Asteroid collisions, rogue spaceships and eggnog

on a clear, bright morning In September 2023, a spacecraft landed at a military base in Utah, and human representatives burst into laughter, tears and applause. It may not look like it to most of us, but at that moment, our species was one step closer to figuring out the origins of eggnog. And mulled wine. And, well, almost everything.

Minutes after the spacecraft gently rendezvoused with the planet, a helicopter flew out to greet it. They orbited the inert circular capsule and dropped a few people nearby. The visitor approaches cautiously. The oven-sized craft, once attached to a much larger mothership, traveled millions of miles around the solar system during its seven-year odyssey. Now it has returned home laden with treasure.

This is the exact opposite of UFOs. Everyone looks forward to its safe arrival. The recovery of this spacecraft is a model for the billion-dollar OSIRIS-REx program – Origins, Spectral Interpretation, Resource Identification, Security and Regolith Explorer. The spacecraft, conceived in the early 2000s and launched in 2016, has many goals. Chief among them was becoming the first U.S. space mission to snatch material from an asteroid and bring it back to Earth. And, despite several comically epic obstacles—from dodging debris from an exploding rocket to escaping the quicksand-like surface of an asteroid—it succeeds.

The capsule, which contained raw cookie crumbs from an asteroid called Bennu, was whisked to NASA’s Johnson Space Center in Houston. A few weeks later, at a grand press conference, scientists announced something that was very exciting for them: the asteroid sample contained, among other things, water.

Many fundamental features of our world are shrouded in mystery. Water is one of them. Scientists have a deep understanding of how water is an extraordinary medium for life, how it morphs between different states of matter, how it dives, flows through and flies across the Earth – how it dominates, shapes and controls the planet’s destiny. world. But they don’t actually know where it comes from.

Earth wasn’t always a marine paradise. Before it was soaked, it was covered by a magma ocean and shattered into pieces by tilting protoplanetary objects at the dawn of the solar system. Earth’s oceans, lakes, rivers and rain did not appear out of thin air. They all have to come from somewhere. Scientists aren’t entirely sure where – there isn’t enough evidence to say with confidence.

It’s worth thinking about. Our bodies are mostly made of water. H₂O falls on our heads and umbrellas. We absorb it in various forms all the time. But its origins are a mystery, which means when you celebrate this winter with your libation of choice, you’re drinking something completely foreign.

Of course, there are some popular ideas. Comets are composed of various frozen materials, including frozen water. For some time it has been thought that this is where our water comes from. Comets have hit Earth quite a lot over the past billions of years, so there’s nothing inherently wrong with the idea that this is how we got our oceans.

But after several robotic emissaries were sent to hunt down comets over the past few decades, that hypothesis became less clear. In the mid-2010s, the European Space Agency’s Rosetta spacecraft conducted a close study of the rubber-duck-shaped comet 67P/Churyumov-Gerasimenko and found that its water did not match the type of water we drink on Earth. Its chemical fingerprint is not the kind found in Earth’s glaciers, rivers, oceans or skies.this means Some Comets may have given Earth some water, but other comets were not involved at all.

And asteroids? Although some are arid, many of them contain surprising amounts of water—not nearly as much as comets, but more than you might think. There are millions of them, most hidden between Mars and Jupiter, swirling in the darkness. Sometimes they find their way to Earth. In fact, because of their closer proximity to Earth, they impact the world far more frequently than their larger, icy cousins, the comets, which mostly spend their lives in the outer reaches of the solar system.

It stands to reason, then, that most of Earth’s water may have been transported by asteroids billions of years ago. And, over the past few decades, the evidence for this has been growing. As recently as 2022, it was revealed that a tiny (harmless) asteroid that crashed into the idyllic English town of Winchcombe a year earlier contained water, with a chemical fingerprint that was strikingly similar to that found in Earth’s oceans. If packages like this fell from the sky millions of times over the course of eons, it’s no wonder the world would be a damp place.

Like so many Earth, space, and planetary science stories, the actual solution to this puzzle is complex and likely involves multiple players: certainly comets and asteroids, but some also suspect a third party. Given that water is so common in the universe, some of Earth’s water may come from free-floating interstellar water that simply condensed on the world as it cooled and crystallized 4.6 billion years ago.

This lingering uncertainty is why OSIRIS-REx is so valuable. The water in the asteroid Bennu samples may or may not match Earth’s water. Both options are exciting possibilities, as they would both bring scientists closer to cracking the recipe behind Earth’s life-sustaining cocktail.

Regardless of the results of the analysis, one thing is certain: asteroids provided some water to Earth. This is a very strange thing.

These stone missiles have struck the Earth countless times during its lifetime. On at least one occasion, their violent violence resulted in mass extinction. In many other cases, they blasted huge cracks in the ground without even touching it, much like non-radioactive airborne nuclear explosions. Near-Earth asteroids are a common source of disruption and pose a contemporary threat that, thankfully, NASA is now taking seriously.

Asteroids are also the arbiters of creation. The water they violently delivered to the young Earth still erupts in volcanoes or cascades down in waterfalls today. These wandering geological creatures possess both the power to destroy life and, to some extent, the power to create and sustain life in the earth. They are the rocky embodiment of chaos.

So please do me a favor. This winter, when you finish your celebratory drink, raise a glass to the memory of an ancient asteroid. These space rocks may make a mess, but without them you probably wouldn’t be here celebrating the end of the year.

Robin George Andrews is a volcano doctor, an award-winning freelance science journalist, and the author of two books: Supervolcanoes: What they reveal about Earth and the world beyond (2021), as well as the upcoming How to Kill an Asteroid: The Ridiculous True Story of Scientists Defending Earth (2024).