Just two days before its approach of Earth last week, astronomers discovered the presence and precarious trajectory of Asteroid 2016 RB1.
Its course brought it to within 24,000 miles of sea level on September 7—close enough to endanger communication satellites—as it whizzed by at more than 18,000 mph.
Astronomers first spotted the 13-46 foot wide asteroid with Mount Lemmon Survey's 60-inch Cassegrin telescope at the University of Arizona. It was later reconfirmed by Gianluca Masi of the Virtual Telescope Project in Italy. Naturally, a space-faring body the size of a bus or trailer is too small to see with the naked eye from the ground, but thankfully Masi had the means on hand to create an animation of the asteroid's motion.
After plotting its trajectory, we could only watch with pallid faces as the asteroid passed within 2,000 miles of the kind of satellites responsible for loading and reloading this very webpage, or awaiting the data stream from your next phone call. But don't fret.
Asteroid 2016 RB1 came from a group of space rocks called the Atens. Essentially this is a group of Near Earth Objects (NEOs) travelling the inner solar system in orbits stochastic enough to sporadically collide with nearby planets—Mars, Earth, Venus and Mercury.
So we've seen this before. Last Sunday, an asteroid of even greater mass called 2016 QA2 zipped betwixt the Earth and Moon to less than 50,000 miles above sea level. Realistically, such encounters are little bumps on our collective proverbial extinction meters.
Because although scientists have assured the media that 2016 RB1 was not big enough to cause a major catastrophe, being roughly a thousand times smaller than the impactor that killed the dinosaurs, the hypothetical inconvenience of just two days' warning pre-impact of great portent should convince us to endorse programs studying close encounters of the rocky kind, like NASA's Planetary Defense Coordination Office (PDCO). Launched early this year, the new organization was founded to coordinate its multi-disciplinary efforts to catalogue NEOs capable of decimating life as we know it.
It's a valid question to ask why NASA or ESA would want to carry out a massive program to catalogue all NEOs capable of seriously messing things up if the only pro is a little foreknowledge of total destruction. This is why NASA is testing out the theoretical basis of countermeasures with missions like OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, REgolith Explorer), an asteroid-specific mission launched at 7:05 EDT last Thursday from Cape Canaveral.
The probe's primary mission is to return a sample of the NEO asteroid called Bennu to Earth, so scientists can learn more about these things that threaten our pale blue dot.
Joined by the Canadian Space Agency, OSIRIS-REx will also study something called the Yarkovsky effect. When an asteroid approaches the sun, its surface heats enough to expel gas and other material, acting like a natural thruster.
Arriving in 2018 and departing in 2021, the probe will measure physical properties—like rotation—that determine how and when an asteroid's orbit changes, turning a potentially hazardous NEO into another harmless miss, and vice-versa.
OSIRIS-REx is an early and small step for NASA's PDCO program, one that most astronomers agree was a long-time coming. Common sense dictates that it may be natural for the beginning of an asteroid-cataloguing program to amass a great number of previously ignored NEOs. However, the cold reality remains that we're likely to see a lot more close-calls than comforting reassurances as we open our eyes to the shooting range we've been living in all these millions of years.
Correction 9/12/2016: This story originally stated that the asteroid 2016 RB1 is 1/30 the size of the impactor that killed the dinosaurs. Estimates put the latter at ten kilometers in diameter or more, which would be 1000 times larger than 2016 RB1. The original headline also stated that the asteroid grazed Earth's upper atmosphere, the upper limit of which is at about 6,200 miles above sea level. 2016 RB1 came within 24,000 miles above of sea level. We regret the error.