There are more than 1,400 ways that Earth could suffer a disastrous collision with a lump of rock from space, and a recently released NASA map visualizes each one of them. Fortunately, none are expected to come to pass for at least another hundred years, as far as we can tell, according to NASA officials.
The map depicts the trajectories of more than 1,400 Potentially Hazardous Asteroids (PHAs), the official term for asteroids that could possible crash into our planet. An asteroid is a PHA if it meets two qualifiers. First, its orbit must take it within 4.7 million miles of Earth—i.e., close enough to Earth that it stands a chance of a collision. Second, the asteroid must be 460 feet or more across—that is, large enough that it would make it through Earth’s atmosphere without burning up.
That 4.7 million-mile span is pretty far—essentially the distance from Earth to the Moon times 20. But asteroids wobble in their pathways around the sun. So if one is within that radius, the wrong ebb or dip in gravity, or an unfortunate pushback from some particulate matter in space, could possibly send it hurtling close enough to us to cause us a serious problem. In any case, astronomers will want to keep an eye on it.
And while 460 feet won’t be big enough to bring on Armageddon, it would potentially ininerate any community that happens to be in its path. Case in point is the Tunguska event of 1908, in which an incoming space rock shattering over a forest in Siberia flattened 830 million trees over 830 square miles. Subsequent tests suggest that the object had measured no more than 60 feet.
NASA is planning a new satellite mission to look more closely at asteroids and comets, including those PHAs. Near-Earth Object Camera, or NEOCam, will orbit Earth and deploy an infrared satellite and camera apparatus to find and photograph “near-Earth objects.”
The mission will try to ascertain the actual risks that the various PHAs actually pose to Earth, but there will be some less-ominous mission objectives, too. It will try to find out more about the asteroids’ earliest origins and their long-term future fate; and identify which of the near-Earth asteroids might be prime targets for future space missions—maybe even human ones—to fly to and visit.
Knowing of an oncoming asteroid strike in advance will give humans time to prepare and, if necessary, oversee mass evacuations of the communities that are within the anticipated asteroid’s likely strike zone. We don’t currently have the technology to fly to destroy an asteroid in space, but space researchers are working on that, too. At least they’ll have a hundred or so years of lead time to get it up and running.