Navigating the Cosmos: New Strategies for Deflecting Asteroids

As we face the genuine threat of asteroids hurtling towards Earth, the question arises: Can we safely change their trajectory without exacerbating the situation? With advancements in technology, experts have developed a sophisticated system that allows scientists to pinpoint the best location on an asteroid for deflection, potentially minimizing the risks involved.

Deflecting an asteroid on a collision course with Earth is a groundbreaking yet perilous endeavor. NASA’s Double Asteroid Redirection Test (DART), successfully executed in 2023, was a pioneering mission that achieved the first-ever diversion of an asteroid. By colliding a spacecraft with the asteroid Dimorphos, which orbits the larger Didymos, scientists managed to alter its orbit by an impressive 30 minutes.

However, changing an asteroid’s trajectory is fraught with risks. Precise adjustments can inadvertently push the asteroid onto a potentially hazardous path through a small area, known as a gravitational keyhole, where the gravitational pull from larger bodies like Earth can alter its trajectory, possibly leading to a later collision with our planet.

Recently, Rahil Makadia and his research team from the University of Illinois at Urbana-Champaign have created an innovative strategy that identifies the optimal impact point on an asteroid’s surface to significantly reduce this risk. By utilizing data from the DART mission, they analyzed various factors, including the asteroid’s shape, mass, and spin rate, to understand how different impact sites could alter the asteroid’s path. Their findings resulted in a probability map of potential impact locations, highlighting areas that pose lower chances of funneling the asteroid into a gravitational keyhole.

“Mapping these keyholes onto the asteroids is feasible and primarily requires computational resources before a mission launches, making it essential to determine the best target for any kinetic impact,” stated Makadia during the Europlanet Science Congress (EPSC) held in Helsinki, Finland, on September 9.

In their research, Makadia’s team focused on the asteroid Bennu, identifying over 2,000 potential gravitational keyholes, thus creating a comprehensive map of safe impact locations for a spacecraft.

Although gathering detailed data about any given asteroid is best achieved with specialized probes, this is not always practical—especially if the asteroid is discovered close to a potential collision course. Nevertheless, rough assessments can still be conducted using Earth-based telescopes, according to Makadia.

One exciting opportunity for testing this data-collecting strategy will occur when the asteroid Apophis makes an exceptionally close approach to Earth in 2029. This 450-meter-long asteroid, which has been confirmed to pose no threat to our planet, will provide a rare chance for astronomers to closely observe an object of such size passing by so closely—a phenomenon that occurs every 7,500 years.

“We’ve never witnessed an asteroid endure stress and natural vibrations caused by the proximity of Earth,” remarked Richard Binzel from the Massachusetts Institute of Technology during the EPSC on September 8.

NASA’s OSIRIS-APEX spacecraft, initially intended to revisit Bennu, has been redirected to observe Apophis, alongside the European Space Agency’s RAMSES spacecraft. Together, they aim to gather crucial data about the asteroid during this near encounter, while also attempting to land smaller probes on its surface to analyze its interior for seismic activities triggered by Earth’s gravitational influence.

Understanding Apophis’s characteristics could play a pivotal role in addressing future asteroid threats. “If we ever face an actual asteroid danger—be it from Apophis or another similar object—knowing its physical properties, including its rotational state, will be essential,” emphasized Binzel.

However, there’s no current need to nudge Apophis off course, given the precision with which astronomers have calculated its orbit. Furthermore, the RAMSES spacecraft is equipped with sensors designed to ensure safe operation, even in the unlikely event it collides with Apophis. Its minimal mass would have negligible impact on the asteroid’s trajectory.