An asteroid will buzz Earth next week, missing our planet by only 27,700 kilometers, making it the closest flyby in history. Asteroid hunters are trying to save our lives. But whenever I hear that an asteroid is coming towards us, I close my eyes and see that ‘dense clouds of dust blocking the sun’s rays, darkening and chilling Earth to deadly levels for us. The frigid and sweltering climatic extremes are causing the extinction of humans and almost all plants and animals.’
Oh My Goosebumps! It suffocates me!
The closest flyby in human history, anyway. I guess the dinosaurs would take you to task on that one.
Mind you, I can think of a few human dinosaurs (like creationists) I wouldn’t mind an asteroid landing on!
; )
NatGeo’s Thrilling Headlines! aside this would better be called the closest known* flyby for an object of this size in the last hundred (actually 105) years.
*”Known” with the caveat that we’ve only been systematically tracking (and therefore likely to know about) such passes for about the last 20 years.
Allow me to provide some reassurance:
1. 2012 DA14 _will not hit_ Earth in the next century. After a series of radar observations I’ll be working on next weekend, we will be able to run its trajectory out even further into the future.
2. When an object the size of 2012 DA14 hits the Earth, it is not a fun day right at the impact point but there is not much global effect. It’s too small to cause a significant impact winter. This is not merely conjecture. The last time an object DA14’s size hit was at 1908 June 30 00:14 UTC, near the Podkamennaya Tunguska River in Siberia. It flattened trees over a city-sized area, and while there was a measurable increase in the amount of dust in the atmosphere there was not significant cooling. The usual threshold for objects being considered globally dangerous is somewhat arbitrarily set at 1 km – that is, about 20 times larger and about 10,000 times more massive than DA14.
3. We have found and tracked almost all near-Earth asteroids larger than 1 km, and none will hit the Earth in the next several hundred years. The last possibility was ruled out last year. Current and pending survey programs have the goal of bringing the completeness limit for the entire near-Earth population down to ~140 m. Going to this size limit will decrease the risk from the impact hazard by another factor of ten, and also approaches the point where finding the objects decades in advance of possible impacts and deflecting them if necessary is more expensive than finding them a few days to weeks before impact (as was done with the little chunk known as 2008 TC3) and simply evacuating the blast radius. The ATLAS project out of U. Hawai’i will take the latter job, among others.
So thanks to everything that Spaceguard and the various follow-up programs have done over the last 20 years, the asteroid impact hazard is rapidly becoming something you do not need to worry about – as long as the surveys continue at current and planned levels.
You can learn more about the asteroid discovery statistics and about the planned DA14 radar observations at the following links:
http://neo.jpl.nasa.gov
http://echo.jpl.nasa.gov/asteroids/2012DA14/2012DA14_planning.html
Just so you have the number:
With the current state of the asteroid surveys, the risk of anyone dying from an asteroid impact is about _one in a million_. That’s more than the chance of dying from botulism poisoning, but lower than the chance of dying from an accident with fireworks.
Before the survey programs showed that there will not be an impact by a >1 km asteroid in the next few centuries, the impact hazard was assessed based on the long-term average rate of such events. That gave a risk about the same of dying in an airplane crash (airplane crashes kill a few people frequently, a >1 km asteroid impacting would kill many people but is unlikely to happen in any hundred-year period). And, again, such an impact has been ruled out for quite a while into the future.
So far, we have not been ‘trying to save our lives’. We have been trying to understand if lives need to be saved from asteroid impact.
Usually, they just trash the trunk of your car or your roof. 😉
It’s true. The cross section of cars for meteorite hits is a lot higher than the cross section for people.
@Nathair:
Exactly. Allowing for all sizes, 2008 TC3 is the closest known flyby. Distance went to zero when it flashed in the sky above the desert in northern Sudan and dropped a few pieces the size of a fingertip on the ground at terminal velocity, which is to say, not fast at all. Objects smaller than 10-30 m get stopped in the upper atmosphere, mostly burn up, and only relatively small pieces reach the ground as a wide scattering of meteorites (depends on density and how strongly they are held together).