Earlier this month, Ukrainian astronomers made a pretty big discovery: a quarter-mile-wide asteroid, to be exact.
From their initial calculations, the astronomers learned that a relatively large, never-seen-before asteroid—named 2013 TV135—had just buzzed safely past Earth but would make an extremely close call on August 26, 2032.
That was enough to instantly move the newly discovered asteroid to the top of NASA’s Near Earth Asteroid watch list, where it remains today.
Coming fresh on the heels of last year’s zero-warning explosion of a much smaller space rock over Russia, which caused over 1,000 injuries and a spectacular light show, the new discovery got the attention of the Russian deputy prime minister in charge of their space program, who quoted the headline of a major Russian news channel:
The headline, via Google Translate, reads: “400-meter asteroid threatens to blow up the Earth.” An asteroid impact the size of 2013 TV135 could cause regional devastation, sure, but to “blow up the Earth” is quite an overstatement. (Never mind that it’s not even physically possible.) Plus, the odds of an impact of any kind are incredibly low. The world is not going to end because of this rock, period.
Thankfully, NASA and astronomer Phil Plait quickly shut that whole thing down. In a press release subtitled “A Reality Check” issued shortly after the asteroid’s discovery, NASA placed the odds of a 2032 impact at one-in-63,000.
We are almost assuredly safe from this errant geological space wanderer. The odds of this rock hitting us in 19 years are about the same as being dealt a straight flush in poker in a five-card hand. Very, very rare—but it happens.
So NASA hasn’t totally ruled out a collision yet. Given that, just how concerned should we be about this particular space rock?
The odds NASA quoted in its press release were based on only a few days of observations, and subject to change. Impact odds typically fluctuate a bit in the first few months after discovery of an object like 2013 TV135, as astronomers gather data from observatories across the world, and attempt to triangulate exactly what path the object is taking as it moves through space. Since NASA’s statement on this particular asteroid about 10 days ago, the number of measurements has more than doubled, helping NASA to better calculate the orbit and further refine the odds of a strike.
So far, the result is mixed news: as of October 27th, the odds of a strike have actually increased a bit to about 1-in-31,000. And, with additional observations, the asteroid is now estimated to be about 10% larger.
But the good news is that 2013 TV135′s orbit is now known with more certainty. This is what really matters. The more certain an orbit is known, the more confident we can be that even unpredictable events over the next two decades—say, a gentle nudge from Jupiter’s gravity, perhaps—wouldn’t steer the asteroid on an unavoidable collision course.
NASA’s job is to concentrate on mapping the orbit of Earth-crossing asteroids like 2013 TV135 with as much accuracy as possible, and to assess the risk of collisions with still-unknown objects too. Scientists use the Palermo Scale to compare the risk of a specific asteroid on a specific impact date to the background risk from all undiscovered asteroids of a similar size or larger up until the impact date. Since astronomers estimate they have only discovered about 10% of all space rocks that could cause significant harm to people on Earth, that background risk is still quite substantial from now up until 2032. According to the Palermo Scale, there’s a whopping 44 times greater likelihood that a yet-undiscovered asteroid will pose a greater risk to Earth than 2013 TV135 currently does.
Odds are, a few more months of observations will allow NASA to further refine the orbit and conclusively state that 2013 TV135 poses no threat to humanity.
For a moment, though, let’s think about what it would mean should this rock defy the odds and hit the Earth.
According to the Earth Impacts Effects Program, a joint project of Imperial College London and Purdue University, 2013 TV135 would carry the energy of about 3,300 megatons of TNT if it were to strike. That’s roughly equivalent to 60% of the world’s remaining nuclear weapons detonated at the same time, in the same place.
The result would surely be impressive: The crater would be about twice the width of Manhattan, and about as deep as the newly constructed Freedom Tower in New York is tall. More than one hundred million cubic meters of rock would be instantly vaporized on impact. The shaking produced would be equivalent of a 7.0 earthquake.
If you were standing about 60 miles (100 km) from the impact site, within two minutes you’d be pelted with debris up to about two inches in size. Within five minutes, the air blast generated by the heat of the impact would create hurricane force winds, shattering your windows.
If you were standing within about 20 miles away (30 km) —for reference, New York City is roughly 20 miles wide—the effects would be much more serious. The average fragment size headed your way would be about the size of a dishwasher, and within 90 seconds wind speeds would top 500 miles per hour. Over 90% of trees, buildings, bridges—pretty much anything, really—would be blown down. Not a pretty picture.
This kind of event occurs about once every 100,000 years or so. Thankfully, in the very unlikely case that NASA can’t rule out this kind of a strike in 2032, we’ll have nearly two decades to deflect 2013 TV135 onto a safer course. Scientists have been investigating ramming dangerous objects with spacecraft, among other tactics. If it comes to that, let’s just hope world governments can agree more quickly about exactly what to do than they have on the much more real threat of climate change.