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  • Writer's pictureSven Piper

Danger from outer space

Barringer Crater in Arizona
Barringer Crater in Arizona (Copyright

There have been increasing reports recently that an asteroid could hit the Earth in the near future. But does this asteroid threat really exist? This special is designed to help you form your own opinion about the real threat.

We have known that asteroids and comets pose a real threat to our existence since films such as “Armageddon” and “Deep Impact”. Cosmic objects have hit the Earth millions of times and caused more than just devastation. Without the cosmic snowballs, better known as comets, the water necessary for life might not have reached our planet. Metalliferous asteroids, on the other hand, have contributed to supplying our planet with important raw materials, in addition to the geological processes on Earth.

While they were a blessing in the early history of our planet, an impact today would be a catastrophe, as such an impact could wipe out the majority of all life forms on our planet. Around 65 million years ago, this happened to the dinosaurs whose impact crater was found on the Yucatán Peninsula in the Gulf of Mexico.

Another impact crater that continues to amaze researchers to this day is a crater in Peru that is only 15 meters in size. A fireball hurtled to Earth here in September 2007, and shortly after this event, hundreds of local residents complained of health problems. The impact occurred near the village of Carancas, 1,300 kilometers south of Lima, and toxic minerals such as arsenic probably evaporated during the impact. [1]

But that's not all, because the crater itself is also very unusual. Most smaller stony meteorites crumble due to friction with the Earth's atmosphere, and only smaller metal meteorites actually reach the Earth's surface relatively unscathed. However, there is no evidence that the meteorite that struck here was an iron meteorite. This is why there were controversial discussions about this event at the 39th Lunar and Planetary Science Conference in League City.

Why are objects just a few kilometers in diameter a danger to us? This has to do with the large kinetic energy generated by their high speed. Most asteroids are located in the asteroid belt between Mars and Jupiter. However, some of them orbit the sun on different paths. Collisions with each other, the gravitational forces of a planet (e.g. Jupiter), or the appearance of a comet can steer asteroids into the inner solar system and put them on a collision course with the Earth.

If the asteroid previously had a speed of 10 km/s (36,000 km/h), it is further accelerated by the gravitational forces of the planet and hurtles towards its target at tremendous speed. The formula for calculating the kinetic energy is 0.5 x mass x speed². With a mass of several thousand tons and a speed of several tens of thousands of km/h, it is easy to achieve energy values that are many times higher than those of an atomic bomb explosion.

The danger of a collision comes not only from asteroids, but also from comets. Comets consist mainly of ice and form a typical tail near the sun, which makes them easier to detect. Smaller comets would break apart before impact due to gravitational and frictional forces with the atmosphere of a planet. However, they could also release devastating energies in the event of an impact.

The last time fragments of a comet hit a planet was in July 1994, when Shoemaker-Levy 9 struck the gas giant Jupiter. If Earth had been the target, there would have been a catastrophe of unprecedented proportions.

Which Asteroids Could Be Dangerous to Us?

One example is the asteroid 2003 QQ47. This asteroid has a diameter of 1.2 kilometers and a mass of 2.6 trillion kilograms. The probability of a collision was very low (1:909,000), yet its discovery on August 24, 2003, caused a sensation.

Another object is 2000 SG344, which caused a sensation in 2000 when the probability of collision was initially estimated at 1:500. However, further calculations showed that a collision in the year 2030 is unlikely.

Scientists at the Infrared Space Observatory (ISO) estimate that there are around 2 million other asteroids with a diameter of more than one kilometer. Thanks to NASA's Planetary Defense Strategy, most of these objects have now been recorded and subjected to a risk assessment. Particular attention is being paid to the asteroid Apophis, which will come very close to Earth in 2029. [4]

The Earth had one last grace period on June 14, 2002, when the approximately 100-meter asteroid 2002MN passed by at a distance of only 120,000 kilometers. If this asteroid had hit the Earth, an area similar in size to the Tunguska event would have been destroyed.

On January 29, 2008, the 250-meter asteroid 2007 TU24 flew past the Earth at a distance of 538,000 kilometers. On December 18, 2018, a cosmic projectile exploded in the Bering Sea. This object had a diameter of 10 meters and released the energy of 173 kilotons of TNT. There was a similar event in February 2013 over Chelyabinsk in the Urals, in which 1,500 people were injured.

Explanation of Some Terms:

  • Meteoroids: Small fragments of asteroids, comets, moons, and planets that move through space.

  • Meteors: The celestial phenomena that occur when meteoroids hit the Earth's atmosphere.

  • Meteorites: The objects that make it through the Earth's atmosphere to the ground. They are divided into stony meteorites, iron meteorites, and stony-iron meteorites.

  • Asteroids: Small planets that are usually found in the asteroid belt between Mars and Jupiter.

  • Comets: "Dirty snowballs" consisting mainly of ice, but also containing rocky material. Their origin lies in the Kuiper Belt and the Oort Cloud.

Note: You can find out more about this topic in my book “Exoplaneten - Die Suche nach einer zweiten Erde”.

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