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Antarctic Craters Reveal Asteroid Strike

Posted by michael on from the rock-of-ages dept.

dhuff writes "Scientists using satellites have mapped huge craters under the Antarctic ice sheet caused by an asteroid as big as the one believed to have wiped out the dinosaurs 65m years ago."

19 of 234 comments (clear)

  1. Curious by ValiantSoul · · Score: 3, Interesting

    "One thing that did happen at exactly the same time was the reversing of the Earth's magnetic field." Darn so the water hasn't always drained the same direction? Does the magnetic field being reversed actually affect anything important?

    1. Re:Curious by oquigley · · Score: 5, Interesting

      The Earths Magnetic field keeps all kind of nasty radiation from hitting the surface.
      So it's always been a bit of a puzzle why there's no correllation between magnetic reversals (where the magnetic field weakens, fades, then reappears with swapped poles) and mass extinctions.
      After all, one would think that floods of radiation washing across the Earths surface would be unhealthy, no?

      But now it appears that when the magnetic field weakens, the solar wind induces a magnetic field in the ionosphere that's pretty much as effective at stopping high energy particles and cosmic rays as is the original field.

      Here's an article about it in New Scientist from a few months ago.
      New Scientist


  2. What are the odds? by erick99 · · Score: 2, Interesting
    I doubt that we could get away with this again:

    Prof Van der Hoeven said: "The extraordinary thing about this meteor strike is that it appeared to do so little damage. Unlike the dinosaur strike there is no telltale layer of dust that demonstrates the history of the event. It may have damaged things and wiped out species but there is no sign of it."

    Cheers,

    Erick

    --
    http://www.busyweather.com/
  3. Well now... by reezle · · Score: 4, Interesting

    I'd like to think we could do something about this problem, but I wonder if any technology we have could alter the course of an asteroid large enough to be a problem. Do we even have a prototype of something like a fusion rocket that could potentialy move the hundreds (thousands/millions) of tons of mass that these big rocks have?

    Have the nuk-lear worryworts made sure that we haven't even researched the possibilities? Best I've ever seen is the occasional schematic of an orion-type starship from decades ago. Screw Ion-Drives. Let's give some money to the big engines...

    1. Re:Well now... by dyfet · · Score: 4, Interesting

      I believe this very question was seriously studied back in the late 60's and early 70's in project Icarus. I think their conclusion at the time was that the best option was to load up a Saturn V with as many nukes as possible, aim carefully, and just hope for the best...

    2. Re:Well now... by e9th · · Score: 2, Interesting

      I've wondered about that. If you're going to explode a bunch of nukes right next to each other, how precisely must the explosions be synchronized? If one bomb goes off a millisecond early, won't it just ruin all the rest?

    3. Re:Well now... by lommer · · Score: 4, Interesting

      Yes, they do have to be timed perfectly. However, in the nuclear explosion world, perfect timing is what it's all about. One of the primary difficulties in constructing a nuclear warhead is timing all the conventional explosives that compound the critical mass of plutonium (or uranium) to produce the nuclear explosion. The science is so precise that they have to account for the time delay it takes the electricity to travel down wires that are only meters long, let alone the rates at which the shockwave propagates through the conventional explosive - all of which must be correct to within thousandths of a second. Add another layer of complexity for hydrogen bombs.

      So yes, they would have to time them perfectly, but that wouldn't be too difficult as it's a problem they've already figure out how to solve when constructing the devices in the first place.

    4. Re:Well now... by jadavis · · Score: 4, Interesting

      Yup. Even an individual nuke requires very precise timing so that it implodes evenly. If not, it will start to break apart and never achieve the pressure required to detonate. Even when a nuke does detonate it only gets a moderate yield (I think "fat man" was about 15% yield) because it breaks itself apart so fast.

      --
      Social scientists are inspired by theories; scientists are humbled by facts.
  4. No layer of dust? by rde · · Score: 4, Interesting

    Quoth the good professor:
    The extraordinary thing about this meteor strike is that it appeared to do so little damage. Unlike the dinosaur strike there is no telltale layer of dust that demonstrates the history of the event.

    It ploughs through millions of tonnes of ice and snow, then leaves no layer of dust... d'you think it might have, I dunno, melted or something?

    More information at The Scotsman, btw.

  5. impact reversing magnetic field? doubtful by Lobachevsky · · Score: 5, Interesting

    I don't dispute Hans' rigor in studying the issue, but how can the correlation of the impact and the magnetic field reversing lead to the conclusion the impact caused the reversal?

    And why even compare this 780K yr old impact to what might've done the dinosaurs in 65m yrs ago? It just would confuse people with poor reading skills (*cough* slashdot readers) and lead them to associate this 780K yr old impact with the extinction of the dinasaurs.

    Also, the article attemps to explain why the 65m yr old impact would've caused climactic change whereas the 780k yr old impact would not -- I didn't quite understand their argument of why the older impact caused dust clouds leading to extinction while the newer impact did not -- was it because of the composition of ice vs rock?

  6. about 65 mil years ago by quewhatque · · Score: 1, Interesting

    The dinosaurs seemed to have disappeared about 65 mil ago, no doubt about that. It is believed that an asteroid hit the yucatan (or however you spell it) peninsula about 65 million years ago. They have found several rocks dating back to 65 million years ago using isotope dating in places like florida and others places in the carribean. It is also believed that the world as we know it goes through a mass extinction every 26 million years on average, and that one has happened since the dinosaurs became extinct. So maybe this crater in antartica is just another one, but not the one for the dinosaurs. All this information is what i can remember from a book i read a couple months ago, "Hyperspace" by Michio Kaku

  7. Magnetic Reversal?? by sciop101 · · Score: 1, Interesting
    I wasn't aware that one could affect the pole reversal in any substantial way, even with someone as large as a meteoric impact.

    Impact affects the strength of magnets! Impact on geologic magnet is awesome. Was the reversal instantaneous? If not, how long and what happened to the planet during that time?

    --
    The only thing new in this world is the history that you don't know.[Harry Truman]
  8. Re:Sounds suspicious by Vreejack · · Score: 2, Interesting

    A gravity anomoly is anything other than what you would expect from a continuous, uncratered surface. It would not be something you could measure without very precise instruments.

    The ice would definitely prevent large tsunami. I have seen even the lightest coating of snow tame the rough north atlantic.

    As far as the meteor causing magnetic pole reversal, I don't see how. The earth's magnetic fields originate in the spinning iron core. Perhaps disturbing the spin slightly might help trigger a field reversal but that would be more likely to occur after an oblique equatorial collision than after a polar strike. The melting of the antarctic ice sheet would not even affect the planet's rotational inertia the way it would if Greenland's suddenly melted. But all of these effects are miniscule. The field reversal timing is almost certainly a coincidence.

    --
    "Will future ages believe that such stupid bigotry ever existed!" -- Ivanhoe
  9. Human evolution by cruachan · · Score: 2, Interesting

    Does this match up with the proposed theory that humans went through a short period of being reduced to a very few individuals - the so called 'mitochondrial eve' hypothesis?

  10. Re:Interception by Kamerynn · · Score: 2, Interesting

    Statistically speaking, death rate by asteroids is non negligible and much higher than by terrorist attacks. The earth gets hit by an asteroid big enough to cause a global catastrophy once every 500,000 years, so the odds of that happening in any given year are 1 in 500,000. Assuming such an impact kills 25% of the Earth's population, that makes the risk from an impact 1 in 4. The odds of any individual dying from an asteroid strike in any given year are 1 in 500,000 multiplied by 4, or 1 in 2 million. But since we live on average 75 years, these odds must be multiplied by 75 to obtain the risk of premature death in any given year. Hence the lifetime odds of dying from an asteroid strike is 75 in 2 million, or 1 in 25,000. More than plane accidents.

  11. Homo Erectus was there by oquigley · · Score: 4, Interesting

    Wow! Only 780 thousand years ago?
    At that point our hominid ancestors were strolling around southern Africa. By then we had stone tools and the occasional use of fire. That's really recent in a hominid lineage that goes back, what 6 million years? They lived through a 3-7 kilometer asteroid impact! Can you imagine?
    Good thing it didn't land a few thousand miles to the north...

    1. Re:Homo Erectus was there by oquigley · · Score: 2, Interesting

      Yeah, hominid fossils are pretty thin on the ground.
      Partly that's because Africa is a difficult and dangerous place to conduct archeological digs. We have a much better sense for the history of the European Neanderthals, for example just because Europe is an easy place to work.

      Homo Erectus is fairly well represented, but as you get deeper in time, the fossil record gets spottier. We've only found a handful of Australopithecus, for example.
      But we know that they were there. At Laetoli in Tanzania, there's that famous set of footprints captured in volcanic ash:
      Laetoli Footprints
      And that was about 3.6 Million years ago. Pretty deep history.

      But I'm curious what you're getting at? Do you support the multi-regional hypothesis? Humans evolved independently from scattered Homo Erectus populations in locations other than Africa?

      Or that we evolved in East Africa, not South Africa (which is, I understand a point of contention)

      Or are you simply arguing for divine creation in the relatively recent past?

  12. Re:Maybe....but I'm not buying it by mshurpik · · Score: 2, Interesting
    From the article:

    The Antarctica strike occurred during an ice age, so even tidal waves would have been weakened to mere ripples by the calming effect of icebergs on the ocean.

    My understanding is that tidal waves are seismic events that travel along the seafloor. They raise the water level only a few feet, and are essentially invisible until they hit shore and start climbing. Since icebergs float, it's not clear how they would suppress a shockwave happening below and around them.

    Prof Van der Hoeven said: "The extraordinary thing about this meteor strike is that it appeared to do so little damage. Unlike the dinosaur strike there is no telltale layer of dust that demonstrates the history of the event.

    Yeah see, this makes more sense. It hit antarctica. Plonk. Except for the magnetic field....
  13. Re:You really are missing something...... by davidsyes · · Score: 3, Interesting

    Or, was it just "a close shave"?

    Don't we pass through an asteroid belt about twice a year? I seem to remember something on Discovery Channel or on an astronomy site that named the belts. I'll revisit the sites, but in the meantime... Aren't there all sorts of odds (in favor of nature/against human populations) that could see us or the Earth being hit once in a while more frequently than we've recorded or claimed? If not, then...

    What are the chances (hi or lo) that we pass through some metallic or iced or similar matter that envelops or fries all the satellites in orbits? I'll concede that it MIGHT NOT happen in our lifetimes, but if it were GOING to happen by fluke or freak of nature, what kind of circumstances would be needed but not rip up large swaths of ground, and not rip away the breathable atmosphere?

    And, if we suffered such a "scrape", what would be needed to make orbital space unusable for say, 5 years, but, again, without the solar event tearing up the terra firma? Would passing through a sort of cometary corona or ice tail for about 6 or 7 days be enough? (And, let's assume or posit that no more than 20% of the the clean water and no more than 30% of the food production are affected.)

    Would anyone speculate on the confluence of events needed?

    David Syes

    --
    Previously: "Linux... Toward the Sunrise..." Now: "Linux... Toward the-- No, now, part of Every Sunrise"