Will an asteroid hit Earth in 2026?

Asteroid Apophis on course for Earth in 2068?

With the ESA-NASA AIDA mission, an asteroid is to be pushed out of its orbit for the first time with an impactor to see whether the earth can be saved in an emergency

Astronomers at the University of Hawaii assume that it cannot be ruled out that the relatively large asteroid Apophis, with a diameter of 300 meters, could fall to Earth in 2068. They discovered a Jarkowski effect: The different warming of the asteroid surfaces by the sunlight could steer the course towards Earth. So far, that has been ruled out.

Apophis, discovered in 2004, is approaching Earth so close by April 13th that it can be seen with the naked eye as it passes near satellite orbits. It has now been discovered that the asteroid deviates from a gravitational orbit by 170 meters per year. So one can no longer rule out that it will hit earth. It is reassuring to say that one knows long beforehand whether there is a real risk of an impact. But what could people do if there actually was a collision?

One is to identify celestial bodies and observe how ESA and NASA use their early warning system to detect NEOs that are threatening to approach Earth, and the other is to keep them off course to Earth and divert them. Even observing is not easy, there are tens of thousands of asteroids in the solar system. Most of them, however, are so small that they would burn up when they entered the atmosphere. 80-100 tons of material from burned up asteroids in the form of dust or meteorites are said to fall on the earth every day. They are sometimes recognizable as star scales, larger meteors also as bolides (fireballs). It is estimated that there are around 25,000 NEOs (near earth objects) with a diameter greater than 140 m. From a diameter of 300 meters, an impact is expected to have major regional consequences, and from a kilometer, global consequences.

The last impact of a larger asteroid or meteor with a presumed diameter of 20 meters occurred in the summer of 2013 near the city of Chelyabinsk in the Russian Urals. It broke apart at a height of 30 km, the pressure wave damaged buildings and windows 90 km away, and 1,200 people were injured. The Tunguska event in 1908, also in Siberia, is likely to be traced back to a larger asteroid that exploded.

Large asteroids are a threat to humanity and life on earth. Their fall to earth has already led to mass extinctions several times. It has long been thought about how such large heavenly bodies could be rendered harmless to life on earth. It was considered, for example, to detonate nuclear missiles on or near an asteroid in order to blow it up or throw it off course. That could also be done with other missiles. Or, if you have the time and the necessary technology, you could mount laser cannons or a rocket engine on the asteroid to steer it off course to Earth.

To this end, NASA founded the Planetary Defense Coordination Office for planetary defense and decided on the DART (Double Asteroid Redirection Test) mission in 2017. The plan is to push the Didymos (twin) satellite, which will come relatively close to Earth in 2022 and 2024, i.e. up to a distance of 16 million kilometers, out of its trajectory.

It is a binary asteroid system in which the larger Didymos A with a diameter of 780 meters is orbited by a smaller one, Didymos B, with a diameter of 160 meters. The intention is to have a refrigerator-sized spaceship hit the smaller asteroid at a speed of over 20,000 km / h in order to see how a change in the trajectory of Didymos B affects the asteroid system, i.e. also changes the trajectory of the larger asteroid . DART is scheduled to launch on July 22, 2021 and hit the asteroid on September 30, 2022.

The ESA, which under the name Don Quijote has already developed and discontinued a "demonstration mission for asteroid defense" mission, is also participating in the mission with the Hera spaceship under the joint mission project AIDA (Asteroid Impact and Deflection Assessment). Funding was approved at the end of 2019. However, Hera is not expected to take off from Earth until 2024 and visit the asteroids in 2026, four years after the alleged DART impact. ESA will then use two mini satellites (CubeSats) to investigate the two asteroids, especially the impact crater and the exact masses. For the first time in 2005, the NASA Deep Impact mission tested the impact of a 370 kg projectile at a speed of 37,000 km / h on the comet Tempel 1 with a diameter of 6 km. The impact could be seen from the spacecraft, but the dust cloud caused by the explosion, which also contained ice, prevented a view of the crater. It wasn't until 2011 that the Stardust space probe flew close to Temple 1 again to measure the crater, which has a diameter of 150 meters.

Originally, ESA wanted to send an Asteroid Impact Mission (AIM) space probe to the pair of asteroids in October 2020 to scout it. A lander was also planned for 2015 to explore the surface more closely. Then the probe should wait for the arrival of DART in order to observe the "historical" impact live and also to be able to compare the state before and after it through measurements. Back then, it was said, somewhat cocky, that DART's shifting the asteroid's orbit would "be the first time that humanity has changed the dynamics of the solar system in a measurable way".

One will have to wait until 2022 to be able to determine this, if the mission is still taking place at all. If so, the first empirical clues will be found as to what force would be necessary to push an asteroid out of its orbit in an emergency. Finally, one could viciously think of doing this not to save the earth, but to hit an opponent on earth through a smaller asteroid. (Florian Rötzer)

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