Is There A Best-Case Asteroid Impact Scenario?

August 7, 2018

If an asteroid was to hit Earth, is it worse for it to hit land or to hit the ocean? Cheddar explores with NASA the difference in energy releases for each impact.


Patrick Jones: [MUSIC] Here's something you may or may not have thought about, what would be better for us life here on earth? An asteroid hitting the ground or an asteroid hitting water? I know the obvious answer is, no asteroids, but let's look at it. If it was to hit the land, it would send debris into the atmosphere causing global cooling. Meanwhile in the water, the thought is that it could send towering tsunamis in every direction. So, let's find out. Hey guys, I'm Patrick Jones and welcome to Cheddar Explores [MUSIC]. The earth is constantly being peppered by space debris. Most of it is dust, thinner than sand at the beach. But once in a while, we're hit by something that alters the entire planet. The last giant asteroid collision with our home was a seven point five mile monster that landed on what's now the Yucatan Peninsula in Mexico. According to a paper published by scientific reports, this was the worst spot to hit. You see, it crashed into an oil heavy area causing the thick debris to fill the atmosphere blocking out the sun and leading to a global cooling event that killed 75 percent of all living species. To get some answers, I spoke with NASA's Lindley Johnson. It's his job to lead a team that scans for potentially hazardous space material coming our way so we all don't die. On top of having a vastly more meaningful gig, Lindley also has arguably the best job title I've ever heard of.

Lindley Johnson: [MUSIC] I'm Lindely Johnson, I'm the Planetary Defense Officer at NASA.

Patrick Jones: Planetary Defense Officer. That's just amazing. Now, of course, when we're talking about asteroids hitting the Earth, we have to state the obvious. An asteroid hitting a major metropolitan area would result in the biggest loss of life. The other thing, is that if it's big enough, it's not going to matter where it hits. For starters, even if you survive the initial blast, large impacts could set off global volcanoes. And we've got large asteroids in our vicinity. For example, the biggest asteroid in the asteroid belt is 625 miles across. If that hits the earth, don't worry about paying rent next month. I spoke earlier about what an asteroid hitting land could do. Giant plumes of debris could jump up into the upper atmosphere, blocking the sun from getting in, chilling things down and killing the food chain from the bottom up. And then, for water, let's let 1998 disaster movie, Deep Impact explain. [NOISE] So, that in every direction. But is that actually what would happen? That's where Lindley comes in.

Lindley Johnson: We once thought that an object hitting in the middle of the ocean, uh, would cause this big tsunami wave. Uh, but, uh, come to find out that the energy released is significantly different than, uh, waves that are caused by, say, earthquakes. You have this point source energy release versus this linear wave that's caused by an earthquake. So, deep ocean, uh, would actually dissipate the wave pretty quickly just like [NOISE] plunking a rock down in- in a pond. So, as long as the object isn't, uh, more than a couple hundred meters in size, uh, we don't have to worry too much about a tsunami, uh, wave unless we're very close, uh, to shore.

Patrick Jones: Basically, if the asteroid isn't the size of a mountain, the answer is clearly water. So, let's all vote that if an asteroid is going to hit Earth, that it smacks into the deep ocean. But, we're not done. Does an asteroid have to hit the Earth? Can we just Bruce Willis it the [NOISE] out of here?

Lindley Johnson: You only have to change the speed of an asteroid, just a fraction, uh, or a percentage, uh, of its overall speed. Something like, uh, couple of kilometers a- a second is enough that, uh, if you do that several years in advance, it will not arrive at the same point as the Earth focus taking a spacecraft. [NOISE] If it's a, uh, smaller asteroid 100 meters or so in size, that is enough force to change its velocity by a not necessarily amount [inaudible 00:04:01] .

Patrick Jones: That doesn't save us from potentially earth ending asteroids, but that's a pretty sunny outlook on city ending asteroids as long as we have enough time. So, if you're at a restaurant and you see Lindley Johnson looking for a phone charger, give him yours. He may be getting an important phone call about asteroids killing us [MUSIC] .