The first, the Torino Impact Hazard Scale, was hashed out in 1999 by a group of scientists from the International Astronomical Union (IAU), at a meeting in the Italian city of Turin. To get a better handle on things, boffins have worked out several scales to classify the danger. Knowing an object’s size, speed and other characteristics are also crucial in risk calculations, but in space these are generally only estimations.ĭetermining the risk sounds like trying to figure out the chances of a car having an accident without knowing who is driving, where, or at what speed.īut evaluating asteroids in this way is crucial to alert scientists and the world to potentially dangerous impacts. For starters, it’s difficult to measure its exact orbit, and, of course, that orbit can change over time as the asteroid interacts with other celestial bodies. Now consider the much more complex task of putting a number on the risk posed by an asteroid. Consider an everyday example: how dangerous is a car on a given road? This answer depends on a range of slippery factors, from vehicle speed to road conditions to driver skill, and even if we were able to draw solid connections between these factors, risk is a function of probability so we would still need to figure out a statistical tool to quantify the danger. That’s a lot of fast-moving objects to keep tabs on – so how exactly do we know which ones might kill us?įiguring out risk in any field is a tricky task. Together, these programs have discovered nearly 20,000 NEOs so far, with the total increasing every month. These survey programs are primarily funded by NASA and are mostly ground-based, although the near-infrared NEOWISE space telescope also spent most of 2010 spotting near-Earth objects (NEOs) from orbit. Since the late 1990s, a host of telescopes around the globe have been scanning the Earth’s neighbourhood to discover and monitor threatening asteroids. Luckily for us, we’ve learnt a thing or two from their misfortune. Unfortunately for the dinosaurs, they didn’t have the capability to detect, predict or prevent asteroids. In an iconic 1980 paper, for example, physicist Luis Alvarez and his geologist son Walter reported the discovery of a thin band of extra-terrestrial sediment between layers of Cretaceous and Tertiary rock – compelling evidence that an asteroid caused a mass extinction 65 million years ago. We’ve only really begun to understand the real threat of these impacts in the past few decades. While the majority have burned up harmlessly in the atmosphere, others have smashed into the surface and caused global devastation. For over four billion years, the Earth has been constantly clobbered by asteroids and other objects zooming around the solar system. This is a fairly accurate doomsday scenario – one that has happened before and will happen again. There’s a good chance your mind might have conjured up an image of an enormous asteroid barrelling down through the atmosphere, wreathed in fire, slamming into the earth and creating worldwide dust storms, heat, and general death.
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