Category: 7. Science

World Asteroid Day started with a real bang.

On June 30, 1908, an asteroid about 65 meters wide collided with Earth’s atmosphere and exploded several miles above Siberia; the force of the blast flattened and burned millions of trees over an area of more than 2,000 square kilometers. Today, the anniversary of the Tunguska blast has become World Asteroid Day: a science holiday co-founded by a rock music legend and an Apollo astronaut.

In 2015, Apollo 9 lunar module pilot Rusty Schweickart helped launch World Asteroid Day with astrophysicist and Queen guitarist Brian May. The United Nations officially recognized the event a year later in 2016. Earlier this month, Arizona senator Mark Kelly – also a former astronaut – introduced a Senate resolution that, if passed, would officially recognize June 30 as World Asteroid Day in the U.S.

I spoke with Kevin Schindler, resident historian at Lowell Observatory in Arizona, about the origins of World Asteroid Day, the history of planetary defense, and what asteroids can reveal about the history of our Solar System.

Discovering the Danger from Outer Space

Around 200 years ago, in the 1830s, geologists began to study fossils and figure out that several mass extinctions had wiped out whole ecosystems of species on Earth in the distant past.

“In recent decades, they realized that those weren’t necessarily caused by something on Earth, but by something impacting from space – like the Cretaceous Tertiary boundary,” says Schindler.

In the 1960s, geologist Walter Alvarez discovered a thin layer of black clay in rocks around the world. Below the black line, the rocks were rich in fossils; above it, they were nearly barren. The same layer of black clay showed up all around in the world: in rock outcroppings in Italy and New Zealand, and in samples from the floor of the Pacific Ocean. And it clearly marked a deadly before-and-after moment in Earth’s history – one that happened around 66 million years ago.

Alvarez suspected that the black clay was something alien; it contained bizarrely large amounts of an element called iridium, which is vanishingly rare here on Earth but more common in asteroids. He began to realize that an asteroid or comet may have slammed into our planet 66 million years ago, kicking off a mass extinction and scattering iridium-rich black dust over the planet like a burial shroud.

The pieces came together in 1978 when geophysicists Glen Penfield and Antonio Camargo discovered the outline of a crater hundreds of kilometers wide at the edge of Mexico’s Yucatan Peninsula. Its center lies at the bottom of the Gulf of Mexico. Penfield and Camargo named the crater for one of the communities that now lies within its boundaries: Chicxulub Pueblo.

Other craters – smaller but still impressive – also make it obvious that our planet has had more than a few run-ins with meteors during its long history.

“And while there’s not as much debris floating around in our Solar System as when it was newly-formed, there’s still stuff out there,” says Schindler. “And it’s inevitable that at some point that stuff will come back and get us again.”

From Deep Impact to DART

So we’ve known almost 60 years that asteroids and comets could threaten life on Earth.

“In the 1980s and 1990s, there was a search to look for bodies that specifically could impact Earth,” says Schindler. “Phase one of all this started with, ‘okay, let’s look for these bodies that could hit us,’ and then a couple decades later is when we got to phase two, ‘what can we do about it if we do find these things?’”

Strangely enough, it was a pair of high-budget, low-scientific-accuracy Hollywood blockbusters that really brought planetary defense to public attention, according to Schindler. The summer of 1998 featured not just one but two movies about humanity trying to save itself from extinction by blowing up an incoming chunk of space rock. In Armageddon, a wildly-improbable effort by a team of offshore drillers saves Earth from an asteroid impact; in Deep Impact, a similarly-improbable effort fails to save Earth from a comet (so the summer ends in a cinematic tie).

“The good thing about those movies is that, even though they’re not scientifically accurate in every way, they certainly built awareness enough to where lawmakers said, you know, we should put some money aside to study this stuff more,” says Schindler. “Hollywood, in some ways, has helped the cause to learn more.”

And, as science fiction often does, Deep Impact and Armageddon provided thought experiments (albeit not super-accurate ones, to put it mildly) for the ideas that would eventually become actual efforts at planetary defense. According to Schindler, theoretical ideas about whether we could destroy an incoming meteor eventually shifted to ideas about just nudging the deadly object off-course.

“This is just something that’s really been developed in the last decade or so and – I wouldn’t say culminated, but really became well-known with the mission that went up to deflect the moon of an asteroid to see if it was possible,” says Schindler.

That mission was NASA’s Double Asteroid Redirection Test, or DART, in which an intrepid little spacecraft flew 7 million miles to crash into the asteroid Dimorphos and knock it off-course. Dimorphos is actually a mini-moon that orbits another, larger asteroid called Didymos. Astronomers at Lowell carefully measured Dimorphos’s orbital path around its parent asteroid before and after the impact – and they saw evidence that DART had succeeded in knocking Dimorphos into a different orbit.

It’s a long, long way from deflecting one tiny asteroid moonlet onto a different path around its parent asteroid to deflecting something the size of the Chicxulub impactor – or even Tunguska – as it’s barreling toward Earth. But the consensus seems to be that DART was a good start.

“The biggest thing, I think, was that it is possible. This was a very controlled initial step,” says Schindler. “This was certainly promising enough that we should keep doing these tests in different sizes of body and different compositions, because depending on what it’s made of, a body might react differently to something impacting it.”

Fossils of the Early Solar System

Meanwhile, Schindler and World Asteroid Day also want the public to know that asteroids are more than potential threats: they’re an orbiting treasure trove of information about the history of our Solar System and even the origins of life.

Most asteroids are chunks of rock that coalesced early in our Solar System’s history but never grew massive enough to become planets; they’re like the seeds of planets that might have been. Others are the debris left behind by collisions between objects in those chaotic early days of the Solar System, when planets were forming and gas giants migrated, scattering lesser objects in their wake.

“They tell us what the early composition was and what a chaotic time it was in the early part of our Solar System,” says Schindler.

Those clues are written not just in the chemical and physical makeup of asteroids, but in their orbital paths around the Sun. By studying and modelling how those paths have changed over the years, scientists can reconstruct how asteroids and planets may have interacted. The orbits of modern asteroids are like the “footprints” of planet formation, migrating gas giants, and long-ago collisions.

Today, NASA’s Lucy mission is exploring the asteroid belt, getting up close and personal with several of these objects. Meanwhile, NASA’s OSIRIS-APEX mission is on its way to study the asteroid Apophis, which will pass close (but not too close!) to Earth in 2029.

“And now we are studying planetary systems around other stars. Better understanding our Solar System, we can now look at others and see how typical we are,” says Schindler. “You don’t know that without knowing your own Solar System pretty well, so it really has helped us to learn about, sort of, our heritage, I guess.”

World Asteroid Day

World Asteroid Day aims to tie all of those things together, promoting awareness of planetary defense but also of the immense scientific value – and maybe monetary value, eventually – of asteroids.

At Lowell Observatory, that awareness is hard to escape; the observatory stands just an hour’s drive from Meteor Crater – which is exactly what the name suggests, a 213-meter-deep, 1200-meter-wide crater where an object about the size of a Boeing 747 slammed into the desert floor around 50,000 years ago.

“The proximity of Lowell Observatory, where we’re studying bodies in space, and Meteor crater, where we’ve seen the result of one of those bodies hitting Earth – how convenient is that? We’re looking at both ends of it, from when it’s still up in space to the final product if something like this hits.”

When humans burst into laughter together, moods lift almost automatically. New research shows that a similar boost happens in our closest cousins.

An international team led by Indiana University scientists has discovered that bonobos become more upbeat after hearing the giggles of their companions. This finding pushes the evolutionary history of positive emotions back millions of years.

Laughter changed ape choices

To explore laughter’s influence, the researchers designed a cognitive-bias test often used in animal psychology to gauge optimism or pessimism.

First, they trained bonobos at the Ape Initiative in Des Moines, Iowa, to recognize two kinds of boxes: black ones that always contained a delicious snack and white ones that were always empty.

Once the apes consistently chose black and ignored white, the experimenters introduced a third, ambiguous gray box. They then played one of two sounds: recorded bonobo laughter or a neutral control noise.

“We know that other apes, like chimpanzees, have contagious laughter during play,” said lead author Sasha Winkler, a primatologist at Duke University. “We were wondering if that behavior could be explained by positive emotions produced from the sound itself.”

If the bonobos felt a surge of good feeling after hearing laughter, the team expected them to treat the uncertain gray box as if it were the rewarding black one.

That is exactly what happened. “Think of it like the rose-colored glasses effect,” Winkler said. “The bonobos were much more likely to approach the gray boxes after hearing laughter, treating them like the rewarded boxes, and indicating a more optimistic expectation of finding a treat.”

Tracing optimism to our ancestors

This study is the first experimental proof that great-ape laughter can shift mood and cognition the way human laughter does.

“The tendency to behave more optimistically after hearing laughter suggests that the sound alone induced a positive emotional state in bonobos,” said senior author Erica Cartmill, the director of Indiana University’s Cognitive Science Program.

“This is the first study of which we’re aware to measure a positive affect shift in nonhuman primates from a brief experimental intervention.”

Great apes –  bonobos, chimpanzees, gorillas, orangutans – all emit play calls that acoustically resemble human chuckles. Earlier work tied those sounds to a common evolutionary origin. The new findings add a cognitive twist.

“Our results suggest that laughter in other apes shares not only phylogenetic and behavioral similarities with human laughter but also perhaps some of the same cognitive-emotional underpinnings,” Winkler noted.

“This emotional contagion appears to have been present in the primate lineage long before the evolution of language.”

Laughter, empathy, and apes

Emotional contagion is often described as a foundational element of empathy – the capacity to share another’s feelings. As Winkler put it, “studies like ours can help to untangle the evolutionary building blocks of empathy, communication, and cooperation in humans.”

By revealing that a simple vocal cue can brighten outlooks in bonobos, the research suggests that the mechanisms linking social sound to positive mood were already in place in a common ancestor millions of years ago.

Cartmill added that the work answers a long-standing bias in emotion research. “Our emotions influence many aspects of cognition, including memory, attention, and decision-making, but research has historically focused on negative emotions with clear behavioral correlates, like fear and aggression.”

“We wanted to better understand the relationship between positive affect and cognition in our closest living relatives.”

Kanzi and the future of empathy

The experiments involved four bonobos, including the celebrated language-using ape Kanzi, who recently passed away.

“I feel incredibly grateful to have had the opportunity to work with Kanzi while he was still alive,” Winkler said.

“We hope this brings greater public awareness of the remarkable similarities between us and bonobos, who are an endangered species. We have so much to learn from these incredible animals.”

Future studies will test whether laughter exerts similar cognitive effects in chimpanzees and other primates. They will also explore how social context – for example, hearing laughs from friends versus strangers – modulates optimism.

For now, the discovery that bonobo giggles brighten expectations highlights a shared emotional heritage and hints that a simple laugh has been boosting group spirits since long before humans walked the Earth.

The study is published in the journal Nature Scientific Reports.

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In June last year, astronomers scanning the sky from the remote deserts of Western Australia picked up a sudden, blinding burst of radio energy. The signal was so powerful, it temporarily outshone every other radio source in the sky, according to a report of CNN.

At first, the team at Curtin University believed they had discovered something extraordinary — perhaps a new type of astronomical object or an ultra-rare fast radio burst (FRB) from within our galaxy.

“We were really excited,” Dr. Clancy James, associate professor at Curtin’s Institute of Radio Astronomy, told CNN. “It looked like we had found an unknown object near Earth.”
The data came from the ASKAP telescope, an advanced array of 36 large antennas spread across the Wajarri Yamaji Country in Western Australia. This setup is usually used to detect FRBs — intense, millisecond-long bursts of radio energy from distant galaxies, potentially caused by exotic phenomena like magnetars, the ultra-magnetic remains of dead stars.

These bursts are not only puzzling but also powerful tools for mapping the “missing” matter in the universe. But this particular signal wasn’t behaving like a normal FRB.

Unlike typical FRBs that originate billions of light-years away, this burst appeared to be shockingly close — just 4,500 kilometers (2,800 miles) from Earth. When the team zoomed into the data, the image became blurry — a telltale sign the source was much closer than expected.After sifting through satellite databases, the astronomers matched the source to Relay 2, a long-defunct U.S. communications satellite launched in 1964. Relay 2 had been orbiting silently since its instruments failed in 1967.But this sparked an even more bizarre question: Could a dead satellite suddenly burst back to life?

A Flash from the Past
The leading theory is an electrostatic discharge — a burst of energy caused by a buildup of electric charge on the satellite’s surface, similar to the shock you get from touching a doorknob after walking on carpet. When the charge releases, it can emit a sharp flash of radio energy.

While these discharges are common and often harmless, the intensity and brevity of this one — just 30 nanoseconds long — was unprecedented. In fact, it was 2,000 to 3,000 times brighter than any other signal the ASKAP instrument typically detects.

Another possibility, though less likely, is that a micrometeorite no larger than a grain of sand slammed into Relay 2 at extreme speed, causing a burst of plasma and radio waves. However, the team estimates there’s only about a 1% chance that was the cause.

Why This Matters
Although this turned out to be a human-made source, the discovery underscores a major challenge in space research: the interference of space junk with astronomical observations. With over 22,000 satellites launched since the dawn of the space age — and thousands no longer functional — Earth’s orbit is becoming a crowded and unpredictable place.

Signals like the one from Relay 2 could easily be mistaken for cosmic phenomena, especially as ground-based observatories like ASKAP and upcoming arrays such as SKA-Low (Square Kilometre Array) continue to scan the skies for fast, faint signals.

While this unexpected “zombie signal” turned out to be from a defunct satellite, it opens up new possibilities for using radio telescopes to monitor aging spacecraft for signs of unusual activity.

When we think of fossils, giant prehistoric creatures like dinosaurs may come to mind. But the fossil record also holds the remains of smaller organisms, such as fish and corals, that tell us about our oceans’ past.

Scientists at the Smithsonian Tropical Research Institute (STRI) recently studied exposed fossilized coral reefs from Panama’s Bocas del Toro Province and the Dominican Republic, comparing them with nearby modern reefs. These exceptionally well-preserved reefs date back 7,000 years, offering a unique window into what Caribbean reefs looked like before human impact. Within the fine sediments of these ancient reefs, the team discovered thousands of tiny fish ear bones and shark scales, allowing them to reconstruct entire ancient fish communities.

The results revealed a dramatic shift in fish communities over time: sharks have declined by 75% and human-targeted fish have become 22% smaller. But the real surprise came from the prey fish species — those eaten by predators like sharks. These have doubled in abundance and grown 17% larger on modern reefs. This study provides the first historical evidence for the “predator release effect” — where removing top predators allows their prey to flourish. Whilst scientists have long predicted such an effect, evidence for it was scarce without knowing what reefs looked like before human impact. Remarkably, the tiniest reef fish that shelter in coral crevices, showed no change in size or abundance over millennia. Their stability suggests a remarkable resilience to the multitude of changes occurring on reefs at higher layers of the food chain.

To compare fossilized and modern reefs, scientists collected, quantified and measured thousands of skeletal remains, including the tiny tooth-like scales that give shark skin a sandpapery texture, called dermal denticles.

To study the abundance and size of prey fish and small coral reef-sheltered fish (also known as cryptobenthic fishes), they also examined fish otoliths — the calcium carbonate structures found in fishes’ inner ears. Because otoliths grow in layers, scientists can estimate a fish’s size at death. In total, the team examined 807 denticles and 5,724 otoliths.

The behavior of some organisms can also leave a fossil record. In this study, scientists measured the frequency and size of damselfish bite marks on coral branches from both fossilized and modern reefs. They found that the number of bites has increased in modern reefs — also indicating the rise in prey fish populations.

These results illustrate an important change in food webs of modern Caribbean reefs: with fewer sharks and other predatory fish to control the population of exposed prey fishes, they have become bigger and more abundant, reflecting release from predation. On the other hand, small reef-sheltered fish remained unchanged in size and abundance over thousands of years, suggesting that the degradation of water quality and habitat in the region did not drive the changes in community structure.

This study demonstrates the power of the fossil record for future conservation. By revealing what reefs looked like before intensive human fishing, these 7,000-year-old fossils provide the missing baseline critical to understand the food webs of pre-human coral reefs, and document which elements of reefs changed and which are resilient.

This research, published in the Proceedings of the National Academy of Sciences, PNAS, was a collaboration among scientists from the Smithsonian Tropical Research Institute (STRI), the Sistema Nacional de Investigación (SENACYT) in Panama, the Marine Science Institute at the University of Texas at Austin, the Center for Biodiversity Outcomes at Arizona State University, the Graduate School of Oceanography at the University of Rhode Island, The Nature Conservancy, the Biodiversity Research Center at Academia Sinica in Taiwan, the Department of Earth & Environmental Sciences at Boston College, and the Cotsen Institute of Archaeology and Department of Anthropology at the University of California, Los Angeles.

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Journal

Proceedings of the National Academy of Sciences

Article Publication Date

30-Jun-2025