Today (Feb 15) at 7:25 pm GMT, a 45-metre-wide asteroid will glide silently past Earth.
The 130,000 metric ton space rock will come within 27,700km of our planet - that's around 1/13th the Earth-Moon distance. It will come close enough to Earth that our planet's gravity will modify its orbit, shortening its passage around the Sun by 51 days. Asteroid 2012 DA14's flyby will provide backyard astronomers in Europe, Asia and Australia with a wonderful opportunity to spot the faint reflected sunlight of this interplanetary interloper. Professional astronomers will also use this opportunity to study the asteroid; Nasa's Goldstone radar dish in the Mojave Desert, California, for example, will track it, providing information about its surface features and composition.
It's worth emphasising the point, however, that there is no chance of 2012 DA14 hitting Earth - its orbit is very well-known. Since it was discovered on Feb 1, 2012 by the La Sagra Sky Survey in Spain, astronomers have diligently tracked the object, continually refining its trajectory.
However, there is a tiny amount of concern for the safety of our communications satellites. The asteroid's flyby will take it dangerously close to geostationary orbit, a ring of satellites that sit around 35,800km from the Earth's surface. But this is extremely unlikely in the grand scheme of things - space is really big, so in all likelihood 2012 DA14 will sail past without incident.
The flyby has been met with some derision in non-science media circles; after all, 27,700km is far, far away, why all the excitement? Science media outlets, on the other hand, have taken a more balanced approach, citing the wonderful scientific opportunity such a flyby provides, while pointing out there are a lot more asteroids where 2012 DA14 comes from. This flyby is also a first, at least in recent asteroid-hunting history - the biggest asteroid to make such a close pass to Earth for decades.
NO TIME AT ALL
Despite all the good news about 2012 DA14's safe passage through the Earth-Moon system, there's also some points in the discussion so far that need emphasising (and may not have caused alarm the first time around).An asteroid more massive than the largest cruise liner ever built will miss us by the width of a gnat's hind leg (cosmically speaking). As pointed out by Bill Nye, CEO of the Planetary Society, in an interview with CNN, the 27,700km close approach represents only 15mins in Earth's orbit around the Sun. If 2012 DA14 arrived 15mins earlier, it would be on a collision course.
Another fun fact: this asteroid was discovered only 12 months ago.
This may well be the case, but 2012 DA14 represents a tricky class of objects that are small enough to go unnoticed for uncomfortably long periods, yet large enough to cause devastation on a local scale. According to Nasa's Near Earth Objects Program, 2012 DA14 is carrying a kinetic energy of 3.5 megatons - 200 times the yield of a Hiroshima-scale atomic bomb blast - most of which would be delivered to its impact site. Yes, this particular space rock is a city killer.
WORST CASE SCENARIO
2012 DA14 is the approximate size of the object that exploded over the Podkamennaya Tunguska River, Siberia, in 1908, an event that, fortunately, happened in a remote region. Still, it flattened over 80m trees over 2,150 square km, the approximate area of Moscow. Eyewitness accounts described a powerful shockwave that broke windows hundreds of miles from the impact epicentre and atmospheric fluctuations were detected thousands of miles away over Great Britain. The Tunguska event is now believed to have been an atmospheric explosion of a cometary fragment or meteoroid.
Interestingly, 2012 DA14 is also the approximate size of the nickel-iron meteorite that blasted into the Arizona Desert some 50,000 years ago, excavating a crater 1.2km wide and 170m deep, forming Meteor Crater. Depending on DA14's composition, either one of these scenarios could be possible if it were on a collision course with Earth. Now imagine if 2012 DA14 was discovered on Feb 1, 2012, but there was one key difference: it was on a collision course with Earth. What could we do about it? As it turns out, there's little that mankind could do in this scenario, certainly with only a few months warning against an asteroid of this size.
Sure, our collective imaginations will fixate on the one thing movie Armageddon taught the world: asteroids hate nukes. But studies into the effectiveness of nuclear warheads against rampaging lumps of asteroid have proven only one thing: we know so little about asteroids we'd be only be guessing the impact of firing nukes into space - it would definitely be a desperate, last-ditch attempt.
Generally, a nuclear strike next to an asteroid could blow it to smithereens; but it could also slam into the asteroid, detonate and just heat it up a little, slightly altering its course. Imagine if the US launched a nuke to avoid an impact with Los Angeles, only to redirect the impact into Beijing? Not so good for foreign relations, needless to say.
A WAKE-UP CALL?
In all likelihood, we'd have to suck it up and get hit by the asteroid. In this event, scientists would have been able to work out where the asteroid will hit with a high degree of precision and, with this cheery knowledge in hand, we'd need to brace for impact. As the majority of the planet is covered in water, there's a high likelihood that impact would occur over an ocean, so the necessary preparation for coastal communities would be organised. Should it hit land, in all likelihood it will hit a remote region. But what if a city is in the crosshairs? Well, the last line of meteorite defence will come into play: evacuation. One could argue that a small impact on Earth's surface (or even high in the atmosphere) would serve as a wake-up call for our civilisation, inspiring us to develop the means to deflect the next asteroid threat. Fear is a great motivator; perhaps such an event would be the catalyst for a new space race; not a space race between communism and capitalism, but between asteroid and survival. But this is a moot point; the worst case scenario isn't going to happen for 2012 DA14. This time.
Asteroid deflection technologies may currently be in their infancy, but some concepts are slowly gathering apace. A promising collaboration between the European Space Agency and Nasa is the Asteroid Impact and Deflection mission. AIDA would see two spacecraft fly to a binary asteroid where one of the spacecraft will impact the smaller asteroid at high speed. The second spacecraft will record the impact and track any changes in the asteroid's orbit. This would be the first mission intended to observe the effects of an impactor on an asteroid, potentially modifying its orbit. In the case of early detection, a slight nudge could be all it takes to avert a catastrophic collision with Earth.
So, as the world gets excited about the passage of 2012 DA14 27,700km above our heads today, remember that although this is a near miss, it certainly isn't a relief - it's a not-so-subtle warning that there are plenty more asteroids out there that have evaded detection and one of them has our name on it. It's up to our civilisation to decide whether we use our technological prowess to confront this cosmic truth or be as powerless as the dinosaurs.