Warning: this article contains mild planetary peril.
Well, that didn’t take long. At the end of last year, it was some anomaly of an ancient Mesoamerican calendar which ramped up irrational concerns that the Universe was out to smite Earth mightily. At the start of this one – having miraculously emerged from the supposed Maya Armageddon unscathed – it seems we have dodged another attempt to wipe us out.
Earlier this month, Nasa announced that Apophis – the “doomsday asteroid” – will not hit the Earth in 2036… which will come as another disappointment of biblical proportions to the doom-sayers and newspaper writers who trumpeted the lump of space rock as the biggest threat to mankind since a misreading of Maya timekeeping.
Nasa’s assessment came as Apophis once again cruised into our cosmic backyard, giving scientists a chance to gather more data so we can better assess the risk. The flybys initially looked like they were good news for headline writers, when the scientists at the European Space Agency managed to determine we had underestimated its size by around 20% – from 270m (900ft) to 325m (1,000ft) wide. But then Nasa had to go and ruin it all.
But what is puzzling about this cosmic tale is where this lump of rock’s fear factor originates. Apophis may now be far and away the most famous threat to life as we know it, but it’s far from the only one. According to recent Nasa estimates it is just one of some 4,700 PHAs: potentially hazardous asteroids that are a minimum of 100m (300ft) in width, are big enough to level a city, and which have orbits that bring them within 8m km (5m miles) of Earth. And, to be absolutely clear, that’s 4,700 PHAs, not 47,000 as reported by various newspapers and scores of other innumerate websites.
Even with its recent super-sizing, Apophis isn’t among the larger PHAs on the list, and it’s not due to enter our immediate neighbourhood until 2029 (this time around it came no nearer than 14 million kilometres). So why does it grab the headlines, rather than 1999 AN10, which is expected to get closer to us than the Moon in 2027; or the almost one-kilometre-wide 2001 WN5, due to get even closer the following year, or perhaps 2012 DA14, which will come within 35,000 kilometres (22,000 miles) of Earth on 15 February. That’s 15 February 2013.
I just thought I’d slip that one in. Yes, depending on when you’re reading this we are only days away from a 130,000-tonne asteroid – massive enough to cause an explosion hundreds of times more powerful than an atom bomb – passing close enough to us to hit orbiting satellites. And yet there’s been far less fuss about 2012 DA14 than the much more distant threat from Apophis.
I suspect that Apophis’ apocalyptic appeal comes in part because of a comsic alignment that meant it was initially thought to be most likely to impact on a Friday 13th. It was also given the name 99942 Apophis. Which scarily sounds like a cross between Apocalypse and prophecy, and according to most media reports derives from an equally scary Egyptian god of destruction or chaos. In fact, two of the asteroid’s co-discoverers Roy Tucker and David Tholen are fans of the TV series Stargate SG-1, and they say they named it after one of the show’s recurring villains. But that would ruin the story wouldn’t it?
Yet, it can’t all be down to the lack of a catchy name. And it isn’t. Although as far as I can tell it’s the only such asteroid to even have a proper name. It’s more the continuing aftershock from when it first smashed into the mainstream media at the end of 2004.
For just a few panicky days Apophis became the first and so far only near-Earth object to reach four on the Torino scale of impact hazards, where zero equals next to no risk and 10 means that a collision is certain with something big enough to threaten the planet. Even that four rating translates as Apophis being more than 97% likely to miss the Earth.
Further observations got that rating drastically downgraded within the week but by then Apophis had been splashed all over the media and become embedded in our cultural consciousness as the “doomsday asteroid”. It has had numerous name checks in poem and song – notably in The Profits of Doom by goth metal outfit Type O Negative (aka “The Drab Four”), which mentions Friday 13th 2029 and how “this stone’s called Apophis; it brings Apocalypse”. Even more impressively, it’s the jumping-off point for 2011 video game Rage, which unfolds in the aftermath of global devastation initiated by a collision with Apophis.
What may also have contributed to our willingness to get into such a lather is that it hit the headlines only a few years after the Earth-imperilled-by-asteroid blockbusters Armageddon and Deep Impact hit multiplexes, giving us further cause to watch the skies. Apophis fitted with what we’d learned from the movies – that we are at the mercy of a capricious cosmos – so it became a focus of fear.
Now, thanks to observations made during its 2013 intersections with our orbit, Apophis is a big fat zero on the Torino scale for all 19 of its Earth fly-bys over the next century. So too are all but one of the hundreds of other Near Earth Objects that Nasa gives a rating to. Even the exception – 2007 VK184 – only scores one because there is an estimated teeny tiny chance (one in 1,820) that it could hit us on 3 June 2048. Probably not worth putting in your forward planner, then.
So, there appears to be no real cause for alarm about any of the many, many chunks of space rock we know of that are out there. But, if you do want something to worry about then bear in mind that – with apologies to Hamlet – there are more things in the heavens and potentially headed to Earth than are dreamt of in our philosophy. Last year, 2012 LZ1 – an asteroid three times bigger than Apophis – was only spotted for the first time four days before its closest approach to Earth. Who’s to say that next time we might have even less notice about something headed straight for us?