THE ENTIRE UNIVERSE IN BLOG FORM
SEPT. 7 2014 7:30 AM
No, We’re Not Facing an Onslaught of Asteroid Impacts
Drawing by Stocktrek Images Inc./Alamy, modified by Phil Plait
Today—Sunday, Sept. 7, 2014—at about 18:00 UTC, a small asteroid named 2014 RC will harmlessly pass by the Earth, though at the close distance of very roughly 40,000 kilometers. I wrote all about it a couple of days ago … and also warned that you can expect a bunch of breathless and fact-free YouTube videos about it, claiming it would hit us.
PHIL PLAIT
I was so, so close.
The very day I posted that, a ridiculous article appeared in the U.K. tabloidExpress, claiming that the Earth “faces 100 YEARS of killer [asteroid] strikes starting 2017.”
How do I phrase this? That claim is really, really, really, really, really wrong. Really.
The author of this article, Nathan Rao, has a history of writing reality-impaired articles; for example, in August he wrote a piece suggesting the Supermoon might kill everyone on Earth. This led to a less-than-satisfying exchange of tweets between Rao and me (and many others), with him trying to defend his writing, and ended with me telling him, “Whatever helps you sleep at night.”
Anyway, this asteroid article he wrote is more of the same. Essentially the only time he gets anything right in that piece is when he quotes some astronomers, but the conclusions he jumps (leaps, launches, hyperspace blasts) to are way, way off the mark.
For example, he claims:
A previously unknown asteroid belt has been located in deep space and is now hurtling towards our part of the solar system. … The terrifying predictions came as NASA revealed disturbing new data showing 400 impacts are expected between 2017 and 2113, based on new observational data of objects seen in space over the past 60 days.
Um, no. Not even close. It’s not an asteroid belt, but a single asteroid. And it’s not 400 impacts, it’s 400 predicted passes of Earth, most missing by a wide margin.
Happily, U.K. amateur astronomer David Wood (who also sent me the note notifying me of Rao’s article) did the footwork for me. He figured out that Rao is talking about the asteroid 2014 NZ64. It fits Rao’s (bizarrely interpreted) description; it was recently discovered (in July, about 60 days ago) and the JPL Earth Impact Risk Summary page has a list of 399 near-Earth passes between the years 2017 and 2113, the exact range Rao listed. It’s obviously what Rao is talking about, but somehow Rao turned a single asteroid that will miss us into hundreds of asteroids that will all hit us.
That’s a somewhat significant error to make.
Image credit: Phil Plait; Earth: ESA/Rosetta;Mathilde:NEAR Spacecraft Team,JHUAPL,NASA
So what’s the science here? NZ64 is a small, 100-meter or so wide, asteroid that has an orbit that does take it pretty close to Earth. Since its discovery it has only been observed a handful of times, and as I’ve written many times before, the fewer observations you have, the harder it is to predict where the asteroid will be in the future. Given that, at this time, NZ64 has only been observed over less than a two-day timespan, I’d say trying to figure out where it’ll be more than a few months in advance is nearly impossible.
So bear that in mind with the impact risk page (which is automatically generated); we really don’t know where this asteroid will be more than a few years in the future … and since Earth is small, and space is very, very big, I’d be willing to bet the chance of an impact will get even smaller once a better orbit is determined.
Even so, take a look at the impact risk page, and you’ll see a column there labeled “Impact Probability.” This gives the fractional chance of an impact at every given encounter, where 0 is no impact for sure, and 1 would definitely be an impact. Note how close to 0 the numbers are! Typical values translate into odds of about a billion to one—even the wildest Vegas spender wouldn’t take that risk—and the highest chance I saw was for a pass in 2023, when it has a one in 6 million chance of hitting us. I have a hard time working up a sweat over that. Note also that each listed probability is actually a link where the numbers are literally spelled out for you, right there for everyone and anyone to see.
That's the central premise of Rao's article, and it's clearly wrong.
I could stop there, but there's one more thing I'd like to point out. He writes:
Asteroid 2012 DA14, discovered by astronomers at the LaSagra Observatory in Spain, currently has less than a one per cent chance of hitting but scientists can't rule out the possibility that it might smash into our planet.
Actually, that is precisely wrong: DA14 was taken off the impact risk list months ago, after observations ruled out any chance of impact in the near future. Update, Sept. 7, 2014, at 17:00 UTC: Ron Baalke notified me that DA14 was taken off the impact list in February 2013, the day it passed the Earth. So it's been over a year and a half that we've known it can't hit us.
Normally I would ignore nonsense like Rao’s article, but I decided to write about it when I saw his piece was relatively popular on Facebook (though the comments there are pretty funny, as most of the commenters fully grasp the, ah, tenuous reality of the article).
Also, to put it mildly, I take a dim view of articles that spin, fold, and mutilate science, doubly so when it’s astronomy on the wrong end of it. And at the very least, this is a chance to show folks how this whole process of flagging asteroids works, so somegood can come of it.
But it also shows that, once again and as always, you can’t believe everything (or anything) you see online (and I certainly would be extremely skeptical of anything I read in the Express). When it comes to things like asteroid impacts, your best bet is to check with JPL, or—ahem—here. If an asteroid has a decent chance of hitting us, I’d write about it … after getting confirmation and as many facts as I could from people who actually understand asteroid science.
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