Meteors are flashes and streaks of light that appear when dust, pebbles and rocks burn up as they enter Earth's atmosphere. These fragments come from Comet Encke, which has left a trail of debris orbiting the sun. Twice a year, this stream intersects with Earth's orbit-once around Halloween, when the Taurids are visible at night, and again in June, during the daytime. The June meteors, known as the Beta Taurids, can't be seen in the daytime sky unless they are exceptionally bright fireballs.
But what would happen if much larger Taurids came a little too close to Earth?
New research led by Research Professor Mark Boslough, recently published in a special issue of Acta Astronautica, the proceedings of this year's Planetary Defense Conference in Cape Town, South Africa, explores this idea. The research titled, "2032 and 2036 risk enhancement from NEOs in the Taurid stream: Is there a significant coherent component to impact risk?" explores the risk assessment for planetary defense.
"Planetary defense is the multidisciplinary and internationally coordinated effort to protect the Earth and its inhabitants from impacts by near-Earth objects (NEOs)," explained Boslough. "It requires surveys to discover and track NEOs, campaigns to characterize those that are hazardous, modeling efforts to understand and predict impact effects and associated consequences, and mitigation through impact avoidance and/or civil defense."
A near-Earth object, or NEO, is an asteroid, comet or fragment whose orbit comes close to or can cross Earth's path around the sun. These objects have the potential to collide with our planet, but only if their orbit intersects Earth's and they arrive there at the exact same time. Small particles, such as the dust and pebbles that create the Taurid "Halloween fireballs," enter our atmosphere regularly. Larger objects, like those responsible for the Chelyabinsk meteor and Tunguska events, strike far less often.
Mitigation requires the development of ways to deflect or disperse an object on a collision course with sufficient warning, as well as emergency response planning for unexpected or unpreventable impacts.
The research incorporated recently published data from observational campaigns associated with the Taurid stream. The researchers found that the risk from airburst-sized near-Earth objects (NEOs), which are small enough to explode in the atmosphere instead of striking the ground, might be larger than currently estimated. Likewise, the researchers also investigated the possibility of a Taurid resonant swarm (TRS).
"The resonant swarm is theoretical, but there is some evidence that a sparse swarm of small objects exists because bright fireballs and seismic signatures of impacts on the moon have been observed at times that the theory has predicted," explained Boslough.
Objects in the Taurid stream orbit the sun seven times for every two orbits of Jupiter. This cycle, known as a resonance, means that part of the stream approaches Jupiter at regular intervals. Because Jupiter is the largest planet in the solar system, its strong gravity can pull these objects together, creating dense clusters. It's somewhat like a prospector panning for gold-swirling the pan at just the right rhythm to make the specks collect in one place.
The findings suggest that if a Taurid swarm does exist it will pass close to Earth in 2032 and 2036. During this time, Earth could experience higher impact risk.
"Our findings are that we have the technology to test the Taurid resonant swarm by using existing telescopes for targeted sky surveys in 2032 and 2036 when the hypothetical swarm will make very close approaches," said Boslough.
In 2032 and 2036, objects in a hypothetical Taurid swarm could be observable according to the researchers and the risk from airburst-sized NEOS might be larger than currently estimated. A concentration of larger (Chelyabinsk or Tunguska-sized) objects in a swarm would be observable by telescopes, if they exist, but only after they miss the Earth and recede into the night-time sky.
Boslough's airburst models during his time at Sandia National Laboratories (SNL) explores the Chelyabinsk explosion and estimate that the asteroid was about 60 feet in diameter and had an explosive yield of about a half megaton (TNT equivalent). Likewise, the Tunguska was probably about 10 times more powerful (3 to 5 megatons), also based on Boslough's SNL analysis.
"If we discover the objects with enough warning time, then we can take measures to reduce or eliminate the risk. If the new infrared telescope (NEO Surveyor) is in operation, then we can potentially have much more warning time," he said.
The research was funded by NASA at UNM and in partnership with NNSA funding at Los Alamos National Laboratory (LANL) in the planetary defense program.
Boslough suggests that it is important for citizens to be aware of various geohazards including weather, fire, earthquakes, and volcanoes, and to put them in perspective, and to be prepared to act.
"Asteroid impacts represent a small but significant risk, and New Mexico's national labs have some of the best minds working on the problem," he said.
One of the key lessons from the Chelyabinsk event is that most injuries were caused by flying glass when people rushed to windows to watch the bright flash in the sky. If a similar event were to occur over New Mexico, this would likely be the primary cause of injury. Experts say the public can learn from Chelyabinsk and to stay away from windows and avoid looking directly at the blast.
The 2032 pass of the hypothetical swarm will arrive from the night-time side of the Earth. Boslough says that the probability of an impact or airburst might be higher than average, if the hypothesis of a significant concentration is correct.
Boslough explains that there are such things as daytime fireballs, but they must be extremely bright in order to compete with the sun. A concentration of objects in a swarm (if it exists) would be observable by telescopes after they miss the Earth and recede into the night.
"The average probability is extremely low, so even an enhanced risk means that the probability would still be low. The swarm will come from the direction of the sun in 2036, so fireballs will not be seen in our blue skies unless they are extremely bright," he explained.
Magdelena Ridge observatory near Socorro is involved in the observational part of planetary defense, and both SNL and LANL have active planetary defense programs. While the university and national laboratories are continuing to research the TRS, Boslough cautions the public about where they get their information from.
"A lot of false information and mythology about this subject has been promulgated on social media, online sources, and sensational TV shows. This media gives the public the wrong impression about NEOs, impacts, and airbursts, and what we can do to reduce the risk," he said.
Boslough has also been active in debunking this misinformation. His published research was instrumental in one journal's decision to retract, due to the authors' misunderstandings of airburst phenomena and evidence, a much-publicized claim that an ancient city in Jordan was destroyed by an Tunguska-sized airburst. He also coauthored a comprehensive refutation of the fringe idea that the Taurid swarm was responsible for a climate catastrophe 12,900 years ago.
Want to get an up-close view of the Taurids show soon? Boslough says that there are a few opportunities coming up to view including the night of Halloween after 2 a.m. They should be visible when the moon is not in the sky. A few days after the next full moon on Nov. 5, the Taurids show should be viewable in the sky in the evening before moonrise.
Research Report: 2032 and 2036 risk enhancement from NEOs in the Taurid stream: Is there a significant coherent component to impact risk?
Related Links
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