As if to underline how limited we are in our ability to track small asteroids, another asteroid was discovered on March 3rd and passed a few days later within two and a half lunar orbit lengths of the earth on Saturday, March 9, 2013.

This small asteroid is probably twice the diameter of the 150 foot asteroid 2012 DA14, discovered a year ago and which passed within 17,200 miles of earth on February 15, 2013.  DA14 was about three times the diameter of the meteor that suddenly appeared a few hours earlier above Chelyabinsk, Russia.

The Russian meteor released the energy of a 500 kiloton bomb in the upper atmosphere close to a large city, about 1,500 were injured and amazingly no one was killed.  The asteroid 2012 DA14, if it had hit the earth, could have released the energy of a 20 megaton bomb.  If we have the relative sizes and densities right, the new asteroid, 2013 ET, if it had hit the earth, could have released the energy of over a 200 megaton super bomb.  Seeing these numbers and how they increase with size of these very small asteroids, we can then better understand how much energy could be released by an asteroid over a mile in diameter (see table at end).

Should we cower in fear?  Should we spend all of our national resources to try to find small asteroids like these and somehow rendezvous with and deflect them if on a collision course?  Probably not.

Perhaps the best advice might be what Pahoran wrote to captain Moroni during a war that threatened the very survival of the Nephites.

“Tell them to fear not, for God will deliver them, yea, and also all those who stand fast in that liberty wherewith God hath made them free.” (Alma 61:21)

PBS had an excellent episode on the meteor, the process of determining its orbit and composition and the efforts to track these small asteroids are available online here. (“Meteor Strike,” PBS Documentary, NOVA, 3/27/13)

The combination of a large estimated diameter and a low lunar diameter (LD) distance is the small group of objects that are rare.  Even though 2013 EC20 is closer than the orbit of the moon, it is only estimated to be 4.2 – 9.3 meters in diameter. 2013 ET is 64 – 140 meters in diameter, much larger, AND only 2.5 lunar diameters away at its closest orbital point. The same may be said of 2013 EN20 like 2013 EC20, close but small.

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0.1427

 Object Name Close Approach Date CA Distance (AU) CA Distance Lunar Diameter Estimated Diameter H Magnitude Relative Velocity (km/s) 2013 CS83 2013-03-05 0.1689 65.7 97 m – 220 m 22.2 15.46 2013 CH129 2013-03-05 0.1385 53.9 43 m – 96 m 23.9 7.16 2012 RJ15 2013-03-06 0.1621 63.1 51 m – 110 m 23.6 2013 ER 2013-03-06 0.0396 15.4 20 m – 44 m 25.7 5.85 2009 EM1 2013-03-08 0.1240 48.3 68 m – 150 m 22.9 11.75 2013 EC20 2013-03-09 0.0010 0.4 4.2 m – 9.3 m 29.0 3.57 >>> 2013 ET 2013-03-09 0.0065 2.5 64 m – 140 m 23.1 11.88 2011 EC12 2013-03-09 0.1825 71.0 18 m – 41 m 25.8 10.93 2013 EN20 2013-03-10 0.0030 1.2 4.0 m – 9.0 m 29.1 7.30 2007 EP88 2013-03-10 55.5 530 m – 1.2 km 18.5 30.03

In the upcoming close approaches table on March 11, 2013 going through June, 2013, the only object that is closer than 5 lunar diameters is 2007 EO88, which is also small at only 14-31 meters in size.

Large object, but far away-58.3 lunar diameters:

2000 ED14            2013-03-12            0.15            58.3            200 m – 440 m             20.6            22.47

Smaller object, and fairly close-4.4 lunar diameters

(It is close to the size of the Russian Meteor):

2007 EO88            2013-03-18            0.0114            4.4            14 m – 31 m                        26.4            10.65

Large object, and fairly close-6.3 lunar diameters:

2013 ES11            2013-03-22            0.0163            6.3            53 m – 120 m            23.5            10.63

Nothing as close or as large as 2013 ET is included in this snapshot and especially not as close or as large as the very rare 2012 DA14 which passed February 15, 2013 within 0.09 lunar diameters of the earth.

Size vs. Energy for Small Asteroids and Large Meteors (Author’s Estimate)

 Object Name Diameter- feet Radius^3 Estimated Energy Chelyabinsk Meteor 55 20,796 500 K tons 2012 DA14 150 421,875 20 M tons 2013 ET 300 3,375,000 200+ M tons 1 Mile Asteroid 5200 17,576,000,000 1,000,000+ M tons Greater Than Russia/US Combined Arsenals

(Melissa Gray, “Asteroid to fly past Earth this weekend,” CNN, March 7, 2013,)

(Laura Smith-spark, “Report: Injured Russians leave hospital, analysis of meteorite begins,” February 22, 2013,)

(Ernesto Gido et all, “Close Approach of Asteroid 2013 ET,” Romanzacco Observatory, 4 Mar 2013, “discovery of the asteroid 2013 ET (discovery magnitude 16.9) by Catalina Sky Survey (mpc code 703) on images taken on March 03.3 with a 0.68-m Schmidt + CCD.” “estimated size of 64 m – 140 m”

(“NEO Earth Close Approach Tables,” NASA Near Earth Object Program, Retrieved March 11, 2013.)