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Peerie Maa
03-23-2017, 06:49 AM
The crater made by the asteroid that killed off the dinosaurs is revealing clues to the origins of life on Earth.
Scientists have drilled into the 200km-wide Chicxulub crater now buried under the Gulf of Mexico.
They say its rocks show evidence of having been home to a large "hydrothermal system", where hot fluids flowed through cracks and fissures.
Similar systems, generated by impacts on the early Earth, could have helped kickstart the first lifeforms.
The hydrothermal system at Chicxulub may have been active for two million years or more, the scientists say.
Dr David Kring, from the Lunar and Planetary Institute in Houston, is one of the researchers who discovered and reported the crater's location.
"The impact generated a very large subsurface hydrothermal system," he told BBC News.
"That's exciting because we are using Chicxulub as a proxy for other, large impact events very early in Earth's history when we think these kinds of systems might have been crucibles for pre-biotic chemistry and the habitats for the evolution of the earliest life on our planet."


From http://www.bbc.co.uk/news/science-environment-39361007

At a briefing here at the Lunar and Planetary Science Conference (LPSC) in Texas, Prof Sonia Tikoo, who studies palaeomagnetism, said the cores had given scientists a lower bound for how long this hydrothermal system lasted.
The direction of Earth's magnetic field flips every few hundred thousand years. When the Chicxulub extinction event occurred it had the reverse polarity to today.
"One thing that was very intriguing was that there were several samples in the breccia melt sequence that had what's now the normal polarity - the same direction as what we have today," the Rutgers University, New Jersey, scientist said.
"Three hundred thousand years [after the impact] the Earth's magnetic field crosses over and assumes the 'normal' polarity - it has the opposite direction [to that which existed at the time of the imapct]. These rocks must have acquired their magnetisation during one of these normal polarity times that came later. Since the first of these happened 300,000 years later - that provides a lower bound constraint for the hydrothermal system, telling us how long hot fluids were going through the crater."
The whole system may at first have been too hot for even the most heat-tolerant microorganisms. However, as time went on, the peak ring would have cooled down, allowing tiny lifeforms to exploit the chemicals dissolved in the hot fluids for fuel.

Jim Mahan
03-23-2017, 07:55 AM
The polarity flipping can be seen in other geology, too. The ocean bottom on either side of the mid-ocean ridges shows the same thing. When the basaltic magna wells up at the ridge, pushing the two oceanic plates away from each other, the magnetic minerals align to the pole as the hot stuff cools and hardens, and the record of the magnetic alignings extending away from the ridge in both directions, alternates directions, flipping one-eighty, on the same time scale as above. If you could see it from the air it would appear as stripes parallel to the ridge.

If I get this correctly, the impact energy drives molten material into fractures expanding from the impact. Sounds sorta like an upside down volcano. That impact cracked a shell of solid basaltic ocean plate twenty miles thick. Thinking about the impact reminds me of the description of a bunker-piercing bomb, the energy of which is so intense it melts the material in the leading edge of the projectile's penetration in the millesecond before it detonates, which is how it gets through meters of reinforced concrete.

Peerie Maa
03-23-2017, 08:55 AM
If I get this correctly, the impact energy drives molten material into fractures expanding from the impact. Sounds sorta like an upside down volcano. That impact cracked a shell of solid basaltic ocean plate twenty miles thick. Thinking about the impact reminds me of the description of a bunker-piercing bomb, the energy of which is so intense it melts the material in the leading edge of the projectile's penetration in the millesecond before it detonates, which is how it gets through meters of reinforced concrete.

I suspect that the length of time the heat persists after the impact that there must be another source of heat. Possibly that the fissures opened by the impact right through the solid crust allowed the underlying magma to well up.