Asteroids and Meteors: Confronting the Impacts

February 16th, 2013 - by admin

Ian O’Neill / Al Jazeera – 2013-02-16 00:23:18

Videos of Meteor Strike in Russia
Russia Today

Asteroid 2012 DA14 Won’t Hit Us…
But What If It Did?

Ian O’Neill / Al Jazeera

(February 15, 2013) — Today 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 27,700 kilometres 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 February 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 35,800 kilometres 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.

Earth: 1; Cosmic Shooting Gallery: 0
The flyby has been met with some derision in non-science media circles; after all, 27,700 kilometres 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 emphasizing (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 27,700 kilometre close approach represents only 15 minutes in Earth’s orbit around the Sun. If 2012 DA14 arrived 15 minutes earlier, it would be on a collision course.

Another fun fact: this asteroid was discovered only 12 months ago. 12 months.

“But really,” I hear you cry, “what damage could a 45 metre-wide asteroid really do?” This isn’t, after all, on the scale of Asteroid Apophis — the 325-metre-wide monster that was thought to be threatening our planet until astronomers recently ruled out the threat of a 2036 impact. If it’s not an Apophis-sized monster, then 2012 DA14 is hardly an apocalyptic event. Get over it.

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 80 million trees over 2,150 square kilometres, 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 1.2 kilometres wide and 170 metres 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 February 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 Bruce Willis’ 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.

However, most recently, research into a double-impactor strike proved that a small asteroid (smaller than 100 metres wide) may be blown up, so long as the nuclear warhead is buried below the space rock’s surface bunker-buster style. But, even if the nuclear strike plan was a good idea, it would be debatable as to whether the world’s governments would be able to develop an effective anti-asteroid system in time for it to make a difference.

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 civilization, 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.

We live in a solar system crammed with asteroids and although the vast majority of large, potentially hazardous asteroids (PHAs) have been recorded and are being tracked, there are countless smaller asteroids that evade detection.

Being prepared for an asteroid strike that will happen in our future is of utmost importance. Therefore we need an in-space infrastructure (i.e., the development of low cost launch capabilities and the ability to send advanced robotic and, if necessary, human missions beyond low-Earth orbit) and we need to develop a network of space telescopes so we can better see what’s out there.

Currently, global collaborations such as Spaceguard and government space agency efforts like NASA’s Near-Earth Object Program have advanced the science of near-Earth asteroid detection. Also, huge advances in observatories and space telescopes have made us acutely aware of the swarm of space rocks that are out there.

Also notable are non-profit organizations such like the B612 Foundation that is developing asteroid deflection techniques. Also, proposed asteroid mining companies such as Planetary Resources hope to use privately funded space telescopes to survey the Solar System for near-Earth asteroids not only to avert catastrophe, but to also prospect for exploitable resources.

Asteroid deflection technologies may currently be in their infancy, but some concepts are slowly gathering apace.

A promising collaboration between the European Space Agency (ESA) and NASA is the Asteroid Impact and Deflection (AIDA) 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 27,700 kilometres 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.

“Asteroids have us in our sight. The dinosaurs didn’t have a space programme, so they’re not here to talk about this problem. We are, and we have the power to do something about it. I don’t want to be the embarrassment of the galaxy, to have had the power to deflect an asteroid, and then not, and end up going extinct. We’d be the laughing stock of the aliens of the cosmos if that were the case.”
— Neil deGrasse Tyson.

Ian O’Neill is Space Science Producer for Discovery News. He is also the founder and editor of space blog Astroengine.

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