Robert Walker

Debunked: NASA researcher says humans face possible future extinction from asteroid impacts - 96% of species extinct equates to 0% chance of humans extinct

ROBERT WALKER First, this is the article I’m commenting on. Earth woefully unprepared for surprise comet or asteroid, Nasa scientist warns . It’s a comment by Dr Joseph Nuth who warns: “But on the other hand they are the extinction-level events, things like dinosaur killers, they’re 50 to 60 million years apart, essentially. You could say, of course, we’re due, but it’s a random course at that point.” Photograph of comet Siding Spring by Hubble - right hand image is more processed. This comet did a close flyby of Mars and at one point was predicted to have a tiny chance of hitting Mars. In the end it missed Mars by more than a quarter of the distance from Earth to the Moon If you read the rest of the article, it’s a worthy goal, to prepare us for asteroid impacts of all sizes from the small Chelyabinsk one up to really large 10 km ones. There are a number of things potentially confusing about this statement if you read it as a non scientist. Although there is a risk of “mass extinction” if a large asteroid hit Earth, “mass extinction” there doesn’t mean “extinction of humans”, we would certainly survive as a species after an asteroid impact. He doesn’t actually say “human extinction” in that quote. We are not “due” an extinction at all. Next giant impact is most likely to happen many millions of years into the future and we can be pretty sure there won’t be one in the next century. If there is an asteroid headed our way we are likely to have decades to deflect it. We can be pretty sure that there isn’t an extinction level asteroidone headed our way in the next century. We know the orbits of all the Near Earth Asteroids that could do this and none will hit Earth over that timescale. That leaves comets, and the chance of that is something like 1 in 100 million per century, as a very rough guess (since 99% of the impacts are thought to be from asteroids). So you can be something like 99.999999% certain this won’t happen. The chance is so tiny it’s negligible for all practical purposes. This risk has been pretty much retired due to the intensive asteroid surveys of the last couple of decades. But the chance of a smaller asteroid impact is still high enough to make it worth working on it, especially since this is the one natural hazard we can not only predict to the minute, decades in advance, with enough information but also prevent also, given a long enough timeline. So, in more detail: NOT DUE A MASS EXTINCTION AND SCALE OF DIAGRAM IS MILLIONS OF YEARS So - that is a scientist speaking as a scientist. But of course the internet picks it up as “we are due” and omits the qualification “but it’s a random course at that point”. To say that we are “due” a mass extinction is a bit like saying that after you throw nine heads, you are due to throw a tail. Not true. The chance that the next coin toss is a tail is 50/50 for a fair coin no matter how many heads you throw. So, since it is random, then an extinction that happens every 60 million years could happen tomorrow or it could be 60 million years or 120 million years before it happens. And on average we would expect to wait 60 million years for the next such mass extinction even if the last one happened hundreds of millions of years ago. It’s just as for the coin toss. Same for an extinction event of a size that happens every 100 million years. If you look at the diagram the big five are irregularly spaced. Some scientists have tried to discern a periodicity in the extinctions of 27 million years. If they are right then we are due the next extinction about 15 million years from now. But that is very controversial and if true, it wouldn’t cover all mass extinctions. We could get a mass extinction in the near future. But not likely in the next century. 70% OF SPECIES EXTINCT - 0% RISK FOR HUMANS EXTINCT If you look at some of the past extinction events, you might think that humans could go extinct very easily. The worst of all of those was the Permian–Triassic extinction event during which 96% of marine species and 70% of land species went extinct according to one estimate. This graph shows some of the major extinctions - note that some of the extinctions spread over several tens of millions of years. This probably doesn’t mean that the extinction took tens of millions of years as this is a graph of the fossil species and due to the Signor–Lipps effect - that a species may seem to go extinct in the fossil record before it actually is extinct because typically you get only a few specimens scattered over time so can easily miss the exact moment of extinction. The extinction that ends the Permian era is thought to have lead to extinction of 96% of all marine species. and 70% of land species. So based on those figures you might well think that there is a 70% chance that humans would go extinct as a result of whatever causes those extinctions. However, even after the extinction of the dinosaurs, birds, dawn sequoia, river turtles, small mammals and many other plants and creatures survived. Many species would go extinct after a gamma ray burst or a large asteroid impact, but humans are great survivors. We were at risk in the past before we developed tools and clothing. But with clothes, tools, boats, etc, we are an extremely adaptable species, able to survive anywhere from the Kalahari desert to the Arctic, with only stone age technology. We had already colonized most of the world by the end of the neolithic period. Overview of Pre-modern human migration - there is debate and controversy about the details, but generally agreed that humans were already present world-wide by the end of the neolithic period (which ends around 2000 BC), or shortly after. So, as long as we retain at least stone age technology, there isn't much that could make us extinct. Even if we have to go back to beachcombing and surviving on shellfish, which was a staple of early human diet in cold places such as Canada and Scotland where I live, one way or another some humans would survive. Conchero al sur de Puerto Desead - a shell midden in Argentina. For long periods of time ancient humans survived on shellfish, for so long that they built up these huge shell middens in many parts of the world. See Shell Midden We can eat shellfish, insects, fish, nuts, fruit, roots, cereals, birds, animals. So long as any of those survive the extinction event, anywhere in the world and so long as humans retain at least stone age level of understanding of technology - ability to make clothes and simple tools and to make boats to cross rivers and seas to find new sources of food - then there would be many survivors and we would not go extinct, even if more than 90% of species went extinct. Without any technology, turtles, crocodiles, alligators, small mammals, flying dinosaurs (the birds), dawn redwood trees, pine trees, many lifeforms survived the dinosaur extinction impact. And humans with the barest minimum of our technology are able to survive anywhere from the Arctic to the hottest of deserts, or in tropical rainforests. We would survive, some of us, a giant impact like that. River turtle, Boremys basking on a Triceratops dinosaur skull, Credit: Brian T. Roach, Yale Peabody Museum How Tough Turtles Survived Dino-Killing Meteor It did become extinct eventually, but not through asteroid impacts. Probably because it was unable to retract its neck and succumbed to predators. Homo Sapiens is listed in the IUCN Red list of threatened species - as one of the species of least concern "Listed as Least Concern as the species is very widely distributed, adaptable, currently increasing, and there are no major threats resulting in an overall population decline." RISKS FROM AN ASTEROID We have already found all the 10 km asteroids that do regular flybys of Earth. We have found 90% of the 1 km asteroids. This makes it very unlikely that we are hit by either a 1 km or 10 km object in the next century. We could be hit by a comet. But they are rare. He mentions the comet Siding Spring which did a flyby of Mars. But it’s important to note that it actually missed Mars by and it was only It was only 400 - 700 meters in diameter, so of a size that would have only local effects if it hit Earth, probably not quite large enough for a tsunami depending on whether it hit into deep or shallow seas and how much it breaks up in the atmosphere - and was discovered 22 months before the flyby, so more than a year and a half. A larger comet would be discovered years before the flyby. This shows the trajectory of Siding Spring: It actually missed Mars at a distance of 140,000 km. That’s 22 times the radius of Earth and 36% of the distance to the Moon. Earth is often “buzzed” by asteroids at that distance. It’s orbit was uncertain when first discovered, as is usual, giving a tiny chance of hitting Mars. But was eventually shown to miss. So if a comet happened to be in a similar orbit but targeting Earth instead of Mars that would be what we’d expect, that it would have a tiny chance of hitting Earth but a few months after discovery or maybe sooner, we’d know for sure that it would miss. It would be exceedingly unlikely for such a comet to hit. Probably only one impact in 100 is by comets. So it doesn’t really make a lot of sense to focus on defense from comets first. We can deal with 99% of the threat by looking at Near Earth Asteroids and they are also easiest to deflect, as if we can find them decades in advance, just the gentlest of nudges will deflect them away, just microns per second of delta v. Now I totally agree that we need to put more work into searching for asteroids and detecting them and preparing to deflect them. And eventually also good to speed up detection of comets too, which will happen anyway as a side effect of the asteroids search. As for having a rocket on standby to deflect a comet, well I think you need to bear in mind that though it could be needed right away, it might also not be used for the several thousand years. So - is that our priority? And as for deflecting asteroids - there are so many different ways to do it and what we use would depend on the exact scenario. For instance for some asteroids, it might be sufficient to “paint” the asteroid white with a white dust. So we would need a spacecraft able to dust it uniformly with white dust to deflect it using the effect. Here is a short video of professor Dave Hyland talking about the idea: And article Asteroids No Match For Paint Gun, Says Prof | Texas A&M Today (or How to Deflect Killer Asteroids With Spray Paint | WIRED ) Its due to the Yarkovsky effect . When the sun heats up a rotating object, then the rotation carries it around some distance before the thermal photons are emitted as heat. The amount of the effect depends on how rapidly the object rotates, but also on how light or dark it is Since most asteroids are very dark, the obvious way to change the amount of this effect is to paint it white. So long as you discover it long in advance, then this may be enough to shift its orbit to miss the Earth (orbital predictions have to take account of the Yarkovsky effect). I think that with unlimited funding we would devise half a dozen ways of deflecting asteroids, test them, and have them in a “ready to launch” state ready to deflect any conceivable asteroid, even if they may have to wait ten thousand years before we need some of the solutions. However in the situation as it is now, with limited funding then I think it makes much more sense to focus our efforts on detection. HOW TO FIND HAZARDOUS ASTEROIDS SWIFTLY There are new developments in asteroid tracking which may help here. Especially, use of synthetic tracking. The idea is explained in techy detail in this paper. Finding Very Small Near-Earth Asteroids using Synthetic Tracking . For an easier to read summary of it, see “Synthetic Tracking” Set to Revolutionise Near-Earth Asteroid Discovery The idea is that instead of doing a 30 second exposure, you do many shorter 2 second exposures. With conventional CCD's that adds to the read noise so you get more errors but there are new CCD's developed for medical imaging that permit fast accurate reading, called Scientific CMOS detectors. The Andor Zyla is an example here. Andor Zyla 5.5 | sCMOS Camera medical imaging camera capable of fast read out with low read error You can then use this to simulate tracking the asteroid with the camera, which makes the asteroid far brighter in the images. This image shows a the result of stacking many photographs of asteroid 2009BL with camera set to follow the stars on the left - notice how the asteroid is shown as a streak, and rather faint. On the right, the same photos are stacked to follow the asteroid which then shows as a much brighter spot, and the stars are streaked and fainter. Image from: DETECTION OF A FAINT FAST-MOVING NEAR-EARTH ASTEROID USING THE SYNTHETIC TRACKING TECHNIQUE When the asteroid is small and traveling faster across the field of view, the trail can be so faint it can’t be distinguished from background noise when the camera follows the stars. If you know its velocity you can make it much brighter by following the asteroid. But what can you do if you haven’t detected it yet and don’t know which way it is moving? The idea of synthetic tracking is that you take lots of short exposure photos and just try stacking them in many different ways until you find the right velocity and an asteroid pops into vie win the photo. This is time consuming but modern graphics cards permit fast parallel processing which makes synthetic tracking feasible. This approach can make it easier to spot fainter asteroids. It might mean for instance that you can spot an asteroid ten times further away than before. That means a thousand times the volume of space covered. So this technique can lead to a huge increase in the detection of asteroids. They found that fewer than eight of these cubesats, fitted with 15 centimeter synthetic tracking telescopes could find more than 70% of NEO's larger than 45 meters in diameter in less than six years. The total cost would be $50 million so a tenth of the cost of Sentinel. With larger 30 cm telescopes they could find 95% of the NEOs in the same time period. For details see their 2016 Annual Progress Report These are the asteroids that are most hazardous for us. And $50 million is not a lot. Any developed country could find that out of loose change from its defense budget and it would retire most of the risk from the larger asteroids within six years. It would still leave the risk of comets, but those are not the priority because they are so rare. If we had loads of funding it would make sense to fund a rocket ready to launch if necessary, even if it is quite possible it won’t be used for 1000 years. That’s the ideal situation, to do both. But with limited funding, detection is surely the priority. See also my Giant Asteroid Headed Your Way? - How We Can Detect And Deflect Them CancelUpdate Post 3 views · Written 30m ago Upvoters0CommentShare

Debunked: 2002 NT7 is going to hit Earth in 2019

ROBERT WALKER

2002 NT7 originally had a risk of 1 in 250,000 of hitting Earth in 2019 on 1st February 2002. This meant it was almost certain to miss, 99.9996% certain to miss. So it was no surprise that a little while later when they refined the orbit, that they found it would miss in 2019. There was a chance of it hitting in 2060 for a while but that was ruled out too. All that happened rapidly in 2002. It was removed from the risk table on the 1st August 2002.

This does not mean that there was any cover up going on as the conspriacy sites claim. It is just the normal thing. If an asteroid has a very low chance of hitting Earth, like 1 in 250,000 then you expect that it will be proven to miss as you refine the observations. That's what is going to happen in 99.9996% of the cases of an orbit like that. It was notable as the first orbit to reach a positive rating in the Palermo scale. More about it here: 2002 NT7.

This is the orbit of 2002 NT7 discovered 1st February 2002. It was briefly categorized as having a 1 in 250,000 chance of hitting Earth on 1st February 2019. That made it 99.9996% certain it would miss. As they say in the initial announcement “By far the most likely scenario is that, with additional data, the possibility of an Earth impact will be eliminated.”, and indeed further calculations showed it would miss. There was still a small chance of it hitting in 2060 until 1st August 2002 when they proved that it was no hazard to Earth at all in the near future through to 2200. You can see a list of all its flybys predicted through to 2200 here.

To check any of these stories just go to the Current Impacts Risk Table and if the first entry is white or blue then that means there is no risk and the story is either a hoax or a misunderstanding because the table is sorted with the entry of most risk at the top. If the first entry is yellow, orange or red, just head over to any major astronomy news site to find out more, as it is sure to be top news there. Red is the only level that means they are sure it will impact. So far none has ever gone higher than yellow. We have had a couple of tiny asteroids that were predicted to impact a short while before they actually hit but they were so small they would have been classified as blue in that table, too small to be a significant hazard. One landed in the middle of a desert in North Africa and one in the sea to the west of India.

13 views · 1 upvote · Written 10h ago Upvoters1CommentShare

Debunked: Earth faces a century of 400 giant impacts starting in 2017

ROBERT WALKER

This is another doomsday fake story, from the UK newspaper, the Express. There is no truth in it at all. It’s easy to check a story like this in detail. Just go to the Current Impact Risks table. If the top entry is blue or white, as is the usual situation, then there are no current predicted future impacts on Earth, so the story is false. If the top entry is yellow, orange or red, well go to any reputable site for astronomical news and it will be a top story so then you can read all about it there. Only red means a predicted impact, the other colours mean there is a chance of an impact.

Details

This is actually a story from 2014 but is naturally gaining more attention as 2017 approaches: SHOCK ASTEROID WARNING: Planet earth faces 100 YEARS of killer strikes starting in 2017 I have just replied in a comment there, here is my comment:

We have already found all the Near Earth Asteroids of 10 km or larger. We have found 90% of the ones of 1 km or larger and are finding them at one per month. Will be nearly finished that survey by the late 2020s. There is a tiny chance of a larger comet from the outer solar system, from the Kuiper belt or the more distant Oort cloud. This belt is not newly discovered but has been known about since the 1980s (building on earlier hypotheses).

Here is a video about the observation of the first verified Kuiper belt object - this which must be what they mean by a “second asteroid belt” though actually it is made up mainly of comets, not asteroids.

But for a 10 km diameter comet to approach Earth from so far afield would be extremely unlikely. We get a 10 km impact every 100 million years on average, and last one was 66 million years ago. Only one impact in a hundred is probably from comets so that makes the chance of such an impact this century, now all the NEAs are found and not headed our way, a negligible 1 in 100 million - that's the risk of it happening at all any time this century. We'd also see such a comet years before it got here in the very remote chance of it happening.

As for a 100 km diameter comet, forget it. The entire inner solar system from Mars inwards hasn't been hit by such a comet for well over 3 billion years from the cratering record of Mercury the Moon, Mars ,and what we have of the records of Earth and Venus. The leading explanation for this is that Jupiter protects us against the largest comets by breaking them up, or they just hit Jupiter, or ejected from solar system or hit the Sun. It seems to do a very effective job of this. Not so effective for smaller ones though it does take many "hits for the team" of smaller asteroids too, as the largest target there is in the solar system.

And there certainly has been no announcement predicting 400 impacts in the next century. I can't imagine where that comes from. It is easy to check these stories. Just go to the JPL Sentry Risk Table and you see the current impact risks ordered with the most risky at top. If the topmost entry on that page is white or blue, as it is now, and as is usually the case, then there are no predicted impact risks at all. So never mind not 400, there aren't any at present.

The risk table is here: Current Impact Risks

MORE ABOUT THE KUIPER BELT

This is a very distant belt of objects. First it was just a theory to explain the distribution of comets, but eventually we started to find objects in them. Now we know a lot of Kuiper Belt objects and we know for sure it exists. Very remote though, well beyond Neptune. However it is a source for comets that sometimes come into the inner solar system. We now know of many objects in it

Here is a very short animation of the newly found objects in the Kuiper belt

This plot shows the Kuiper belt objects in blue. The giant gas giants are shown in red.

The N stands for Neptune. Mars, Earth and Venus are all closer to the sun than Jupiter which is labeled J.

The other colours here label various kinds of objects. For details see Kuiper belt plot objects of outer solar system

Objects can hit Earth from the distant Kuiper belt. But the chance of this happening is almost vanishingly small for a 10 km comet - and no chance at all for a 100 km comet as that hasn’t happened in over three billion years. Also we’d see them coming years in advance.