Some 66 million years ago, a giant space object of some kind slammed into Earth right around the Yucatan peninsula. The resultant explosion sent debris high into the atmosphere; the dust resettled to earth newly enriched with the elements iridium and osmium--elements that are much more abundant in space than on Earth--and formed a thin layer in the rock strata now called the K-Pg boundary. A side effect of this violent impact was the extinction of most of the megafauna--dinosaurs, etc--living during that time. The impact site itself was discovered in 1978 by a geologist working for an oil company, but it wasn't until 1990 that the now-named Chicxulub crater was associated with the proposed impact that caused the mass extinctions. Since 1990, scientists have debated the nature of the rock that hit Earth--asteroid or comet? The scientists know generally how big the explosion would have had to be in order to create the fallout found in drill samples. Based on the size of the explosion and the amount of iridium and osmium deposited at the K-Pg boundary, the most common theory is that the impactor was carbonaceous asteroid about 13 kilometers across. But scientists from Darmouth College argue that the real culprit was a comet.
Presenting their findings at the 44th Lunar and Planetary Science Conference in Texas this week, Jason Moore explained two separate findings that lead to the team's conclusions. First, Moore and colleagues re-evaluated the iridium and osmium deposits at the K-Pa boundary. New data on those deposits indicate that the overall amount of space-derived iridium in the layer is lower than previously measured. As such, Moore and his colleagues concluded that the bolide -- the impactor -- was not 13 kilometers wide, because an asteroid that size would have left more iridium in the K-Pa boundary than what has been found. This by itself presents a problem, though: most asteroids are traveling too slowly for a smaller rock to generate the 3x10^23 J-giant boom that created Chicxulub crater. Comets, on the other hand, travel a lot faster than asteroids. A comet of 7 kilometers across traveling at typical comet velocities could release enough energy upon impact to create the crater and extinction event.
When Moore and colleagues looked at the catalogues of the currently known populations of asteroids and comets in the solar system, they found that some 99.99% of all impactor candidates with masses and velocities in the right ranges are comets. Obviously, this is only one study (or, well, two studies that lead to one conclusion), and Moore et al. are not the first scientists to suggest that T. rex was pwnd by a comet. But it's a pretty cool study and it certainly provides more fuel for those who are freaked out about the future of civilization: There are only about 2 million asteroids over one kilometer wide in the solar system; scientists estimate that there are up to a trillion comets out there. Given that the average comet is about the same size as the one that Moore et al. suggested hit Earth 66 million years ago, then maybe the worrywarts are on to something...
"Walter Alvarez and his father Luis W. Alvarez are most widely known for their discovery (with Frank Asaro and Helen Michel) that a clay layer occurring right at the Cretaceous-Tertiary (K-T) boundary was highly enriched in the element iridium." -wikipedia
I hate when writers don't give credit to the scientists who worked so hard to prove their theory and bring about a scientific paradigm shift - as was done by the Alvarezes.
O.K., So how do you deflect a comet?
@African Rover. By firing monkeys at it, thousands of them. No seriously, there are a few ways it can be done, but like the evolution of weapons and gunpowder, they need exploring in design and method and actual testing too, it's no good waiting for the one that could potentially cause the extinction of mankind.
Yes it probably did, perhaps it won the lottery and hit the super volcano jackpot triggering a giant fart..
A really fast bullet type comet with the jackpot could have been sufficient to trigger the fart...
Comet C2013/A1 freaks me out. Not because it's going to hit Earth but that it very well could hit Mars on October 19th, 2014. It's orbit has been calculated and recalculated numerous times in the last month and it's gone from a near miss of 67,000 miles to 33,000 miles and back to 73,000 miles currently. But that's before we know what is going to happen with it's mass when it swings around the sun and gases change it's orbit slightly as does the change in mass. So we won't know if will impact for another year or so and then it will be too late to do anything about it if it's going to hit Mars.
Why worry? Because it's 30 miles wide and traveling at 128,000 mph at impact which is 1800 times more energetic than the dino killer here. That's right. 1800 more times energetic.
Energetic enough to blast billions of tons of rocks into space and some obviously will impact Earth. Some might be big too. Much bigger than the Russian Comet recently.
So that's a worry as there is probably nothing we can do about it. There just won't be enough time with the alignment of the planets at the time.
It is quite possible that perhaps, where the Bermuda triangle is was once a super volcano, the Yukatan peninsula was nearer the then hotspot, like those of yellow stone these are strong points of magnetism. Someone said Iridium? If like todays rainforest that specific area was once dense woodland in comparison to other parts of the planet + the methane release that would almost certainly be sufficient to kill a lot -of everything. Isn't one of the explanations for the Bermuda something to do with Methane?
We see the cause of the dinosaur’s extinction, and Neanderthals even today by Migratory diseases. The migratory birds filled the gaps of birds killed by the meteor. They could travel farther to find food to survive the harsh new conditions. This connected species of birds from all continents that showered dinosaurs with flu and other viruses. Killing off small dinosaurs in holes in the ground, and dinosaurs on the oceans as well as the big ones in our museums. This also prevented them from ever coming back too.
We see it in Neanderthal when the boat was invented, the evidence of shells being traded from one human community to another. Shells from distant locations were not only traded with each other, but disease, and genetic immunity was too. However, the Neanderthal did not get that pace of genetic exchange and died out.
It is also seen in written times of the Black Death as it followed trading routes, or the American Indians sent to demographic oblivion.
In time this will be seen as a more conservative argument and may even be proven by finding DNA of disease in the teeth of the late period Neanderthals.
Asteroids and even comets are not selective enough. Extinction is a process an eco-biological process.
a little off topic, but did large (non-mammal) sea life die off because of the comet/asteroid also?
What never got mentioned was that at the K-Pg boundary dinosaurs were pretty well gone--T rex, Triceratops--and a few others--but nothing like what once was--so that still leaves the question--"What killed the dinosaurs?"