NASA’s Planetary Defense Experiment Successfully Alters Binary Asteroid’s Orbit Around the Sun

New findings reveal that the 2022 DART collision not only decreased the orbit of the moon Dimorphos around its parent asteroid Didymos but also subtly altered the trajectory of the entire binary asteroid system around the sun.

This artist’s illustration depicts a cloud of debris ejected after NASA’s DART spacecraft collides with the asteroid Dimorphos. Image credit: ESO/M. Kornmesser.

During the NASA DART mission, the collision with Dimorphos generated a massive cloud of rock debris and altered the shape of the 170-meter (560-foot) asteroid.

This debris not only escaped but also provided Dimorphos with an explosive thrust—what scientists refer to as a momentum enhancer.

The momentum enhancement factor from the DART impact was approximately 2, indicating that the spacecraft’s impact was effectively doubled due to the debris expelled.

Previous studies have determined that the moon’s 12-hour orbit around the 805-meter-wide Didymos was shortened by 33 minutes.

The latest research indicates that the collision ejected so much material from the binary asteroid system that it even modified the binary star’s 770-day orbital period around the sun by 0.15 seconds.

Dr. Rahil McAdia from the University of Illinois at Urbana-Champaign stated, “The change in the orbital velocity of the binary system was about 11.7 microns per second, or 1.7 inches per hour.”

“Over time, even minor adjustments in an asteroid’s motion can influence the likelihood of a dangerous object colliding with Earth.”

To demonstrate the DART mission’s measurable influence on the binary star system, the researchers meticulously tracked DART’s solar orbit.

In addition to radar and ground-based asteroid observations, they monitored stellar occultations—events where an asteroid passes directly in front of a star, briefly blocking its light.

This method enables precise measurements of the asteroid’s speed, shape, and position.

The research team relied on volunteers worldwide who observed 22 stellar eclipses between October 2022 and March 2025.

“These stellar occultation observations, combined with years of existing data, were essential in calculating how DART altered Didymos’s orbit,” said Dr. Steve Chesley from NASA’s Jet Propulsion Laboratory.

“This research is highly dependent on weather conditions, often requires travel to remote areas, and success is not guaranteed.”

“This breakthrough would not have been possible without the unwavering support of numerous volunteer observers globally.”

Analyzing Didymos’ motion also enabled scientists to ascertain the density of both asteroids.

Dimorphos was found to be slightly less dense than previously estimated, aligning with the theory that it formed from rock fragments shed by the rapidly rotating Didymos.

This loose material eventually coalesced, creating what is known as a “rubble pile” asteroid, Dimorphos.

Our findings indicate that targeting secondary asteroids in binary systems could be a viable strategy for deflecting kinetic impacts and enhancing planetary defense.

Dr. Preity Cowan from the University of Auckland remarked, “The DART mission proved to be a triumph. An asteroid system deemed safe for Earth was meticulously chosen, allowing NASA to impact the small satellite, leading to a faster orbit around its parent asteroid.”

“This new analysis unveils even more stunning and safe outcomes.”

“The combination of the spacecraft’s impact and the resulting ‘shock’ from the ejected material from the satellite was enough to visibly alter the binary star system’s path around the sun.”

“These adjustments may seem trivial, but in terms of trajectory, even minor changes, particularly if applied early on, can have significant repercussions.”

This milestone is crucial for developments in planetary defense,” said Professor Roberto Armelin from the University of Auckland.

“In a genuine hazardous scenario, small adjustments implemented promptly could prevent a potentially dangerous asteroid from colliding with Earth.”

The next phase is ESA’s Hera mission, set to launch in 2024, which will visit the Didymos system to measure its crater, asteroid mass and structure, and the efficiency of the impact.

“These measurements will aid in transitioning this historic experiment into a reliable planetary defense technology.”

For more information, check the result published in Scientific Progress.

_____

Rahil Makadia et al. 2026. Direct Detection of Geocentric Deflections of Asteroids: Didymos System After DART. Scientific Progress 12 (10): 10.1126/sciadv.aea4259

Source: www.sci.news

Armored Dinosaur’s “Crazy” Spikes: Beyond Just Defense

Reconstructing the life of Spicomellus Afer – Fossils of ankylosaurus discovered in Morocco

Matthew Dempsey

The dinosaur fossils unearthed in Morocco may represent some of the most bizarre and intricately armored vertebrates to have roamed the Earth.

The initial discover of Spicomellus Afer in Morocco was reported in 2021. This suggests that it comprises only rib bone fragments, adorned with fused spikes, from a group of dinosaurs categorized as Ankylosaurs. These herbivorous dinosaurs with stout bodies are known for their protective plates and spiked coverings.

In October 2022, farmers in the Badlands of the Middle Atlas Mountains began to uncover a much more complete Spicomellus skeleton. This fossil has been dated back to approximately 165 million years ago during the Jurassic period, suggesting that the creature may have reached lengths of about 4 meters and weighed as much as 2 tons.

Like modern crocodiles, armored dinosaurs such as Stegosaurs and Ankylosaurs possessed osteoderms—bony plates embedded within their skin. However, in the case of Spicomellus, its fossil reveals two distinct types of bone structures: the bony skin and spikes are fused together.

“This is unprecedented among armored dinosaurs, and indeed among any species with bony skin, making it totally astonishing,” remarked Susanna Maidment, a member of the team analyzing these fossils at the Natural History Museum in London.

Overall, the Spicomellus specimen boasts numerous armored spikes that cover nearly its entire body. Spikes attached to the neck region can measure around 1 meter in length. Additionally, fused vertebrae in the tail suggest it could serve as a potent weapon.

The creature’s peculiar attributes led Maidment to conclude that extreme descriptors were warranted in their explanations. “In scientific literature, phrases like ‘crazy’ are not acceptable. I opted for more elaborate language,” she noted. “One of my colleagues suggested that referring to its anomaly as ‘baroque’ could also be fitting for our research.”

This extreme form of armor would likely hinder the species’ movement through various environments, leading it to inhabit areas dense with vegetation, according to Maidment. “It would have been quite cumbersome,” she added.

Given the complexity of its armor, researchers speculate it served purposes beyond mere defense, potentially playing a role in mate attraction. “Elements that seem entirely extraordinary in the fossil record are often connected to reproduction, and I believe this complex armor was likely some form of display,” she concluded.

Dinosaur hunting in the Gobi Desert, Mongolia

Join an exhilarating and unique expedition that explores the fossil remains of dinosaurs amidst the vast wilderness of the Gobi Desert, one of the world’s most renowned paleontological sites.

Topics:

Source: www.newscientist.com

Untangling the Chaos: Analyzing the U.S. Climate Disaster Defense Strategy

The National Weather Service is gearing up to deliver compromised forecasts. Scientists are advised to suspend all but essential travel, while university-based researchers report that a multi-million dollar federal grant for climate modeling has been abruptly withdrawn.

This represents a new standard within the National Oceanic and Atmospheric Administration (NOAA), the US’s primary weather and climate agency, as indicated by interviews with current and past personnel, along with research collaborators.

Six months into the new US administration, the ramifications of significant political shifts are becoming apparent. Although official budget discussions are ongoing, a quiet dismantling is already in progress. Employees warn this jeopardizes the agency’s capacity to safeguard the public against climate-related threats such as floods, wildfires, and hurricanes.

The repercussions extend beyond US borders. NOAA’s research and data underpin the initiatives of global organizations like the Intergovernmental Panel on Climate Change and the World Weather Organization.

If the US steps back, other nations might need to fill that void, risking missed early warnings for imminent disasters. In fact, EU countries and academic institutions are already racing to recruit former NOAA staff in hopes of bridging the gap.

“It’s nothing but confusion and uncertainty,” said a current NOAA scientist with over 15 years of experience, as reported by BBC Science Focus. “Planning anything is incredibly challenging due to persistent unpredictability.”

Service Reductions and Research Loss

Earlier this year, the National Weather Service (NWS), a division of NOAA, entered into an agreement that led to a reduction of services at 122 weather offices nationwide, stemming from a significant staffing shortage after a wave of early retirements and layoffs.

Currently, public forecasts remain available. However, as wildfire and hurricane seasons peak, vulnerabilities in the system could quickly surface.

The NWS is permitted to hire meteorologists, hydrologists, and radar engineers to fill 450 critical vacancies, but former staff members caution that it might already be too late.

“Public safety is undeniably at risk due to a hastily executed process led by individuals who are overwhelmed by this new role in the NWS,” said meteorologist Alan Gerald, who spent 35 years with NOAA before accepting an early retirement package this year.

While recruitment and training could take months, the departure of senior personnel means lost institutional knowledge could be permanent, Gerald noted.

Even if staffing shortages are ultimately addressed, current personnel are warned that the repercussions may impact long-term preparedness. “What is sacrificed is the research aspect and our ability to continue advancing our modeling and prediction expertise,” stated NOAA scientists.

NOAA’s National Hurricane Centre provides crucial forecasts for tracking the paths of powerful storms, such as the devastating Hurricane Beryl in 2024. – Photo credit: Getty

External partners are already experiencing the consequences. A researcher associated with NOAA shared with BBC Science Focus that a multi-million dollar next-generation weather modeling initiative is now in jeopardy after losing federal backing.

“We’re already not perfect in our work,” the researcher remarked. “And with the climate changing, leading to more extreme events, if we don’t evolve accordingly, lives will be lost, property damage will escalate, and we risk missing critical storm warnings.”

Read more:

“Avoid the term climate.”

Internally, scientists have been instructed to halt all non-essential travel, including attending conferences, which are vital for collaboration across scientific disciplines. This policy was reportedly communicated verbally without formal documentation.

Several sources noted that oral directives have become the norm, often lacking written records.

Scientists added that there is growing reluctance to mention the term “climate.”

“While I’ve never been directly told, ‘Don’t publish this’ or ‘Don’t address climate,’ it’s implicit. For example, external funding guidelines suggest we approach topics differently,” explained a NOAA scientist. “So when working with external colleagues, we often hear ‘don’t mention climate and let’s frame this differently.’

This self-censorship is part of a broader crackdown on climate-related initiatives.

In April, the Commerce Department withdrew nearly $4 million in NOAA funding from Princeton University, effectively terminating three significant collaborative agreements aimed at predicting coastal flooding, sea-level rise, droughts, fires, and floods.

In a general statement, the department criticized one of the Princeton awards for promoting “unfounded and inflated climate threats” and creating “climate anxiety.” Another was deemed no longer aligned with the Trump administration’s priorities, justifying that it suggested significant fluctuations in water availability due to global warming.

The statement proceeded to describe changes in precipitation patterns and rising sea levels as “suspected” effects.

Protesters gathered at a rally outside NOAA Headquarters to protest recent staff reductions on March 3, 2025 – Credit: Getty

In May, NOAA’s Grant Management Department terminated the Northwest Climate Resilience Collaborative (NCRC), a University of Washington initiative that assisted rural communities and tribes in adapting to flooding and intensified heat.

Reports indicate that grants are being cut to “rationalize and reduce federal expenditures and size” since they no longer align with “program goals or agency priorities.”

Separately, the White House also slashed funds associated with the Sixth National Climate Assessment (NCA), despite legal mandates to prepare a comprehensive climate report every four years. Originally scheduled for release in 2028, its future now hangs in uncertainty.

“Part of this is a tactic to downplay the significance of the work being done,” remarked a NOAA scientist.

“For instance, we now refer to what we consider ‘climate’ as something broader than weather patterns. While we traditionally described forecasts as ‘climate,’ we’ve stopped using that term to avoid attracting attention to it.”

Erosion of Knowledge

Since the new administration took office, NOAA has lost around a fifth of its workforce, with over 1,000 employees, many holding senior leadership positions, opting for early retirement or buyouts this year.

“When experienced staff leave due to exhaustion, that’s one thing,” Gerald remarked. “But losing a significant portion of seasoned personnel is a different issue entirely.”

Morale has plummeted. Employees report that independent programs are being restructured or eliminated with little notice or explanation, and even if funding is restored, considerable damage may already be irreversible.

“We’re talking about a research infrastructure cultivated over 50 or 60 years,” Gerald stated. “That could essentially collapse within a year.”

Carl Gouldman, who recently led the US Integrated Ocean Observing Systems office within NOAA, echoes these concerns.

“The relationships and partnerships necessary for innovation and creating essential features are at substantial risk and may never recover,” he warned. “Humpty Dumpty is shattered, and you can’t reassemble him.”

Negotiations for NOAA’s 2026 budget are still proceeding. The White House’s proposal suggests a 40% cut in institutional funding. Alternate proposals from the House and Senate are more generous, but a compromise could still be months away.

However, Gerald is particularly worried about the interim actions of the administration. He recently referred to a public statement from Russ Vought, director of the Office of Management and Budget, who indicated that the administration “is not aligned with the legislative department’s understanding of its own authorities and responsibilities.”

“We still have a chance to reevaluate this and consider its implications,” Gerald said. “With climate change and the expanding human footprint—more people causing harm for various reasons—the demand for warnings and predictions is only escalating.”

NOAA has not responded to requests for comment.

Read more:

About Our Experts

Alan Gerald is a meteorologist with over 35 years of experience in issuing warnings and forecasts, focusing on reducing the social impacts of hazardous weather, water, and climate events. He has served for more than 20 years in senior leadership roles at NOAA and most recently was the director of analysis and understanding for the National Intense Storm Institute until March 2025.

Karl Golman is a recently retired director of NOAA’s US Integrated Ocean Observing Systems office, with 25 years of leadership experience in the agency. During his tenure at NOAA, he oversaw annual budgets ranging from $5 billion to $200 million.

Source: www.sciencefocus.com

Trump’s Golden Dome Defense Initiative May Ignite Space Force Rivalry

US President Donald Trump (left) announces the Golden Dome Missile Defense Shield, joined by US Secretary of Defense Pete Hegseth (right).

Chris Kleponis/Pool/EPA-EFE/Shutterstock

US President Donald Trump has introduced the Golden Dome defense initiative, designed to intercept threats like polar sounds, ballistic missiles, and advanced cruise missiles.

“Once fully operational, the Golden Dome is engineered to intercept missiles launched from around the globe or even from outer space,” Trump stated during a White House announcement on May 20th. Watch here.

However, many experts express skepticism regarding the feasibility of such a comprehensive interception system. Concerns have been raised that, even if successful, the Golden Dome could require over a decade to implement and exceed $50 trillion in costs, potentially exacerbating global nuclear arms races and space militarization.

What is the Golden Dome?

The project is inspired by Israel’s Iron Dome system, which utilizes ground-based missiles to intercept incoming artillery and rockets launched from shorter ranges. In contrast, the Golden Dome aims to safeguard a significantly larger area, with the landmass of the contiguous US being over 350 times that of Israel.

According to Trump and his team, the system should be capable of targeting ballistic missiles fired from distant locations, advanced cruise missiles operating at lower altitudes, and hypersonic missiles traveling at speeds exceeding five times the speed of sound. These could possess nuclear or conventional warheads.

To detect and neutralize threats, the Golden Dome is expected to employ a mix of “space-based sensors alongside air and missile defenses,” as noted by U.S. Secretary of Defense Pete Hegseth in a statement. Essentially, the Golden Dome would represent an umbrella system integrating multiple technologies to combat various threats, as explained by David Berbach in an article with New Scientist.

Nevertheless, many of these defense capabilities are still in development or do not currently exist. For instance, the proposal mentions space-based interceptors in low Earth orbit, which remains a technological hurdle yet to be overcome. Thomas Gonzalez Roberts from Georgia Tech pointed this out.

A similar concept known as Star Wars was initially suggested by President Ronald Reagan as part of his strategic defense initiatives during the Cold War. Trump characterized the Golden Dome as an endeavor to complete “the mission President Reagan initiated 40 years ago.”

How does the Golden Dome function?

Experts in missile defense have likened the challenge of intercepting long-range nuclear missiles to “shooting bullets at bullets,” given that “the targets are minuscule, emit minimal signals, and move rapidly.” Even the most optimistic technical specialists acknowledge that achieving a 100% interception rate is unlikely.

The U.S. already possesses an array of ground-based interceptor missiles located predominantly in Alaska, capable of countering “dozens of oncoming warheads at best,” according to Burbach. He also highlighted that both Russia and China are working on countermeasures to complicate missile detection and interception.

“Interception of subsonic cruise or short-range ballistic missiles launched from just outside the U.S. borders employs established technology, yet effectively implementing those defenses across the nation can be cost-prohibitive,” said Burbach. He further emphasized the difficulty of the Golden Dome’s goal to thwart a significant volume of intercontinental missiles, particularly from China and Russia.

Trump’s vow to shield the Golden Dome against missile strikes from distant points, even from space, “requires a densely packed constellation of space-based missile interceptors in low-Earth orbit that could engage missiles within moments of their launch,” indicated Roberts.

“The number of satellites necessary far exceeds the current constellations launched,” he noted. Presently, the largest constellations consist of about 7,000 Starlink satellites managed by SpaceX.

What is the estimated cost of the Golden Dome?

Trump has suggested a budget of $175 billion for the Golden Dome, though this funding remains unapproved by Congress. The Congressional Budget Office, a nonpartisan agency, has estimated that space-based interceptor systems akin to the Golden Dome may cost upwards of $542 billion.

“It’s uncertain what expenses are incorporated in the $175 billion figure,” noted Patrycja Bazylczyk of the Center for Strategic and International Studies in Washington, DC.

Trump also asserted that the Golden Dome would be “fully operational” by the conclusion of his second term, a claim that experts find dubious. “The three-year timetable is overly ambitious. Realistically, this initiative will take at least a decade or more,” Bazylczyk added.

The timelines could significantly depend on existing military system capabilities. “Notable advancements could arise in the short term, including the deployment of new interceptors, radar systems, space-based sensors, and technology demonstrations,” Bazylczyk mentioned.

Ultimately, considerable challenges exist regarding the rapid deployment of thousands of satellites required for the Golden Dome. Additionally, developing the necessary space-based interceptor technology remains a daunting task.

“Finding a launch schedule capable of supporting a massive satellite constellation emerging in just three years is extremely challenging,” Roberts pointed out. “SpaceX has launched more than any other entity in the history of space operations, raising the question of how to surpass that threshold even more.”

Burbach added, “It seems unlikely that the system will achieve a complete defense against missile attacks. We might attain some limited operational capabilities, but accomplishing this quickly is fraught with difficulties.”

Will the Golden Dome enhance U.S. security?

Currently, an arms race is underway among the U.S., China, and Russia, with each nation enhancing its space-based capabilities to modernize and grow their nuclear arsenals and military strength.

Should the Golden Dome effectively bolster U.S. air and missile defenses, it might lessen adversaries’ confidence in their missile capabilities, possibly altering strategic calculations and discouraging them from launching attacks, according to Bazylczyk.

In contrast, the Golden Dome could potentially “contribute to instability” by signaling distrust towards nuclear adversaries, indicated Roberts. China’s Ministry of Foreign Affairs responded to Trump’s announcement, arguing that the Golden Dome carries a “strongly offensive implication” and could spur an arms race in space. Likewise, a Kremlin spokesperson suggested that the Golden Dome might restart discussions on nuclear arms control between Russia and the U.S.

In response to the system, both China and Russia “may attempt to destroy or disrupt U.S. satellites,” posited Burbach. Both nations have already developed missiles capable of targeting satellites, and they have demonstrated the capacity to jam or hack into satellite systems. In February 2024, U.S. intelligence agencies alerted that they intended to develop space weapons capable of using nuclear detonations to incapacitate or obliterate satellites.

Moreover, these countries could increase their missile arsenals and create more versatile weapons equipped with decoys, Burbach noted. He pointed out that Russia is already advancing technologies like underwater intercontinental nuclear torpedoes designed to evade space-based interception.

Topic:

Source: www.newscientist.com

Swedish Cabins: A Strategic Defense Against Hybrid Warfare in Sweden

aAt the end of an unmarked path on a small island on the edge of Stockholm's vast Baltic Sea archipelago, there is a small, unremarkable wooden hut painted dark red. The water gently hits the snow-capped rocks and the scent of pine fills the air.

The site offers few clues to the geopolitical drama that has gripped Scandinavia in recent months with accusations of infrastructure vandalism. But in reality, this cabin holds a vital cog of Europe's digital connectivity and a vulnerable point in a potential hybrid war. It's a data center that amplifies signals from a 1,615-mile fiber-optic cable that stretches from northern Sweden to Berlin.

Last month, two nearby fiber optic cables were severed, sparking an ongoing investigation by Swedish authorities. Western intelligence officials from several countries have said they believe a Chinese ship leaving the Russian port of Ustiluga caused the disconnection, but it was possible the disconnection was accidental or intentional. Opinions are divided as to whether this is the case.

Inside a data center, you'll find the “normal stuff” like alarms, CCTV, and access control. Photo: Josefin Stenersen/Guardian

Since Russia's invasion of Ukraine in 2022, Sweden has experienced an increase in hybrid warfare (attacks against adversaries using methods other than traditional military action) by pro-Russian factions. The Guardian was given exclusive access to the Stockholm data center site as Nordic governments are on high alert against Hybrid Russia's activities.

Daniel Aldstam, chief security officer at GlobalConnect, which transports 50% of Scandinavia's internet capacity and operates the center, described its approach to its location and normal appearance as “security through concealment.”

“There are basically two different approaches,” he said. “Either put a lot of fencing around it so it's obvious there's something important, or you can do what we've done here and make things a little more discreet. But , Of course, the usual facilities such as alarms, CCTV and access control are in place.'' Inside, cages full of equipment emit flashing lights and cables of different colors line the ceiling.

Following recent incidents of suspected sabotage, Polish Prime Minister Donald Tusk proposed a “naval security” initiative involving joint military patrols by countries around the Baltic Sea.

Map of where the cable was cut

A helicopter ride from Stockholm over the archipelago of 30,000 islands, rocks and reefs highlights just how difficult it is to protect the coastline. But its vastness also suggests how the “security through concealment” approach can be effective, at least up to a point. A map has been published showing where all submarine cables are laid.

We have hundreds of thousands of kilometers of fiber. How can I physically protect it? You can’t do that,” Aldstam said. “The key here is redundancy.” [using multiple cables offering alternative routes if one is cut off]. You need to eat more fiber. ”

Infrastructure is seen as particularly vulnerable to hybrid warfare, and there are signs of tweaks to the “covert” approach to reflect difficult times.

(From left) Daniel Aldstam, Chief Security Officer at GlobalConnect; Patrik Gylesjö, Project Manager. and Per Jansson, Senior Vice President. Photo: Josefin Stenersen/Guardian

GlobalConnect is building a larger, more modern-looking data center nearby. This data center is still unmarked and painted in a similar shade of red, but it is a building that clearly serves a more important function. It has an internal diesel-powered backup generator that allows it to continue operating even if the electricity is cut off.

Since Russia's full-scale invasion of Ukraine, the vulnerability of submarine cables and other critical infrastructure to sabotage has been highlighted, particularly in the relatively shallow and busy Baltic Sea region.

European submarine data cable map

In September 2022, the Nord Stream pipeline carrying natural gas from Russia to Germany exploded. Initially, many thought Russia was responsible. But in August, German media reported that German authorities had issued an arrest warrant for a Ukrainian man suspected of being part of the team that planted explosives on the pipeline. Both sides in the Ukraine war deny responsibility and blame each other for the attack.

NATO, which has established a dedicated center for undersea security, says vulnerabilities in the infrastructure of wind farms, pipelines and power cables put the security of around 1 billion people in Europe and North America at risk of hybrid warfare by the alliance's adversaries. He warned that he was being exposed. Earlier this month, NATO Secretary-General Mark Rutte urged Europeans to “shift to a wartime mindset.”

Despite all the warnings, the number of undersea cables lying or buried on the ocean floor appears to be surprisingly small.

“We call it a super-mega cable, but it doesn't sound super-mega, and it doesn't look super-mega,” said the director of Global Connect's entire Sweden-to-Berlin cable project, which was completed earlier this year. Director Patrick Gailshaw said. “The name refers to capacity, not size.”

A 2cm fiber optic cable can support 1 billion Netflix streams simultaneously. Photo: Josefin Stenersen/Guardian

Inside the cable, which is just over 2cm in diameter, is a small section made up of 96 hair-thin fiber pairs, enough to support 1 billion simultaneous Netflix streams. The rest consists of a steel cladding and waterproof material.

Gailshaw said a relatively small ship's anchor would be enough to destroy the cable. “You don't need a super big tool to break or cut this cable. It's pretty fragile.”

Making it more powerful means it's heavier, more expensive and “more complex to deploy,” he added.

Accidental breaks in submarine cables are extremely rare. “It is very rare for damage to occur in general,” says Gylesjö. “It's very unusual. I think something like this has happened up to two or three times during our time as submarine cable operators.”

Source: www.theguardian.com

I have rewritten the title as: “Using Lights on Surfboards and Wetsuits as a Defense Against Shark Attacks”

A great white shark attacks a dummy seal during an experiment in which lights were used to deter shark attacks

Nathan Hart, Macquarie University

Lighting the underside of surfboards, kayaks, and wetsuits could prevent the majority of great white shark attacks on humans.

It has long been known that sharks often attack humans, mistaking their silhouettes on the water for prey such as seals. Now, researchers have conducted an experiment to see what happens when a decoy seal's silhouette is distorted by illuminating its underside to disguise its shape.

laura ryan Researchers from Macquarie University in Sydney spent nearly 500 hours towing seal-shaped decoys around Mossel Bay in South Africa's Western Cape region, where great white sharks (carcharodon carcharius) gather in large numbers to hunt.

The team tested multiple light treatments. I covered the underside of the decoy with dim, medium, and bright LED and strobe lighting, as well as horizontal and vertical strip lighting. Each time we towed with any of the light treatments, we immediately towed the control decoy seal without using any underside lighting. As an additional experiment, we conducted a paired test in which an unlit control dummy was towed 3 meters away from a lit dummy.

Unlit decoys were more likely to be attacked or chased by sharks than lit decoys. The brightest light appeared to be the most effective, with zero predator incidents when the decoy illumination was at its brightest.

Vertical strip lighting was less effective than horizontal strips, Ryan said, perhaps because it broke up the silhouette into long sections that could be identified as seals.

Strobe lighting was less effective than continuous lighting, likely because the sharks could still see the silhouette of their likely prey between flashes.

Ryan said the team expected it would be important to match the decoy's lighting with the background light and make sure it was no brighter than the surrounding underwater conditions, but that wasn't the case.

“The most important thing was that the brightness of the decoy had to be brighter than the background light,” she says. “As long as the lighting doesn't make the silhouette look black, it seems to work.”

The research team has now developed a prototype lighting array to be used as a deterrent for great white sharks. “We are now moving from research to providing protection for swimmers and surfers,” Ryan says. “We took an approach that involved understanding the sensory systems of these animals, how they see the world, and their behavior.”

Ryan cautioned that lighting deterrents have not been tested against other species known to attack humans, such as tiger sharks (Galeocerdo Cuvier) and bull sharks (Porgy whale), each with a different hunting strategy.

david booth The University of Technology Sydney conducts a number of field studies off the Sydney coastline, where sharks, including great whites, are common. Based on these findings, he says he will definitely order a counter-illuminated wetsuit when it becomes available.

“I was surprised to find that ‘destructive camouflage’ was more effective, as I thought low lighting to match the background was most effective,” he says.

“These results apply only to great white sharks, and only to this feeding mode, so it is unclear at this point how broadly applicable they are.”

topic:

Source: www.newscientist.com