[Hi folks, this is Fred! G. Sallust is out this week, dodging brickbats. Really, some of you are just too serious about politics! G makes a perfectly innocent comment, about how Ted Cruz lacks judgment and is in love with the sound of his own voice, and you – or some of you – respond with vitriol and gall. The things you said! G’s not in hiding; don’t get the wrong idea; but he is out, doing chores and running errands. You know, like cleaning dead chickens out of the mail box, changing phone numbers, renewing his concealed carry permit, updating a passport, that kind of thing. No doubt he’ll be back soon.

In the meantime, let’s change the subject. Let’s turn from politics and elections – after all, we have nine more months until November and plenty of time to talk about politicians – and focus on some of the good things from last year. Now don’t get all negative on me! I know 2015 wasn’t kind to a lot of us. We had too much debt, didn’t make enough money, worried about terror attacks, and worried even more about another war.

Some say that we’ve won the last three wars – the one in Afghanistan and the two in Iraq – and each victory simply led to pressure for another one, war, that is. If we win many more like that we’ll soon be bankrupt. No matter how hard we try, for some reason we can’t seem to fight a successful war to end all wars in the Middle East.

Nevertheless there’s at least one thing about 2015 that’s indisputably good, and I say this with little fear of contradiction.  At no time last year was our planet, Earth, struck by an object that was big enough to end all intelligent life here. And please, no bad jokes about if there ever were intelligent life on our planet, it probably ended when the dinosaurs went extinct. I know for a fact that I’m intelligent; and you are too, if you read this blog.]

Every couple of years we do a piece on meteors, meteorites, and off-planet things that might harm us in a major way. Why? Well, the original inspiration was Death from the Skies[1], a neat book we picked up a few years ago. There are lots of ways – esoteric and mundane – the Universe could finish us off, but the most likely is by dropping rocks.[2] Things from outer space hit us every day, and sometimes they’re big. For a recent example from Russia, take a look at the video at


Of course, that one wasn’t big enough to end all or any life down here, but it does make a basic point. There are accidents out there ready to happen [to us].

To start our review, let’s distinguish between meteoroids, meteors, and meteorites. Why? Well, I’m told professional astronomers get mad if we confuse these things.[4] A meteoroid is anything small and solid that may collide with our planet[5]. If it does that, most assuredly it will catch fire when it enters the atmosphere – producing a flash or a fiery trail across the sky. That’s the meteor: the fire in the sky. If anything remains of the meteoroid after it combusts, and it hits the ground, that’s called a meteorite. These are the distinctions NASA makes, and I’m sticking with them.[6]

NASA makes other distinctions as well, especially when it talks about the big stuff that might hurt us. Things in that category generally are called Near Earth Objects [NEOS], not because they’re always near us, like the moon, but because they pass close by from time to time. Why do they do that? Well, because a NEO’s orbit around the sun comes close to or intersects our planet’s orbit. If we both arrive at the same place at the same time, hopefully there’s a fly-by, not a collision.[7]

Most NEOS are either wayward asteroids or comets.

  • Generally asteroids are pieces of rock, left over from the creation of our solar system, 4.5 billion years ago. There are millions of them out there, but only a small subset comes near us.
  • Comets also date back 4.5 billion years, but originate much further out in the solar system. Basically they’re dirty snowballs. “When far from the sun, comets are very cold, icy dirtballs. As they approach the sun, their surfaces begin to warm and volatile materials vaporize.”[8]

NASA tells us that every day about 100 tons of meteoroids enter our atmosphere.[9] Most of them are really small, and never make it to the ground. Then there are the really big collisions – most likely with asteroids – the ones that create so-called Impact Events. Today we think the dinosaurs were done in by one of those. [10]  In between, of course, are many other objects large enough to cause damage, but they will not exterminate us if they hit.

So who’s watching for this stuff? Is anybody on alert, or are we just ignoring the problem? Are we in the United States meteor-deniers, or do we accept that there might be danger? Well, that’s why we do these occasional updates. You see, some people are paying attention, principally NASA and its contractors. NASA has a central office devoted to the work[11]; and they do give progress reports from time-to-time. The news is always interesting, especially the stuff from NASA’s JPL/Cal Tech. operation.

For example, last November NASA reported that in fiscal year 2015 it had 54 ongoing projects to identify NEOS. “NASA-funded survey projects,” it said, “have found 98 percent of the known catalogue of more than 13,000 NEOs. NASA funded surveys are currently finding NEOs at a rate of about 1,500 per year.”[12] Just think of that: NASA’s finding and charting 1500 new potential threats per year, apparently with no end in sight.

The news is even better, if you like this kind of thing. NASA publishes, and updates daily, tables that show which NEOS are likely to get close at any given time. They are called, unsurprisingly, the NEO Earth Close Approach Tables.[13] The version I have – it’s several days old – shows that, in January about 53 NEOS will get close, but not uncomfortably so. Their size will vary from 2 meters[14] to 3.4 kilometers.[15] The closest any one of them will come to us is about 5 times the distance from the earth to the moon.[16] So, I guess we can all relax for the rest of the month.

But don’t get over-confident. These days we know a lot, but we don’t know everything. There’s still other stuff out there, uncharted by us, and each time a known NEO passes by, the gravity generated by our planet might alter its orbit somewhat, so that next time it comes a bit closer.[17] Yesterday’s miss could be tomorrow’s collision.

And more to the point, it’s not really clear what we would do if NASA finds a big NEO that actually will collide with us. In the sci-fi movies, of course, Hollywood has a ready-made solution. Just send up a suitably diverse group of heroic astronauts to plant a nuke on the NEO, and detonate it. It helps if the characters have previous associations and/or conflicts, just to make the trip more interesting. But while the movie-makers are sure that will work, the scientists aren’t. They’re considering lots of other ways to do the job, but nobody has settled on a fool-proof plan.[18] It’s because of all those unknowns, don’t you know; and the unknown ones as well.

In short, for those who may not know, often there’s a big gap between fiction and what’s currently possible. If you don’t believe me, just try to book a flight to Tatooine next week.



[1] See Plait, Death from the Skies (Viking, 2008). Henceforth, the Plait book will be cited as Sky Death at  __.

[2] See Sky Death at Ch. 1, Target Earth: Asteroid and Comet Impacts, p. 1 – 32.

[3]See Meteor hits Russia, lightening sky, shattering windows (02/15/2013) available at https://www.bing.com/videos/search?q=Meteor+Hits+Russia&view=detail&&mid=4C23DF4CE3CDED03579F4C23DF4CE3CDED03579F

[4] See Sky Death at p. 11, note.

[5] See Compact Oxford English Dictionary (Third Edition, 2005) at meteoroid, p. 639: “[A} small body that would become a meteor if it entered the earth’s atmosphere.”

[6] See NASA’s Marshall Center, Meteor Moment: Is it a Meteor, Meteoroid or Meteorite? (December 13, 2015), available at https://www.youtube.com/watch?v=IG5O-A-0zTM

[7] See NASA/JPL, Asteroids, Comets and Meteorites (no date), available at http://www.jpl.nasa.gov/asteroidwatch/asteroids-comets.php

[8] Id.

[9] See NASA, What’s Hitting Earth? (March 1, 2011) at http://science.nasa.gov/science-news/science-at-nasa/2011/01mar_meteornetwork/

[10] For those of you who are interested, check out Wikipedia on Impact Events, available at https://en.wikipedia.org/wiki/Impact_event

[11] That’s the Meteoroid Environment Office, accessible at http://www.nasa.gov/offices/meo/home/index.html .  See also NASA/JPL, Asteroid Watch, NASA Office to Coordinate Asteroid Detection, Hazard Mitigation (January 7, 2016), available at http://www.jpl.nasa.gov/asteroidwatch/

[12] See NASA/JPL, Secondhand Spacecraft Has First Hand Asteroid Experience (November 11, 2015), available at http://www.jpl.nasa.gov/news/news.php?feature=4767  

[13] See NASA, Near Earth Object Program, Close Approach Tables (updated daily), at http://neo.jpl.nasa.gov/ca/

[14] That’s the low estimate for NEO 2014WE6.

[15] That’s the high estimate for NEO 1685 Toro

[16] That’s the estimate for NEO 2015YC2. Actually, the closest approach will be 4.9 Lunar Distances, which amounts to 1,881,600 kilometers. The Lunar Distance is measured from the center of the earth to the center of the moon.

[17] See NASA/JPL, Asteroids, Comets and Meteorites (no date), available at http://www.jpl.nasa.gov/asteroidwatch/asteroids-comets.php  “Occasionally, asteroids’ orbital paths are influenced by the gravitational tug of planets, which cause their paths to alter. Scientists believe stray asteroids or fragments from earlier collisions have slammed into Earth in the past, playing a major role in the evolution of our planet.”

[18] See, e.g., Discovery Channel.com, Lamb, Top 10 Ways to Stop an Asteroid (January 30, 2013), available at http://news.discovery.com/space/asteroids-meteors-meteorites/top-10-asteroid-deflection-130130.htm