Tech UPTechnologyRichard Binzel:

Richard Binzel:

binzel Will a space stone be the cause of the end of the world? Angela Posada-Swafford has spoken with this MIT expert on meteorites and asteroids, who has devised a method to calculate the chances of them hitting the Earth and studies systems to stop them.

Shapeless rocks with strange orbits and dark intentions, asteroids have traditionally been fourth-rate citizens in the Solar System. But Obama’s plans to send astronauts to fly over its surface and launch other unmanned missions – such as theDon Quixote– to divert the most dangerous are changing our view of these celestial bodies. Theastronomer Richard Binzel, from the Massachusetts Institute of Technology (MIT), shows whyasteroids aren’t that fierce. Binzel and other researchers, such as Pierre Vernazza of the European Space Agency (ESA), have launched several hypotheses that illuminate these space rocks – and their representatives on Earth, meteorites – in new lights.

His telescopic infrared observations, complemented by the comparative study of meteorites in the laboratory, yield several interesting conclusions. The first, thatthe quarry for most of the fragments that fall on our planet is the distant asteroid belt, located between Mars and Jupiter. This houses numerous objects that date from the formation of the Solar System, 4,550 million years ago, and that did not become planets due to the Jovian gravitational disturbances. The second, that this location affects not only the internal composition of the asteroids, but also their chances of colliding with Earth, which can help us find a way to defend ourselves from a devastating impact. And the third, Binzel and his colleagues have proven that, in turn, Earth’s gravitation is capable of leaving its traces on the surface of asteroids.

“This is the case of the man who bites the dog,” says Binzel in a telephone interview from his laboratory at MIT. And he adds: “We have taken telescopic measurements of the so-called near-Earth objects -the NEO-, which are asteroids that travel less than 48 million kilometers, and we verified that if one gets close to 95,000 km, a tremor can occur. strong enough to bring regoliths – rock fragments, minerals and other unconsolidated materials – out to its surface. ” In the same way that the attraction of Jupiter alters the appearance of its moon Europa,Earth’s gravity can transform an asteroid. ? The surprising thing is that this power reaches objects that are at a distance of 16 times the earth’s radius. Our gravity is a million times greater than that of these bodies, but, for the Earth to produce this alteration, the asteroid has to have a certain structure. It only happens in the rocky ones, which we call class S, not in the cast iron ones, which are class M ?, Binzel notes. “These boulders transformed by Earth’s influence – he continues – are not seen in the asteroid belt because the Sun obscures them, but when they approach they become visible.”

The spectrography of these modified asteroids matches meteorites that fell to Earth that Binzel has studied in the laboratory, solving a dilemma as astronomers tried to understand why asteroids compatible with meteorites could not be found in space. discovered on our planet. Who would have guessed that they were unrecognizable because they were tanned by sunlight?

Heats and changes of route

“There is a revolution taking place in the study of asteroids,” says astronomer Clark Chapman of the Southwest Research Institute in Colorado. “Before – it continues – it was thought that collisions were the cause of its changes. Now we know that there are more characters in this story. Perhaps a new science is being born that could be called asteroid seismic .” Binzel, who among other things has created the so-called Turin scale -a tool to measure the probabilities of collisions of these bodies with the Earth- , has also discovered the reason that spectral traces -the reflection and absorption of electromagnetic radiation- of the belt asteroids coincide with those of the meteorites that fall on us and the cause of them arriving from so far here: “It is the so-called Yarkovsky effect. This modifies the orbits of the rotating space bodies, because the different faces of their surface receives solar radiation unevenly, which causes them to end up changing their trajectory over time. The phenomenon is more pronounced in small objects and that is why it influences asteroids so much. “

Binzel adds that? Two-thirds of the objects in the belt correspond to a class of meteorites known ascondritas LL, which represent only 8% of those discovered. It seemed strange to us that with so many asteroids of this type we received so few equivalent meteorites, and we discovered that the cause is the Yarkovsky effect, which limits the size of the rocks transported from the belt.? LL chondrites are rocks rich in minerals such as pyroxene and olivine, and poor in iron. “Knowing their composition is important to know how to divert them from Earth, since they constitute one of our main threats”, Binzel warns. The group of chondrites in general, which includes several species in addition to LL, are the most common meteorites: they account for 80% of those that reach our planet, while there are barely a hundred fragments of Martian or lunar rocks in scientific institutions of all the world. The analysis of chondrites is also key to studying the origin of life, because they are rocks that have not been fused or melted, so they store information on the synthesis of organic compounds or the existence of water on Earth.

The asteroid belt is estimated to be made up of 1.9 million of these objects over 1 km in diameter and several million smaller specimens. Beyond, at the edges of the Solar System, are theKuiper belt asteroidsand the trans-Neptunian bodies of thenube de Oort, the main reservoir for dormant or inactive kites. Most asteroids are porous, so half are nearly hollow, according to Binzel. Some have moons and others occupy binary systems or travel in groups loosely linked by gravity. And recently it was discovered that there are ice water in their entrails and that they could have carried it to Earth in ancient times. Others, denser, are made of iron and are the remains of dead nuclei of larger asteroids.

The adventures of Sancho and Hidalgo

Some are so dark that they have gone unnoticed for years. However theinfrared space telescope WISENASA has been unmasking these carbonaceous objects, which emit very little light, through extensive tracking, according to Binzel. Scientists estimate that there are about 100,000 asteroids and comets near Earth, of which 20,000 have a chance of reaching it. NASA has located about 7,000, of which about a thousand fly in potentially threatening orbits.

Currently, there are several unmanned missions underway to study asteroids. The Japanese shipHayabusa just came back from visiting and collecting samples of a huge object calledItokawa. Meanwhile, NASA’s robotic probeDawnpropelled by ions, it heads to the asteroid belt to meet withVesta, one of the largest rocks in the Solar System. Then, in a maneuver unprecedented in the history of space flight, it will leave the orbit of that body to fly to another, that of theasteroid Ceres. Perhaps the most exciting of all is the missionDon Quixote, of the ESA, whose objective is theasteroid Apophis, 270 meters, which in 2029 will come very close to Earth. The idea is to tap it in the opposite direction of your movement. The plan involves two spacecraft: Sancho would study the composition of the asteroid before and after impact, and Hidalgo would ram it to modify its speed.

“Knowing the microporosity and grain density of Apophis would help us calculate how much energy we have to apply to it,” says Binzel. And he adds: “We know that it is an LL chondrite and that it could return in 2036. The probability that it collides with us on that date is 1 in 250,000. If it happened, it would not devastate the planet, since it lacks the size for this to happen, although, yes, it would cause great damage “.

It all depends on the reaction time

 

“The method to defend ourselves from an asteroid also depends on the time we have. If it is more than 30 years, Don Quixote’s plan is valid. In other cases, the so-called gravity tractor could be used, which consists of placing a spacecraft at the side of the object to remove it from its orbit. But, if the rock is more than 2 km long and it is expected that it can arrive in two decades, the best option is a nuclear detonation that changes its trajectory, “says Binzel. Among the apocalyptics, 2012 is a key date – rivers of ink have been written about the supposed Mayan prophecy that then predicts the end of time – but asteroids are not suspicious. According to this expert, none have been detected in Earth-intersecting orbit for that year. However, collisions do happen: Earth has 170 impact craters . The largest, Vredefort, in South Africa, measures 300 km. And the dinosaurs might still be here if they had an anti-steroid space program .

 

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