On July 25th, asteroid 2019 OK flew by Earth at a distance of only 40,000 miles (65,000 kms). Measuring around 330 feet (100 meters) wide, asteroids the size of 2019 OK are relatively common in the solar system, and according to the European Space Agency (ESA) tend to strike the Earth on average once every 100,000 years.
2019 OK Impact Calamity Averted
Earth still bears the scars of slightly more than 300 cometary and meteoritic impacts on its surface, and while the largest of these scars were inflicted during Earth’s distant youth, impacts that are more recent abound. Two examples include the the aptly named Meteor Crater in Wyoming, USA that was created about 50,000 years ago, and the now-water filled Tswaing Crater in South Africa that was created about 200,000 ± 52,000 years ago.
What does this have to do with the near miss that occurred on July 25th, 2019? Simply that the Wyoming meteorite was only about 50 metres in diameter, but being made of iron and nickel, it created a crater that is 170 meters deep and 1200 meters across. The Tswaing meteorite on the other hand was also roughly 50 meters in diameter, and although it was rocky in nature, it still created a hole in the ground that is (now) 100 meters deep, and 1100 meters across.
By way of comparison, the asteroid (designated Asteroid 2019 OK)) that whizzed past Earth at a distance of only 65, 000 km is 100 meters in diameter, and although almost nothing is known of its mass and structure, the above statistics serve as valid comparisons of might have happened had this asteroid struck a big metropolitan area.
Existence Unknown One Day Prior to Appearance
While what might have occurred is a frightening thought, Asteroid 2019 OK was actually too far away and moving too fast to have been captured by Earth’s gravity. Nonetheless, its existence was unknown until a day before the flyby, when the Southern Observatory for Near-Earth Asteroids Research (SONEAR) in Brazil first detected it. Although the European Space Agency had enough time to investigate this particular asteroid before the flyby, the fact is that there are thousands of other, equally massive NEO’s in a dense swarm around Earth, many of which could be nudged out of their orbits by collisions or even near-collisions between objects in the swarm.
As a result of this possibility, several sky surveys, including Pan-STARRS, ATLAS, SONEAR, and the Catalina Sky Survey are maintained to detect significant changes in the orbits of objects in near-earth orbits. A good case in point is the detection of Asteroid 2006 QQ23, an Empire Building-sized asteroid that will pass by Earth on August 10th, 2109 at a distance of about 7.5 million kilometers.
The problem with detecting NEO’s however is that they are very small and not very luminous, which means that in practice, it is very difficult to spot a threat in time. Exactly this happened with the asteroid that exploded over Russia in 2013; in this case, the 20-metre object had appeared from the direction of the Sun, and it went completely undetected until it exploded in the atmosphere, causing severe damage to buildings and infrastructure on the ground.
The obvious threats that NEO’s present are real, and many research institutions are involved in detecting these threats. To do this, most institutions use small telescopes coupled to high-resolution cameras that can monitor huge swathes of sky, as opposed to using large telescopes that can monitor only small sections of the sky, albeit at a higher resolution than small telescopes can.
Next Asteroid Impact 50,000 Years Overdue
Despite the best efforts of many astronomers, scientists, and national governments to detect possible impacts in time, however, there is virtually nothing anybody can do to mitigate the effects of a major impact. It has been suggested that an inbound object might be destroyed by a nuclear-tipped cruise missile, but the effects of such a measure is unpredictable at best. What is likely to happen though, is that the break up (if it breaks up, that is) will cause multiple impacts by fragments of the original object, which could have cumulative, and potentially, more dire consequences than one large impact.
One other option that has been suggested might be to somehow change the orbits of objects that weigh hundreds of thousands, or even millions of tons, and that move at several tens of kms per second. Exactly how this might be accomplished has yet to be explained, but until effective methods of diverting inbound NEO’s are developed, we have to live with the possibility that Earth might be struck by a large object that nobody knew existed. In fact, based on the historical record, such an impact is about 50,000 years overdue.