The sky disk of nebra, sun gods or lunar eclipses: Sun, moon and stars have fascinated people for millennia. And shooting stars are considered romantic. The observer can make a wish for every celestial body that burns up in the earth’s atmosphere – however, the dinosaurs no longer had any wish. Could a rock from space wipe out as much life as it did 65 million years ago?
Danger cannot be excluded
“The risk of a major impact is small, but cannot be ruled out,” says asteroid researcher Alan Harris from the Institute for Planetary Research at the German Aerospace Center. The probability of a block measuring 100 meters in size is one percent in 100 years. “Something like this could destroy a large city or parts of Germany,” he explains on Asteroid Day.
It happens again and again that larger asteroids hit Earth. In February 2013, the explosion of a 20-meter boulder devastated the Russian city of Chelyabinsk. The pressure wave injured around 1,500 people, mostly with broken glass, without any warning. The asteroid came out of nowhere.
“If we had discovered that beforehand, it would have been enough to open the windows,” says the asteroid expert at the European Space Agency, Detlef Koschny. “It would be enough if we informed people about the radio the day before.” An asteroid of this size releases an energy of 500 kilotons of the TNT explosive when it explodes in the atmosphere. The Hiroshima bomb was 15 kilotons.
On June 30, 1908, an asteroid explosion also occurred in Russia: in the Tunguska region in Siberia, the pressure wave swept away millions of trees in an area almost as large as the Saarland. Because of this natural disaster, the United Nations declared June 30th International Asteroid Day.
Just last year, the scientists feared that the up to 50 meter large asteroid “2006 QV89” could hit Earth. The chance for a collision before the all-clear was given by the experts, according to the ESA risk list, was 1 in 7299. For comparison: For a lottery win with six numbers plus an additional number, the chance is 1 in 140 million.
Small boulders fly into the earth’s atmosphere almost every day and burn up. It’s not unusual in space. Such collisions also created the planets of our solar system. Most objects made of stone and Koschny are not, as sometimes feared, radioactive. “It is nothing more than what we find on earth.” The process didn’t stop, Harris says. It only weakened in the billions of years.
“There are two large surveillance programs, both funded by NASA, that scan the sky almost every night and search for these objects,” explains Koschny. The data could then be used to calculate orbits of the asteroids. An additional surveillance telescope is currently being developed in Europe and is scheduled to go into operation in Sicily in 2022. The Americans were working on a satellite-based telescope. “A telescope on the side of the moon facing away from the earth would of course be even better,” said Koschny. Only it would be very expensive.
From 50 meters in diameter, things get hot
With asteroids 50 meters and larger, one has to think about a distraction. “At 50 meters, you would have to evacuate an entire state,” says Koschny. The scenario would then be to send a satellite on a confrontation course and to deflect the trajectory of the chunks, which were traveling many kilometers per second. The US movie hit “Armageddon” is also not pure science fiction. According to Harris, there are discussions in the United States about the use of nuclear missiles.
According to the experts, the risk of a major impact is rather small, but cannot be completely ruled out. “95 percent of the really big ones, larger than a kilometer, are known,” Koschny is certain. The dinokiller was 12 kilometers tall, according to Harris. Such a chunk would be seen centuries ago with today’s technology. “We have enough time there.”