Rusty's Blog

Hello. I’m Rusty Schweickart and I’m writing this blog in order to introduce you to the basics of what we refer to as Planetary Defence or simply PD. Planetary Defence is the name given to the process of protecting the planet from asteroid impacts. More to the point, protecting life on planet Earth from the destructive effects of future asteroid impacts.

Rusty's Blog

Rusty’s Planetary Defense – You Count! Sign The 100x Declaration And Be Heard | Part Five

15 AD Supporters

One of the most frustrating questions I’ve had to deal with when making public presentations on the planetary defense and asteroid impact issue is “what can I do to help?”  The issue of asteroids impacting Earth is so far outside the experience of most people, and the “solutions” so arcane and technical that identifying anything a regular person could do that would really be helpful has just been beyond me.

Well that has now changed and I couldn’t be happier!  The answer is… sign the 100x Asteroid Day Declaration.  Really!?  Yes indeed, and I hope to tell you why in this blog.

I think that everyone understands that you can’t protect yourself if you don’t know what’s coming at you.  Early warning is the sine qua non of planetary defense.  In earlier blogs I’ve gone into the population of objects out there, circulating around the Sun, minding their own business, which can cause death and destruction if they were to impact Earth.  To shorten it dramatically there are approximately 10 million NEOs out there of the Chelyabinsk impactor size and 1 million objects out there of the Tunguska impact size.  Of all those millions of objects we have, to date, discovered less than 1% of the Tunguskas and less than 0.1% of the Chelyabinsks.  In other words, at the moment, the probability is over 99% that we’ve never seen, let alone tracked, the next object of Chelyabinsk size or larger that’s going to hit us.

Now let’s put this in perspective.  NASA, the telescope teams it supports, and a few others, have done an excellent job in finding and tracking the larger, far more dangerous objects that can do continental or global level damage.  In fact, since 1998 NASA has discovered over 95% of the objects larger than 1 kilometer in diameter that would cause global devastation if they were to hit.  These comprise the largest 1,000 or so of the over 12,000 NEOs that have been discovered to date.

That’s great… but those objects hit only about once every 500,000 years! How about the ones that hit every 50 years or several hundred years? Most people who look seriously at this issue realize that what we want to know about and be able to prevent are impacts from all the asteroids out there that could cause death if we permit them to hit.  Preventable death.

The 20 meter diameter Chelyabinsk asteroid came very close to causing death on the morning of 15 Feb 2013.  Experts have concluded that had it come in just a bit steeper than the 16 degree dive angle it followed it might well have killed people.  And the 40 meter Tunguska NEOs, deemed “city killers” by the U.S. Congress in a hearing on planetary defense, would likely kill millions if one were to impact directly over a major city. This is, of course, highly unlikely, even if one were to impact given the 70% of the Earth’s surface that is ocean and the low average density of cities on the solid land. Still, do we want to continue to run around with our eyes closed (effectively) and have one arrive unannounced?  Surprise!!  I’m here!  All 30 Hiroshima equivalents (Chelyabinsk) or 267 Hiroshimas of me (Tunguska)!  I don’t think so.

But time is an issue here.  At the current rate of discovery of 20 meter NEOs and larger, about 1000/year, it will take over 1,000 years to find 1 million new NEOs.  That’s a long time and even then we’d have reached only 10% or so of the Chelyabinsk objects that potentially threaten impact.  This then is the reason why when Asteroid Day was first discussed we came up with a goal of 100,000 (or 100x) new discoveries per year, within ten years.  We’ve simply got to get at it!

Can this be done?  Is it possible to make this goal?  When it was initially discussed it seemed possible, but a real reach.  Happily it now seems to be quite possible indeed, given a recent decision and assuming a positive outcome on other decisions to be made in the near future.  And that’s just where you, and your signature on the 100x Declaration come in.

So what’s happened?  The first key event was the NSF funding commitment to the construction of the LSST (see “Future Asteroid Surveys…” http://www.asteroidday.org/learn/ and http://www.lsst.org/lsst).  This 8.4 meter ground-based survey telescope will be a tremendously capable NEO discovery machine after it becomes operational, hopefully in 2022.

As to the additional key decisions I mentioned, the first among them is the selection to be made over the next year or so for NASA’s next Discovery science mission.  Among the 28 candidates competing for this funding is NEOCam (see http://neocam.ipac.caltech.edu), an infra-red space telescope with great capability for discovering NEOs.  NEOCam would be placed in a unique location in the space referred to as L1 (Lagrangian point #1), located about 1 million miles from Earth in the direction of the Sun.  The unique feature of this location is that L1 (and NEOCam) stays in that relative position as the Earth orbits the Sun.  Unlike LSST which relies on sunlight reflected from the asteroids, NEOCam will be above the atmosphere looking for NEOs using the heat radiated from the asteroids it discovers.  This is a powerful capability only available to space-based telescopes and it will enable NEOCam to complement the discoveries made by LSST.

An alternative to NEOCam is the Sentinel IR space telescope being championed by the B612 Foundation(seehttp://sentinelmission.org).  While Sentinel’s eyes, similar to those of NEOCam, will detect the heat radiated from asteroids, it would be located in a very different place in space.  Sentinel would be placed in an orbit around the Sun between the Earth and Venus.  In this orbit Sentinel would move around the Sun slightly faster than the Earth, looking outward from the Sun and scanning for asteroids that cross the Earth’s orbit.  Unlike NEOCam Sentinel will spend the bulk of its time looking at portions of the Earth’s orbit not visible from Earth and it will therefore experience less overlap with LSST in its discoveries than will NEOCam. Additionally, because it is moving around the Sun faster than the Earth it will more readily discover asteroids that have an orbital period very near 1 year.  These very important NEOs are only seen by “Earth locked” telescopes (ground or space based) on an infrequent basis.

The bottom line here is that the combination of the LSST and either NEOCam or Sentinel will be very powerful in discovering the 99% of dangerous NEOs that we don’t now know about.  And either space telescope, in combination with the ground based LSST, will approach or exceed the 100,000 NEO discoveries per year that are called for in the Asteroid Day 100x declaration.

So why is your signature so important?  Because neither NEOCam nor Sentinel is yet funded and without one or both of them to work along with LSST we will be locked for decades into knowing only a small fraction of the asteroids out there that can cause death on impact.  LSST alone will make a pretty good dent in the larger sized asteroids that are missing in our inventory.  Over its lifetime it will probably reach or approach the current Congressional goal of discovering and tracking 90% of the NEOs larger than 140 meters in diameter.

But planetary defense, in my book, necessitates knowing all of the NEOs out there that are likely to to cause human death on impact. That translates into discovering all of the asteroids larger than 20 meters in diameter (think Chelyabinsk, about 30 times the explosive power of the Hiroshima bomb) that are in those orbits most likely to impact earth (the so-called “impactor population”; see sidebar).

The Sentinel team has calculated that, in combination with LSST, and by focusing on the smaller objects, they can discover, in 10 years of coordinated observations, over 80% of the 40 meter (Tunguska) population and over 45% of the 20 meter (Chelyabinsk) population. They have also estimated the productivity of a similar cooperative observing program between LSST and NEOCam, and it is not far behind.

This is an amazing breakthrough potential and I believe a truly unique opportunity.  With LSST funded and two viable candidates for a companion IR space telescope to work with it we can come very close to having, in the next 10-20 years, a full inventory of the NEOs out there that could cause loss of life. (remember… unnecessary loss of life!)  If, that is, we act now.  Remember, this is cheap!  What we’re talking about here is approximately three tenths of one percent of the NASA budget over 10 years!

If NEOCam is selected in the Discovery mission process over the next year, we can all cheer and anticipate the exciting results. However, if it is not the winning candidate in the Discovery selection then your signature, along with (hopefully) a million like signatures on the Asteroid Day 100x Declaration will go a long way to insuring that the Unites States and/or other nations and their space programs will initiate and fully fund a dedicated infrared space telescope to capitalize on this unique opportunity to fully inventory the life-threatening asteroid population.

What greater gift could we possibly give to the future of life here on Earth?  We can do this… and do it now.  To make certain your signature counts please register below so that we can personally notify you as soon as the petition system is set up.  And when you are notified, please join the initial signers of the100x Declaration and add your signature to let our governmental leaders know that we want this done!



read more
Rusty's Blog

Rusty’s Planetary Defense – Time Out For The Big Picture | Part Four


Enough with numbers and the technical bits for the moment.  I want to take some time early on to touch on the philosophical, the overview, the big picture of just what it is we’re about with this initiative to prevent asteroid impacts.

In 2001, when those of us who formed B612 Foundation first got together, we knew that asteroids could hit anywhere on the planet, but we did not realize for several years that one could not prevent an impact without, in the process, temporarily putting at risk people who were no where near the impact site.  People in other countries; on other continents; across oceans.  It took us awhile to understand that, for any potential asteroid impact, there extended across the entire planet a “risk corridor” representing the uncertainty in precisely where the asteroid would impact, if it were indeed going to impact Earth.


This risk corridor picture became even more important a bit later when we figured out that a deflection (forget, for the moment, the Hollywood solution of blowing it to smithereens) was effectively “dragging” or “jumping” the impact point along that same line across the Earth’s surface until it was off the Earth entirely.  At which point (good news) everyone is now safe.  But (bad news) if something interrupts the deflection part way through, the asteroid is going to hit elsewhere along the risk corridor from it’s original “act of God” spot.  Enter geopolitics, liability, risk sharing, national self interest, etc, etc.

Not only is a pending asteroid impact a planetary threat but the “solution”, a preventive deflection (or diversion) requires risk sharing (temporary, assuming a successful deflection).  Message… we are all in this together… the threat to life from a pending impact cannot be prevented without people (read nations, people, politicians) not originally threatened accepting a temporary risk to eliminate the threat to all.

Is our collective survival instinct robust enough to overcome our national and personal self interest?  The first substantial impact threat that materializes will unavoidably confront humanity with this ethical dilemma.

I remember clearly how I first “got” the distinction between my own death and the extinction of humanity.  I was reading Jonathan Schell’s Fate of the Earth (1982) where in considering the consequences of nuclear war he explored in very clear language the qualitative difference we all hold deeply, if sometimes unrealized, between individual death and the termination of all humanity.  Of course an extremely small percentage of asteroids that impact Earth will create a significant loss of any life, let alone the extinction of humanity.  Nevertheless, there are big ones out there among the small ones and left to chance it will happen.   Tomorrow; next year; on my granddaughter’s wedding day; just before humans terraform Mars.  Ask Mr. T. Rex.

What does it say if we are within a proverbial stone’s throw of being able to predict all significant asteroid impacts decades ahead and have the technology in hand to prevent them – and we don’t?  Geopolitically, we don’t?

Especially if it costs $1.98?  Well, make that $300m/year for 10 years and then $75m/year thereafter, which equates to ~1.7% of NASA’s budget for the first 10 years and <0.5% of it thereafter?  That, adjudged the NASA Advisory Committee’s Task Force on Planetary Defense (http://www.nasa.gov/pdf/493115main_10-10_TFPD_BRIEFING.pdf), was what it would cost to be fully prepared to protect life here on our home planet from asteroid impacts; a full inventory of the 1,000,000+ objects that circulate past Earth that could cause loss of life on impact, plus having demonstrated the basic deflection technologies available today, and then dropping back to continual tracking of the census of NEOs at issue until we find one with our address on it.  Then, of course the $1B or so to mount a deflection campaign would come into play as needed; perhaps once per 100 years or so.  Or 200 years, or 500 years… depending on how we value life.  But… we would be ready… we would have done what we can to prevent a potentially species ending cosmic natural hazard from ending this marvelous evolutionary experiment we are all part of here in our little corner of the universe.

Don’t we have that shared responsibility?  And just who is the “we” in the paragraphs above?  NASA?  Certainly.  The European Space Agency?  Yep.  Russia, China, India, Japan, and other future space-faring nations?  You bet.  All nation states?  I’d say so.  Isn’t security, the defense of their citizens, one of the (if not the) primary functions of all governments?  But what is government other than a system of organization for life to manage and express the values it collectively holds?

Unless we express these values, however, we can’t expect the governance systems of the world to respond as we wish.  The squeaky wheel gets the grease, as they say.  Business gets attention.  Power?  Definitely.  Potholes in the road?  Yessir.  Even science and environment.  But planetary defense?  The only issue that can actually wipe us out; sooner or later; but eventually?  Not present.  So now comes Asteroid Day.

We who, if we think about it, propose that we can and should subtly and carefully adjust very slightly the clockwork of the solar system in order to enhance the survival of life here on planet Earth must accept, and welcome, this great responsibility.  We can do this!  Think about that amazing but true statement.

Many times when I end a public presentation I show a slide taken from the Hubble ultra deep field image.  There are 10s of 1000s of points of light in the slide, none of which is a star, each of which is a galaxy.  Each point billions of stars.  For me it is impossible to conceive that there is not out there somewhere among the billions of stars in the billions of galaxies a diverse community of sentient beings each from its own home star, not unlike ours.  If such a community of sentient beings exists they will each have passed this great test… they will have prevented extinction by protecting life on their home planets until they achieved the ability to spread life outward from their local womb.  Now it’s our turn to face this great challenge… this great entrance exam qualifying us for eligibility to join this cosmic community.

This is no small calling.  Will we sufficiently recognize that we are one life on this small planet?  That our common survival ultimately depends on elevating our vision above the multiplicity of smaller interests that separate us?  I believe so.  Exam day is here.  Let’s get on it!


read more
Rusty's Blog

Rusty’s Planetary Defense – How Many Are We Talking About, Anyway? | Part Three

Asteroid belt

Stand by friends, I’m afraid we’re going to get into numbers here.  This is a subject where numbers reign supreme!  Happily there won’t be any real math here, but when you get into how many asteroids are out there (of interest), how frequently they are likely to impact Earth, what sizes do what amount of damage, and how much energy they release during an impact… you’re talking numbers!

When you’re talking how many asteroids, whether in the main asteroid belt or just the near-Earth objects (NEOs) it’s pretty much a meaningless question unless you specify some minimum size.  In the main asteroid belt between Mars and Jupiter scientists have estimated that there are over 750,000 asteroids greater then 1 kilometer in diameter.  There are millions of smaller ones and if one counts objects down to a few meters across I’d be surprised if we’re not talking billions.  That said, the total mass of all of the asteroids in the main belt taken together amount to less than the mass of the Earth’s moon.


But while these main belters are of great scientific interest, it is those that have been gravitationally diverted out of the main belt (largely by Jupiter) and whose perihelions (point of closest approach to the Sun) lie inside the Earth’s orbit that are the focus of planetary defense.  By way of comparison, among this NEO population there are approximately 1000 total with diameters greater than 1 kilometer.  At the smaller sizes the numbers increase rapidly until at the 40 meter diameter of the Tunguska impactor the population reaches about 1 million.  Here’s a simple table that gives you a sense of the size distribution of these guys.

That’s all well and good, you may say, but how can we possibly know how many are out there?  The answer to this critical question is that we don’t… precisely.  But we have excellent statistical approximations, and we think they’re pretty good.

How do we make such approximations?  Several ways, actually, and since they are independent of each other and come up with approximately the same numbers we’re pretty confident that we’ve got a good handle on the issue.

For example, the easiest method to grasp is to recognize that we have a neighbor called the Moon which has no atmosphere (nor has it ever) and therefore serves as a kind of tabula rasa for us here on Earth.  All of those impact craters on the Moon provide a graphic record of what’s flown through the Earth-Moon system since the Moon was formed back 4.5 billion years ago.  So knowing the sizes of craters that would be caused by the impact of various sizes of asteroids crashing into the Moon, we can count the craters and get a pretty good approximation of the frequency with which various sized objects come flying by.

Another method is illustrated by thinking of a farm (say 247 acres, or one square kilometer) that sits in mushroom country.  How would one estimate the total number of mushrooms on the farm?  Well if we counted the mushrooms in one typical square meter of the farm and multiplied by 1 million then we’d have a good approximation, right?  Obviously the devil is in the details since the soils vary across the farm, as does moisture, sunlight etc.  But you get the idea.  And shifting this up into space we know the equivalent volume of space we’ve looked at and not looked at… and knowing what we’ve found we can thereby approximate the total out there.  Devil in the details, but again, you get the idea.

A third, and interesting way to get a good approximation is to think of a big jar of full of beans.  How many beans?  That’s what we’re interested in.  So we pick out a handful, count them, make a little mark on them and throw them back in.  Now we shake the jar and randomize the contents.  Again we pick out a handful count the marked ones (re-discoveries), mark the unmarked ones, throw them back in and shake the jar.  And again, and again.  Each time the percentage of re-discoveries is higher and in fact ultimately approaches 100%.  The plotted curve of re-discoveries over time is well understood and from it we can approximate the total bean count quite accurately.  So it is with NEOs.

The result?  OK readers… we’re going to break into two groups here.  Those who are interested a simple answer to the question of how many objects of a given size are there out there and how frequently (on average) do they impact the Earth are referred to the table above.  (see you around).  Those interested in more detail and the latest & greatest “size, frequency” graphic… continue… and welcome aboard.

[Note:  I consider the table above in the you should know category; the details below in the you might want to know class.]

The diagram below is the now “classic” size-frequency chart produced by Alan Harris, who by my accounting is the world’s NEO demographer.  This latest version of it incorporates the latest data and analysis with most of the changes occurring in the NEO population at the smaller sizes (i.e. 40 meters and below). The paper, currently in press, is entitled Updated Population and Risk Assessment for Airbursts from Near-Earth Objects (NEOs), and authored by Mark Boslough, Peter Brown, and Alan Harris.


Now let me try to simplify this informative but messy graph somewhat.  Forget the text box in the upper right.  Look at only the straight dashed blue line, the small blue circles, and the red line.  As to the axes, forget the Absolute Magnitude, H axis at the bottom (unless you are an astronomer) and pay attention to the NEO diameter on the bottom.  So then this becomes a plot of NEO diameter (bottom) vs. the total number of NEOs out there (left), the frequency they impact (right), and the energy they deliver when they do (top).

The dashed blue line is (sort of) what scientists might expect for the distribution in nature.  The small blue circles are what we anticipate finding based on optical surveys to date.  You can see that in the middle sizes (say 30 – 600 meters) the anticipated population dips below the “expected” (the so-called inverse-power function line).  Conversely at the small end of the spectrum the numbers we’re finding indicate a slightly higher than “expected” population.  And then the red line is simply the plot of those we’ve actually discovered to date and are now tracking.

So, for example, if you pick 1 km diameter asteroids, you go up from the 1 km green tick to the dotted blue line and then horizontally left to find that the population out there is ~ 1000 objects.  Go to the right axis and you’ll see that one of those would be expected to hit Earth (on average) once every 700,000 years.  And if you want to know (if it happens to be of average density and come in at average speed) what energy it would impact with you go to the top and find it would deliver ~60,000 million tons of TNT’s worth of BANG!

If you go up to the red line from the 1 km green tick and then left you’ll see we’ve already already discovered about 1000 objects.  In other words we’ve essentially discovered all of them out there.  Most important, we’re now monitoring and tracking them all!  (Actually, we have 962 of them in the database which we believe to be ~96% of the total out there.  See http://neo.jpl.nasa.gov/stats if you’re interested)  That’s the good news… we know almost where each one of these big guys is and we’re keeping track of them!

The bad (or worse anyway) news is that if you now go into the table at any smaller size the picture gets less rosy.  I.e. below ~ 1 km the red line of actual knowledge drops below the statistical expectation numbers (blue dots).  Figures, right?  The smaller they are the more of them there are out there and the harder they are to find.

So just to take an example at the lower end, say the 40 meter size of the Tunguska impactor, you’d go up to the dotted line and left to find there are about 1 million of those out there which would impact on average once every 400 years.  And, stopping at the red line and going to the left, that we only have about 10,000 of them in our tracking database!  That’s 1%!  Since these 40 meter guys are the ones that were referred to in a Congressional hearing just after the Chelyabinsk impact 2 years ago as “city killers”, you get the picture of why we planetary defense folk are concerned with upping the discovery rate for NEOs.

A perfectly legitimate way to state this situation is that, if we were to be hit by a 40 meter object tomorrow the chances are 99% that it would be a total surprise!  We would have no prior knowledge it was coming.  Relax (a little bit) though, in that the probability of that happening is only 1 in 146,000 (i.e. one day in 400 years)!  Still, this situation is why Don Yeomans is famed (among other things) for pointing out that the three most important things to attend to if you want to protect the Earth from NEO impacts is 1) find them early, 2) find them early, and 3) find them early.

OK Don, we’ve got the priority.


read more
Rusty's Blog

Rusty’s Planetary Defense – Deflect, Or Duck And Cover? | Part Two


Alright, so just what is it that I think you need to know or should know about asteroid impacts?  Well there are several rather distinctive, and not so obvious aspects to preventing the potential damage of impacts.

The most important goal of all planetary defense efforts is to prevent the loss of life.  Preventing damage to property is also important, but clearly secondary.  The first step in being able to prevent any kind of damage is to have early warning of a future impact.  No way to protect anything if we don’t know what’s coming at us!

Early warning means knowing that an asteroid is headed toward an impact with us and then, based on the specific information we have, taking action to protect life, and perhaps property as well.

Predicting an impact ahead of time is based on a sequence of actions beginning with the discovery of the asteroid using telescopes.  Generally these are optical telescopes on the ground, but there some are space telescopes in use as well, and there will be more capable space telescopes in the future.  The most productive system of telescopes used to date is that run by NASA (http://neo.jpl.nasa.gov/programs/intro.html).  This search program is often referred to as the Spaceguard Survey.

The nice thing about asteroids, or any object in space, for that matter, is that they are well behaved, i.e., they follow predictable paths.  It’s important to remember that asteroids, like comets and planets, orbit the Sun, and as long as an asteroid is not close to any other large object (like 99.99999+% of the time!) it follows a very predictable path around the sun… i.e. its orbit.  So the trick is getting enough tracking information on an asteroid, once it is discovered, that its orbit can be calculated and therefore its position can be predicted at any desired time in the future.

The asteroids of particular interest to us (we planetary defense folk) are those which happen to be in orbits that cross the orbit of planet Earth.  Now recall that we’re dealing with three dimensions here so unlike two orbits that cross on a flat piece of paper, the dangerous asteroids are those where this orbital intersection is real in all three dimensions.  These asteroids (millions of them!) are called near-Earth asteroids, or NEAs.  Mostly we talk about near-Earth objects (NEOs) where we also count the occasional near-Earth comet.  (“if it looks like a duck, hangs out with ducks, and quacks like a duck… it’s a duck!”)

If we discover an asteroid and track it a bit, we can then calculate its orbit and predict whether, in the next 100 years or so, it and the Earth will be in that three dimensional intersection at the same time!  If so, that’s a collision.  <duh>

The goal, of course, is that if we know about this pending collision far enough ahead of time (think 15-20 years) then we could use our space technology to intercept and deflect the asteroid from that predicted impact.  That’s the idea.  It’s also the ideal!

There are lots of blanks, of course, to be filled in here.  This is not (at all!) some slam-dunk.  Among the sticky issues is the fact that there are imperfections in the telescopic measurements (no such thing as a perfect measurement) and therefore uncertainty in the predicted orbits and therefore in the future positions of the asteroid.  There is also the challenge of deflecting an asteroid (i.e. changing its orbit enough to avoid an impact) with our current space technology.  These and other realities I’ll deal with in future blogs, but for now let’s assume that we have an adequate handle on these issues.

So if we can predict a future impact, and deflect it, what’s to worry?  Well recall that I said above that we’d need 15-20 years of early warning.  So what if we don’t have that much warning time?  Aye, there’s the rub!

At this point (to be revisited in the future) let’s say that with “adequate” early warning, we can prevent future asteroid impacts.  OK, so for that category of future asteroid impacts we can protect both life – and property.  If we can make the asteroid miss the Earth entirely then there’s no loss!  And that’s our ideal planetary defense goal.

Fine.  But what about situations where we have inadequate future knowledge?  And what would those situations be?  Well, a couple of things.  We might discover a sizable asteroid, figure out its orbit, and find that it has an impact with the Earth with too little time to mount a successful deflection campaign.  But this is a highly improbable situation since even for the smallest, most populous asteroids that would cause damage on the surface, they only impact (on average) once every 50 years.  (Think the Chelyabinsk impact)  And to happen to find “the one” of those that is going to hit in say 7 years isseriously improbable.  Nevertheless possible.

Another, more likely scenario, is that we could happen to be looking in just the right direction that we see an asteroid just before it hits!  Literally we’re talking about looking up the approach path and seeing an asteroid on “final approach”, something like standing at the end of a runway and seeing an airplane about to land (hopefully not crash!)

Ironically this is not as improbable as it may seem, because impacting asteroids approach the Earth from two preferential directions.  In the last weeks and months prior to impact an asteroid will appear in the sky in either the approximate direction of the Sun, or from the anti-solar point (or opposition).  Those that hit at night will approach from near opposition, whereas those that hit in the daytime come from near the Sun.  Think Chelyabinsk.  It occurred in Russia at 9:20 in the morning coming out of the sky within just a few degrees of the Sun.


So you should know that NASA is today funding the development of the ATLAS system (http://www.fallingstar.com/home.php), a set of small telescopes that will preferentially look in the direction of opposition (it can’t look at the Sun!) to watch for any asteroids on final approach to an impact.  It will see lots of asteroids, but mostly below the size where they will do any damage.  But every once in awhile ATLAS (or other similar systems) will find one headed for impact that can do damage – and we can thereby generate a warning.

What do we do when we don’t have enough time for a deflection but still we know that an impact is about to occur?  We take “civil defense” actions, i.e. we do what we can to prevent the loss of life.  Think hurricane or storm warning.  We head for the basement until it’s over, or we evacuate – head out of town.  No way to save buildings, etc.  But we can save lives.  And this is the value of short term early warning.

So to summarize, you should know that with long term early warning, i.e. with an impact predicted 15-20 or more years in the future we aim to deflect it (more to come on that) and prevent the impact entirely.  And if we have a prediction of an impact in 2 days, or a month, we can evacuate or otherwise take simple measures to minimize the threat to life.

In summary then, you should know that long term early warning is underway and in the long term once we have a “full” inventory of NEOs that can do serious damage, we can either deflect them, or if they’re pretty small, evacuate or take other protective measures to avoid the loss of life.  What you need to know is until that full inventory of NEOs is in hand (more on what we will know and when we will know it in a later blog) we will have soon a short term warning system that can provide a few days or weeks of warning so that you can take action to protect yourself.

The action party in discovering a threat, and in the instance of an adequate long term warning, deflecting the NEO (i.e. preventing the impact) is government(s).  The action party in the instance of a short term warning being issued is you!  And what you should do is to follow the instructions and guidance provided by the local disaster response agency in your area.  Once, of course, that “system” is in place (see my prior blog, Chelyabinsk Warning – One Day)

Final word here… since I know it’s on your mind… the good people of Chelyabinsk could not have had a near-term warning of the impact 2 years ago.  For several reasons.  First it was a daytime impact and the asteroid came “from out of the Sun”, so even an operational ATLAS system could not have seen it ahead of time.  Furthermore it was only 20 meters in diameter and the long term warning telescopes can find only an extremely low percentage of NEOs this small.  (While we’ve found over 95% of the NEOs larger than 1 km in diameter, we’ve found much less than 1% of the objects of Chelyabinsk size)  Therefore the Chelyabinsk object was outside our capability to predict ahead of time.  Still, because of the nascent ATLAS system, in the near future we should be able to have a couple of days warning for Chelyabinsk-sized objects that will hit at night.  That’s about 50+% of the total… better than none!

Well and good, but how many of these guys are out there and how often do then hit?


read more
Rusty's Blog

Rusty’s Planetary Defense – Chelyabinsk Warning | Part One


It was a bright, clear morning not in any way but one different from any other mid-February morning.  The whole city beginning the long wait for the first signs of spring, the only hope being the fading memory of the last.  But despite there being no physical signs it was different from any other February morning anyone had experienced, ever.

There was fear in the air, palpable fear.  An hour to go and yet with the Sun barely over the Eastern horizon the jam of traffic headed out of the city to the North was worse than any rush hour in memory, and flowing in the wrong direction!  The emergency meeting held in city hall two days ago combined with the continual blather on the radio ever since had finally broken through the facade of bravado, or denial, or just plain disbelief for a surprising number of families.  Mostly families.  The singles and others without kids, and the curious I suppose, had, for the most part, decided to ride it out in place.

The civil defense authorities, of course, were pretty confused themselves.  They had never before issued such a warning and they had a pretty ragged story at best.  Especially at first.  The announcement on the radio and TV that there would be an impact and that there would be a public meeting to brief people on what to expect and how to protect themselves was pretty widely treated as a joke of some kind.  And even after repeated appeals to attend the briefings at local high schools, the attendance was pretty sparse at most.

Nor was their story very believable.  At first.  A bright contrail coming out of the Eastern sky just to the right of the sun and then the head of the trail exploding, perhaps several times, in one or more extremely bright flashes, before fading out to the southwest.  Don’t look at it!  Why?  How bright is extremely bright!?  What do you mean, you don’t know?  Then, many seconds or even a minute of so later a terrific BOOM… a shock wave would arrive and you might be knocked over.  Certainly windows will blow in and shatter glass, so don’t be anywhere near a window.  Well where do we go?  Do we go down into our basements?? Do we run outdoors?  In the freezing cold?  If we board up our windows will they survive?  How about opening them?  No answers.  Just blank stares and shrugs.  Thanks.

Safest course of action?  Leave the city.  What!?  Well where do we go?  What about our valuables and homes?  Are they going to be protected?  Well when will you know?  If we have to decide in a hurry, how do we make such a decision?  And how far do we go anyway? Will our homes survive?  Maybe?? What kind of an answer is that?

Of course the information got a bit more definitive after those first briefings.  If one listened carefully, that is, to the “official” announcements and not the incredible speculation and craziness from damned near every pseudo-authority spreading everything from “the whole thing is a joke” to “no sense running; we’re all dead anyway”.

So many people obviously waited until this morning before making up their minds that it isn’t a joke and that they’ll head out 50-100 km to the North and watch.  Some put their valuables in the basement; some in the car with them.  The police claim that they will be on duty and protecting the neighborhoods against any looting.  After all, the event will be over in a few moments, as suddenly as it happens.  People will be flooding back into town almost immediately to see what happened… if anything!  So the cops might not have too hard a time against looters.

Mostly the police, and the ambulance drivers will be gathering up people who, despite all efforts to the contrary, will run over to the windows and look out to see what the hell that big flash was!  As the man said… no problem looking… just wait for a minute until the shock wave passes (or knocks you off your feet!) and then go over and look out.  Through the hole in the wall… maybe.

Anyway… “shelter in place” or “evacuate” better make sure to get the kids dressed in their snow suits because it might just be a long time before any rooms with South facing windows (or any direction??) hold in heat again.  Except, of course, if like me you’ve already bought spare glass and caulking compound at the hardware outlet during the mad shopping crush yesterday!

So I’m ready.  I’m staying put for the big show.  I’ve got my thermos of hot coffee and I’ve even got a bottle of vodka with me down here in the basement just in case Uncle Vanya gets back with the rest of the family and the stash upstairs is no longer intact.  It ought to be a great show.  I’ve heard that there are even tourists… “eco-tourists!!”… in the air, headed our way!  Whatta joke!  Paying thousands of $ to get here from Los Angeles and here we are with guaranteed front row seats!


Something like this hypothetical will be happening to real people when the first prediction of a Chelyabinsk-sized impact is about to occur.  It will likely emerge out of a set of small distributed telescopes that detect asteroids about to impact.  (ref. www.fallingstar.org) Their observations will pass through the current near-Earth asteroid network (ref.neo.jpl.nasa.gov/programs/intro.html) and on to the currently forming IAWN (International Asteroid Warning Network, ref. www.minorplanetcenter.net/IAWN/) and from there into the world’s jumble of national and local disaster response agencies.  And thence to the relevant public.  It will likely not, the first few times, be a pretty picture.

Hence the efforts of Asteroid Day (ref. www.asteroidday.org) to begin preparing the public with the basic knowledge almost totally missing in our collective experience.  The basics are simple; shelter in place (stay away from windows!) or evacuate if legitimate authority recommends.  But understanding a bit about the context of asteroid impacts is both interesting and perhaps important in building toward a successful public response to the eventual warnings that will issue over time.


read more
Rusty's Blog

Rusty’s Planetary Defense Blog – Introduction


Hello. I’m Rusty Schweickart and I’m writing this blog in order to introduce you to the basics of what we refer to as Planetary Defence or simply PD. Planetary Defence is the name given to the process of protecting the planet from asteroid impacts.  More to the point, protecting life on planet Earth from the destructive effects of future asteroid impacts.

In particular, I’m writing this blog as a primer on what the public should know about asteroids, asteroid impacts, and the actions being taken to either mitigate the effects of impacts or actually prevent their occurrence entirely. Most important is what you should know to protect yourself if you should have the incredibly bad luck to be located near where one impacts.  Happily the actions you should take are pretty simple, as you’ll see.

I’ll be dealing with the information in this blog with three priorities in mind; 1) what you need to know, 2) what you should know, and 3) what you might like to know.  I may end up highlighting these so that you know which category of importance I believe is relevant to what’s being said.

And as we go ahead it will be very helpful to have feedback from you so that I don’t make the terrible mistake of assuming that I said something so clearly that of course you got it!  I’ll attempt to answer all questions and some I’ll also replicate within the blog to share with everyone.

From time to time I may also add a sidebar on some particular item in order to explain something in a bit more detail without disrupting the general flow of the mainline thought.  My goal in all of this is to present useful information about a pretty technical subject in a plain and understandable way.  This is tricky because in making some issues easily understandable the precise details of a highly complex matter will have to be approximated.  This will cause consternation for some, but making the issues understandable for non-technical people is my objective and in general, a first order approximation is good enough.

Another important element of this blog will be inserting specific references to many, if not most, of the subjects I’ll be introducing.  These references will most often be links to expert or informative sources on the internet that you can click on to get more detailed information.  From time to time I may also ask a specific expert to also add his/her own comment or expansion on something I’ve said.  Or perhaps to respond to one of your questions.

Finally, before we get started, I’ll just mention here the scope of what we’ll be dealing with.  Obviously asteroids themselves, per se.  But mainly what’s of importance is their orbits, their sizes, their speed and how they come to crash into the Earth in the first place.  How we discover near-Earth asteroids (NEAs) or near-Earth objects (NEOs), the asteroids that are of interest here, is important.  How many are there of what sizes and how frequently do they impact Earth is also important.  More fun perhaps will be when we get into predicting impacts and actually preventing impacts by deflecting incoming asteroids.  And then there’s the somewhat puzzling issue to many people of why the PD challenge has a critical international dimension.  In fact the UN is involved, and as we will see, this is important and essential, even if not quite obvious.

We’ll get there.  But first we’ll start with some what-you-need-to-know-information.  To introduce this I’ll ask you to imagine yourself being a homeowner in Chelyabinsk, Russia in early February, 2013.  Only in this instance, instead of being completely surprised by an asteroid impact, as the citizens of Chelyabinsk were on that morning, we’re going to assume that the planetary defense system we’re in the process of forming was already, albeit barely, in place.

So off we go…


read more