Astronomers have been so horrified by press scares over asteroids that they are toning down the scale they use to rate the threat posed in an attempt to discourage journalists from covering potential collisions. The most prominent recent furore involved asteroid QQ47, which briefly had a one-in-a-million chance of crashing into our planet in 2014.
Some astronomers even want the way asteroids are assessed to be completely overhauled. The Torino scale, developed in 1999 by Rick Binzel of the Massachusetts Institute of Technology, is used to inform the public about potential impacts. It rates an asteroid鈥檚 threat on a scale of zero to 10, based on its speed, size and probability of impact with Earth (see graphic).
No asteroid has ever exceeded a hazard rating of one 鈥� the same chance as a random object of the same size hitting Earth in the next few decades. Despite that, last week鈥檚 category-1 asteroid made headlines. And as searches for near-Earth asteroids grow more systematic, sightings of potentially dangerous rocks are becoming routine.
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Even as the commotion over QQ47 was dying down, astronomers found another, even larger asteroid that earned a similar hazard rating. QQ104 is 2.7 kilometres across, and for a couple of days last week looked to be heading for a possible impact as early as 2009.
While journalists insist they reported the information on QQ47 accurately, astronomers feel they were misrepresented. 鈥淭hat was certainly much ado about nothing,鈥� says Steve Chesley of NASA鈥檚 Jet Propulsion Laboratory in Pasadena, California. 鈥淚t was like a virus solely within the realm of the press鈥�.
False alarms
Binzel himself is so upset by the press coverage of asteroid scares that he is toning down the scale鈥檚 wording. Instead of 鈥渞equiring careful monitoring鈥�, a category-1 event will now be described as 鈥渘ormal鈥�.
Brian Marsden of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, worries that the public will stop taking the asteroid threat seriously if false alarms continue. He says altering the scale is not enough: 鈥淚t鈥檚 time we got rid of it.鈥�
At the moment, newly discovered 鈥渢hreats鈥� tend to start higher on the scale, when astronomers still have little information on them, and then drop down as further observations rule out the hazard. Marsden says incorporating a measure of how long the asteroid has been tracked would help prevent false alarms.
His colleague John Remo also believes the Torino and related Palermo scales have got it wrong. 鈥淭hey are scare indexes,鈥� he says. 鈥淭hey tend to create anxiety.鈥� Rather than quantify the damage an asteroid will cause on impact, Remo says it would be more positive to rate how difficult an asteroid would be to deflect into a safe orbit.
But despite disagreements over how best to avoid crying wolf too often, astronomers insist keeping the data secret is not an option. 鈥淚 hope people take away the idea that if there is actual news, it will be out in the open,鈥� says Binzel.