Scientists Reckon We're (Probably) Safe From Asteroids For At Least Another Century

Photo: Deep Impact / DreamWorks Pictures

If there's one thing I'm sure we can all agree on, it's that learning how space agencies protect Earth from asteroids kicks arse.

Early this morning, experts from NASA and the Johns Hopkins University Applied Physics Lab did an 'Ask Me Anything' on Reddit, answering questions about asteroid detection and redirection, some of which are, frankly, quite terrifying. The three experts are all involved in the Double Asteroid Redirection Test.

"Known as DART for short, this is the first mission to demonstrate the kinetic impactor technique, which involves slamming a spacecraft into the moon of an asteroid at high speed to change its orbit," the AMA description reads.

"In October 2022, DART is planned to intercept the secondary member of the Didymos system, a binary Near-Earth Asteroid system with characteristics of great interest to NASA's overall planetary defence efforts. At the time of the impact, Didymos will be 11 million kilometres away from Earth."

You can watch a video on how DART is planned to work below, which features two of the experts who participated in the AMA.

In other words, these folks know a thing or two about deflecting enormous foreign bodies away from Earth. You can check out the AMA here if you're keen, but keep reading to see a few of the most interesting exchanges below.

Q (ThProphet): At this point, what would you say is the largest asteroid you could deflect, and what would be the consequences if it wasn't deflected?

A (Andy Rivkin, APL DART investigation co-lead): The DART spacecraft will change the speed of Didymos B by a bit less than a millimeter per second. So, my question in return is how much warning time we have. If we had decades to a century of warning time, and could build as big an impactor as we want, we could move something a kilometer or two in diameter. if one of those made it through, we think it would cause civilizational collapse. With less warning time, we might need to use a nuclear device to deflect large asteroids. This is part of the impetus to find potential impactors early!

Q (Dar2De2): Hi team! Thanks for doing this AMA. To your knowledge, what is the closest to major catastrophe have large populations been and not really known? And, what is the most boring or mundane part of your job?

A (Andy Rivkin): To my knowledge, that'd be the Tunguska impact in 1908. If its incoming path was only slightly different, it would have hit St. Petersburg, the Russian capital. Because it hit in Siberia just before a period of European unrest, it took a while to figure out what happened.

As for number two, that'd be the telecons and nearly-endless parade of spreadsheets that come from making sure a project will be done correctly...

Q (SaltyMarmot5819): Hey team! My question is are we looking at a big possibility in the near future (say 1000 years) to face a problem of this kind and are we ready to prevent it? Other than that thanks for your work towards saving this blue dot!

A (Tom Statler, NASA program scientist): We are pretty sure we have found 90% to 95% of the NEOs of dinosaur-killing scale, and none of them is a danger in the next century. Beyond that, we have to make statistical predictions. Statistically, over 1000 years, we'd expect a handful or two of impacts of a scale that could be locally or regionally very serious. Unless we find the objects and prevent the impacts, of course.

Q (TylerSpicknell): What would you do for incredibly large meteors the size of a small country?

A (Andy Rivkin): Small country like Monaco, or small country like Ecuador? :)

Q (TylerSpicknell): I guess Monaco.

A (Andy Rivkin): OK, For a Monaco-sized impactor (maybe a mile or so across), we can handle it given enough warning time by ramming it with spacecraft like DART or perhaps using nuclear devices to vaporize and propel the asteroid. Not necessarily a situation we want to be in, but I think it is doable given current technology.

Q (TylerSpicknell): Alright, but what about an Ecuador-sized one?

A (Andy Rivkin): Luckily, there is only one asteroid that big, and it's not going anywhere. :) Otherwise, I suppose I might point you toward the movie Melancholia, which I understand might be relevant...

For anyone who hasn't seen Melancholia, let's just say it, uh, doesn't end well.

If that taste has got you all revved up for more, do yourself a favour and check out the rest of the AMA, it's a real treat, if not, kinda scary at times.

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