The Ten Most Significant Science Stories of 2024

Joe Spring and Carlyn Kranking

This year, Smithsonian magazine published more than 900 science stories. Most of those appeared in our Smart News Science section, but we also published more than 100 features, in addition to reprinting stellar pieces from other sites and sharing the occasional book excerpt. Our stories included a feature on the discovery of the world’s oldest scrap of skin, an interview with a computer scientist and meteorologist on using artificial intelligence to predict extreme weather, a photo gallery of stunning images captured by the Chandra X-Ray Observatory over its 25-year history, several pieces on viral animals including Flaco the owl and Moo Deng the hippo, a feature on scientists examining the rocks from the asteroid Bennu, and a news article examining a 51,200-year-old cave painting that may be the earliest known instance of visual storytelling. Though these pieces were important and captivating—and many could have made our list of the top ten moments of the year—for various reasons, other stories won out.

Though we considered metrics like page views and readers’ time spent reading each article, we mostly picked our top ten the old-fashioned way. As the site’s two science editors, we both met several times over the latter part of the year and discussed at length what to include. We were looking not only at events or discoveries that represented the biggest scientific milestones, but also at those moments or finds that inspired the most awe. And we wanted stories that represented a diversity of fields—astronomy, climatology, geology, meteorology, biology and archaeology all made it into our final list.

In the end, we picked ten stories that covered the scope of topics we published on throughout the year, often catered to subjects our readers like to spend time with. Leaving some significant events and amazing discoveries out is always difficult, but we think we ended up with a diverse collection of memorable stories that highlight what an important year 2024 was for science.

A total solar eclipse wowed North American viewers

Solar Eclipse Viewers — People gather at Green-Wood Cemetery in New York City to witness a partial solar eclipse. Michael Nigro / Pacific Press / LightRocket via Getty Images

On April 8, tens of millions of North Americans donned funky glasses and looked skyward at a total solar eclipse. Such a rare and spectacular celestial event occurs when the moon passes between the sun and the Earth—and our beloved satellite casts a shadow over a patch beneath it, creating darkness during the day. Over the course of an hour and 40 minutes, this year’s path of totality—the area marked by total darkness—stretched from Mazatlán, Mexico, to Newfoundland, Canada.

An estimated 32 million people resided in the path, and another 12 million people were expected to travel to the area, defining the moment as one of the biggest mass-transit events to ever occur in the United States. Throughout world history, ancient civilizations that witnessed solar eclipses thought them to be anything from a message from the gods to a signal to end a battle. This year, amateur astronomers, knowing what to expect, pointed high-end cameras at the moon and sun to capture stunning images, while citizen scientists noted unusual animal behavior around them.

Unless North American residents travel beyond the lower 48, they will not have another opportunity to view a total solar eclipse until 2044, making this year’s occurrence even more special. In all, a couple hundred million people had the ability to see at least a partial eclipse. In Washington, D.C., while viewing a partial eclipse, National Air and Space Museum curator Teasel Muir-Harmony noted the importance of the occasion. “This,” she told the Associated Press, “may be the most viewed astronomical event in history.” —Joe Spring

Scientists unveiled the first-ever complete map of an adult fruit fly’s brain

Fruit Fly Brain — Researchers mapped all 139,255 neurons in the brain of an adult fruit fly, which are linked by more than 50 million synapses. Tyler Sloan for FlyWire, Princeton University, (Dorkenwald, S. et al. Nature 634, 124–138 (2024))

The brain of a fruit fly is no larger than a poppy seed, but to chart the intricacies of its cells took a historic collaboration, leveraging hundreds of volunteers, an artificial intelligence model and thousands of painstakingly imaged brain slices. In October, that effort came to fruition when researchers unveiled a nine-paper package published in Nature that described the first-ever full map of an adult fruit fly’s brain.

The stunning diagram contains roughly 140,000 neurons—including 8,453 different types of neurons—and more than 54.5 million connections among them, known as synapses. The findings represent the most complex map of a complete brain to date.

By following the connections throughout the insect’s brain, scientists are even beginning to parse which parts of the organ have certain functions. They created a computerized version of the model brain and simulated exposing it to various stimuli. It reacted just as a fly would—when presented with a sugary scent, the model activated the brain region for sticking out its proboscis.

But that wasn’t the only leap forward in brain mapping this year—in May, scientists released a data set charting the neurons, synapses and connections in a tiny piece of a human brain. The study, published in Science, details the complexity packed into a little slice of an anterior temporal lobe, thought to be involved in memory. The team mapped 57,000 cells and 150 million synapses, demonstrating the dense connections among them.

Though it might not seem like it, the human brain has a lot in common with that of a fruit fly. Some 75 percent of the genes that cause genetic diseases in humans are also found in fruit flies, so understanding their neural underpinnings could shed light on our own. Fruit flies sing, get drunk and can be kept awake with caffeine, suggesting even more similarities between their brains and ours. As Sebastian Seung, a co-senior author of the research, told the Guardian’s Ian Sample, “if we can truly understand how any brain functions, it’s bound to tell us something about all brains.” —Carlyn Kranking

2024 marked the hottest year on record

Heatwave in India — Boys bathe at a public water facility along a street on a hot June day during a heat wave in Jalandhar, India. Shammi Mehra / AFP via Getty Images

Once again, we’re ending a year that is set to be the hottest on record. According to leading weather and climate organizations, 2024 is on track to eclipse 2023 for the warmest temperatures since records have been kept. Just about any time readers looked online—April, June, August—headlines noted the hottest given month of its kind in history. In fact, from June 2023 to September 2024—16 consecutive months—the global average temperature exceeded previous records for each month, according to the World Meteorological Organization. In all, 2024 is expected to be the first year Earth is more than 1.5 Celsius hotter than the pre-industrial period. That one-year record does not mean the world has breached the Paris Agreement goal to limit the temperature increase to 1.5 Celsius, as such a mark has to be sustained over a longer period. But the past decade has been the warmest on record, and experts say this year’s high signals a dangerous milestone.

Global warming continues to accelerate, caused primarily by the burning of oil, gas and coal, which release heat-trapping greenhouse gases. Carbon dioxide levels in the atmosphere have increased by more than 50 percent since 1750, and they are set for a new record again this year. As they increase, glaciers recede, the ocean grows hotter, sea level rises, and the most extreme weather disasters are made worse.

“The record-breaking rainfall and flooding, rapidly intensifying tropical cyclones, deadly heat, relentless drought, and raging wildfires that we have seen in different parts of the world this year are unfortunately our new reality and a foretaste of our future,” Celeste Saulo, the secretary general of the World Meteorological Organization, said in a statement. “We urgently need to reduce greenhouse gas emissions and strengthen our monitoring and understanding of our changing climate.” —J.S.

Dams were torn down on the Klamath River, clearing a path for salmon

Salmon returned to Oregon’s Klamath Basin for the first time in 112 years in October, aided by a historic dam demolition project. Four dams were torn down—the largest undertaking of its kind in U.S. history—to restore the Klamath River in California and Oregon to its historic flow.

The $500 million effort removed aging dams that had been constructed in the 20th century, some having stood for more than 100 years. After the smallest dam, Copco No. 2, was taken down in fall 2023, the remaining three were deconstructed this year, beginning in January. The gates of each dam, in turn, were opened slowly, giving passage to the water that had built up behind them. Then, crews removed the remaining aging infrastructure.

Decades of advocacy by local Native American tribes and environmentalists helped lead to the project’s approval in November 2022. These pleas were centered on restoring the health of the river and once again providing salmon with an unobstructed migration path upstream to their birth waters, where they return to spawn as adults.

Since the dams have been taken out, experts reported fewer algal blooms and that the water temperature was 14 degrees Fahrenheit cooler, conditions that help prevent some bacterial infections in salmon. Toz Soto, fisheries program manager with the Karuk tribe, said at a press conference that the fish coming up the river were “really healthy.” Others echoed that sentiment: Karuk tribe member Ron Reed told the Los Angeles Times’ Ian James that the salmon have been “so much more beautiful this year.” —C.K.

Two hurricanes destroyed parts of the Southeast

Hurricane Helene Damage — Community members look through debris in the aftermath of Hurricane Helene in Marshall, North Carolina. Jabin Botsford / The Washington Post via Getty Images

The 2024 Atlantic hurricane season started off this summer with the storms Beryl, Debby and Francine, but the season really walloped the U.S. in the fall, when two powerful back-to-back hurricanes devastated the Southeast. Hurricane Helene hit Florida as a Category 4 storm on September 26, then moved north over the Southeast U.S. and caused wreckage across the region, especially in western North Carolina. The storm spurred landslides, destroyed wildlife habitat, knocked out power to millions of people and flooded towns. More than 200 people across six states died due to the storm, making it the deadliest hurricane since Katrina. Not long after that, on October 9 and 10, Hurricane Milton whirled across Florida, spawning tornadoes and leaving rubble and at least 24 people dead in its wake.

Both hurricanes had characteristics consistent with climate change’s impact on storms. With warmer temperatures, storms are intensifying more rapidly. Helene grew disturbingly fast and Hurricane Milton even more so, morphing from a tropical storm to a Category 5 hurricane with winds of 180 miles per hour in a day. Scientists also found the rain from Hurricane Helene was 10 percent heavier as a result of climate change. In addition to those impacts, and the fact that hurricanes are increasingly moving slower, warming ocean waters due to climate change will give future hurricanes a greater range. —J.S.

An ambitious space mission launched to search for signs of life on a moon

As skies cleared over Florida after Hurricane Milton passed over the state, a rocket carrying NASA’s Europa Clipper blasted off on October 14. The interplanetary spacecraft successfully started its mission toward Europa, the fourth-largest moon of Jupiter, the eldest and most enormous planet in our solar system. While many of the planet’s biggest moons are geologically active, NASA targeted Europa because it has a subsurface ocean that may harbor life.

Scientists sent NASA’s largest spacecraft ever launched to another planet not to detect life itself, but to see if the moon has conditions that can support life. The Clipper is equipped with spectrometers, a dust analyzer, a thermal camera, instruments for measuring a magnetic field and gravity, and a radar. The craft’s tools will help it find hot spots of activity, search for organic compounds and understand details about the ocean. Any discoveries that result from the trip could help scientists target a future effort to the surface that would search for signs of life.

“The mission’s goals are just to assess the habitability,” Tracy Becker, a planetary scientist with the Southwest Research Institute in San Antonio told Smithsonian magazine. “It’s the first step in that sort of long-term discovery of: Are we alone in the solar system? Or in the universe?” —J.S.

Archaeologists find that mammoth was on the menu for Ice Age Americans

Mammoth Hunt — In an illustration, the Anzick-1 infant is shown with his mother eating mammoth meat as other Clovis individuals butcher a mammoth. Artist Eric Carlson created the scene in collaboration with archaeologists Ben Potter (UAF) and Jim Chatters (McMaster University)

The diets of the Clovis people, who crossed the Bering Strait from Asia into Ice Age North America, have been an enduring mystery. Though archaeologists have uncovered indirect signs of the culture’s habits—stone points for hunting and animal bones—drawing conclusions from that assemblage relied on a lot of assumptions. But in a study published this December in Science Advances, archaeologists looked for an answer using direct evidence: the 13,000-year-old remains of the only known Clovis individual, an 18-month-old boy known as Anzick-1.

Scientists examined the infant’s bones, conducting tests known as stable isotope analysis. In this method, they studied atoms of an element with varying weights, which can act as a record of what an organism ate and drank. Being a baby, Anzick-1 primarily drank his mother’s milk, but one-third of his diet was composed of solid foods—and chief among them was woolly mammoth.

The team also reconstructed what was on his mother’s menu, based on the remnants of her milk in his bones. Mammoths made up 40 percent of what she ate, supplemented by elk, bison and, in rarer cases, small mammals such as rodents.

If the Clovis people were hunting mammoths, it would align with evidence that they migrated, perhaps driven by the mammals’ seasonal movements. But at the end of the Ice Age, mammoth populations had dwindled and fragmented. The authors add that it’s possible the natural environmental changes put stress on the mammoths—and hunting pressure from humans eventually drove them to extinction. But other researchers are less ready to jump to those continent-wide conclusions based only on evidence from one individual and his mother. The only way to verify this finding, researchers say, is to get more data—so archaeologists will need to discover more human remains from the Clovis culture. —C.K.

Iceland erupted again and again

Iceland Volcano — Lava flows from the Sundhnukur volcano on the Reykjanes Peninsula near Grindavik, Iceland. John Moore / Getty Images

The rumblings that alarmed officials near the town of Grindavik, Iceland, began last October. After earthquakes suggested a possible volcanic eruption, the town was evacuated. In December, lava poured out of the earth. But the eruptions really got going this year. Molten rock spewed out in January, February, March, May, August and November—seven eruptions in just one year’s time.

Grindavik’s residents grew used to evacuations in a country that is no stranger to volcanoes. Iceland experiences at least one eruption every five years or so. There, the mid-ocean ridge rises above the ocean and molten rock from the deep rises as the North American and Eurasian plates move away from each other. Beneath southeast Iceland, a column of molten rock—known as a hot spot—spurs even more eruptions. But on the Reykjanes Peninsula, where Grindavik sits, the earth was quiet for quite a while. Before the recent period of eruptions there began in March 2021, the last volcanic activity had occurred around 1200 C.E.

Now, while Grindavik’s residents worry, scientists flock to the blazing rock to learn more. One thing they are finding is that the lavas from different eruptions have chemical similarities, suggesting they are somehow connected deep below—a surprising find. And geologists will likely have plenty of opportunities to discover more, as they think this latest burst of molten rock signals the onset of centuries of eruptions for the area. In the meantime, the lava continues to move, recently threatening to steamroll Iceland’s iconic Blue Lagoon. —J.S.

Bird flu infected cows and dairy workers

Since it was first spotted in 1996, the H5N1 strain of avian flu has been spreading in domestic and wild birds. But in 2020, the strain experienced a mutation that makes it more infective in waterfowl. From there, it hit new milestones—the strain left its typical range of Europe, Asia and Africa to reach the Americas and the Antarctic, wreaking havoc on birds. In 2022, scientists detected the strain in mammals. And in 2024, it made headlines once again as the virus cropped up in dairy cows in the United States.

First, the strain infected a young goat in Minnesota, marking the first U.S. livestock to be infected. Then, dairy cows in Texas and Kansas were reported sick, experiencing symptoms and producing discolored milk. At the time of this writing, more than 800 dairy herds have been affected across 16 states. Researchers detected bird flu in grocery store milk, but federal health officials spread the word that pasteurization kills the virus—so the only milk that could potentially be dangerous was raw milk.

Texas’ health department announced a dairy worker in the state had contracted H5N1 in March, marking only the second person infected with the strain in U.S. history. Scientists have expressed concerns about potential under-reporting of human cases and worried that the nation as a whole is “underprepared” to deal with the virus if it spreads quickly. Now, the country’s reported total of human cases has approached 60.

In recent weeks, the pathogen has made headlines again, as epidemiologists and policymakers share concerns about what disease preparedness might look like under the upcoming Trump administration. In December, the Department of Agriculture announced it would test all raw milk for avian flu. But because the virus does not appear to be spreading between people, the Biden administration reportedly has no plans to authorize a vaccine for humans. For now, though, the Centers for Disease Control and Prevention maintains that the risk to the general public remains low. —C.K.

Colorful auroras dazzled viewers across the planet

Northern Lights — Northern lights are seen in Sugarloaf Key, just 15 miles from Key West, Florida. Jen Golbeck / SOPA Images / LightRocket via Getty Images

Ethereal greens and reds lit the skies across the Earth on May 10 and 11, during the most dramatic geomagnetic storm in more than 20 years. Some people spotted the shimmering colors with the naked eye, while others caught the glow with their cameras. But all experienced something highly unusual: The northern lights were even seen as far south as Florida—something that surprised some seasoned aurora chasers.

The source of this extreme space weather event can be traced to the sun, which is currently near the climax of its 11-year cycle of fluctuating activity. This period of high magnetic turbulence, known as the solar maximum, results in our nearest star launching elevated amounts of radiation as solar flares, as well as spewing more magnetic fields and plasma as coronal mass ejections. When these charged particles hit Earth’s atmosphere, our planet’s own magnetic field drags them to the poles, where they energize molecules of gas. In turn, the gases emit a colorful glow as they release the excess energy. Oxygen and nitrogen at various altitudes create different hues, and they blend together into the dazzling sights we know as auroras.

Even during these periods of high solar activity, a storm like May’s is rare. Not only does the sun have to hurl a huge amount of material out into space, but that material also has to hit the Earth—a small target on the grand scale of the solar system. Still, far-reaching auroras happened again in October, putting on a show for skywatchers in every U.S. state, except for Hawaii, as Forbes’ Jamie Carter reported.

As the sun shifts closer to its solar maximum, astronomers expect widespread auroras to happen again. Aurora chasers are looking toward 2025 with hopeful anticipation: Historically, the highest solar activity has come on the tail end of the maximum, so we might be in for even more stunning displays of lights in the coming years. —C.K.