An asteroid made its closest approach to Earth around 7:50 a.m. EST last Monday. Astronomers did not see it coming until two days before the actual flyby.

The near-Earth object 2017 AG13, with an estimated width of 36 to 111 feet, passed between the planet and the moon at a speed of 9.9 miles per second. It’s nothing like a killer space rock, but the asteroid that exploded over Chelyabinsk in Russia back in 2013 is enough to cause some damage at a 65-ft measurement.

The question is: are we actually prepared for asteroids hurtling toward us?

Planetary Defense

The recent asteroid pass occurred less than a month after White House released its “National Near-Earth Object Preparedness Strategy,” which outlines how it seeks to develop international capacity for responding to asteroid threats. Its seven primary objectives include improving tracking, deflecting, and modeling technologies, as well as developing emergency and recovery protocols.

On a more concrete level, NASA has consolidated such efforts under its Planetary Defense Coordination Office (PDCO), which prioritized asteroid detection and defense of the planet through inter-agency partnerships and mobilizing the global community.

“[T]he agency is committed to perform a leadership role in national and international efforts for detection of these natural impact hazards, and to be engaged in planning if there is a need for planetary defense," said planetary defense officer Lindley Johnson in a statement.

For starters, do astronomers know what is out there? This month so far, NASA’s database of all documented asteroids has logged almost 40 new heavenly objects. In its monitoring of over 700,000 space rocks, NASA appears to know where more than 90 percent of the dinosaur-killing-size ones are.

Astronomers hunt for near-Earth objects using ground-based telescopes and NASA’s space-based NEOWISE infrared telescope and tracking data are channeled to an international database. Once detected, orbits are predicted and monitored at the Jet Propulsion Laboratory in California, with select asteroids furthered described by equipment such as the InfraRed Telescope Facility and interplanetary radars.

Other Asteroid-Deflecting Strategies

There are a number of strategies in place that can potentially deflect space rocks confirmed to be on a collision course. The gravity tractor, for instance, banks on parking a spacecraft near an asteroid to slowly draw the rock into a new trajectory by the force of gravity. While effective for asteroids that are either metal or a mere chunk of dirt, this technique poses slower change with bigger objects.

Another technique is to take advantage of the so-called Yarkovsky effect or dark asteroid’s uneven solar heat intake and release. This method has been found to change the rock’s orbit by around 100 miles over a 12-year period.

As these plans take years to effect measurable changes, we can also opt to give asteroids a quick shove. A collaboration between NASA and the European Space Agency aimed to be launched in 2020, the Asteroid Impact and Deflection Assessment (AIDA) Mission seeks to blast a “kinetic impactor” into the asteroid Didymos and see if the collision could change its speed by a projected fraction of a percent.

There’s also the possibility of using nuclear power, with a spacecraft creating a crater with an atomic explosion impact and a second one following behind with a bomb.

In 2013, the Chelyabinsk meteor exploded with around 30 times the power of the Hiroshima explosion, the shockwave injuring over 1,600 people. The good news, however, is extinction-causing strikes are a one-in-a-million year affairs, so the U.S. space agency is not foreseeing the need for a nuclear strategy anytime soon.

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