In 1908, a powerful asteroid struck the Podkamennaya Tunguska River in a remote Siberian forest of Russia. The event leveled trees and destroyed forests over 770 square miles, the size of three quarters of the state of Rhode Island. The impact threw people in a city 40 miles off the ground.
Five years ago, an asteroid entered the Earth's atmosphere over Chelyabinsk in Russia. It exploded in the air and released 20 to 30 times more energy than the first atomic bombs. It generated more brightness than the sun, radiated heat, damaged more than 7,000 buildings and injured more than 1,000 people.
The shockwave broke into windows 58 miles away. It went undetected because the asteroid came from the same direction and the same way as the sun.
NASA and other space organizations around the world focus on detecting the threat of near-Earth objects or NEOs. Near-Earth objects are asteroids and comets whose orbits they place within 30 million miles of the Earth.
There are currently no known NEOs that pose a significant threat, NASA announced last week. NASA's NEO program finances and relies on the capture and tracking of US and space observatories and collaborates with other observatories around the world.
According to Dante Lauretta, principal investigator of NASA's OSIRIS Rex mission, asteroids hit Earth every day. Most of them are so small that they burn in the atmosphere. But small asteroids can still cause damage, especially if they explode in the air over a city like Chelyabinsk. And the smaller they are, the harder they are to recognize the asteroids.
But new technologies and planetary defense plans could change that.
An Asteroid Action Plan
The plan's goals include improving NEO detection, tracking and identification, Improve predictive modeling, develop NEO distraction and disruption technologies, step up international cooperation to prepare for NEOs, and establish emergency response and action protocols.
The damage an asteroid can cause depends on its size. The one who killed the dinosaurs was 15 kilometers wide. Scientists have mapped 90% of the asteroids one kilometer or more in size and know that they are not a threat, said Detlef Koschny, head of the European Space Agency's near-Earth object team.
But we only detected and mapped less than one percent of NEOs that are less than one kilometer in length. The smaller the asteroid, the greater the likelihood that it hits the earth. According to Koschny, every 10,000 years, 10,000 asteroids meet every 10,000 years and 50-meter asteroids.
Asteroids, which like Chelyabinsk are about 20 meters long, occur on average every 10 to 100 years. "We will definitely see such a thing in our lives again," Koshcny said.
According to the new report, NASA will search for asteroids that are only 50 meters wide. So far, they have focused on larger, 100-meter-wide and larger, because they can affect entire regions and continents. But also asteroids smaller than 50 meters can cause considerable damage. There are 10 million NEOs larger than 20 meters and 300,000 objects larger than 40 meters which, according to NASA, could pose a risk of collision, but they are hard to spot just days in advance.
The Asteroid Institute is also partnering with Google Cloud and Analytical Graphics Inc. to track asteroid discoveries using a cloud-based platform for the Asteroid Decision Analysis and Mapping Project.
"There will be a lot more data and observations on asteroids," Lu said. "We are getting ready for this flood of data and, together with our partners, we are working to understand how well we can determine if an asteroid will hit Earth, and more observations will mean less uncertainty." 
In 2005, Congress mandated NASA to detect at least 90% of NEOs that are at least 140 meters tall by 2020. Since then, the total number of cataloged NEOs has risen by five. Current capabilities however, estimates indicate that by 2033 we will find less than half of these objects. For this reason, the new plan focuses on improving NEO detection and promoting those skills.
At present, several missions are planned that are currently aimed at investigating and distracting asteroids.
The spaceship is 12.4 miles from the asteroid, from where it will launch a projectile into the rock to excavate subsurface samples. Later, Hayabusa2 will sit on the asteroid and collect the samples. It will leave Ryugu in December 2019 and eventually return to Earth by the end of 2020.