Asteroid Flyby a Little Too Close for Comfort

Asteroid 2013 TX68 could get as "close" as 11,000 miles from the Earth when it passes by on March 5.

Asteroid 2013 TX68 could get as "close" as 11,000 miles from the Earth when it passes by on March 5. (P.Carril/European Space Agency)

Two years ago, asteroid 2013 TX68 flew by the Earth at a distance of 1.3 million miles—about five times the distance between the Earth and the Moon. Sometime between March 5 to March 8, this asteroid will give an encore performance, in case any  Near Earth Object (NEO) fans missed it the first time.

First and foremost, remember what is printed in big, friendly letters on the cover of “The Hitchhiker’s Guide to the Galaxy”: Don’t Panic.

NASA’s Center for NEO Studies (CNEOS) has determined that there is a zero-percent chance that 2013 TX68 will hit the Earth—on this pass at least.

The mathematical certainty of a miss aside, the exact distance of closest approach is somewhat murkier.

This asteroid is predicted to fly by at roughly 3 million miles from Earth. Thankfully, it’s not going to hit us.

Why the uncertainty about the exact distance? In a nutshell, we don’t know enough about this asteroid’s orbit around the sun to pin it down with any more precision. From the moment it was first detected to when it faded and became undetectable, observers had only ten days to track it—too little time to gain a clear understanding of its orbit.

The longer we can observe and track a NEO, the better we understand its orbit and therefore the probability of a future collision with Earth.

The range of possible distances of closest approach of asteroid 2013 TX68 on March 5, 2016
The range of possible distances of closest approach of asteroid 2013 TX68 on March 5, 2016 (NASA)

There is a very small chance—1-in-250 million—that this asteroid could hit us on September 30, 2071. But you have a better chance of winning the Super Lotto jackpot than being crushed by this asteroid.

Even if 2013 TX68 were to hit the Earth, it wouldn’t wipe us out. It could easily spoil someone’s day, make no mistake: this asteroid is about 100 feet in diameter, almost twice the size of the object that exploded in the atmosphere above Chelyabinsk, Russia, three years ago.

The Chelyabinsk air-burst produced a shockwave that damaged buildings and shattered windows across a wide area, and, had it struck the ground intact, would have left a significant crater. 2013 TX68 would release about twice the energy as the Chelyabinsk event.

Radar image of the "Halloween Asteroid"--a large Near Earth Object that passed relatively close on October 31, 2015
Radar image of the “Halloween Asteroid”–a large Near Earth Object that passed relatively close on October 31, 2015 (NASA)

2013 TX68 is a good reminder that Earth shares its space with millions of rocks—potentially hazardous asteroids ranging in size from a few feet to hundreds of feet across, or more.

We know of about 14,000 NEOs, including practically all of the big ones. The big ones are easier to detect at greater distances, and we have a lot more orbital tracking data on them and understand their orbits best.

But the smaller the rock, the harder it is to see, and it is estimated that there may be over a million NEOs that have not yet been discovered.

The smallest NEOs that we’re concerned about aren’t detectable until they’re almost upon us. In fact, on average, between 25 and 30 NEOs pass closer to Earth than the Moon’s orbit each year.

Presently, there isn’t a lot we could do to avoid an impact, especially with little or no warning.

Smaller asteroids strike the Earth more often than you might think, though usually in less populated areas. Remember, 75 percent of Earth’s surface is ocean, and some regions on Earth are uninhabited. Think of a dartboard, where the bull’s-eye represents the Earth’s highest populated areas, and the dart has no particular aim.

Census of Near Earth Asteroids, both known and estimated.
Census of Near Earth Asteroids, both known and estimated. (NASA)

There are ideas about how to protect us from large asteroid impacts. One is to send a massive robotic spacecraft to an asteroid we know will likely hit the Earth, and use the gravitational attraction between the two to “nudge” the asteroid into a safer orbit.

It’s sort of like a small tugboat nudging a large ocean cargo ship to avoid striking a bridge pier, something the tug is capable of doing given enough lead time.

This plan requires precise knowledge of an asteroid’s orbit and the ability to predict an impact years in advance, which is one good reason to learn as much about NEOs now as possible!

  • disqus_QiVYNk1Omi

    The Truth is that someone wins the Lottery multiple times a year so don’t use that analogy. It is not comforting to say that it is a guarantee that it will not hit yet the tracking is 11,000-9 million guesstimate. Track it and evacuate the zone, but you can let the rock evacuate the zone for you. Where is everyone’s STUPID hat, oh yea they are wearing it.

    • Someone wins the lottery every few weeks, yes, but the chances for any specific individual winning the lottery is vanishingly small. That was the intent of the analogy.


Ben Burress

Benjamin Burress has been a staff astronomer at Chabot Space & Science Center since July 1999. He graduated from Sonoma State University in 1985 with a bachelor’s degree in physics (and minor in astronomy), after which he signed on for a two-year stint in the Peace Corps, where he taught physics and mathematics in the African nation of Cameroon. From 1989-96 he served on the crew of NASA’s Kuiper Airborne Observatory at Ames Research Center in Mountain View, CA. From 1996-99, he was Head Observer at the Naval Prototype Optical Interferometer program at Lowell Observatory in Flagstaff, AZ.

Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.

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