Updated: July 23, 2020 9:36:48 am
Asteroids classified as PHAs do not need to affect Earth. (Representative Image / Getty Images)
NASA has issued a warning that a huge “Asteroid 2020 ND” will pass Earth July 24. The asteroid, about 170 meters long, will be as close as 0.034 astronomical units (5,086,328 kilometers) to our planet, and is traveling at a speed of 48,000 kilometers per hour. Its distance from Earth has placed it in the “potentially dangerous” category.
Potentially Dangerous Asteroids (PHAs)
According to NASA, “Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid’s potential to make threatening approaches to Earth. Specifically, all asteroids with a minimum orbiting distance (MOID) 0.05 au or less are considered PHAs. “
NASA classifies objects like these as ‘Near Earth Objects’ (NEO) as they are pushed by the gravitational pull of other planets, resulting in their proximity to our solar system.
Still, it is not necessary for asteroids classified as PHAs to affect Earth. “It just means that there is a possibility of such a threat. By monitoring these PHAs and updating their orbits as new observations become available, we can better predict the near-approach statistics and therefore their threat of impact on Earth, “says NASA.
The study of near-Earth objects (NEO)
NEOs are comets and asteroids pushed by the gravitational pull of nearby planets in orbits that allows them to enter Earth’s neighborhood. These objects are primarily composed of water ice with embedded dust particles, and occasionally get closer to Earth as they orbit around the Sun. NASA’s Center for the Study of Near-Earth Objects (CNEOS) determines the times and distances of these objects as they get closer to Earth.
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The level of threat
According to the Planetary Society, there are an estimated 1 billion asteroids with a diameter greater than 1 meter. Objects that can cause significant damage on impact are larger than 30 meters. Every year, about 30 small asteroids hit Earth, but they don’t do any major damage to the ground.
NASA’s Near-Earth Object Observation Program finds, tracks, and characterizes more than 90 percent of NEO’s predicted number of 140 meters or more (larger than a small soccer stadium), which the space agency says are “the greatest concern” due to the level of devastation that its impact is capable of causing. However, it is important to note that no asteroid over 140 meters has a “significant” chance of hitting Earth for the next 100 years.
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Deflecting asteroids
Over the years, scientists have suggested different ways to avoid such threats, such as flying the asteroid before it reaches Earth, or deflecting it from its course toward Earth by hitting it with a spacecraft.
The most drastic measure undertaken so far is the Asteroid Deflection and Impact Assessment (AIDA), which includes the mission of NASA’s Double Asteroid Redirection Test (DART) and Hera from the European Space Agency (ESA). The mission’s target is Didymos, a near-Earth binary asteroid, one of whose bodies is the size that could pose the most likely significant threat to Earth.
In 2018, NASA announced that it had begun construction of the DART, which is slated to launch in 2021 with the goal of crashing into the smallest asteroid in the Didymos system at about 6km per second in 2022. Hera, which is slated to launch in 2024, it will arrive at the Didymos system in 2027 to measure the impact crater produced by the DART collision and study the change in the orbital trajectory of the asteroid.
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