The Earth, our beautiful blue planet, is constantly under threat from objects hurtling through space. While many of these celestial travelers burn up harmlessly in our atmosphere as meteoroids, some have the potential to unleash catastrophic devastation if they collide with our planet. One of the most pressing global threats we face is the possibility of a massive asteroid strike, capable of causing mass extinctions and upheaval on an unprecedented scale.
To counter this existential danger, countries around the world are actively developing innovative technologies to both destroy and deflect these cosmic menaces. In this article, we delve into the global efforts to monitor, deflect, and prepare for the potentially devastating consequences of asteroid impacts.
The Menace of Near-Earth Asteroids (NEAs)
Asteroids, the remnants of our solar system’s formation, are rocky or metallic objects that orbit the sun, often in the asteroid belt between Mars and Jupiter. While most asteroids reside harmlessly in the asteroid belt between Mars and Jupiter, some, known as near-Earth asteroids, orbit closer and have the potential to cross Earth’s path. These asteroids, comprising three groups known as Atens, Amors, and Apollos, spiral in the inner regions of the solar system, occasionally intersecting Earth’s and Mars’ orbits.
NEAs are a subset of asteroids whose orbits come into proximity with Earth’s orbit. They may spend most of their time beyond Earth’s orbit but occasionally come close to our planet due to the gravitational interactions between celestial bodies in the solar system. The positions in an asteroid’s orbit where it is farthest from the Sun are called “aphelion,” while the points where it is closest to the Sun are known as “perihelion.” NEAs typically cross Earth’s orbit somewhere between their aphelion and perihelion points. NEAs cross Earth’s orbit at one or more points in their orbits. When an NEA is on a trajectory that intersects with Earth’s orbital path, it has the potential to pose a threat if their paths coincide in both time and space.
Remembering Chelyabinsk and Tunguska
Since it formed over 4.5 billion years ago, Earth has been hit many times by asteroids and comets, collectively known as Near Earth Objects or NEOs, and they still pose a danger to Earth today.
While most asteroids are small and relatively harmless, some are enormous, and their impact on Earth could be cataclysmic. The most infamous example is the asteroid that caused the extinction of the dinosaurs around 66 million years ago.
The Chelyabinsk meteor incident in Russia in February 2013 was a stark reminder of our vulnerability. An object just 65 feet (20 meters) wide caused widespread damage and injuries. However, the Tunguska event in 1908 was even more powerful, with a 130-foot-wide space rock(40 m) flattening vast Siberian forests. These events highlight the real danger posed by asteroids of varying sizes.
Recent Asteroid Threats
Bennu: This celestial behemoth, known as Bennu, is a near-Earth asteroid measuring roughly 500 meters in diameter. While it may seem distant, its potential to intersect with our planet raises concern. Scientists have calculated that Bennu carries a 1 in 2,700 chance of impacting Earth sometime within the extensive window spanning from 2178 to 2261. As such, it has rightfully garnered significant attention and scrutiny from the scientific community.
2010 WC9: Another formidable presence in the realm of near-Earth asteroids is 2010 WC9, boasting a diameter of approximately 400 meters. Though its risk may appear relatively low, it still presents a 1 in 25,000 probability of Earth impact, with the ominous year being 2053. Scientists diligently track this cosmic wanderer to ensure we remain vigilant against potential threats.
These two space rocks, Bennu and 2010 WC9, remain under constant surveillance by astrophysicists and space agencies, including NASA. In fact, NASA has crafted a contingency plan should Bennu’s trajectory pose a genuine hazard to our planet.
In addition to Bennu and 2010 WC9, several other asteroids have made it to the watchlist of potential Earth threats:
1950 DA: This near-Earth asteroid ranks as one of the larger ones, with a diameter of around 1,300 meters. Although its colossal size might instill fear, its chances of Earth impact are reassuringly remote, at 1 in 332,000. This eventuality, if it ever occurs, is projected for the distant year 2880.
(99942) Apophis: Named after the Egyptian god of chaos and evil, Apophis is a near-Earth asteroid with a diameter of approximately 370 meters. Despite its ominous moniker, the likelihood of it striking Earth is exceptionally low, with odds of just 1 in 12.5 million. The hypothetical date of concern is 2068.
(35396) 1997 XR2: In the grand cosmic tapestry, we find 1997 XR2, another near-Earth asteroid, though this one measures around 2 kilometers in diameter. While its size might be imposing, its odds of impacting Earth are incredibly slim, at 1 in 10 million. If such an event were to materialize, it’s a far-off prospect for the year 2880.
These celestial bodies, despite their menacing dimensions, serve as reminders of the importance of ongoing asteroid detection and monitoring efforts to safeguard our planet from potential cosmic collisions.
Government agencies, including NASA and FEMA, conducted a planetary protection exercise, examining the catastrophic consequences of a 330-foot asteroid colliding with Earth in 2020. The simulation envisioned a worst-case scenario, including a blast wave that could level structures over a 30-mile radius, necessitating mass evacuations in Los Angeles and resulting in tens of thousands of casualties.
The impact of an asteroid striking Earth at speeds between 15 and 30 km/s unleashes immense kinetic energy, causing devastating effects such as blast waves, tsunamis, atmospheric and electromagnetic disturbances. This impact can surpass the energy released by the most powerful nuclear bombs, with the scale of damage depending on the asteroid’s size. The Chelyabinsk meteor, approximately 20 meters in diameter, caused a 500-kiloton explosion over Russia in 2013.
Asteroids measuring around 140 meters are significant enough to destroy a U.S. state or an entire European country, highlighting the potential regional and global consequences. Impact events involving objects larger than 1 km in diameter could lead to worldwide damage, potentially resulting in the extinction of human species. Additionally, long-period comets pose a threat with their higher impact speeds, making their collisions even more destructive, often with minimal warning time.
International Collaboration: A Unified Front
International cooperation is essential in tackling this global threat. Organizations like the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG), under the United Nations, help nations share information and coordinate efforts. Space agencies worldwide, including NASA, ESA, and China’s CNSA, are actively involved in missions to study and protect Earth from asteroids.
Tracking and Monitoring Near-Earth Objects
Scientists continuously monitor the orbits of NEAs, precisely calculating their positions and trajectories. This monitoring allows them to predict whether a particular asteroid will approach Earth closely in the future.
Ground telescopes excel at spotting asteroids approaching from the night side of Earth but struggle to detect those leaving the solar system, as seen in the Chelyabinsk event. The U.S. National Academies of Sciences, Engineering, and Medicine’s decadal survey highlights the potential of ground-based radar as a critical tool for Earth’s protection against asteroid threats.
NASA’s Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE, spacecraft, in orbit around Earth, uses asteroid-hunting thermal sensors that allow an infrared view of asteroids without the obscuring effects of Earth’s atmosphere. The space agency said they have fond 788 NEOs and 136 comets. Of the near-Earth objects (NEOs) discovered so far, over 1700 are considered hazardous due to their potential to impact Earth.
As of September 2023, NASA has cataloged over 18,310 near-Earth objects (NEOs), of which slightly more than 800 are 460 feet (140 meters) or larger in diameter. These objects are considered to be potentially hazardous asteroids (PHAs), as they are large enough to cause significant damage to Earth if they were to impact.
NASA’s Near-Earth Object Observations Program found no imminent asteroid or comet impacts in the foreseeable future. While the chance of impact by known potentially hazardous asteroids in the next century is only 0.01 percent, approximately 10 percent of these objects remain unidentified by NASA.
NASA is currently tracking over 95% of all known PHAs, but there are still an estimated 25% of PHAs that have yet to be discovered. This is due to the fact that PHAs can be difficult to detect, especially if they are small or have dim orbits.
In October 2019, the European Space Agency (ESA) added asteroid 2019 SU3 to its risk list, indicating a high probability of impact within 70 years. This asteroid is ranked as the fourth most dangerous on ESA’s list, with a 1 in 152 chance of collision.
NASA is working to improve its ability to detect and track PHAs through a variety of programs, including the Near-Earth Object Observations Program (NEOO) and the Planetary Defense Coordination Office (PDCO). The NEOO is responsible for searching for and tracking NEOs, while the PDCO is responsible for coordinating NASA’s response to a potential NEO impact.
Tracking Asteroids with Microsatellites
Paulo Lozano, the director of the Space Propulsion Lab at the Massachusetts Institute of Technology, suggests using microsatellites to revolutionize asteroid research and potentially protect Earth from asteroid threats. Rather than relying on traditional missions that visit asteroids every five to ten years, Lozano proposes deploying fleets of tiny CubeSats to visit hundreds of asteroids inexpensively. This approach is not only cost-effective but also crucial for identifying and understanding asteroids, particularly small ones that could pose a collision risk to Earth.
Lozano has developed electrospray thrusters with remarkable efficiency, capable of carrying minimal propellant (fuel tanks the size of sugar cubes). These thrusters could power CubeSats to reach Mars or embark on asteroid reconnaissance missions. With their small size, CubeSats could even land on asteroids and take off again, offering the opportunity to study asteroid compositions up close. This knowledge is vital for devising strategies to deflect or destroy asteroids, as the composition can significantly impact the difficulty of such efforts. For instance, an asteroid made of silicon might prove more challenging to redirect than one composed of iron.
Furthermore, CubeSats equipped with propulsion systems could serve as a cost-effective means to test new space technologies, opening doors to innovative approaches for space exploration and asteroid mitigation.
APIES (Asteroid Population Investigation and Exploration Swarm)
APIES (Asteroid Population Investigation and Exploration Swarm) is a mission developed by EADS Astrium in response to a European Space Agency (ESA) Call for Ideas for “swarm” missions, based on the utilization of a large number of spacecraft working cooperatively to achieve the mission objectives.
The APIES baseline concept is centred on a “swarm” of 19 BElt Explorer (BEE) identical microsatellites, weighing less than 45 kg each, including their scientific payload, visiting over 100 Main Belt asteroids in multiple flybys. The BEEs are carried to the asteroid belt by a Hub and Interplanetary VEhicle (HIVE), a conventional spacecraft launched with a Soyuz–Fregat rocket, using solar electric propulsion for the transfer to the asteroid belt and acting as communication hub and control centre for the mission after the swarm deployment.
The APIES mission is still in the conceptual stage. The European Space Agency (ESA) is currently conducting a feasibility study to assess the feasibility of the mission. The feasibility study is expected to be completed in 2024. If the feasibility study is positive, ESA will begin to develop the APIES mission. The mission is expected to launch in the early 2030s.
The APIES mission is a complex and ambitious mission. It will require the development of new technologies, such as microsatellites with advanced propulsion systems and navigation capabilities. The mission will also require the development of new algorithms for controlling and coordinating the swarm of microsatellites.
Technological Innovations: From Kinetic Impactors to Gravity Tractors
Recognizing the potentially dire consequences of an asteroid impact, nations worldwide are taking action to protect our planet. The focus is on two main strategies: asteroid destruction and asteroid deflection.
Asteroid Destruction Technologies
Destruction concentrates on rendering the impactor harmless by fragmenting it and scattering the fragments so that they miss the Earth or burn up in the atmosphere. Kinetic impactors are spacecraft designed to collide with an asteroid, altering its course. Nuclear deflection, a more potent but challenging option, involves using nuclear explosives to change an asteroid’s trajectory.
Kinetic Impactors: A Precise Cosmic Collision
One strategy for mitigating the threat of an asteroid impact is the use of kinetic impactors. These spacecraft are specially designed to perform a cosmic ballet with an asteroid, requiring precision and timing. The goal is to send a kinetic impactor on a collision course with the asteroid, impacting it at high speeds. This collision can serve two main purposes: altering the asteroid’s trajectory or disintegrating it into smaller, less dangerous fragments.
Nuclear Deflection: The Power of Controlled Explosions
In certain scenarios where precision alone may not suffice, nuclear deflection emerges as a powerful option. This strategy involves employing nuclear explosives to address the threat posed by an incoming asteroid. However, it is important to emphasize that the use of nuclear explosives in space demands meticulous planning, international cooperation, and adherence to stringent safety protocols.
Russian researchers have assessed that a 3-megaton nuclear bomb would be required to obliterate a 650-foot stony asteroid, with greater efficacy achieved by detonating it within a crater on the asteroid’s surface.
Nuclear deflection serves a dual purpose: it can either destroy the asteroid entirely or alter its course sufficiently to divert it away from Earth’s path. This approach requires a deep understanding of the asteroid’s composition, size, and trajectory to determine the most effective use of nuclear devices.
Destruction of Asteroid by “nuking it”, carries the risk that shattered asteroid could merely become a swarm of slightly smaller and still very destructive space rocks heading towards our planet, hence it is only considered at a very, very last resort.
International collaboration and diplomacy play a pivotal role in the feasibility of nuclear deflection. Coordinated efforts among space agencies and nations are essential to ensure the safe and responsible use of nuclear technology in planetary defense. While this approach carries significant challenges and ethical considerations, it remains a potent tool in our cosmic arsenal, ready to be deployed if the need arises to protect our planet from a celestial threat.
Asteroid Deflection Technologies
Gravity tractors, solar sails, and laser ablation are gentler methods that use gravitational forces or energy to nudge asteroids away from Earth’s path.
Delay: This strategy leverages the fact that both Earth and the incoming impactor are in orbit. By altering the arrival time of the impactor, even by a few minutes, it can potentially miss Earth.
Gravity Tractors: Nudging Asteroids with Subtle Force
Another ingenious approach to mitigating the threat of an asteroid impact is the use of gravity tractors. These spacecraft operate on a principle as old as the universe itself: gravitational attraction. The strategy involves sending a specially designed spacecraft to rendezvous with the target asteroid. Once in proximity, the spacecraft maneuvers to position itself alongside the asteroid.
Here’s where the magic happens: the spacecraft’s own gravitational field, though minuscule in comparison to a planet, exerts a gentle but persistent force on the asteroid. Over an extended period, this subtle gravitational tug can slowly alter the asteroid’s course. Gravity tractors are a patient and precise method for diverting asteroids, requiring a long lead time but avoiding the risks associated with more forceful approaches like nuclear deflection.
Solar Sails and Laser Ablation: Riding the Cosmic Breeze
Solar sails and laser ablation represent innovative technologies that harness the power of sunlight or directed energy beams to exert force on an asteroid. These approaches focus on delicately nudging the asteroid away from its collision trajectory.
Solar Sails: A solar sail is a spacecraft equipped with a large, ultra-thin, and highly reflective sail. When sunlight strikes this sail, it imparts momentum to the spacecraft through the transfer of photons. While the force from each photon is minuscule, the cumulative effect of countless photons can produce a significant thrust. By positioning a solar sail-equipped spacecraft near the asteroid, it can harness the constant stream of sunlight to gently push the asteroid onto a different trajectory, away from Earth’s path.
Laser Ablation: Laser ablation takes a different approach, utilizing powerful directed energy beams, often from ground-based or space-based laser systems. These energy beams are precisely aimed at the asteroid’s surface. As they strike the asteroid, they vaporize or ablate material, creating a reaction force that propels the asteroid in the opposite direction. Laser ablation technology allows for precise control of the force applied, making it possible to steer the asteroid gradually away from its collision course.
Both solar sails and laser ablation offer non-explosive and less invasive alternatives to asteroid deflection. They leverage the subtle but consistent forces of nature, sunlight, and directed energy, to gently guide these celestial objects away from potential collisions with Earth.
The International Effort
Cooperation among nations is vital in addressing this global threat. The United Nations has established the International Asteroid Warning Network (IAWN) and the Space Mission Planning Advisory Group (SMPAG) to facilitate coordination and information sharing. Space agencies from the United States, Europe, Russia, China, and more are actively participating in missions and research aimed at understanding, tracking, and mitigating the threat of asteroids.
NASA’s DART (Double Asteroid Redirection Test) mission
DART aims to demonstrate the effectiveness of kinetic impactors by targeting a binary asteroid system. Kinetic impactors offer a non-nuclear solution to diverting potential threats from Earth.
NASA’s Double Asteroid Redirection Test (DART) mission successfully impacted the asteroid Dimorphos on September 26, 2022. This was the first time that humanity had intentionally changed the motion of a celestial object.
The DART mission was a test of the kinetic impactor method of asteroid deflection. Kinetic impactors are spacecraft that are designed to collide with asteroids and change their course. The DART spacecraft impacted Dimorphos at a speed of about 14,000 miles per hour.
The impact created a large crater on Dimorphos and ejected a plume of material into space. Scientists are still analyzing the data from the impact, but they believe that the DART mission was a success. They estimate that the impact shortened Dimorphos’s orbit around its larger companion asteroid, Didymos, by about 32 minutes.
The DART mission is a significant step forward in our ability to defend Earth from asteroid impacts. It has shown that we can successfully deflect asteroids using the kinetic impactor method. This is important because it gives us an option to protect ourselves from asteroids that may be on a collision course with Earth.
NASA is currently planning a follow-up mission to DART called the Hera mission. The Hera mission will launch in 2024 and arrive at the Didymos system in 2026. The Hera mission will study the impact crater on Dimorphos and gather more data about the kinetic impactor method of asteroid deflection.
The DART mission is a major milestone in the field of planetary defense. It has shown that we have the technology to protect ourselves from asteroid impacts. This is a reassuring development, given the fact that there are millions of asteroids in our solar system, and some of them may be on a collision course with Earth.
China’s Fuyan project
The China Fuyan project is a major initiative to develop a system for tracking and deflecting hazardous asteroids. The project is being led by the Beijing Institute of Technology and is expected to be completed in three phases.
Key elements of China’s asteroid defense initiative include the development of both ground-based and space-based monitoring and warning systems. These systems will be responsible for cataloging and analyzing asteroids that could pose risks to human space activities. Subsequently, China will focus on the advancement of technology and engineering solutions to mitigate these threats effectively.
The first phase of the project, which was completed in December 2022, involved the construction of four radar antennas in Chongqing, China. These antennas are being used to track asteroids and to gather data on their size, shape, and trajectory.
The second phase of the project, which is currently underway, involves the construction of an additional 20 radar antennas. These antennas will be located in different parts of China and will work together to create a high-resolution radar network that will be able to track asteroids at a distance of up to 150 million kilometers.
The finished system will include more than 20 radar antennas, each with a diameter of 82 to 98 feet (25 to 30 meters). Chinese news reports claim that the system will be the world’s farthest-reaching radar system, but few details about the project, such as the wavelengths at which it will operate, are available.
The third phase of the project, which is scheduled to be completed in 2025, will involve the development of a spacecraft that will be able to deflect asteroids. The spacecraft is expected to be launched in 2025 and will conduct a technical experiment involving tracking and deflecting an asteroid.
One particularly noteworthy aspect of China’s plan is the intention to conduct practical exercises involving more than 20 of China’s largest rockets. These exercises aim to practice diverting a sizable asteroid from its collision course with Earth, representing a vital technique for planetary defense. Researchers at China’s National Space Science Center have conducted simulations indicating that 23 Long March 5 rockets striking an asteroid simultaneously could successfully alter its trajectory, moving it away from Earth by a distance equivalent to 1.4 times Earth’s radius. Their calculations are based on a hypothetical scenario involving an asteroid similar in size to the Empire State Building.
This innovative approach, involving the use of a “kinetic impactor” composed of the upper stage of a launch rocket and a guiding spacecraft, has garnered interest from experts like Professor Alan Fitzsimmons from Queen’s University Belfast. Fitzsimmons highlights the potential of increasing mass to enhance the impact on an asteroid, although he emphasizes the need for further detailed study regarding the operational aspects of such missions. China’s proactive efforts in asteroid defense represent a significant step toward safeguarding our planet from potential celestial threats.
Russia’s Pursuit of Nuclear Asteroid Deflection
Russian researchers are actively exploring the concept of using nuclear weaponry to deflect hazardous asteroids. In laboratory experiments, they have replicated asteroid-like structures using artificial models and simulated the impact of laser blasts, akin to nuclear warheads. Their findings suggest that a formidable 3-megaton nuclear bomb may be required to obliterate a stony asteroid measuring approximately 650 feet (200 meters) in diameter. Furthermore, detonating a nuclear device within a crater or cavity on the asteroid’s surface appears to enhance its destructive potential.
These experiments stem from Russia’s involvement in the NEOShield project under the EU seventh framework program, aimed at researching various methods to mitigate threats from hazardous space objects. Russia, represented by the Central Machine Building Research Institute, was tasked with investigating the possibility of deflecting such objects through nuclear explosions.
While the use of nuclear explosions in space is currently prohibited, Russian scientists assert that it may become necessary if an asteroid poses a grave threat to Earth’s well-being or even its existence. In such dire circumstances, existing bans could be reconsidered. Notably, Russian experts emphasize that detonating a nuclear device in deep space, well in advance of an asteroid’s approach to Earth, is the safest approach. This would involve directing the explosion in a manner that ejects material from the asteroid, generating thrust that alters its orbit. The effects of this orbit change would become more apparent as the asteroid nears Earth, ultimately diverting it to a safer distance from our planet.
Evaluation of Asteroid Deflection Strategies
In the pursuit of defending against potentially threatening asteroids, experts have extensively evaluated various strategies to respond effectively, particularly in scenarios with short notice of a year or less. These assessments shed light on the most viable approaches to safeguard Earth from asteroid impacts.
Bong Wie, the director of the Asteroid Deflection Research Center at Iowa State University, conducted a study in 2011 to address the challenge of responding to a menacing asteroid within a limited timeframe. His research concluded that, when confronted with a very large asteroid and only a year or so of preparation, a nuclear explosion is likely the most feasible solution in terms of providing the necessary energy. Alternative systems like tugboats, gravity tractors, solar sails, and mass drivers, while effective, typically require much longer lead times of 10 to 20 years to divert an asteroid successfully.
In a separate investigation carried out by Jason C. Reinhardt, Matthew Daniels, and M. Elisabeth Paté-Cornell from Stanford University, the effectiveness of different space missions for altering the orbits of hazardous asteroids was compared. The three primary strategies under scrutiny were kinetic impactors, standoff nuclear explosions, and gravity tractors.
Their findings indicated that standoff nuclear detonations outperform kinetic impactors and gravity tractors across the board, particularly when considering near-Earth asteroids (NEAs) of various diameters. Gravity tractors exhibit superiority over kinetic impactors for NEAs with diameters exceeding approximately 400 meters. On the other hand, kinetic impactors are deemed fairly effective for NEAs with diameters below this threshold.
In summary, these assessments suggest that, given sufficient time between the discovery of a near-Earth asteroid and its potential impact with Earth, current technologies offer promising means to mitigate the risk effectively. The choice of strategy, however, depends on the specific characteristics of the asteroid and the available preparation time.
The Importance of Preparedness
While the probability of a major impact in the near term remains low, we must remain vigilant. Researchers warn that events like the Chelyabinsk impact happen once every hundred years, and more destructive meteorites have hit Earth three times in the last century. We must heed this warning and be prepared for these rare but potentially devastating events.
The global threat of mass extinction from asteroid impacts is a sobering reality. However, the incredible advancements in asteroid detection and deflection technologies offer hope for humanity’s ability to protect our planet. The key lies in international collaboration, as this is not a challenge any single nation can tackle alone. By pooling our knowledge, resources, and innovative solutions, we can enhance our planet’s resilience against the cosmic hazards that lurk in the depths of space. It’s a testament to human ingenuity and determination that we are actively working to safeguard our world from the cataclysmic forces of the universe.