To emphasize the need for planetary defense, scientists have explained what would happen if an asteroid were on a collision course with Earth. The hypothetical asteroid scenario illustrates how an asteroid threat could evolve over several years and the potential devastation of such a strike.
The team led by Paul Chodas, manager of NASA’s Near Earth Object (NEO) Program Office, presented the exercise. 8th Planetary Defense Conference (opens in new tab) Monday, April 4 in Vienna, Austria.
The hypothetical scenario set up by Chodas begins with a new discovery on January 10, 2023. the asteroid which takes the name 2023 PDC. The object was initially designated a “Potentially Hazardous Asteroid” (PHA), which NASA defines as an intersecting asteroid. the worldIt orbits at a distance of about 4.6 million miles (7.4 million kilometers) from the planet and was of magnitude 22.0 when it was discovered, slightly brighter than the faint stars visible to the Hubble Space Telescope.
The odds of an impact with the 2023 PDC are initially only 1 in 10,000, but Chodas explained that this continues to increase, as asteroid tracking facilities on Earth continue to follow the rock and better constrain its orbit around it. the sun. The scene became serious on April 3, 2023, at the point designated “Epoch 1” by Chodas.
Related: Asteroid Apocalypse: How Big Does a Space Rock Have to Be to End Human Civilization?
“Today in Epoch 1, the impact probability has now reached 1%,” Chodas said. “The potential impact is 13 years from now, so it’s not imminent, but we can already predict the date that impact is possible.”
The possible impact date is calculated as October 22, 2036, and despite the preparation time of more than this decade, the NEO program manager explained that important decisions must be made now. However, there are still several uncertainties, some of which feature the 2023 PDC asteroid, which will be key to how humanity deals with the threat.
Asteroid size estimation 2023 PDC problem
The first thing astronomers will do with their 13-year lead time is better calculate the asteroid’s size. NASA says (opens in new tab) This is done by measuring the amount of light reflected by asteroids returning to space, a quality called albedo. The more light reflected, in principle, the larger the asteroid.
The Difficulty with this measure (opens in new tab) Albedo is also determined by the reflectivity of the asteroid’s surface. This means that a small light colored asteroid can have a larger albedo than a large dark asteroid. As a result, there can be large uncertainties in the size of asteroids.
The size of 2023 PDC is calculated to be between 720 and 2,200 feet (220 to 660 m), but could be as large as 1.3 miles (2 km) if the asteroid’s surface is dark.
The size of the asteroid is important because it will not only determine how much damage it does, but also what measures need to be taken to remove it, or whether it will be possible at all.
“When you have a massive object, even as big as 2 kilometers (1.2 miles), and it has very low probability, nuclear is really the primary approach on the table,” Chodas said. This means that a high-speed impactor heading toward Earth for a large asteroid, as recently demonstrated by NASA’s Double Asteroid Redirection Test (DART), would not be a diversion option.
Chodas explained that the 2023 PDC could use infrared astronomy to help determine its size because it is so close to the Sun, as this light would be “washed out” by the Sun’s bright light. As a result, space-based telescopes that rely primarily on infrared observations such as the James Webb Space Telescope (JWST) and the Hubble Space Telescope will not be of much help in observing these rocks. Similarly, the asteroid would be too early in its approach to be measured by radar.
According to Chodas, this means we will primarily be limited to optical observations to determine the size of asteroids. This limits the amount of data astronomers can gather about the 2023 PDC, data that can better constrain the asteroid’s size and orbit.
An alternative decision makers would send a recovery spacecraft to the 2023 PDC with a lead time of 13 years.
Not only would this help us better determine the asteroid’s size and mass, but such a mission would help better constrain another important aspect of the asteroid that’s important for minimizing its impact on Earth: its orbit.
At the time of discovery in this hypothetical scenario, 2023 PDC is about 124 million miles (200 million km) from Earth, too far to accurately assess its orbit.
“It is distant and obscure, but it has a very similar orbital period to Earth, in fact, it is slightly shorter, which means that the asteroid will catch up to Earth slowly, and in 13 years, there is a possibility that the two will meet in a slightly red color. Box (Earth’s orbit and represents the intersection of 2023 PDC),” Chodas said. “There is great uncertainty about where the asteroid will be 13 years from now. As we continue to track the asteroid that uncertainty will shrink until it is smaller than Earth.”
The red “hitbox” in the team’s calculations being less than the size of Earth means the 2023 PDC is about to hit the planet. Astronomers can then begin to predict exactly where on Earth the asteroid will interact with the planet.
So… what’s the harm?
NASA advanced supercomputing expert Lorien Wheeler explained that assessing the potential damage to the 2023 PDC involved developing an asteroid impact risk assessment model and considering factors such as asteroid size and other characteristics from limited observational data.
“There are three main types of impact risk that we model. These include localized land damage from an explosive blast or fireball,” Wheeler said. “There is also the potential for large ocean impacts from tsunamis and, in the largest case, the potential for global climate impacts.
“We model all of these cases and then combine the results to see the probability of different damage sizes and damage intensities, how many people could be harmed, and which areas are potentially at risk.”
For the possible size of the 2023 PDC, a lower size estimate of about 1,000 feet (300 m) in diameter represents destruction on the scale of a continent with an energy release of 2,000 megatons. This is equivalent to 133,000 times the estimated energy released by the bomb that destroyed Hiroshima at the end of World War II. As the size of the 2023 PDC increases, the impact of potential disasters increases significantly. At 2,000 feet (600 meters) in diameter, the impact would have set boundaries on the scale of a global disaster. A strike by a 2023 PDC of this size would release 20,000 megatons of energy, meaning a nearly 10-fold increase in destructive power at a doubling in size.
At 3,330 feet (1 km) wide, the 2023 PDC impact scene becomes exceptionally grim. At this rate, the team calculates that the 2023 PDC is highly likely to trigger a global catastrophe. Such an impact would release about 100,000 megatons of energy, equivalent to 6.6 million Hiroshima nuclear explosions.
Wheeler explained that there are factors other than size such as the angle of entry of the asteroid into the atmosphere that contribute to uncertainty in the range of potential impact energies and thus the severity of damage.
“The biggest hazard is going to be a large ground impact or a very destructive blast wave and fireball from a low wind explosion,” Wheeler added. “Given the size of the object we have here, the severity of the damage is expected to reach unsafe levels with larger areas of damage extending into surrounding areas, structural damage from the fire and extending into areas of shattered windows.”
Wheeler continued that for smaller impacts, outer damage zones are a band that can extend from 62 miles to 124 miles (100 to 200 kilometers) in diameter beyond the main impact zone. This extended damage zone can extend up to 372 miles (600 kilometers) in diameter under conditions where the hypothetical asteroid approaches 2,000 feet (600 meters) in size.
“There are potentially high numbers of people who could be affected across the swath, mostly in the range of hundreds of thousands to millions of people,” Wheeler said. “Impacts on land average 10,000 to 10 million people, depending on location. And if the impact is large, those ranges can go into the 10 million to 100 million range.”
He continued by explaining that if the 2023 PDC hits any ocean, it will trigger a tsunami, but the greatest damage to the population would be a strike from an asteroid landing in the Atlantic Ocean, which has the greatest risk of triggering a tsunami that could reach the population. Area The ultimate climate change effects of a larger 2023 PDC asteroid strike could eventually affect anywhere from millions to billions of people around the world.
“So the bottom line here is that there is a very large range of potential harm,” Wheeler concluded. “If it impacts Earth, it could be very damaging because the potential consequences are so extreme.”
How worried should we be?
It is important to emphasize that the 2023 PDC is a purely hypothetical object and may not impact Earth. In fact, currently, there are no major asteroids predicted to hit Earth for the next 100 years. The object most likely to collide with Earth was the 1,100-foot (340 m) wide asteroid 99942. Apophiswhich is predicted to come dangerously close to Earth in 2068 NASA ruled out this effect in 2021, and 99942 Apophis will instead pass the planet harmlessly.
Of course, that doesn’t mean there couldn’t be an object waiting to be discovered in an orbit that intersects Earth’s path around the Sun. Still, the scenario Chondas and Wheeler describe for the 2023 PDC is quite extreme. In fact, European Space Agency (ESA) Director of Operations Rolf Densing congratulated the scientists for developing a challenging and dramatically unfolding scenario for decision makers to consider.
To consider how likely such a scenario is, the team created the possibility of Earth being bombarded by space objects of various sizes, suggesting that impacts involving larger bodies should be rare. The average time between impacts for objects with a diameter of about 1,000 feet (300 m) is about 70,000 years, while asteroids with a diameter of about 2,000 feet (600 m) are predicted to hit the planet roughly once every 200,000 years.
Massively destructive global impact asteroids with a diameter of about 3,300 feet (1 km) are estimated to hit the planet once every 700,000 years. Even larger 3-mile (5 km) wide asteroids are predicted to hit Earth once every 30 million years.
If you’re concerned about asteroid impacts, NASA maintains a log of possible brushes with asteroids. Sentry Risk Table. (opens in new tab)
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