One of my interests is the subject of impacts on Earth by comets or sear earth objects (NEOs). (Everybody has something…)
Now, on the eve of the anniversary of the Chelyabinsk “event” of last year, it is a time to reflect on “what could have been.”
Not much real damage was done last year. Fortunately the atmosphere absorbed about 90% of the energy of the meteor over Russia. All that brilliance we all saw was meteoric material melting away, so by the time the big flare-up occurred, there wasn’t a lot of the object still left to explode. Lucky Chelyabinsk! Imagine if even half of it still had been holding together, how large that explosion might have been. Certainly more thousands would have been injured. Certainly many thousands of windows would have blown out. Most likely some other weakly built buildings would have been damaged.
We happen to live in a solar system that has big freaking rocks flying around, occasionally whacking planets. It’s a virtual certainty that there are solar systems out there that do not have such rocks whizzing around. Ours may be even in the minority. There is nothing intrinsic about solar systems that requires them, though some paper out there may make that assertion. Even if it exists, that paper may or may not be right – and we would never know one way or another. Ours, not being one of those rock-free environments, is a relatively dangerous place to have started sentient life. The danger may not happen often, but when it does, it can be a doozy.
In one of those systems without asteroids and comets and that also has developed sentient life and then some sort of civilization, the development of that sentient species would never have anything except the literal end of that world to stop its progress (whatever flavor of progress that might be). (Yes, I am one of those people who think that such sentience exists out there. So sue me.)
Since we don’t seem to live in such a solar system, then if we are going to avoid those really big rocks, we are some day going to need to learn how to protect ourselves from them. While right now may not necessarily be the right time, that time may not be too far ahead. The first step toward protecting ourselves is for us to realize that such events DO happen – in a solar system such as ours.
For us, that realization began just about 200 years ago when in France rocks were really seen to fall out of the sky. After all, common sense told us that heavy things cannot exist up in the air. Once we became aware that those rocks were real, eventually we had to ask became how big of a rock is out there that might fall out of the sky. After all, big rocks hurt.
The recent but undated impact on Mars adds to our realization that PLANETS DO GET WHACKED BY BIG ROCKS – AND IT HAPPENS IN OUR TIME. It is amazing that Shoemaker-Levy 9 did not wake the world up sufficiently. But we were lucky and may continue to be lucky for a long time to come. Chelyabinsk could have EASILY been as big s SL-9, and if it had been, would any of us even exist now?
We wouldn’t have had the capacity to DO anything about it, even if, like SL-9, we saw it coming a year in advance. Early on, it looked like this:
Can you imagine us trying to shoot down the three of those 20 fragments that were a kilometer and more wide? Their impact plumes – even in the heavier gravity of Jupiter – were bigger than our entire planet. And there were others not so much smaller. Here is one view of several of those impacts and then the Earth to scale with Jupiter:
Prior to SL-9, you couldn’t have gotten even one astronomer in the entire world to admit that they expected to see even ONE comet hitting a planet – any planet – in his/her lifetime. More or less they were all caught with their pants down. If SL-9 had been Earth bound we would all be dead now. Now, 20 years later, the impression of SL-9 is fading, and not much is in the works. Perhaps the biggest effort is a private effort. Even the Chelyabinsk event last year has barely awakened an effort (especially by NASA) to DO something about this possible threat.
So in 200 years we have progressed from denying rocks fall from the sky to denying that it is important to look into what to do about such rocks. After all, the Darwinists don’t want to admit that something other than evolution can possibly happen on planet Earth, so they don’t want to put energy into something that may – if it happened in the past – have thrown a monkey wrench into the works of evolution and gradualism. But let’s give us SOME credit. At LEAST we (kind of) are out there looking to find ones that might come our way. That may give us a leg up when we do prepare to protect ourselves. And that is good.
Underlying my interest – at least partially – is the idea that it would be really monumentally stupid if we lived in a time with the technological possibility of batting away a doomsday rock and didn’t take the possibility seriously enough to look into doing it. I hope we are smart enough and have a strong enough survival instinct to prepare well enough soon enough.
Assessing the Threat a Bit
As long as the objects restrict themselves to being 50 meters or so, there is no real danger. We could probably manage if an entire swarm of those the size of Chelyabinsk arrived. An SL-9 event with 50 meter fragments would be a helluva show, but no real damage would have been done. Certainly there would be some deaths (if not directly, then from an ocean-impact-induced tsunami). Even if such fragments rained down on a large city, the effect would be frightening to the inhabitants and a VERY good news story, but would be no risk for humanity as a whole. Life would go on, and very easily so. It would be hardly a hiccup in the history of man on Earth. But we might have some hair-raising tales to tell our grandchildren.
At some size point, however, such an event would be large enough that we DO get seriously threatened. The threat is quite real, as SL-9 showed us and Chelyabinsk reiterated.
The risk is NOT measured by how often they might hit Earth. The risk is that if it happens in our time, we are all dead – except for a handful of Noahs or Gilgameshes – whose lives would be changed forever. It depends on onlyAt that point any hope of having civilization again would be thousands of years out in the future.
What shall we do about it, now that we are aware of the threat? Again: We don’t have to do anything about Chelyabinsk objects, no matter how many. But there IS some size that we need to worry about.
Chelyabinsk was 50 meters, and SL-9 had three 1000 meter ones – extinction events. One was even about 1300 meters. Somewhere in between 50 and 1000 meters, we would need to be concerned about kissing our collective arses goodbye.
This post is not about me sounding an alarm. Others can do that. I’d rather simply point out some of what I see are facts about it all.
- Our solar system has rocks flying around
- Some of those rocks are 1000 meters across. Some are several kms across.
- They are flying through space at about the speed of Earth (30 km/sec)
- When they hit, the 1000 meter ones can very possibly send us back to the stone age – but 99.99999% of us would simply be killed or die soon afterward.
The Damage Prognosis – How Bad Can It Be?
Have scientists looked into how much damage might ensue if a big one hits? Yes., they have They don’t all agree on the particulars, but they do acknowledge that it would be bad.
One of the really likely scenarios is if the object impacted in the ocean instead of flaring in the atmosphere or impacting a continent. 71% of the surface is ocean. so more or less 70% of them will hit in the ocean. <b>This is not a pretty picture.</b>
The tsunamis of 2004 and 2011 were babies – even zygotes – by comparison with the tsunamis what researchers Hills and Goda determined to be likely. At 1,000 kilometers from such an impact, here is what they determined would happen:
- For a stony meteor
- If 50 meters across, it would make a tsunami 32 meters high.
- For a 100 meter object the tsunami would be 80 meters high.
- For a 1 km object the tsunami would be about 8000 meters high.
- For a metallic meteor
- 50 meters wide would cause an 80 meter tsunami.
- At 100 meters, it would be 280 meters.
- At 1km wide, the tsunami would be about 2,800 meters high.
Think of those numbers. Chelyabinsk was an object 50 meters across. Had it come in at a steep angle and hit the ocean, the tsunami would have been 32 meters high. The Japanese and Sumatran tsunamis were about 10-15 meters high.
The 8000 meters for an object the size of the three biggest fragments of SL-9 makes a tsunami basically the height of Mt Everest. It would be travelling about 800 km/hr as it approaches the shore.
Cusco, Peru is at about 3,000 meters elevation – about 10,000 feet. A stony object 1 km wide would create a tsunami nearly that high.
By comparison, global warming enthusiasts predict a rise in sea level of 200 FEET (about 60 meters) if Greenland’s ice cap melts (which would take several centuries).
Yes, these numbers are real scientific estimates, and they are not joking.
Do I make too strong a case in this brief presentation? Maybe and maybe not.
David Morrison [current Director of NASA] posted a summary on the World Wide Web which made it clear that Edward Teller [father of the Hydrogen bomb] and colleagues were paying increased attention to the work of Hills and Goda… and that the likelihood of a devastating tsunami created by an ocean impact might be as low as a few percent in the next century. This converts to one tsunami catastrophe every 5,000 years…
…Duncan Steel suggests that the comet impacts on Jupiter… may even have something to offer as regards calculating odds. Jupiter is likely to be struck about 1000 times as often as the earth and there is tantalizing evidence for dark markings such as followed the July 1994 impacts having been seen on at least four previous occasions: in 1885, 1928, 1939, and 1948, or five collision events per century. That would imply that earth might be hit every 20,000 years.
While researching old books and technical articles for this chapter, I noticed something fascinating that illustrates how our conception of what the future holds depends so intimately on our knowledge base. In two centuries, the typical estimated time between comet impacts (from old books) to impacts capable of producing global catastrophe (from new research) has decreased from once every 281 million years (which held for most of the 19th century) to about once ever 5 to 10,000 years in the past year.
[Gerrit L. Verschuur. Impact!: The Threat of Comets and Asteroids (p. 164)]
Verschur goes on to ask how this reduction in the estimated gaps between impacts on Earth might continue to decrease. To decrease from 5,000 or 10,000 is to put impacts close to or within the historical era.
On the other hand, many normally knowledgeable people continue to think that such impacts happen once every million years or so. MANY of such people certainly think that there has not been a catastrophic one since the dinosaur killer of 65 million years ago. This kind of thinking may certainly be true. They are no less certain than those astronomers in 1994 were that they would never see a comet impacting a planet.
How often are we at risk? The answer is that no one really knows. The more we have learned, the more likely it seems that shorter intervals (a few thousand years) are more likely than really long intervals (hundreds of thousands of years).
With civilization only dating back about to about 10,000 years – more or less the time of Plato’s account of Atlantis that everyone discounts – it seems that it may be a 50-50 chance that one has hit in that time, though there is no evidence of one in those 10,000 years. Or hasn’t there been?
There IS some reasonably strong forensic evidence – on several fronts and in many locations – that a large impact occurred about 12,800 years ago, at a time when the climate of Earth suddenly reverted to an ice age for about 1,300 years.
The jury is still out on that impact being real or not. But even if it didn’t happen, the odds of one happening somewhere about that time is fairly substantial. Especially if one has not hit since then..
And if one did hit then, according to the reduced interval estimates, then one might be due just about any time now. Or one may have hit in 535 AD, when there was a severe climate downturn, the Black Plague, and several indications, including tree rings, all of which some very smart people think could be evidence on several fronts that an impact may have occurred.
At the same time, when such estimates as the above are made, the uncertainty of the numbers is pretty great. In addition, even if based on solid, direct experience, such averages can still vary by maybe 200% or more on the high side or 75% on the lows side. So we may not get such an impact for thousands of years, or we may be overdue now. No one knows for sure. They are, as far as we now can calculate, randomly spaced in time.
Mitigation Plans – Dealing with Ones we Know Are Coming
Does it make sense to devise a big mitigation plan, at many billions of dollars at this time? I don’t know. At any given time before one hits, it will always seem like a fool’s errand, since it might be thousands of years before one on a dangerous orbit presents itself – but when it does we will likely have run out of time.
That is, given the tech of today. Who knows how much tech will improve in 50 or 100 or 500 years? Or more? Certainly the farther out into the solar system we can detect objects gives us more time and thus more options. Perhaps Moon and Mars observatories will exist and extend our views out into the solar system. Perhaps our astrophysics will develop more precise formulas. Perhaps observatories might be put on asteroids or NEOs themselves. Maybe we will be able to put satellites with telescopes at the Earth’s Lagrange points (1/3 around the orbit ahead and behind the Earth) as well – these I think will give the best view of the NEOs., which orbit fairly close to Earth’s orbit and don’t wander too far away. And perhaps Mars’ Lagrange points, too. The more eyes, the better. These will prove to not be terribly expensive.
As to delivery systems, perhaps we will have more powerful rockets and better guidance systems. Maybe thorium reactors small enough to put into rockets will allow for us to think of new possibilities, since ion drives require electricity to ionize particles and LFTR reactors provide just that, in a small package. We may be able to put up long-term remote telescope stations (if not rocket platforms eventually) – perhaps at those Lagrange points of Earth and Mars – to extend our reach deeper out into the solar system, essentially platforms for delivering rockets to dangerous bodies when they are still far away from Earth. This would likely give us extra time to deflect bodies much earlier in their orbits (rather than trying to blast them and deal with the remnants). Expensive? More so than mere telescopes.
Perhaps the “eventually” above is the right approach – to do at each step what we can think of as prudent and that is a step in the right direction, and then simply build on it as we learn more and get some experience. By doing what we CAN, maybe we can do it without bankrupting any treasuries. It might be possible that by the time “the Big One” comes along we might have enough know-how to get the job done – and buy humanity a few more thousand years.
If interested enough in this, visit the next post… coming soon to a blog near you…