Guide to the Cosmos
         Making the Wonders of our Universe Accessible to Everyone.

Protecting Earth From Asteroids


My November 2012 newsletter discussed the vital role of asteroids in Earth’s development. Asteroids brought water from the Solar System’s “snow line” to our initially dry rock. Much later, a devastating asteroid impact aided the ascension of mammals by killing off the dinosaurs and about 75% of all then-living species. That asteroid is estimated to have been 12 kilometers (7 miles) across.


But now that humans are Earth’s dominant species, asteroids are no longer a good thing. More devastating impacts would be “overkill.”


In February 2012, an 18-meter (60-feet) wide asteroid exploded near Chelyabinsk, Russia, with more than 20 times the energy of the Hiroshima bomb. The asteroid arrived without any warning, in part because it came from the direction of the Sun, where conventional telescopes are useless.


In 1908, a 40-meter (130-feet) wide asteroid exploded over the remote Siberian region of Tunguska, releasing the energy of a 10-megaton bomb and killing everything in 1000 square miles, about the size of the San Francisco Bay Area.


The question is not: “Is an asteroid coming that could kill millions of people, or even all of us?” Such an asteroid is certainly coming; the only question is: “When?” It is unlikely to come in the near future, but it will come one day.


Here’s the good news: of the many recurring natural disasters – earthquakes, tsunamis, hurricanes, tornados, etc. — asteroid impacts are the only catastrophes that we could prevent. But we must choose to act.


Saving Earth doesn’t require new science — we already know enough — but it does require technology development and political will and consensus. Shielding Earth involves three basic steps: (1) detecting asteroids that pose serious threats; (2) establishing plans to deflect dangerous asteroids into new orbits that avoid Earth; and (3) implementing those plans.


Here’s a technical overview. Earth and billions of asteroids orbit the Sun. An asteroid will hit us if it and Earth arrive at the same time, at an “intersection”, a place where their orbits cross. We can avoid a collision by deflecting the asteroid, by pushing it so it either: (1) orbits faster and goes through the intersection before Earth does; or (2) orbits slower and arrives after Earth has passed. Earth’s orbital velocity is 19 miles per second, which means the intersection point will sweep all the way across Earth’s surface in about 7 minutes. If an asteroid is going to hit us, we need to speed up or slow down its arrival by several minutes.


Deflecting an asteroid can be done by: (1) slamming a rocket into it; (2) gravitationally pulling on it with a rocket hovering nearby; or (3) a combination of both — brute force and precision.


If we reach that asteroid 7 years before impact, we only need to change its velocity by 1 part per million. If we get there 20 days before impact, the velocity change must be 1 part per thousand. Therefore, it pays to detect dangerous asteroids far in advance — we should avoid “crash” programs.


Now let’s discuss the greatest challenge: politics.


Below is a map showing one possible example. The “risk corridor” is the red line, with X marking the asteroid’s impact point if we do nothing. Speeding up the asteroid moves X along the risk corridor toward the right, while slowing it down moves X left.



If we deflect the asteroid sufficiently, its impact point moves off either the left or right end of the risk corridor and all Earthlings are saved. But, here’s the rub: what if the deflection is only partially successful? What if we move the impact only part way along the risk corridor?


In the above example, with no deflection the asteroid would impact the northeast Pacific Ocean, possibly causing devastating tsunamis in Hawaii and the West Coast. We might choose to slow the asteroid and move X left toward Siberia. But, the Russians would likely prefer moving X to the right toward the Panama Canal and Central America. Who gets to choose?


Imagine the nightmare scenario: four irreconcilable nations launch rockets that push a major asteroid in different directions, cancelling each other’s deflections, and ensuring the demise of all mankind.


It would be sensible for all nations to agree on an equitable decision-making procedure well in advance of a specific threat. (What am I smoking?)


Where do we stand, back in the real world?


Governments are doing very little about asteroids. None is developing rocket technology for asteroid deflection. Annual NASA spending on asteroid detection was $20M in 2012. That’s what the U.S. government spends every 3 minutes. Since the U.S. has found 98% of all detected asteroids, the rest of the world must be doing even less. NASA claims to have detected 90% of near-Earth asteroids over 1 kilometer (0.6 miles) across, which could devastate an entire nation, and only 1% of the smaller city-killers.


Former astronauts Ed Lu and Rusty Schweikart and others formed the private non-profit B612 Foundation to do what the Feds won’t. (In March 2013, I interviewed Schweikart on my radio show; listen to it for free here.). B612 is soliciting $400M in private donations to design, build, and launch Sentinel, an advanced infrared telescope that will orbit the Sun at about the same distance as Venus. Looking outward, every relevant asteroid will be in Sentinel’s field of view. During its 6½ year mission, Sentinel is expected to detect 500,000 near-Earth asteroids, including over 90% of those over 140 meters (500 feet) across with impact energies over 100 megatons.


The B612 Foundation says we should stop being passive passengers on spacecraft Earth, and become its crew. They sell a coffee mug that says:

“Don’t be a Dinosaur!”


Best Regards,


January 21st, 2014



Author of 3 print books



and 26 Everyone's Guide Series e-Books

Web: GuidetotheCosmos


Note: Previous newsletters can be found on my website.


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