to have the crater recognised by Unesco. There is precious little for visitors to see as the impact was so long ago. Tourists who do visit one of the few remnants – the stunning cenotes, where you can swim among fish and dangling tree roots – may be unaware that these geological features exist only because the soft limestone they are made of was forced to the surface from deep underground by the impact. Over thousands of years, dripping water has carved out the sinkholes. It is a unique place in our planet – It truly is Ocampo has visited the peninsula numerous times since her discoveries there in the late 1980s, but when asked if people are aware of the importance of this place, she responds unhappily.“The short answer is no,” she replied. “We need to do better. We need to educate, we need to make them aware of the extraordinary ground that they are living on.”“They [local people and authorities] are trying to raise the knowledge base and it would be wonderful to help,” said Ocampo, who is also a proponent of planetary science education in Latin America. “It is a unique place in our planet. It truly is.”“It should be preserved as a World Heritage site.”Places That Changed the World is a BBC Travel series looking into how a destination has made a significant impact on the entire planet.Join more than three million BBC Travel fans by liking us on Facebook, or follow us on Twitter and Instagram.If you liked this story, sign up for the weekly bbc.com features newsletter called "If You Only Read 6 Things This Week". A handpicked selection of stories from BBC Future, Earth, Culture, Capital and Travel, delivered to your inbox every Friday.