The astronomer Josep Maria Trigo (Valencia, 52 years old) is passionate about planetary defense: the science and technology dedicated to preventing a space rock from leaving us like the dinosaurs. Above all, because he believes that we are not prepared and that the population lacks information. That’s why he just posted Earth in danger (Universitat de Barcelona Edicions), to warn about the fears that he has been learning as a researcher at the Institute of Space Sciences (CSIC) and the Institute of Space Studies of Catalonia.
Ask. Is the Earth in danger?
Response. We are exposed. But we are very used to all this set of sensational news, which does not hit a single one, because it is not really understood what the danger of impact consists of. The press fails and the scientists fail when it comes to explaining the danger of impact and that this is understood by the general public. When an asteroid approaches, many times the typical news appears that there is going to be an impact, but it is not. However, small asteroids the size of Chelyabinsk are there and there may be one tomorrow. Most of these objects from a few tens of meters, up to even 100 meters, we still do not know about. Our current knowledge says that large impacts on the scale of centuries are unlikely to occur, but we are detecting larger impact fluxes from objects of a few tens of meters than would be expected. We’re finding that these fragile bodies that break apart and pass close to Earth, in a very, very close encounter, and if it breaks apart, the pieces can fall into our planet’s gravity well and be thrown out in very different orbits. But the objects return to Earth at the same time. In the short and medium term, the danger comes from this type of object. That would explain, for example, that when the Duende asteroid arrived [descubierto desde Granada], which skimmed past artificial satellites, Chelyabinsk took place on the same day. And although the orbits do not coincide at all, many of us think that there is a correlation.
P. And where are the scientists wrong?
R. Scientists sometimes do not explain well that they are small bodies that change their orbits. The main mistake is to make people believe that you know well the orbits of objects, when in reality we are obtaining orbits with a precision that is not very high. And when they happen again, we correct them. A clear example is Apophis, an asteroid that has been in the limelight and impact was recently ruled out, thanks to the following observations. This has to be explained to the public: when they are near-Earth asteroids, we do not do continuous monitoring and there is a very important bias. I think the way we should approach this in front of the public is: scientists have discovered this asteroid that will pass at such a distance and these objects are going to be tracked, and the pages where you can find more information are these. People should know that those media that predict impacts are pamphlets, they are not serious media.
P. Are you more worried about those that can give us a scare, like Chelyabinsk?
R. In Chelyabinsk there were more than 1,500 wounded and they could have been prevented. And if this happens in a city like Madrid or Barcelona or New York, well, we could talk about tens or hundreds of thousands of injured. The risk also arises from our ignorance. That is, you see a huge ball of fire and you stand there looking at it. You have to inform people: don’t do it or it will cause serious burns. Or when it hits the shockwave, if you’re in front of glass or any building that’s crashing down on you, you obviously have the loser. It is information that the media should give, rather than the fact that the sky is going to come down on us.
If you see a huge ball of fire in the sky, don’t just stand there looking at it or you’ll get seriously burned.
P. What is the scenario that worries you the most?
R. Asteroid 2015 TB145 particularly gave me goosebumps. An extinct, dark, 600 meter, extremely fast comet, discovered with three weeks to spare, and passing slightly farther than the Moon. And I think there may be many more objects of this type. Jupiter, due to its presence, has a very important protective role for the Earth, with respect to perhaps the most dangerous impacts, which would be the impacts of very eccentric objects that arrive with a lot of energy. I am referring mainly to these comets, with long periods, with very eccentric orbits, that go beyond the orbit of Jupiter. They are extinct comets that approach the Earth, with periods that can be three, four or five years, and we really don’t see them because they are tremendously dark. 2015 TB 145 was a monster on the edge of what could be a hecatomb or at least a devastation on a regional scale. These are the ones that perhaps should concern us the most, because we don’t know all of them, they are so dark and eccentric that there could be some more.
P. With unlimited budget, how would you organize planetary defense?
R. With a series of telescopes in Earth orbit working in the infrared range, where you see more than just reflected light, and are no longer bothered as much by stars and other background objects. It would be ideal to have a set of telescopes monitoring the sky to achieve this monitoring. The key is always to have a good prediction of when the impact is going to take place. Knowing the movement, being able to study how they evolve, extending that observation for months: there a lot of information would be gained on those processes that we are most ignorant of. And from Earth, it would put more radio telescopes the size of the one that has been inaugurated in China. And of course, of course, with space missions.
P. Missions like DART, which is going to hit an asteroid?
R. That binary system that DART is going to intercept is a good example of the type of asteroids that reach us: Dídymo is almost 780 meters and Dimorfo is 160, therefore, they are of those dimensions that may concern us. Studying these two objects closely is an advance, because depending on the characteristics of each body, it is necessary to see what type of solutions are given. We have been to asteroids like Ryugu and Bennu. And these missions are key to mitigate the risk of future impact. In the case of Bennu, it has been shown that on the surface that body has a very low consistency, more fragile than the wet sand that dries when you build a castle on the beach. And these are good examples of the technological scientific challenge you face when you want to deflect an asteroid. Because of course, on the surface it is very fragile, but what is inside? There is a monolithic block, what dimensions? Such a fine, porous material that cushions any impact indicates that this may not be the best solution. We would have to propose other types of alternatives, but they involve knowledge decades in advance of the body’s orbit. You have to know that in 50 years you have the asteroid that will hit you and, therefore, be able to carry out that mission with what it would entail, because it would have to be a collective mission of all the space agencies in unison. We are talking, obviously, about creating a monster that would stand next to the asteroid or perch on it and move it away from its trajectory. Thanks to these missions that bring back asteroid samples, we are learning many more details about these properties, which are a tremendous challenge, because they are not properties that we are used to.
Extinct dark comets are the ones we should be most concerned about, because we don’t know all of them
P. Do you think that in the face of a dangerous comet there would be planetary unity?
R. I think it would work well, I’m convinced. There are clear examples that space agencies are working in continuous collaboration, and Russia has shown it. A comet is already a priori very unlikely, it could be a billion years old. But if it happens, faced with a challenge of this magnitude, it is clear that either we do it together, in a unitary way, or we do not do it. Because it is unfeasible to consider that a single agency set up a process to mitigate the impact of these characteristics. Be it a ship with missiles or whatever you want to do to face such a monster. You have to coordinate between the different agencies, look for alternatives, maybe even set up two or three options in parallel.
P. It would take years of preparation.
R. With a small asteroid, no. Perhaps with a mission like DART, totally robotic, it goes directly towards its objective. Having a robot with these characteristics can be very useful for the future. But realistically, we would have to know the asteroid’s orbit years in advance. And we have great shortcomings before we get there: we do not have monitoring programs from space that allow us to improve our knowledge of orbits. We lack radio telescopes to discover what these objects really look like. We have to go a long way. We have convinced the UN to implement Asteroid Day every year to raise awareness that it is necessary to remain vigilant and expand our knowledge of these objectives.
P. And if we see a flare in the air, don’t stop to take a selfie.
R. It is important to discuss at a social level that this is a latent danger. I try to emphasize that we are based on the historical record of humanity, but it is something that is greatly biased, we are unaware of many events of this type that have taken place in the past. Because our ancestors, faced with a Tunguska-type disruption event, interpreted it in many other ways. And surely they believed that God intervened.
The impact hazard has multiple heads, like the hydra
P. Marian apparitions that were actually asteroids?
R. It has even been proposed that the Sodom and Gomorrah events of the Scriptures were actually an atmospheric outburst. It may be that many of these events interpreted as fire coming from heaven could be attributed to some such event. Recently, it was discovered that also in the Chilean desert there are materials from what is supposed to be an outburst. And in the Libyan desert there was also evidence of an impact, or an atmospheric outburst, as happened in Tunguska. In these cases, when the fireballs hit the ground, everything is incinerated and the materials melted: they leave no evidence. This is another example of the bias that such an event can have.
P. In other words, we may have miscalculated the probabilities.
R. The impact hazard has multiple heads, like the hydra. One is the direct impact with a Chicxulub-type asteroid, an asteroid 12 kilometers away, associated with the extinction of the dinosaurs. Another may be a Tunguska style, which produces a shock wave, scatters trees across 2,000 square kilometers of taiga, and then incinerates them when the fireball arrives. And others halfway between the two: objects of hundreds of meters that may cause craters, because they are fragile, but that incinerates everything, causes a change on a regional scale. Sources of danger that perhaps we underestimate.
P. Do you have nightmares with asteroids?
R. No, I’m quite happy in that sense. I really enjoy studying them, but I prefer not to think about such things. Because if it is discovered that a comet is coming, that they are authentic chemical bombs, it does not matter where we take shelter. We would face a global winter of unknown dimensions and extent: weeks, months, years. And so why worry? Let’s hope it doesn’t happen for a long time, at least in thousands of years, so that we already have small colonies on the Moon or on Mars that guarantee the survival of the species. It is a latent danger: if a large object were to fall, it would completely exterminate our civilization.
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