The Earth has a long history of things banging into it. By currently accepted theory, our Moon was created about 4.5 billion years ago when something the size of a planet struck the Earth. One of the more important events in the biological history of Earth was the impact of (probably) a comet fragment called Chicxulub in the Gulf of Mexico about 65 million years ago at what is now called the K-T boundary (Cretaceous-Tertiary extinction event). There are numerous places on Earth where you can visit a significant impact site, such as Barringer Crater in the state of Arizona, USA, or the Henbury Crater in Australia. Every day the Earth is bombarded by tons of material from space, mostly space particles and tiny meteors, of which only a very few make it to the surface as meteorites.
While there is debate about the frequency and severity of strikes by celestial bodies (comets, asteroids, meteors, or even planets), there is a growing consensus that significant impacts occur with relative frequency. Frequent, that is, in geologic time, say about every 20,000 years, which means for humanity – not often. However, any ‘significant’ impact has the potential for damage ranging from catastrophic (like the destruction of a major city), to apocalyptic (the end of civilization). This puts impact events in a peculiar category of risk: They’re not very likely, but if one does occur the consequences are very significant. This poses a problem for people. How much money and attention should be given to something that isn’t very probable, but very important if it does happen? Historically, human beings have a strong tendency to put off dealing with non-immediate, low probability risks – even if the potential result could be catastrophic.
Add to this tendency the fact that it’s only within the last few decades that we can even envision doing something about the risk of impact events. Given modern telescopes, we are in a position to find and track most of the significantly large celestial bodies (asteroids, comets, or meteoroids approximately ½ kilometer in diameter). We can also conceive of mounting rocketry to land on or ‘bomb’ threats in efforts to redirect them from Earth. The problem is; these are expensive resources, facing competitive claims from many other endeavors. So far, money and effort has been committed to find and track potential impact problems, and not much more.
The notion of Earth being struck by a large object from space is so apocalyptic that it’s no surprise there’s a corresponding sub-genre of disaster movies and novels. From the American canon of science fiction, movies such as Deep Impact and Armageddon come to mind, along with novels such as Lucifer’s Hammer (Nevin and Pournelle) and Arthur C. Clark’s Rendezvous with Rama. Explosions and big impacts sell because they’re dramatic and visually spectacular, even when depicting the deaths of millions of people. Still, the popularized images blend with recent scientific discoveries to make the possibility of an impact event seem more plausible.
In following the Impact Event as a scientific and technological impact area (sorry about the redundancy), SciTechStory will concentrate on the related sciences, such as asteroid tracking, and potentially relevant developments in rocketry and space exploration – particularly the growing idea of landing probes or people on a periodic asteroid (an NEO, a Near Earth Orbit body).