Scientists have spent decades debating whether asteroids and comets hit the Earth at regular intervals. At the same time, a few studies have found evidence that the large extinction events on Earth such as the one that wiped out the dinosaurs 66 million years ago repeat themselves every 26 million to 30 million years. Given that theres good evidence that an asteroid triggered the dinosaur extinction, it makes sense to ask whether showers of asteroids could be to blame for regular extinction events.
The question is extremely important if we could prove that this is the case, then we might be able to predict and even prevent asteroids causing mass extinctions in the future. We have tried to find out the answer.
Today, there are approximately 190 impact craters from asteroids and comets on Earth. They range in size from only a few meters to more than 100km across. And they formed anywhere between a few years ago and more than two billion years ago. Only a few, like the famous Meteor crater in Arizona, are visible to the untrained eye, but scientists have learned to recognize impact craters even if they are covered by lakes, the ocean or thick layers of sediment.
But have these craters formed as a result of regular asteroid collisions? And if so, why? There have been many suggestions, but most prominently, some scientists have suggested that the sun has a companion star (called Nemesis) on a very wide orbit, which approaches the solar system every 26m to 30m years and thereby triggers showers of comets.
Nemesis would be a red/brown dwarf star a faint type of star orbiting the sun at a distance of about 1.5 light years. This is not an impossible idea, since the majority of stars actually belong to systems with more than one star. However, despite searching for it for decades, astronomers have failed to observe it, and think they can now exclude its existence.
Yet, the idea of periodic impacts persists. There are other suggestions. One idea is based on the observation that the sun moves up and down slightly as it orbits the galaxy, crossing the galactic disk every 30m years or so. Some have suggested that this could somehow trigger comet showers.
But is there any evidence that asteroid impacts occur at regular intervals? Most research so far has failed to show this. But that doesnt mean it isnt the case its tricky getting the statistics right. There are a lot of variables involved: craters disappear as they age, and some are never found in the first place as they are on the ocean floor. Rocks from some periods are easier to find than from others. And determining the ages of the craters is difficult.
A recent study claimed to have found evidence of periodicity. However, the crater age data it used included many craters with poorly known, or even incorrect and outdated ages. The methods used to determine age based on radioactive decay or looking at microscopic fossils with known ages are continuously improved by scientists. Therefore, today, the age of an impact event can be improved significantly from an initial analysis made, say, ten or 20 years ago.
Another problem involves impacts that have near identical ages with exactly the same uncertainty in age: known as clustered ages. The age of an impact crater may be, for example, 65.5 0.5m years while another is be 66.1 0.5m years. In this case, both craters might have the same true age of 65.8m years. Such craters have in some instances been produced by impacts of asteroids accompanied by small moons, or by asteroids that broke up in the Earths atmosphere.
The double impact craters they produce can make it look like they hit a time when there were lots of asteroid impacts, when actually the craters were formed in the same event. In some cases, clustered impact craters are spaced too far apart to be explained as double impacts. So how could we explain them? The occasional collision of asteroids in the asteroid belt between Mars and Jupiter might trigger short-lived showers of asteroids impacting the Earth. Only a few of these showers are necessary to lead to the false impression of periodicity.
In contrast to previous studies, we restricted our statistical analysis to 22 impact craters with very well defined ages from the past 260 million years. In fact, these all have age uncertainties of less than 0.8%. We also accounted for impacts with clustered ages.
Our article, recently published in Monthly Notices of the Royal Astronomical Society, shows that, to the best of our current knowledge, asteroid impacts do not happen at regular intervals they seem to occur randomly.
Of course, we cant be sure that there isnt any periodicity. But the good news is that, as more impact craters are dated with robust ages, the statistical analysis we did can be repeated over and over again if there is such a pattern, it should become visible at some point.
That means that there is presently no way to predict when a large asteroid collision may once again threaten life on Earth. But then when it comes to facing the apocalypse, maybe not knowing is not so bad after all.
This article was originally published on The Conversation. Learn how to write for Quartz Ideas. We welcome your comments at ideas@qz.com.
Go here to read the rest:
The statistical likelihood that asteroids will destroy us all in 10 million years - Quartz
- Comet - Wikipedia, the free encyclopedia - November 21st, 2013 [November 21st, 2013]
- Comets - The Nine Planets - November 21st, 2013 [November 21st, 2013]
- Comets - Astronomy For Kids - KidsAstronomy.com - November 21st, 2013 [November 21st, 2013]
- Views of the Solar System: Comets - November 21st, 2013 [November 21st, 2013]
- Comets (extra footage) - Video - November 21st, 2013 [November 21st, 2013]
- Solar flare update. 6 comets! Nov 28th ISON perihelion! - Video - November 21st, 2013 [November 21st, 2013]
- Comets game 2end goal - Video - November 21st, 2013 [November 21st, 2013]
- Missouri Comets vs. Milwaukee Wave - Video - November 21st, 2013 [November 21st, 2013]
- Football: Comets Advance Past Momence - Video - November 21st, 2013 [November 21st, 2013]
- Caliber Cheer Comets Nov 9 2013 - Video - November 21st, 2013 [November 21st, 2013]
- Two Comets Are About to Fly By Mercury | NASA Space Science HD Video - Video - November 21st, 2013 [November 21st, 2013]
- Comets win on tiebreaker - December 20th, 2013 [December 20th, 2013]
- Comets fend off Wildcat attack - December 20th, 2013 [December 20th, 2013]
- Free throws bring Comets down - December 20th, 2013 [December 20th, 2013]
- Comets continue solid play on their home ice - December 20th, 2013 [December 20th, 2013]
- Comets Beat Heat 4-2 - December 20th, 2013 [December 20th, 2013]
- Comets in the Community - December 20th, 2013 [December 20th, 2013]
- Comets pick up third straight win over Heat - December 20th, 2013 [December 20th, 2013]
- Comets Welcome Back Old Rival - December 20th, 2013 [December 20th, 2013]
- Comets Cool Abbotsford 4-2 - December 20th, 2013 [December 20th, 2013]
- Comets – Facts and Information about Comets | Space.com - December 20th, 2013 [December 20th, 2013]
- Comets v Wave 121313 Highlights - Video - December 20th, 2013 [December 20th, 2013]
- Highlights - Comets vs. Monsters 12/15/13 - Video - December 20th, 2013 [December 20th, 2013]
- Weekly Space Hangout - Preventing Asteroids, More Comets, Worldview Balloon - Video - December 20th, 2013 [December 20th, 2013]
- Pens 1 - Comets 0 - Video - December 20th, 2013 [December 20th, 2013]
- Milwaukee Waves Cheap Shot Vs. Missouri Comets - 12.13.13 - Video - December 20th, 2013 [December 20th, 2013]
- Hometown Nights - Tarso Miller and the Wild Comets - Video - December 20th, 2013 [December 20th, 2013]
- Hangout with Comets Nova and Deathlyhall - Video - December 20th, 2013 [December 20th, 2013]
- Comets vs St. Louis Ambush - Video - December 20th, 2013 [December 20th, 2013]
- Shake, Rattle and Roll Bill Haley and His Comets - Sheet Music - Easy Alto Sax Version - Video - December 20th, 2013 [December 20th, 2013]
- Comets Shut Out Heat 3-0 - December 21st, 2013 [December 21st, 2013]
- Administration - December 21st, 2013 [December 21st, 2013]
- Bill Haley And His Comets ' R-O-C-K' 78 rpm - Video - December 21st, 2013 [December 21st, 2013]
- Bill Haley And His Comets ' The Saints Rock 'N Roll' 78 rpm - Video - December 21st, 2013 [December 21st, 2013]
- Nicklas Jensen's Shootout Winning Deke 12-15-13 - Video - December 21st, 2013 [December 21st, 2013]
- Missouri Comets Night with Miles - 12.13.13 - Video - December 21st, 2013 [December 21st, 2013]
- 12/13/13 Comets 5 vs. Senators 2 - Video - December 21st, 2013 [December 21st, 2013]
- Comets rock Bulldogs for first win - December 22nd, 2013 [December 22nd, 2013]
- Comets Deposit Life's Building Blocks Across the Cosmos!(Dr.Ruehl) - Video - December 22nd, 2013 [December 22nd, 2013]
- Comets beat AHL rival Abbotsford again with shutout - December 23rd, 2013 [December 23rd, 2013]
- Comets Win Streak Grows to Four Games - December 23rd, 2013 [December 23rd, 2013]
- Comets Corner: On the Mask - December 23rd, 2013 [December 23rd, 2013]
- 'Comets of the Centuries': 500 Years of the Greatest Comets Ever Seen - December 23rd, 2013 [December 23rd, 2013]
- Hackensack High School (NJ) Football Home - MaxPreps.com - December 23rd, 2013 [December 23rd, 2013]
- Little Comets - Isles (Music Video) - Video - December 23rd, 2013 [December 23rd, 2013]
- Comets Have Two Players on MISL Team of Week - December 25th, 2013 [December 25th, 2013]
- ONE FOR THE RECORD DECEMBER 20 2013 21 FUKUSHIMA COMETS EARTHQUAKES NMR GZ PAUL AND BP - Video - December 25th, 2013 [December 25th, 2013]
- Comets in the Community: Christmas at St. Luke's - December 26th, 2013 [December 26th, 2013]
- Best comets of last 500 years - December 26th, 2013 [December 26th, 2013]
- STRANGE EVENTS In 2013 Earthquakes, Mass Animal Deaths, Extreme Weather, OORT Cloud Comets - Video - December 26th, 2013 [December 26th, 2013]
- Utica Comets " 'Twas the Night" - Video - December 26th, 2013 [December 26th, 2013]
- Missouri Comets vs. Rochester Lancers - Video - December 26th, 2013 [December 26th, 2013]
- Chasing Comets: In search of secrets about our origins - Video - December 26th, 2013 [December 26th, 2013]
- DREAM X2 COMETS/STARS FLYING OVERHEAD, MASSIVE SONIC BOOMS EARTH HIT POSSIBLY. - Video - December 26th, 2013 [December 26th, 2013]
- What are comets? - Video - December 26th, 2013 [December 26th, 2013]
- Game Preview: Syracuse Silver Knights at Missouri Comets and St. Louis Ambush - December 27th, 2013 [December 27th, 2013]
- Clark's performance boosts Clayton over Moss Point - December 27th, 2013 [December 27th, 2013]
- Gameday: Comets vs. Binghamton - December 27th, 2013 [December 27th, 2013]
- Comets Battle for First Place - December 27th, 2013 [December 27th, 2013]
- Gameday: Comets vs. Hamilton - December 28th, 2013 [December 28th, 2013]
- Comets fall to Senators - December 28th, 2013 [December 28th, 2013]
- Comets end winning streak - December 28th, 2013 [December 28th, 2013]
- Comets vs Syracuse Silver Knights - Video - December 28th, 2013 [December 28th, 2013]
- Winning Comets Soccer - Video - December 28th, 2013 [December 28th, 2013]
- Comets Lose in Final Minutes - December 29th, 2013 [December 29th, 2013]
- CometsTV: 12-27-13 Utica Comets vs. Binghamton Senators Highlights - Video - December 29th, 2013 [December 29th, 2013]
- Comets knock off Aquin for second time this season - December 31st, 2013 [December 31st, 2013]
- Comets fall after late rally - December 31st, 2013 [December 31st, 2013]
- CometsTV: 12-28-13 Utica Comets vs. Hamilton Bulldogs Highlights - Video - December 31st, 2013 [December 31st, 2013]
- Comets Corner: Kellan Lain - January 1st, 2014 [January 1st, 2014]
- Comets Welcome New Year - January 1st, 2014 [January 1st, 2014]
- Comets Media Game 2013 - Video - January 1st, 2014 [January 1st, 2014]
- 1957 AMI H200 playing Bill Haley and his Comets Rock Around The Clock. - Video - January 1st, 2014 [January 1st, 2014]
- 7 Amazing Christmas Kinder Surprise Eggs SMURFS cars, comets Unwrapping Review Chocolate Easter Toys - Video - January 1st, 2014 [January 1st, 2014]
- Shootout - Dogs @ Comets - 12/2813 - END - Video - January 1st, 2014 [January 1st, 2014]
- Shootout - Dogs @ Comets - 12/2813 - Video - January 1st, 2014 [January 1st, 2014]
- Catonsville girls basketball shows promise for another strong season - January 2nd, 2014 [January 2nd, 2014]
- Gameday: Comets vs. Lake Erie - January 2nd, 2014 [January 2nd, 2014]
- Comets Kick off New Year with Exciting Win - January 2nd, 2014 [January 2nd, 2014]
- Comets Remain Hot at Home with 3-2 Decision over Lake Erie - January 2nd, 2014 [January 2nd, 2014]