Science is Cool....

[Fish]

This is a repository for all cool scientific discussion and fascination. Scientific facts, theories, and overall cool scientific stuff that you'd like to share with others. Stuff that makes you smile and wonder at the amazing shit going on around us, that most people don't notice.

Post pictures, vidoes, stories, or links. Ask questions. Share science.

Why should I care?:

['Hamas' Jenkins]

Protein Kinase C is an important molecule for signal transduction. An investigational compound would need to selectively target it without it affecting the numerous other cellular processes. That's likely why this is limited to solid, superficial tumors such as the one the woman with melanoma had. I wonder if it is too broad for liquid tumors (leukemias), and that's not to speak of the issues with scaling up and monitoring side effects in a patient population.

It's an interesting theory, but I'd still put much more of my anticancer money on monoclonal antibodies.

[Nickhead]

https://simplecapacity.com/2016/04/i...cient-secrets/

For the first time in history, a combination of drought and overconsumption of water have pushed the river in India, the Shamala river in Karnataka to its limits, revealing under its bank secrets that have shocked the archaeological community. The receding river has revealed the presence of thousands of Shiva Lingas which were carved in the distant past along the river bed.

this poses more questions too. like, why was this river bed so shallow so long ago, which allowed these relics to be placed.

way more in link

[GloryDayz]

Originally Posted by Nickhead

https://simplecapacity.com/2016/04/i...cient-secrets/





this poses more questions too. like, why was this river bed so shallow so long ago, which allowed these relics to be placed.

way more in link

The water was probably sucked out of the river and to the polar caps to bolster them because they'e thinning.

[Baby Lee]

Lots of great stuff in here. Not much of it all that new, but nice to get all the inside info in one place

[displacedinMN]

Inside this small room — lined on all six sides with deep, fiberglass spikes — there is no background noise. No sounds from the street, the vents, the outside world. Only silence.

But in that silence, many visitors find their own bodies become quite noisy.

Sitting in this anechoic chamber, they suddenly hear their blood flow, their inner ears buzz, their artificial heart valves click.

“Oh my goodness,” says Rita Dibble, after just four minutes in the chamber alone, “I could actually hear every vertebra.

“This is the coolest thing I’ve ever seen.”

“Or heard,” says RickAllen Meek, a lab technician who, on this afternoon, was playing tour guide.

“Or not heard,” Dibble replies, grinning.

This room, within Orfield Laboratories Inc. in south Minneapolis, is so quiet that it measures negative 13 decibels. So quiet that Guinness World Records called it “the quietest place on Earth.” So quiet that film crews, acoustics nerds and curious kids journey here just to sit inside it.

“This is a room within a room within a room,” says Steve Orfield, 69, the lab’s longtime owner, “which is why it’s so quiet.”

The anechoic chamber — one of several testing spaces within the building — feels small: 8 by 10 by 12 feet. But surrounding that space, on all six sides, are fiberglass wedges, 3 feet deep. The chamber floats on vibration-damping springs. The outermost room is made of 12-inch-thick solid concrete.

For nearly five decades, Orfield has helped companies from 3M to Medtronic understand how people experience the look and sound of their products. Having a quiet room means that Orfield and his team can test quiet things. Heart valves, CPAP machines, cellphones.

But these days, Orfield is more interested in talking about how the room might help people with post-traumatic stress disorder, autism and other hypersensitivities. Those who have sat in the chamber’s silence described how it “reset their brains,” he said. “We think there’s great potential for therapeutic uses.”

Soon after installing the anechoic chamber in the addition to this building — the former home of Sound 80 studio, where Bob Dylan famously rerecorded five songs off “Blood on the Tracks” — Orfield set up $20,000 microphones that could measure up to minus 2.5 decibels. “It floored the mics,” Orfield says.

Guinness World Records recognized the chamber as the world’s quietest place twice — at negative 9.3 decibels in 2005 and minus 13 decibels in 2013. Some context: A human infant’s hearing limit is considered to be about 0 decibels.

But in 2015, Orfield Labs got bad news. Guinness was now bestowing its “quietest” title on an anechoic chamber at Microsoft’s headquarters in Washington. Their reading hit an “unimaginably quiet -20.35 dBA,” according to Guinness’ site (dBA is a decibel measurement).

Orfield disputes the claim. His lab was held to higher standards, he pointed out, including a requirement that the reading be maintained for an hour. His anechoic chamber, too, got instantaneous readings in the negative 20s, he says.

“We’re hoping to make a claim” to regain the title, Orfield says.

But Microsoft’s title hasn’t affected interest in this Minneapolis spot. The laboratories used to do free tours, asking visitors to donate $20 to a food shelf. But the visits were taking the lab’s handful of employees away from their work. Today, the lab charges $125 a person, with a $250 minimum.

“We charge them and they come,” Orfield says. “They come from all over the world.”

Dibble, who recently moved to St. Paul, had spotted the anechoic chamber in Atlas Obscura and was intrigued. “I thought, well, everybody’s going to the Capitol and to the cathedral,” she says. “I’m going to the anechoic chamber.”

She has long sung in choirs, appreciating the grand acoustics of a domed ceiling. So Dibble was fascinated by the idea of the opposite: a room that would allow no echo. “It’s like an antidote,” she says after her hourlong tour. “Even if you love something, you occasionally need a break from it.” 

[Otter]

This is insane...

[GayFrogs]

Q...but should've been in this thread in the first place

[Fish]

NASA announcing a new discovery today. Live conference at noon. Watch here: https://www.nasa.gov/live

NASA has announced plans to livestream a major media briefing on Thursday, December 14. The agency says the event will focus on the latest Kepler discovery, which was facilitated by machine learning techniques from Google.

NEW FINDINGS
NASA has announced a media teleconference set to take place at 1 p.m. EST on Thursday, December 14. The agency says the purpose of the event, which will stream live via the NASA website, is to reveal a new Kepler discovery. According to the announcement, the researchers used machine learning techniques developed by Google to draw new knowledge from data collected by the craft.

Kepler was launched in 2009, and it has already profoundly affected our understanding of space. When it set out on its voyage, we didn’t know how common planets were outside of our solar system. Now, thanks to the insights provided by Kepler, astronomers believe there might be one or more planets orbiting every star.



Due to issues with Kepler’s reaction wheels, its initial planet-hunting mission was brought to an end in 2013. Since then, it’s been on the hunt for exoplanets using its remaining capabilities.

Kepler has been used to observe the seven planets that comprise the TRAPPIST-1 system. NASA announced the discovery of these worlds in February 2017, and since then, the agency has been using Kepler, Spitzer, and Hubble to find out more about these bodies and their potential to support life.

NASA isn’t the only space agency that’s been consistently sharing major discoveries. In October, the European Southern Observatory (ESO) shared news of an “unprecedented” finding pertaining to gravitational waves. That announcement turned out to be the first time we were able to observe gravitational waves and light from the same event concurrently.

We don’t know what this latest Kepler discovery will be about, but the last time NASA announced a major news conference like the one scheduled for December 14, TRAPPIST-1 was the focus, so it’s reasonable to assume this week’s announcement will be something suitably exciting. Thankfully, the wait to find out for sure is a brief one.

https://futurism.com/nasa-hosting-co...net-discovery/

[Holladay]

Well?

[Fish]

Using robits!

Artificial Intelligence, NASA Data Used to Discover Eighth Planet Circling Distant Star

Our solar system now is tied for most number of planets around a single star, with the recent discovery of an eighth planet circling Kepler-90, a Sun-like star 2,545 light-years from Earth. The planet was discovered in data from NASA’s Kepler Space Telescope.

The newly-discovered Kepler-90i – a sizzling hot, rocky planet that orbits its star once every 14.4 days – was found using machine learning from Google. Machine learning is an approach to artificial intelligence in which computers “learn.” In this case, computers learned to identify planets by finding in Kepler data instances where the telescope recorded signals from planets beyond our solar system, known as exoplanets.



“Just as we expected, there are exciting discoveries lurking in our archived Kepler data, waiting for the right tool or technology to unearth them,” said Paul Hertz, director of NASA’s Astrophysics Division in Washington. “This finding shows that our data will be a treasure trove available to innovative researchers for years to come.”

The discovery came about after researchers Christopher Shallue and Andrew Vanderburg trained a computer to learn how to identify exoplanets in the light readings recorded by Kepler – the minuscule change in brightness captured when a planet passed in front of, or transited, a star. Inspired by the way neurons connect in the human brain, this artificial “neural network” sifted through Kepler data and found weak transit signals from a previously-missed eighth planet orbiting Kepler-90, in the constellation Draco.

While machine learning has previously been used in searches of the Kepler database, this research demonstrates that neural networks are a promising tool in finding some of the weakest signals of distant worlds.

Other planetary systems probably hold more promise for life than Kepler-90. About 30 percent larger than Earth, Kepler-90i is so close to its star that its average surface temperature is believed to exceed 800 degrees Fahrenheit, on par with Mercury. Its outermost planet, Kepler-90h, orbits at a similar distance to its star as Earth does to the Sun.

“The Kepler-90 star system is like a mini version of our solar system. You have small planets inside and big planets outside, but everything is scrunched in much closer,” said Vanderburg, a NASA Sagan Postdoctoral Fellow and astronomer at the University of Texas at Austin.

Shallue, a senior software engineer with Google’s research team Google AI, came up with the idea to apply a neural network to Kepler data. He became interested in exoplanet discovery after learning that astronomy, like other branches of science, is rapidly being inundated with data as the technology for data collection from space advances.

“In my spare time, I started googling for ‘finding exoplanets with large data sets’ and found out about the Kepler mission and the huge data set available,” said Shallue. "Machine learning really shines in situations where there is so much data that humans can't search it for themselves.”

Kepler’s four-year dataset consists of 35,000 possible planetary signals. Automated tests, and sometimes human eyes, are used to verify the most promising signals in the data. However, the weakest signals often are missed using these methods. Shallue and Vanderburg thought there could be more interesting exoplanet discoveries faintly lurking in the data.

First, they trained the neural network to identify transiting exoplanets using a set of 15,000 previously-vetted signals from the Kepler exoplanet catalogue. In the test set, the neural network correctly identified true planets and false positives 96 percent of the time. Then, with the neural network having "learned" to detect the pattern of a transiting exoplanet, the researchers directed their model to search for weaker signals in 670 star systems that already had multiple known planets. Their assumption was that multiple-planet systems would be the best places to look for more exoplanets.

“We got lots of false positives of planets, but also potentially more real planets,” said Vanderburg. “It’s like sifting through rocks to find jewels. If you have a finer sieve then you will catch more rocks but you might catch more jewels, as well.”

Kepler-90i wasn’t the only jewel this neural network sifted out. In the Kepler-80 system, they found a sixth planet. This one, the Earth-sized Kepler-80g, and four of its neighboring planets form what is called a resonant chain – where planets are locked by their mutual gravity in a rhythmic orbital dance. The result is an extremely stable system, similar to the seven planets in the TRAPPIST-1 system.

Their research paper reporting these findings has been accepted for publication in The Astronomical Journal. Shallue and Vanderburg plan to apply their neural network to Kepler’s full set of more than 150,000 stars.

Kepler has produced an unprecedented data set for exoplanet hunting. After gazing at one patch of space for four years, the spacecraft now is operating on an extended mission and switches its field of view every 80 days.

“These results demonstrate the enduring value of Kepler’s mission,” said Jessie Dotson, Kepler’s project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “New ways of looking at the data – such as this early-stage research to apply machine learning algorithms – promises to continue to yield significant advances in our understanding of planetary systems around other stars. I’m sure there are more firsts in the data waiting for people to find them.”

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate in Washington. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. This work was performed through the Carl Sagan Postdoctoral Fellowship Program executed by the NASA Exoplanet Science Institute.

[Fish]

Oumuamua

Solar System’s First Interstellar Visitor Dazzles Scientists

Astronomers recently scrambled to observe an intriguing asteroid that zipped through the solar system on a steep trajectory from interstellar space—the first confirmed object from another star.



Now, new data reveal the interstellar interloper to be a rocky, cigar-shaped object with a somewhat reddish hue. The asteroid, named ‘Oumuamua by its discoverers, is up to one-quarter mile (400 meters) long and highly-elongated—perhaps 10 times as long as it is wide. That aspect ratio is greater than that of any asteroid or comet observed in our solar system to date. While its elongated shape is quite surprising, and unlike asteroids seen in our solar system, it may provide new clues into how other solar systems formed.

The observations and analyses were funded in part by NASA and appear in the Nov. 20 issue of the journal Nature. They suggest this unusual object had been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our star system.

“For decades we’ve theorized that such interstellar objects are out there, and now – for the first time – we have direct evidence they exist,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “This history-making discovery is opening a new window to study formation of solar systems beyond our own.”

Immediately after its discovery, telescopes around the world, including ESO’s Very Large Telescope in Chile and other observatories around the world were called into action to measure the object’s orbit, brightness and color. Urgency for viewing from ground-based telescopes was vital to get the best data.

Combining the images from the FORS instrument on the ESO telescope using four different filters with those of other large telescopes, a team of astronomers led by Karen Meech of the Institute for Astronomy in Hawaii found that ‘Oumuamua varies in brightness by a factor of ten as it spins on its axis every 7.3 hours. No known asteroid or comet from our solar system varies so widely in brightness, with such a large ratio between length and width. The most elongated objects we have seen to date are no more than three times longer than they are wide.

“This unusually big variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape,” said Meech. We also found that it had a reddish color, similar to objects in the outer solar system, and confirmed that it is completely inert, without the faintest hint of dust around it.”

These properties suggest that ‘Oumuamua is dense, comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.

A few large ground-based telescopes continue to track the asteroid, though it’s rapidly fading as it recedes from our planet. Two of NASA’s space telescopes (Hubble and Spitzer) are tracking the object the week of Nov. 20. As of Nov. 20, ‘Oumuamua is travelling about 85,700 miles per hour (38.3 kilometers per second) relative to the Sun. Its location is approximately 124 million miles (200 million kilometers) from Earth -- the distance between Mars and Jupiter – though its outbound path is about 20 degrees above the plane of planets that orbit the Sun. The object passed Mars’s orbit around Nov. 1 and will pass Jupiter’s orbit in May of 2018. It will travel beyond Saturn’s orbit in January 2019; as it leaves our solar system, ‘Oumuamua will head for the constellation Pegasus.

Observations from large ground-based telescopes will continue until the object becomes too faint to be detected, sometime after mid-December. NASA’s Center for Near-Earth Object Studies (CNEOS) continues to take all available tracking measurements to refine the trajectory of 1I/2017 U1 as it exits our solar system.

This remarkable object was discovered Oct. 19 by the University of Hawaii’s Pan-STARRS1 telescope, funded by NASA’s Near-Earth Object Observations (NEOO) Program, which finds and tracks asteroids and comets in Earth’s neighborhood. NASA Planetary Defense Officer Lindley Johnson said, “We are fortunate that our sky survey telescope was looking in the right place at the right time to capture this historic moment. This serendipitous discovery is bonus science enabled by NASA’s efforts to find, track and characterize near-Earth objects that could potentially pose a threat to our planet.”

Preliminary orbital calculations suggest that the object came from the approximate direction of the bright star Vega, in the northern constellation of Lyra. However, it took so long for the interstellar object to make the journey – even at the speed of about 59,000 miles per hour (26.4 kilometers per second) -- that Vega was not near that position when the asteroid was there about 300,000 years ago.

While originally classified as a comet, observations from ESO and elsewhere revealed no signs of cometary activity after it slingshotted past the Sun on Sept. 9 at a blistering speed of 196,000 miles per hour (87.3 kilometers per second).

The object has since been reclassified as interstellar asteroid 1I/2017 U1 by the International Astronomical Union (IAU), which is responsible for granting official names to bodies in the solar system and beyond. In addition to the technical name, the Pan-STARRS team dubbed it ‘Oumuamua (pronounced oh MOO-uh MOO-uh), which is Hawaiian for “a messenger from afar arriving first.”

Astronomers estimate that an interstellar asteroid similar to ‘Oumuamua passes through the inner solar system about once per year, but they are faint and hard to spot and have been missed until now. It is only recently that survey telescopes, such as Pan-STARRS, are powerful enough to have a chance to discover them.

“What a fascinating discovery this is!” said Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory, Pasadena, California. “It’s a strange visitor from a faraway star system, shaped like nothing we’ve ever seen in our own solar system neighborhood.”

[Amnorix]

Once one understands how absurdly vast the universe is, then the question fo whether there are planets around other stars, and inevitably life of some sort on some of those other planets, becomes completely academic.

We estimate roughly 100 billion STARS in the Milky Way alone. Our sun is just one of them. Nobody knows how many galaxies there are, but ten trillion is about the best guess we have.

So 100 billion times ten trillion stars. And whatever innumerable number of planets around those. Unquestionably the odds of life on any given planet are infinitesimally low, but given the number of planets around that ridiculous number of stars....yeah.

[Rain Man]

400 meters long with a slender cigar shape is how I would envision an interstellar scout ship. Just saying.

[Dave Lane]

We await your wisdom space dildo!

[Fish]

This was a really interesting read...

HOW TO KILL A DINOSAUR IN 10 MINUTES

Spoiler!

Ten minutes difference, and Earth would still be Planet of the Dinosaurs

We have suspected for some decades that the dinosaurs1 became extinct as the result of a massive meteorite, an asteroid, hitting the Earth. We have known where the impact site was since 1990, if not before. But it is only last year that we successfully drilled into the impact site, and only now, for the first time, do we really understand why the impact was so fatal. And if the meteorite had arrived ten minutes earlier, or ten minutes later, it would still no doubt have inflicted devastation, but the dinosaurs would still be here and you wouldn't.

Too many suspects

66.1 million years ago, dinosaurs covered the Earth. 66 million years ago, there were none. And not only the dinosaurs, but the pterosaurs in the skies, the long necked plesiosaurs and even the ammonites in the oceans, and 75% of all complex animal life. No terrestrial vertebrate heavier than around 25 kg seem s to have survived. What happened?

There was no shortage of theories. Quite a lot was going on, geologically, at the time. There was massive volcanic activity in India, giving rise to what are known as the Deccan Traps, containing over a million cubic kilometres of basalt. Such major volcanic episodes have been connected with other mass extinctions. They are accompanied by the ejection into the stratosphere of sulphur dioxide, which in turn slowly reacts with atmospheric oxygen and water vapour, forming a haze of sulphuric acid far above the Earth's surface. This partly blocks out the Sun, affecting the plant growth on which almost2 all life on Earth depends. We saw such an effect on a much smaller scale with the 1991 eruption of Mt Pinatubo in the Philippines, which caused a two-year slowdown in global warming and reduced crop yields worldwide, far beyond the reach of the actual dust cloud. Continents were on the move, with the reopening of the North Atlantic, polar icecaps reappeared after prolonged absence and led to lowering of sea levels, affecting ocean productivity, and all these things may have added to ecological stress. But all this hardly seems enough for such a wide-reaching die-back, nor does it account for the suddenness of the process.

And so, we saw the emergence of the asteroid impact hypothesis. The Solar System still contains fragments of rocky material left over from its formation. This material is mainly concentrated in the asteroid belt, between Mars and Jupiter, but small fragments continually come our way. Most of these are tiny particles, which burn up in our atmosphere (meteors or shooting stars). Some are large enough to survive, falling to earth as meteorites, and their chemical composition tells us a great deal about the stuff from which Earth was originally formed. Very occasionally, the meteorite is large enough to dig out a crater, such as Meteor Crater in Arizona. During the early years of the Solar System, major impacts were frequent and dramatic, as we can see by looking at the Moon and at the other inner planets, but on a geologically active planet such as Earth the evidence will long since have eroded away. However, there are still plenty of small asteroids whose orbits intersect the Earth's. What if one of these happened to crash into the Earth, and trigger catastrophe?

The search for a smoking gun

But would such a collision have left any trace, still detectable 66 million years on? In a word, yes. Worldwide, there is a layer of mudstone separating the rocks of the Cretaceous period from those of its successor, the Palaeogene. Up to this K/Pg (Cretaceous-Palaeogen)3 boundary, you find dinosaurs, ammonites, and the other creatures I mentioned. Above it, none; but then, within a few million years, a dramatic proliferation of mammals as they evolved to fill the niches left vacant by this mass extinction. Yet there is no difference in the nature and chemical composition of the rocks directly above and below the boundary layer, showing that the boundary event was a single catastrophic occurrence, rather than part of a long-term trend. And embedded in the boundary mud are glassy spherules, like those formed when molten rock ejected by volcanoes cools in the upper atmosphere. There are also traces of soot, microdiamonds, and shocked quartz, a substance formed from normal quartz when subjected to enormous sudden forces.

A crucial question here is how long it took to form this layer, and the father and son team of Louis and Walter Alvarez thought they had an ingenious way of finding out (Louis, the father, was a Nobel Prize nuclear physicist; Walter, his son, a geologist studying the boundary layer where it lies exposed in Italy's Appenine mountains). They would test the layer for the element iridium. Iridium is rare in the solar system, as we can tell from analysis of meteorites, but it is even rarer in the Earth's crust. That is because iridium is very soluble in iron, so that when the Earth's iron core formed, it took most of the iridium down to the centre with it. (The same, incidentally, is true of gold.) Yet some iridium rains in on Earth continuously from meteors, at a rate that can be estimated, so the total amount of iridium in the layer would tell them how long it took to accumulate.

To their surprise, the boundary layer was enriched twenty-fold in iridium, relative to the rocks above and below, and other geologists soon confirmed high amounts of iridium in that layer wherever it was exposed. Where could it all have come from? Nowhere on Earth; comparison with natural waters showed that no amount of concentration could have generated such amounts. The boundary layer also anomalously high amounts of other metals, including nickel, cobalt, and zinc. (As I have said before, scientists where possible seek multiple lines of evidence.) And within three years, the iridium spike in the boundary layer had been confirmed at 50 other sites around the globe.

So we are looking at the debris thrown up by the impact of an iridium-containing extraterrestrial body, that is to say a small asteroid. Moreover, the K/Pg boundary corresponds precisely to the general mass extinction. Not only of the dinosaurs, but of ammonites, and even many single-celled marine organisms that flourished up to the very boundary but are completely absent beyond it. Cause and effect?

Rush to judgment?

The general public readily accepted this idea. The scientific community was more circumspect, and rightly. As I already mentioned, there were a lot of other things that might have been involved. The sharpness of the extinction event was for some time a matter of controversy, obscured by statistical fluctuations and by local die-backs in the last million or so years before the impact, while checking that the impact and the extinction happened at the same time required precision dating by the then still relatively novel argon/argon method. The history of the controversy is detailed in a full-length book (Night Comes to the Cretaceous, critically reviewed here), while the Wikipedia entry on the timeline of the research has over 130 references. As late as 2010 the presitigious journal Science published (here and here) papers arguing over single versus multiple causation. It was not until 2013 that we had sufficiently precise datings for the impact and the extinctions to be sure that they really coincided, and even then debate continued as to whether we should consider the impact as a single dominant cause, or merely as the last straw for a biosphere already under stress.

First find the gun

The next step, then, is to find the crater and see what it tells us.

We can roughly locate the impact by the thickness of the boundary layer. This is measured in centimeters away from the Americas, rising to metres in northern Mexico and tens of metres further south, pointing to a location in the Caribbean. More than one group seems to have discovered the exact location. The area was explored from the 1950s onwards by Pemex, Mexico's state-owned petroleum company, who understandably regarded their findings as commercial secrets, but eventually released drill samples showing shocked quartz. Further information came from studies of gravitational anomalies (places where the Earth's gravitational pull is slightly stronger or weaker than average), and aerial photography. Stronger gravity signifies pileup of material, as at the rim of a crater, while aerial photography shows sinkholes, places where the rock has been weakened. In the figure below, the US Geological Survey has combined both of these in a single map of the impact area.



The map shows the northern coastline (white line) of the Yucatán peninsula at the southern tip of the North American Plate, and the sea area directly to the North of it. The entire region is a limestone plateau, formed (and, where submerged, still forming) by deposition from the shallow waters of the continental shelf. The gravitational map clearly shows two concentric rings, known collectively as the Chicxulub crater, after the Mayan name of the village nearest the centre. The centre itself is a few miles offshore. The outer ring is 120 miles across, the inner ring some 55 miles. The white dots are sinkholes, such as commonly occur in limestone landscapes, in an arc along the outer ring, corresponding to weakness in the limestone. What does this mean?

Most of us have seen slow motion images of drops hitting water, forming a crater with an inner mound (see image, R), before the water collapsed back down again. But recently I saw one where the inner mound was so large that it was unstable under its own weight, and collapsed to form an inner ring within the crater. Similar effects are predicted when a sufficiently large impact occurs at the surface of a moon or planet. While the shock wave of the impact is travelling through the rock, the rock moves almost like a liquid, with a column of material bouncing upwards, and these features are preserved when the shock has passed and the rock once more sets solid. So what we are normally left with is a crater with an outer rim and a central impact mound, and we see such features routinely on the Moon. But with the very fiercest impacts, as with the largest water drops, the central mound it so high that it collapses outwards under its own weight, and instead of a central peak we are left with what is called an impact ring. This is what we are looking at here; an outer crater rim, and an inner impact ring. The Chicxulub crater is the only one on Earth known to show this kind of structure, although it has been observed in craters on the Moon and on Venus.

If we want to sample the rocks most severely affected when the crater was formed, that impact ring is the right place to look. And so, last year, a team involving 38 scientists from 34 separate institutions in 11 different countries, under the auspices of the International Ocean Discovery Project, drilled (see here and here) through overlying younger sediments into the impact ring. The drilled cores are now in a repository in Bremen, Germany, where they are stored at low temperature to prevent the growth of bacteria, and can be examined at leisure. We will be learning more about them in detail over the next year or so, but an overall picture is already emerging.

The findings tell us just how drastically the Earth's crust was deformed by the impact, and finally give us the answer to those two long-standing questions; was it really this impact that killed off the dinosaurs, and, if so, how exactly. The investigation was the subject of an excellent recent BBC programme, The Day the Dinosaurs Died, on which the rest of this post draws heavily, and which I hope will be made widely available for educational viewing.

Here's what the drilling found:

As expected, 600m thickness of marine deposited sediments, dating from recent (top) through Palaeocene (bottom), as shown by examination of index fossils.4 Confirmation that at the time of the impact this area was, and has been ever since, part of a shallow sea at the southern tip of the North American continent, lying between the Pacific to the West and the newly opened mid-Atlantic to the East. The sediments, mainly limestone (calcium carbonate) and gypsum (calcium sulphate), characteristic of such an environment. This will turn out to be extremely important.

At the base of this section, a 12m thick layer of sand, coarser at the bottom. This is ascribed to the tsunami produced by the impact, with the coarser grains having fallen out from the water more quickly. Beneath this, we have the rocks disturbed by the actual impact. There is a layer of rock that had been molten, with different texture and colour, followed by a jumble of granite derived from deep beneath the impact site, with fragments of the pre-impact sedimentary rock that had lain above it. There is shocked quartz, and the granite fragments also show shock damage, and are so greatly weakened that they can be snapped by hand. And significantly, there is a shortage of the expected fragments of gypsum in the entrapped sedimentary debris.

The asteroid itself would no doubt have been volatilised by the energy of the impact. So large an object could not have been appreciably slowed down by air resistance, and would have landed at a speed of some 40,000 miles an hour into the shallow sea. As for its size, we can estimate this in a rather surprising and indirect way. Nuclear testing in Nevada released known amounts of energy, and left craters containing shocked quartz. By comparing what is observed there with the Chicxulub crater system, we can estimate the total energy of the impact. It works out at the equivalent of 10 billion Hiroshimas. From the energy and the speed, we can work out the total mass, and hence the size. About nine miles across, a little bit larger than the Alvarez estimate, but still I think remarkably close. Since the most reliable Alvarez estimate was based on the amount of iridium, I suspect that their shortfall may be due to part of the impactor vapour having escaped earth gravity altogether.

Then survey the carnage

We can now estimate what the effects would have been at different distances, using what we know about the behaviour of materials under extreme forces, and compare these estimates with what we observe.

The initial impact would dig a hole 20 miles deep, and 120 miles across. Deep rock would rise as high as the Himalayas, and then collapse to form the observed impact ring, all within 10 minutes. The impact fireball would kill everything within a 600 mile radius. A shock wave would spread out through the solid earth, and a monstrous tsunami through the oceans. The atmosphere would have seen hurricane force winds, and rock condensing in the upper atmosphere would produce a rain of tiny glass spheres, such as those still preserved in the mudstone boundary layer. The glowing hot rockdust would generate heat several times greater than that coming from the Sun, roasting to death all surface animal life up to a distance greater than a thousand miles, and starting firestorms in the vegetation.

We can see the effects of the tsunami at Edelman Fossil Park in New Jersey, 1700 miles from the impact site. There we find the expected range of Cretaceous remains up to the boundary layer, with a clear cut-off above it. The boundary layer itself is around four inches thick, but full of a jumbled assortment of fossils, and fragments of wood. There is a surprising mixture of species, bird next to crocodile next to giant turtle, land creatures next to shallow water turtles next to deep sea turtles. No tooth marks, no scattering of limbs; this was sudden indiscriminate killing.

At the tip of South America, in Patagonia, 4000 miles from the impact, abundant fossils show that at the time of the impact the area was home to herds of hadrosaurs, duck-billed dinosaurs thirty foot long. It was also home to trees not too different from the southern beech trees still flourishing in the area. So the trees survived, but the dinosaurs didn't. Why not?

At last, the gunsmoke

The drilled cores give us the answer. As I mentioned earlier, they are surprisingly deficient in gypsum, although gypsum is abundant both in the more recent sediments, and in nearby sediments laid down before the impact. So the missing gypsum must have been destroyed by the heat of the impact, sending sulphur dioxide gas up into the atmosphere.5 We already know from studies of volcanic eruptions that over months or years this sulphur dioxide would slowly react in the atmosphere to form a haze of sulphuric acid droplets, scattering sunlight and cooling the Earth. That haze, rather than simply dust, is how the Mt Pinatubo eruption affected climate.

Extrapolating from Mt Pinatubo and other recent eruptions, and taking into account the enormous volume of gypsum sediments in the impact zone, we can estimate that the haze produced by the Chicxulub impact would have blocked enough sunlight to reduce temperatures worldwide by more than 10oC (18oF), while acid rain would also have contributed to the death of much marine life. On land, trees would have shed leaves and shut down as if for what would turn out to be an unusually long winter. The dinosaurs, hugely diverse and successful as they had been through some 180 million years, had no such way of adapting. The herbivores, and the carnivores that fed on them, perished.

Where did those ten minutes come from? From the rotation of the Earth. The asteroid is falling towards Earth on a fixed trajectory, but the Earth itself is spinning beneath it, one revolution every 24 hours. This corresponds to around 1,000 miles an hour in the region of interest. So arriving ten minutes earlier or later would have placed the impact some 150 miles further to the East or West. And if this had happened, the asteroid would have missed the shallow gypsum-rich continental shelf, and encountered only the oceans on either side. No gypsum in the impact zone, no sulphuric acid haze, no long deep winter. While things might have been pretty rough for anything living within a couple of thousand miles or so, the rest of the world would hardly have noticed.

The fossil record tells us that over the following months or years, ferns, and then other plants, resumed their cycle, and whatever animals survived would be free to adapt to new niches. Who survived? Small creatures able to feed on insects and seeds, not dependent on the products of day-by-day photosynthesis. And larger creatures if they can survive for long periods between meals, and become torpid in cold weather. Snakes and crocodiles, birds, and those small mammals that had managed to survive in the shadow of the dinosaurs. Among them, our ancestors.