A small number, but not zero.
En los confines del sistema solar, un asteroide de 500 metros llamado Bennu lleva siglos trazando su camino silencioso, y por primera vez en la historia, una especie ha logrado calcular ese camino con una precisión de dos metros para los próximos tres siglos. La misión OSIRIS-REx de la NASA no solo ha devuelto muestras de material de 4.500 millones de años de antigüedad, sino que ha convertido una amenaza abstracta en un problema concreto y, quizás, manejable. Con una probabilidad de impacto de 1 en 1.750 antes del año 2300, Bennu nos recuerda que habitar el cosmos implica aprender a negociar con él.
- Un asteroide del tamaño de una montaña podría liberar la energía de 70.000 bombas de Hiroshima si impactara la Tierra, y el 24 de septiembre de 2182 es la fecha de mayor riesgo identificada hasta ahora.
- La existencia de 'agujeros gravitacionales' en la trayectoria de Bennu significa que un roce aparentemente inocente con la gravedad terrestre en 2135 podría convertirse en una colisión catastrófica décadas después.
- La misión DART demostró en 2022 que la humanidad puede alterar el rumbo de un asteroide, transformando la defensa planetaria de teoría científica en capacidad operativa real.
- NASA trabaja para catalogar el 90% de los objetos cercanos a la Tierra mayores de 140 metros, mientras China propone lanzar 23 cohetes para desviar a Bennu directamente, señalando que la respuesta global ya está en marcha.
Durante seis años, la nave OSIRIS-REx de la NASA acompañó de cerca a Bennu, un asteroide de 500 metros y 74 millones de toneladas que orbita el sistema solar interior. En 2018, la nave llegó hasta él, recogió muestras de material formado hace 4.500 millones de años y permitió a los científicos calcular su trayectoria con una precisión sin precedentes: dos metros de margen de error para los próximos siglos. Esas muestras se distribuyen ahora entre investigadores de todo el mundo.
Lo que esos cálculos revelan es incómodo. Bennu pasará varias veces peligrosamente cerca de la Tierra en los próximos siglos, y el 24 de septiembre de 2182 representa la ventana de mayor riesgo, con un 0,037% de probabilidad de impacto. El peligro no reside solo en ese encuentro: si el asteroide atraviesa ciertos 'agujeros gravitacionales' durante un paso cercano, la gravedad terrestre podría desviar su trayectoria de formas impredecibles, preparando una colisión futura. En total, la probabilidad acumulada de impacto hasta el año 2300 es de 1 en 1.750, un número pequeño, pero no cero.
Las consecuencias de ese escenario serían devastadoras. Un impacto de Bennu liberaría energía equivalente a 70.000 bombas atómicas como la de Hiroshima, remodelando por completo la región afectada y enviando ondas de choque por todo el planeta. Es precisamente esta magnitud lo que ha llevado a la NASA a pasar de la observación pasiva a la intervención activa.
En 2022, la agencia lanzó la misión DART, que demostró que es posible desviar un asteroide enviando una nave a colisionar contra él. La técnica podría aplicarse a Bennu si fuera necesario. Paralelamente, China ha propuesto una respuesta aún más ambiciosa: lanzar 23 cohetes para alterar directamente su trayectoria. Mientras tanto, NASA avanza en su objetivo de identificar el 90% de los objetos cercanos a la Tierra mayores de 140 metros, apostando por el conocimiento anticipado como primera línea de defensa.
Las muestras de Bennu que circulan por laboratorios y museos cumplen una función doble: afinar los modelos científicos sobre el comportamiento de los asteroides y recordarnos, de forma tangible, que vivimos en un sistema solar dinámico. El trabajo que se realiza hoy en centros de investigación y control de misiones es, en esencia, el trabajo de la prevención: la apuesta de que comprender el cosmos a tiempo puede cambiar el destino.
For six years, NASA scientists have kept close watch on a rotating pile of rock and dust called Bennu, a 500-meter asteroid with a mass of roughly 74 million tons. The agency's OSIRIS-REx spacecraft reached the object in 2018 and has since collected samples—material that dates back 4.5 billion years—which researchers are now distributing to scientists around the world for study. The reason for this attention is straightforward: Bennu might one day collide with Earth.
The mission has accomplished something remarkable in precision. Using data gathered from the spacecraft's close encounter, NASA scientists have calculated Bennu's orbital path for the next several centuries with an accuracy of just two meters. That level of detail matters when you're trying to predict where a mountain-sized object will be in the year 2135, 2182, or 2300. The calculations show that Bennu will pass uncomfortably close to our planet multiple times over the coming centuries. Of particular concern is September 24, 2182—a date that carries a 0.037 percent chance of impact, the highest risk window identified so far.
The physics involved is both elegant and unsettling. As Bennu approaches Earth, it could pass through what scientists call a gravitational keyhole—a region of space where Earth's gravity would bend the asteroid's trajectory in unpredictable ways. A slight deflection during one pass could set up a collision on a later approach. NASA emphasizes, however, that only a handful of these dangerous keyholes actually exist along Bennu's path. When you add up all the risk across the entire 300-year window through the year 2300, the probability of impact is one in 1,750—or 0.057 percent. It is a small number, but not zero.
If that small-number scenario were to occur, the consequences would be catastrophic. Scientists estimate that a Bennu impact would release energy equivalent to 70,000 atomic bombs of the size that destroyed Hiroshima. The blast would not end human civilization, but it would reshape the region where it struck and send shockwaves across the planet. This is why NASA takes the threat seriously, even at odds of less than one percent.
The agency is not waiting passively. In 2022, NASA launched the DART mission—a spacecraft designed to test humanity's ability to defend itself against asteroid threats. The concept is direct: send a half-ton spacecraft on a collision course with an asteroid to nudge it slightly off course. If the technique works, it could be deployed against Bennu or any other near-Earth object that poses a genuine danger. The mission represents a shift in how space agencies think about planetary security—from passive observation to active intervention.
Beyond Bennu, NASA has committed to identifying more than 90 percent of all near-Earth objects larger than 140 meters across. The goal is to eliminate surprises, to know what is out there before it becomes a problem. China has proposed an even more ambitious response to the Bennu question: launching 23 rockets to alter the asteroid's trajectory directly. Bennu currently orbits at a distance of more than 320 million kilometers from Earth, far enough away that there is time to plan, to study, to prepare.
The samples NASA is sharing with the scientific community serve multiple purposes. They will help researchers refine their models of how asteroids behave and how their orbits change over time. They will also be displayed in museums and educational institutions, turning an abstract threat into something tangible—a piece of ancient stone that reminds us we live in a dynamic solar system. The work happening now, in laboratories and mission control centers, is the work of prevention. It assumes that knowledge and preparation can change outcomes, that humanity need not be passive in the face of the cosmos.
Notable Quotes
NASA emphasizes that only a handful of dangerous gravitational keyholes actually exist along Bennu's path.— NASA scientists
The Hearth Conversation Another angle on the story
Why does NASA care so much about this particular asteroid when the odds of impact are less than one percent?
Because one percent over three centuries means there are real moments when Bennu will be close enough to matter. And because we've never actually prevented an asteroid impact before. This is practice for the day when we might have to.
The gravitational keyhole concept—is that something we can predict or control?
We can predict where the keyholes are. Whether Bennu actually passes through one depends on its exact position when it approaches Earth. That's why the two-meter precision matters so much. Small errors compound over centuries.
If DART works, could we use it on Bennu itself?
In theory, yes. But Bennu is much larger than the asteroid DART is designed to test on. We'd need to know more about how it responds to impact. That's partly why the samples matter—they help us understand the asteroid's composition and how it might behave.
What does it mean that China wants to launch 23 rockets at it?
It means different countries are thinking about planetary defense differently. The U.S. approach is precise and measured. China's proposal is more direct—overwhelming force. Both assume the threat is real enough to spend resources on.
Are people afraid of this?
Most people don't know about it. The ones who do understand the math tend to see it as a long-term problem with a long-term solution. Fear requires immediacy. This is too far away, too uncertain, too manageable to trigger real panic.