Sixty-five million years ago, a meteorite six miles across struck the Earth, ejecting enough dirt and rock into the atmosphere to cause a global firestorm. Seventy percent of extant species were driven extinct, including the dinosaurs. The Yucatan Peninsula still bears the scar of that impact: a crater 110 miles wide.
Such cataclysms are rare, but similar events are not out of the question during our lifetimes. In 1908, the Tunguska Event was caused by a small meteorite that exploded above Russia, leveling over 800 square miles of forest but hurting nobody. A similar blast (recorded in all its visual glory by hundreds of dash cams) rocked Chelyabinsk this past February. Fragments struck buildings, and the sound of the shockwave shattered glass windows throughout the city. Nearly 1,500 people were injured. The occasional incursion into our atmosphere by an asteroid may cause up a stir in the news, but what is being done to actually protect our planet from these space rocks?
In the 1998 film "Armageddon," Bruce Willis and a ragtag crew of oil drillers fly off to nuke a killer asteroid. This solution is hardly reasonable: Blowing up a massive rock could lead to many smaller problems hurling toward us on unpredictable trajectories. Most solutions seek to deflect, not destroy, near-earth objects on a collision course. One idea is to use a focused laser to burn a small area of an asteroid, releasing gas and particles that push the massive body like a small jet engine. Another concept uses a "gravity tractor" that works by parking a small spacecraft near an object and dragging it away using its weak gravitational field. An alternative, elegant solution is to spray-paint the asteroid with a reflective coating. The photons that make up incoming light impart a greater pressure on the reflective area as they bounce off versus the darker parts of the asteroid, which absorb them. The force directs the object like a sail pulls a boat along. All of these methods can be used to make small course corrections, but they all hinge on the assumption that an asteroid is detected years or months in advance.
Thus, the root of the problem is that we cannot see most of the asteroids that menace us. The one that struck Chelyabinsk is estimated to have been around the size of a house. The meteorite that exploded over Tunguska a century ago was a little larger; experts have speculated that it was on the scale of about one to two football fields. Currently, NASA thinks it knows about a quarter of the Tunguska sized rocks in our vicinity and very few of the smaller ones.
Although these asteroids do have the potential to devastate a small country, they are but grains of sand to our telescopes, which are designed to seek out objects on the scale of astronomical bodies. NASA's continued effort over the last 15 years has mapped 10,000 Near Earth Objects. The European Union has launched its own program, called NEOshield, to account for all asteroids threatening the planet.
Detection has certainly not been left in the hands of governments: Astronauts Ed Lu and Russell Schweickart have started the B612 Foundation. They intend to launch the first privately funded infrared space telescope; the so-called Sentinel Mission is poised to map more asteroids in a month than NASA's telescopes have so far.
Protecting the Earth from space rocks may not seem like an important task when the threat is not imminent. Fortunately, the effort is shaping up to be a global collaboration between the public and private sectors. Hopefully it will keep our species from going the way of the dinosaurs.
Petar Todorov is a senior majoring in chemistry. He can be reached at Petar.Todorov@tufts.edu.
