Protect Earth from the 'cosmic shooting gallery' Here's how

Tuesday, June 30, 2015, 12:12 PM - Near-Earth space is like a cosmic shooting gallery, with thousands of potentially dangerous asteroids whizzing about. Today, June 30, 2015, is the first official Asteroid Day - a day to draw attention to this danger and to address ways of protecting ourselves from extinction.

On June 30, 1908, a massive object - whether a comet or an asteroid is still debated - entered Earth's atmosphere above the Tunguska region of central Russia (now known as Krasnoyarsk Krai), exploding with a force of between 10 and 15 million metric tons of TNT (or about two-fifths of the energy emitted by the largest nuclear detonation ever, Tsar Bomba). Trees were flattened across an area of over 2,000 square kilometres, and the blast would have rated as a magnitude 5.0 earthquake at ground zero. Noone was apparently killed in the event, as it happened in a very remote area of the world.

The Chelyabinsk meteorite of February 2013, by comparison, exploded with the force of a few hundred kilotons of TNT. At only a fraction of the impact at Tunguska, the Chelyabinsk event still resulted in nearly 1,500 injuries and tens of millions of dollars in damages. With this as a model, if another Tunguska-like object fell from the skies over a populated area, the effects would be devastating.

If these past events weren't enough to highlight the potential dangers from the abundant rocks flying around us in space, more attention is being drawn to the dangers thanks to the efforts of NASA, as well as private organizations like the Planetary Society and the B612 Foundation. Not only have there been calls to increase the amount of funding towards projects that will locate more of these objects, but also to find ways of defending ourselves against the ones that may pose a threat in the future. The focus here is clear - it's not a matter of if the Earth will suffer another catastrophic impact, it's a matter of when.

This is the purpose of Asteroid Day, which is held on June 30 to commemorate the anniversary of the Tunguska Event, to raise awareness of this important issue, and to gather support for projects that could, ultimately, end up protecting humanity from extinction.

What can we do about asteroids?

Unlike other natural disasters, such as intense earthquakes, volcanic eruptions and powerful storms, we actually have a chance of detecting the threat from an asteroid far in advance of an impact, and we also have the chance to do something about it.

This is where the 100x Asteroid Declaration comes in.

Tap or click the image to go sign the Asteroid Declaration. Credit: Asteroid Day Foundation

Need a compelling reason to sign? Retired Canadian astronaut Chris Hadfield makes the case in this short, succinct video:

Exactly what are we looking at here?

Over the years, astronomers using telescopes on the ground and in space have discovered several hundred thousand asteroids flying around in the inner solar system. Most of these reside in the asteroid belt between Mars and Jupiter, however, as of June 27, 2015, NASA has identified a total of 12,860 of these that are classified as "near-Earth objects" (NEOs) - asteroids or comets that dip closer to the Sun, crossing an imaginary line set at around 1.3 astronomical units from the Sun, or about three-fifths of the distance between the orbits of Earth and Mars.

Of these near-Earth objects, 872 have been classified as asteroids at least 1 kilometre across, and 1597 are considered to be Potentially Hazardous Asteroids (PHAs) - ones that cross Earth's orbit or come close enough to Earth's orbit to potentially pose a threat to us. According to the latest numbers from NASA's Near Earth Object Program, 153 asteroids are classified as both - potentially hazardous asteroids that are at least 1 km across.

These two images, courtesy the Armagh Observatory, in the UK, show the current map of asteroids in the inner solar system (left) and those currently being tracked within 0.3 astronomical units of Earth (left), revealing the "shooting gallery" that Chris Hadfield mentioned above. Tap or click the images to enlarge them.

On the left, green objects are those identified as safe, while yellow objects are NEOs that approach close enough to be a concern and red objects are those that are classified as Apollo or Aten asteroids - ones that actually cross Earth's orbit (indicated in light blue).

On the right, all objects are plotted as small coloured dots, with a like-coloured arrow indicating their direction and speed of travel. Each object is joined by a dotted line connected to the "plane" of Earth's orbit (the imaginary disk traced out by a line from the Sun that passes directly through the Earth). If the object dot is at the top of the dotted line, the NEO is above Earth's orbit, and if at the bottom of the dotted line, the NEO is below Earth's orbit. NEOs on the right in green have a perihelion (closest approach to the Sun) outside of Earth's orbit, yellow have a perihelion inside of Earth's orbit. Red objects in this view are those that come within 10 lunar distances (indicated by the red oval). The closest object in this view is 2015 HP116, at just over 1.6 million kilometres, or over 4 times the distance to the Moon. The closest object that will be approaching in the near future is visible in yellow just "above" and "behind" Earth - 2015 HM10, which will come within 1.1 lunar distances on July 7.

What would happen in the case of a killer asteroid impact?

Scientists have modeled and studied the physical effects of an impact for years now, plotting the energy of airbursts, the blast radius and earthquake magnitude of ground impacts, crater formation and so forth. Now, a new film titled 51 Degrees North attempts to show what the social impact of such an event would be, in the days leading up to a disaster where humanity can only sit back and watch its approaching doom.

"This is a very different kind of disaster movie. No Bruce Willis here to save life on Earth from extinction," said Dr. Brian May, founding member of the rock band Queen, composer for the 51 Degrees North movie, and Asteroid Day Signatory.

Want to learn more?

The Slooh Community Observatory will be hosting a live webcast featuring host Will Gater, Slooh astronomer Bob Berman, game designer and first ever 2nd-gen astronaut Richard Garriott, along with documentary producer Duncan Copp, to show us images of 3-gigatonne asteroid Icarus, which just made its latest flyby of Earth on June 16, 2015, and to discuss how ready we are for a potential impact.

"Planets can't hit us, while comet debris doesn't survive to strike our surface," Bob Berman said in a Slooh press release. "But asteroids - chunks of stone or metal - arrive by the thousands every day, and are responsible for nearly all of the 50,000 catalogued meteorites. The largest asteroids are fascinating to observe, while the hazardous ones need to be watched while defenses are being conceived."

Tune in below starting at 6 p.m. Eastern Time, and follow along with the conversations on social media with the hashtags #AsteroidDay and #AsteroidDayIcarus.

Sources: Asteroid Day | NASA | B612 Foundation | Armagh Observatory