It’s easy to reflect on 2024 as a tumultuous year, but there is some comfort in knowing that humanity can now claim to know more about the universe than ever before. As a species, we have never been more enlightened, because scientists are always learning more, and because science is always unfinished.
But which scientific discoveries of 2024 proved to be the most thrilling and revelatory?
Making this determination is a somewhat difficult task. Sometimes, there is an obvious eureka moment, one whose paradigm-shifting implications for humanity, the wider world, or the cosmos itself, are immediately evident. But often, what may seem like a small step forward in our scientific understanding of something in the present is just another domino falling on the way to something unimaginably epic and game-changing.
Whether it’s expanding our knowledge of the microscopic world, or transforming the way we perceive our galactic neighborhood, every advance is noteworthy.
But, for our money, these are the most astonishing scientific discoveries of 2024.
Astronomers discover hidden oceans in the outer solar system
Earth’s oceans were long thought to be unique. As far as scientists could tell, Mars was a radioactive desert, Venus was an arid volcanic hellscape, and the myriad icy moons of Jupiter, Saturn, Uranus and Neptune were frozen balls of ice. But in the 1980s, strange electrical signals coming from Jupiter’s moon Europa strongly suggested that an ancient, warm, salty liquid-water ocean was hiding beneath its ice shell.
This revelation precipitated the launch of NASA’s Europa Clipper mission, a spacecraft that left Earth this October with the hope of remotely studying that ocean and determining if it’s amenable to life.
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Nowadays, scientists cannot stop finding compelling evidence for oceans in the outer solar system.
Saturn’s Enceladus is certain to contain another watery ocean, but several others are extremely promising candidates—and this year, we got several more. In February, astronomers announced that they had found evidence of an ocean hidden on Saturn’s moon Mimas. Then, in October, convincing data pointed to yet another ocean buried within Miranda, a Uranian moon.
Finding evidence that oceans are common in the solar system matters.
Life as we know it loves water and, although we do not know if these aquatic moons contain life (whether that’s microbial of something fishier), we now have so many more places to search for it in our own cosmic backyard than scientists could have ever dreamt of.
The 50 largest neurons of the fly brain, including the APL, which is the largest cell in the brain and has over 120,000 synapses.
Illustration by Illustration by Tyler Sloan and Amy Sterling for FlyWire, Princeton University, (Dorkenwald et al/Nature, 2024)
Fruit fly brain mapped out
You probably haven’t given much thought to the humble, sometimes irritatingly persistent, fruit fly. But to many scientists, this little critter—Drosophila melanogaster—is one of the most important species on the planet. It may have a tiny brain, but it performs many of the same basic neurological processes as a human’s, whether that’s when the fly is searching for food or when it’s “socializing” with another member of its species. That means its minuscule brain can tell us about every type of brain, including our own.
In October, the brain of an adult fruit fly was comprehensively mapped out, with 50 million connections between around 140,000 individual neurons placed upon a special sort of map.
Cerebral cartography of any organism is as difficult as it is promising.
What does a healthy or an unhealthy connection between brain cells looks like? How is 3D navigation wired into the brain? Where does behavior come from? What exactly is a thought, or a memory?
A fruit fly’s brain is considerably less complex than a human’s, but this map will provide clues that can help neuroscientists understand what makes you, well, you.
The 1.5°C global warming limit will (almost certainly) be breached
In some ways, this isn’t surprising at all: the world’s most prolific greenhouse gas emitters have comprehensively failed to stem their output, and the planet has continued to warm at a breakneck pace, bringing with it all sorts of climatic chaos. But this year, for the first time, global average temperatures were extremely likely to jump to more than 1.5°C above pre-industrial levels.
The oft-cited 1.5°C boundary is somewhat arbitrary; nothing dramatic (other than the extreme weather and climatic convulsions we are already witnessing today) is suddenly going to happen the moment we cross this Rubicon. But that boundary still matters.
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Under the Paris Agreement, nearly 200 countries agreed to prevent Earth’s temperature from rising above 2°C above pre-industrial levels, but ideally, they wanted to keep it below 1.5°C. The warmer the planet gets, the more deleterious effects of climate change we will experience; every 0.1°C increase in the average global temperature raises the risk of more potent storms, lengthier heatwaves, catastrophic flooding, and so on.
1.5°C was an aspirational target. Crossing it marks this as a grim discovery, but an important one. Alarm bells are ringing louder than ever before: if this temperature rise isn’t reversed, or at the very least stopped, all our futures will be increasingly troubled by the wrath of climate change.
Humans age in bursts
It’s not uncommon to wake up one day, try to tie a shoelace, painfully pull something in our lower backs, and suddenly feel much older than you were yesterday.
Weirdly, although we do indeed age on a daily basis, scientists discovered in August that the human body appears to go through two rapid aging bursts: once around the age of 44, and again when we reach 60.
Using 108 volunteers, who handed researchers all sorts of biological samples, scientists tracked the changing inventory of various biochemicals and microbes across different ages. For reasons unclear to scientists, both men and women seem to undergo a major shift in their mid-40s: the way our bodies handle cardiovascular disease, and how we break down things like alcohol, fats, and caffeine, changes. Then, when we enter our 60s, our bodies undergo shifts in (among other things) immune regulation and carbohydrate metabolism.
Although it’s not yet clear how many of these shifts are influenced by lifestyle changes (people tend to drink a lot more during their oft-stressful 40s, for example), as opposed to being purely biological, the fact that we age in spurts is still fascinating and downright unexpected.
In 2020, NASA’s OSIRIS-REx mission retrieved 12.6 grams of asteroid dust. This year, insights from that sample were finally revealed.
Photograph by Erika Blumenfeld & Joseph Aebersold, NASA
In this sample, scientists have found prebiotics and molecules that suggest the asteroid came from a geologically active world.
Photograph by Erika Blumenfeld & Joseph Aebersold, NASA
Scientists open a cosmic treasure chest
The late, great Carl Sagan once said: “We are made of star-stuff.” That is quite literally true, as all the elements that make us, and the planets, and everything in-between, came from the deaths of countless ancient stars. Now, we are on the verge of finding out exactly where all this star stuff came from, thanks to NASA’s OSIRIS-REx mission.
In 2020, the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer spacecraft managed to briefly touchdown on the asteroid Bennu, steal some of its pristine material, then drop it off back on Earth in September 2023. This isn’t the first time a spacecraft has stolen matter from an asteroid (Japan has accomplished this twice), but OSIRIS-REx’s 121.6 grams of asteroidal grains is by far the largest sample of pristine matter ever retrieved.
Asteroids are the debris left over from the violent formation of the solar system. These building blocks not only contain the minerals that went into making the planets—including Earth—but also the chemistry that created our seas and oceans, and perhaps even the compounds that seeded the very first lifeforms.
This year, scientists got their very first look at OSIRIS-REx’s sample, and they are in awe at what it’s telling them: the Sun was forged via the deaths of multiple stars, from low-mass ones to those big enough to detonate as powerful supernovae; strange molecules in the sample suggest it came from a destroyed geologically active world; and an array of prebiotic compounds, including all sorts of amino acids, were found within that primeval asteroid.
In short, this sample is already rewriting what we know about the solar system’s origins—and scientists have only studied one percent of it. Who knows what else it has in store?
Artificial Intelligence unravels the secrets of proteins
As AI becomes more visibly part of our lives, it’s regarded with more suspicion, but this year, it became clear that it was going to help reveal how life itself works.
In October, the Nobel Prize in Chemistry was awarded to several researchers involved in studying proteins, the squiggle-like machines that underpin much of biochemistry.
Understanding how proteins work means (among other things) knowing how diseases—from Malaria to Parkinson’s—proliferate, then identifying ways to stop them.
Notably, two of the three recipients of the prize—Demis Hassabis and John Jumper, both at Google DeepMind—owe their revelations to their AI model, named AlphaFold2.
With ruthless efficiency, this AI was able predict the structure of pretty much all the 200 million proteins that scientists have found to exist—meaning that scientists now have a tool that can quickly and accurately work out what sorts of proteins will be involved in, or result from, all sorts of chemical reactions or sets of starting conditions.
The ability of scientists to decode so many puzzling aspects of biochemistry, from antibiotic resistance to neurological illnesses, has never been more acute.
