? What is the size of asteroids that may threaten human civilization
NASA made history after the DART mission successfully hit the asteroid Dimorphos, the first time life on Earth has changed the course of a celestial body.
This is the first mission of its kind to test the possibility of changing the course of dangerous constellations, which could one day threaten life on Earth.
Sherry Weber-Bayer, assistant professor of space studies at the University of North Dakota, told the British newspaper, The Independent, that the DART mission “is very important. The impact of a small meteorite or comet nucleus is the only avoidable natural disaster that could threaten human civilization or the life of a large part of the human race.”
The collision of NASA's DART spacecraft with the small asteroid 6.8 million miles from Earth in an attempt to change the asteroid's orbit is a training measure to divert future space rocks that may endanger Earth.
? What are the potentially dangerous asteroids
While the asteroid Dimorphos did not pose any threat to Earth, the potential threat from other asteroids or comets is real, even if it is relatively rare, and the results range from large impacts that could wipe out most life on Earth, to Nearby accidents don't quite hit the planet, but they do disrupt human civilization anyway.
Not all asteroids pose a threat to Earth, as many are in orbits that will never intersect with Earth, while others are so small that they may burn up in Earth's atmosphere without damage.
More than 48 tons of space rocks, some the size of footballs, some the size of grains of sand, enter Earth's atmosphere each year, according to NASA.
But about 2,259 known asteroids have been classified as "Potential Hazard Objects" (PHA), which are potentially dangerous asteroids, according to Dr. Weber-Bayer, which were identified based on their closest approach to Earth's orbit and their sizes.
If the space rock is about 140 meters (460 feet) in diameter or larger, and its orbit is about 46 million miles from Earth's orbit, or about 19.5 times the distance from Earth to the Moon, it is potentially dangerous.
This makes about 7.7% of the objects known "potential hazards" near the Earth.
? How dangerous are asteroids
It's easy to see why the criteria for 'latent hazards' status are what they are, at least in terms of size.
More specifically, an asteroid with a diameter of about 140 meters, traveling at 44,000 miles per hour, typical of an asteroid strike, will release energy equal to 170 million tons of explosive “TNT”, according to Dr. Pfeffer-Bayer, or “about three times the energy release.” One of the largest hydrogen bombs ever exploded on Earth.
Even small space rocks can be dangerous, depending on how tightly they hold together as they enter Earth's atmosphere.
In 2013, Dr. Weber-Beyer observed that a small meteor exploded at an altitude of 97,000 feet over the Chelyabinsk region of Russia, causing a shock wave that shattered windows and damaged buildings. That meteorite was only about 20 meters (66 feet) in diameter, “and what it released was an energy equivalent to about 400 to 500 kilotons of TNT,” she said.
A kiloton is a unit of weight equal to 1000 tons.
For comparison, the nuclear bomb dropped by the United States on the Japanese city of Hiroshima generated energy equivalent to only 15 kilotons, so if the Chelyabinsk meteorite held together longer and exploded close to Earth, as Dr. Weber-Bayer noted, “close to a million people would have been affected. From this air blast alone.”
? How much should we worry about asteroids
Fortunately, such large asteroid strikes are relatively rare, and “maybe once in a century there is an asteroid that we are concerned about and want to derail,” Lindley Johnson, NASA's planetary defense officer, told a news reporter at a Thursday briefing about the DART mission. .
Dr. Johnson explained that the key, and perhaps most important to developing technologies such as DART to divert asteroid tracks, “is making sure we find them all” (dangerous asteroids). NASA plans to launch a new satellite by 2026 to help do just that, with the Near Earth Object Surveyor or NEO Surveyor space telescope.
"NEO Surveyor will be able to find the number of asteroids with a diameter of 140 meters or larger within about 10 years," Johnson told reporters. This is a very short period of geological time.”
This is also enough time for NASA to explain and understand the results of the Dart mission and ascertain whether an expanded version of the Dart spacecraft, or some other technology, can be used to eliminate a major threat to an asteroid or comet.
"We will not have a permanent fleet of spacecraft like DART," Johnson explained. It is possible that the technology has evolved further. And in 30 or 40 years from now, who can imagine what
?” technology might be available to us to deflect an asteroid
http://tira1.com/archives/482106?fbclid=IwAR39M2megekxnFlAWlJ0GZijMFu57wWdCM83i7gbHHSJY7245Q4sHBN2oxQ