| What would happen if something the size of a | | | | environment of space. These pock-marks should act |
| mountain, flying at 26 000 miles per hour (41 843 | | | | as a reminder that "It's not a matter of If an impact will |
| kilometers per hour), hit the Earth? Do our | | | | happen, but when!" |
| Governments have a plan in place to protect us from | | | | According to David Morrison at NASA-AMES in an |
| such a calamitous event? Judging by the | | | | article he wrote in September 1998, on average a |
| administration's sluggish response both before and | | | | NEO with about 1 million megatons energy (roughly 2 |
| after Hurricane Katrina the likely answer is 'No'. | | | | km in diameter) collides with the Earth once or twice |
| We live in a busy Solar System with lots of moving | | | | per million years, statistically speaking. An impact of this |
| parts. Many of those parts consist of stony-iron | | | | size would kill a substantial proportion of the Earth's |
| materials known as asteroids and many of these | | | | population and have a devastating and lasting effect |
| rocky bodies have yet to be discovered and could | | | | on Earth's environment. What such a statistic does not |
| impact with Earth at any time. | | | | tell you of course is whether the impact will occur one |
| There are also many icy bodies, known as Comets. | | | | million years from today, or one week from today. |
| They live out past the orbits of Neptune. Any stirring of | | | | What is interesting to note is that the impact that most |
| their orbits, perhaps nudged by gravitational forces of | | | | scientists believe is responsible for causing the |
| nearby stars can change their trajectories for a visit | | | | extinction of the dinosaurs occurred 65 million years |
| into the inner Solar System putting them on a potential | | | | ago. That may well make us long overdue for an |
| collision course with Earth, also at any time. | | | | extinction-level strike. |
| Scientists Study Recent Developments | | | | Is Anyone Doing Anything About This Situation? |
| In January 2008 there was some news that an | | | | US Military budgets do not include Earth's protection. |
| asteroid, known as 2007 WD5, might hit Mars. The | | | | The US military does not even have a mission to |
| resulting impact was projected to be similar in size to | | | | worry about it. The military agenda of all countries is to |
| Meteor Crater, an impact crater a mile-wide in Arizona, | | | | defend their respective countries' interests. To date, |
| formed in a flash of white light and fireball, when an | | | | NEO's are not of formal interest to any military. No |
| asteroid struck there 50 000 years ago. | | | | country or conglomerate of countries has undertaken |
| Around the same time, another asteroid known as | | | | the task, officially, to protect the Earth from NEOs. |
| 2007 TU 24 was discovered in November 2007 by | | | | Were an imminent impact to happen, would the |
| the Catalina Sky Survey on October 11, 2007. | | | | government(s) even tell us at all? We have already |
| Calculations determined it would pass near the Earth, | | | | determined that governments are not prepared to |
| on January 29, 2008, just outside the orbit of the Moon, | | | | intercede, intercept and save the day. In February |
| which is considered very close in astronomical terms. | | | | 2008 the US Air Force shot down an orbiting US Spy |
| 2007 TU 24 is between 150 and 600 meters in | | | | Satellite. The satellite was traveling at near asteroid |
| diameter. The average interval between actual Earth | | | | speeds, at 23 000 miles per hour. Impressive as that |
| impacts for an object this size is estimated to be | | | | was, who would save Earth from an impending |
| about 37 000 years. Radar Observations of 2007 TU | | | | impact? |
| 24 were made at the Goldstone, California in late | | | | "Space Guardians" around the world are hunting for |
| January and early February. This will permit later 3D | | | | these potentially hazardous Near Earth Objects. (That |
| shape reconstruction. | | | | term, Space Guardians, was created by myself and |
| In July 1994, twenty-one fragments of Comet | | | | based on Sir Arthur C. Clarke's novel "Rendezvous |
| Shoemaker-Levy 9 smashed into Jupiter, leaving black | | | | with Rama" which featured an NEO search program |
| and brown blotches on the planet for over a year, | | | | called Space Guard. Sir Arthur C. Clarke very much |
| each blotch itself, the size of Earth. Astronomers have | | | | appreciates that reference.) |
| yet to witness an asteroid impact with another planet. | | | | The major US-based searches include the most |
| Therefore the opportunity to witness the 2007 WD5 | | | | productive sky survey, the Catalina Sky Survey, run by |
| impact on Mars was exciting to astronomers and | | | | Steve Larson, with searches in both the Northern and |
| scientists who wanted to make measurements of | | | | Southern hemispheres. The remaining searches are all |
| these types of objects as well as calculations and | | | | uniquely located in the Northern hemisphere with |
| impact scenarios of what might happen should an | | | | money provided by NASA. They include: the US Air |
| asteroid, or a comet, impact with the Earth. | | | | Force operated LINEAR program from Lincoln |
| The Mars impact never took place as the asteroid | | | | Laboratories, run by Grant Stokes and NEAT (Near |
| cruised by without incident; a disappointment to | | | | Earth Asteroid Tracking) a JPL run operation. |
| astronomers who lost an opportunity to observe the | | | | Spacewatch is yet another NEO search founded by |
| direct effects of an asteroid impact on a planet similar | | | | Tom Gehrels and Robert McMillan and run by Robert |
| to Earth. | | | | McMillan, based near Tucson, Arizona. Finally, the |
| Luckily for us though, the asteroid 2007 TU 24 also | | | | Lowell Observatory in Flagstaff, Arizona, has a search |
| missed Earth. I couldn't help wondering how we would | | | | called LONEOS (Lowell Observatory Near Earth |
| actually have responded if the scientists had told us | | | | Object Search) run by Ted Bowell. There are also |
| that the Earth-bound asteroid was headed directly for | | | | countless amateur astronomers around the world that |
| us and that, according to their calculations there was | | | | help in tracking the known asteroids (sometimes even |
| no way it was going to miss us! | | | | finding a few new ones themselves). |
| How Worried Should We Be? | | | | Is Luck a Sensible Strategy? |
| One of the main problems we have right now is the | | | | We know what will happen. It is inevitable. We've |
| lack of an effective response. Even if we knew that | | | | witnessed impacts on other worlds. Scientists are |
| an asteroid or comet was headed straight for us, and | | | | convinced that it was a Comet that wiped out the |
| even if we had plenty of warning ahead of time, what | | | | dinosaurs 65 million years ago. |
| would we do? Once we detect them we still have to | | | | The big impact at Tunguska in 1908 is the latest major |
| figure out some way to safely and reliably destroy or | | | | event of its kind on Earth. Luckily it exploded over an |
| deflect them. To date, such methods do not exist in | | | | uninhabited part of Siberia and only one person died as |
| practicum, only in theory. No missions to prove the | | | | a result. However, the explosion was equal to that at |
| ability to move or destroy an asteroid or comet have | | | | Hiroshima and the trees that were felled for miles |
| ever been undertaken by any country. | | | | around the impact site remain so to this day. |
| If an asteroid were to hit Earth, impact would likely be | | | | While very few people on Earth consider these very |
| in the oceans as Earth is over 70% water. The | | | | real dangers from Space, thousands of relentless |
| effects of such an impact could include Tsunamis, | | | | NEO's traveling silently through the night go on |
| which would be devastating to small Island nations and | | | | indifferently about their business. |
| coastlines on the main land on both sides of the ocean, | | | | Learn More |
| or could be as devastating as planet-wide | | | | Videos |
| environmental collapse if the projectile is large enough | | | | For a thorough understanding of the NEO hazard and |
| to punch through the ocean floor. | | | | what is being done about it, watch the seminal film on |
| An asteroid could also hit land, including cities, again | | | | this subject, “Planetary Defense”. |
| causing anywhere from local to global devastation | | | | "Planetary Defense" speaks with military, scientific and |
| depending on the size of the impactor. Food chains, | | | | governmental experts about the dangers we currently |
| transportation, infrastructure could all be leveled with a | | | | face and any plans for dealing with NEOs in the future. |
| moderate impact and civilization itself can be | | | | The film also features eminent science fiction author |
| jeopardized. | | | | Sir Arthur C. Clarke and Apollo 9 astronaut, Rusty |
| A big impact would jeopardize the survival of the | | | | Schweickart, who will be advising the United Nations |
| entire planet, not just food chains and civilization, by | | | | about the NEO risk in 2009. |
| kicking up tones of dust and soot high into the | | | | The film runs 48 minutes and has nearly one hour of |
| atmosphere, similar to gigantic volcanic eruptions which | | | | Bonus Features in the form of two silent slideshows. |
| would block out the sun and change climate, killing off | | | | One slideshow shows a collection of asteroids and |
| vegetation as temperatures plummet and no access | | | | comets from NASA, JPL and other sources; the other |
| to solar energy for photosynthesis. | | | | is dedicated to impact sites here on Earth. |
| When looking at the Moon, Mercury, Mars and even | | | | Find out more about the film, Planetary Defense at |
| the Earth itself, we can see the pock-marks that tell | | | | Online |
| the tale of their respective histories. As the Moon and | | | | For more information about NEO’s visit There you |
| Mercury are not subject to the forces of erosion, their | | | | will find comprehensive coverage about NEO’s by |
| battle-worn landscapes bear the scars of countless | | | | David Morrison of NASA-AMES. |
| impact craters displayed in plain view; harsh reminders | | | | A plethora of other material about the NEO hazard |
| of the reality of every planet's life in the brutal | | | | can be found online. |