Inside the Boardroom with Alan Bagley - SETI Institute

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gabbro, another igneous rock. Upon keeping the load constant for 30 minutes, the two currents flow with barely any loss in their intensities. Even keeping the load constant for 12 hours leads to not more than a 15-20% reduction of the currents. This shows that, once activated, the p-holes and electrons in the stressed rock volume have a very long lifetime. Use for Earthquake Prediction How can we apply this new knowledge to earthquakes and to those hidden processes that take place deep in the Earth’s crust before tectonic stresses reach a critical level where rupture occurs and the ground starts to shake Though we stand only at the beginning of a long road to discoveries yet to come, we can already project some of our findings into geophysical reality. In Figure B, you can see a sketch of a very simplified model depicting a section through the Earth’s crust where tectonic forces begin to act on a large block of strong, rigid rocks, maybe 100 - 1000 km wide, 20 km thick and 50 - 10 km in the thrust direction. As stresses build up from the left, they cause plastic deformation propagating toward the right. The volume of rocks undergoing deformation becomes the source of p-holes and electrons. The p-holes can flow out horizontally. The electrons can flow out only if they can connect downward into the deeper, hotter and, hence, n-type conducting portions of the lower crust. In this model we obviously neglect to take into account the role of water which fills faults that deeply dissect the Earth’s crust in all tectonically active regions. Faults filled with water or brines will introduce complications, but we already know from laboratory experiments that water may short-circuit the p-hole conduction through the rocks but it does not “kill” it. Therefore we can cautiously go ahead and project some of the consequences of the p-hole activation in rocks that experience ever-increasing levels of stress. One of these consequences is that the p-hole current flowing horizontally through the crust should couple to the electron current flowing downward. The coupling is provided by their respective electric fields. As a result, both currents can be expected to fluctuate just like the p-hole and electron currents did in our laboratory experiments. Fluctuating currents are a source of low frequency electromagnetic (EM) radiation. Thus our model, simple as it may be, points to the possibility that the often reported pre-earthquake low frequency EM emissions arise from ground currents flowing deep in the Earth’s crust. The ground currents may be very powerful. For instance, taking the currents flowing out of the squeezed end of the granite slab in our experiment, we may ask what would be the current flowing out of a cubic kilometer of granite or gabbro in the crust, all other conditions being the same. The answer is a surprisingly large value, somewhere between 100,000 and 1,000,000 amperes. Since huge volumes of rocks – tens of thousands of cubic kilometers – come under increasing stress during the build-up of large earthquakes, the ground currents could indeed be enormous. Looking at it from a different perspective, we can say that, even if most of the currents generated in the ground are short-circuited or annihilated by other factors, those that remain might still reach impressively large values. Atmospheric Disturbances Another result of stress-activated currents flowing in the ground would be that some p-holes will reach the surface of the Earth. They would change the ground potential over large areas, making it more positive relative to the surrounding areas. This would have many consequences, of which I only want to mention one. Roughly 90 - 120 km above the Earth’s surface the ionosphere begins, which is composed of a highly dynamic plasma of electrons and ions generated under the daily assault of extreme ultraviolet radiation from the Sun, solar wind bombardment, and cosmic rays. If the land surface below becomes increasingly positive, this plasma sheet will react. Maybe the source for the well-documented pre-earthquake ionospheric perturbations lies in the activation of p-holes deep in the Earth’s crust and the mischief that they play at the Earth’s surface. In hindsight it is quite amazing to see how a line of basic research that, at its outset three decades ago, seemed to have no connection whatsoever to the origin of life and to earthquakes, has become a treasure trove of insights and discoveries. It is certainly too early to say that earthquake prediction is just around the corner. However, I feel confident that the discovery of p-holes in rocks and their activation by stress represents a crucial step toward cracking the code of the Earth’s multifaceted preearthquake signals. Figure B - Simple model of a large, rigid block of the Earth’s crust being pushed from the left and undergoing increasing levels of stress. Friedemann Freund Dr. Friedemann Freund Physicist, SETI Institute Dr. Freund is associated with the SETI Institute, San Jose State University and NASA’s Goddard Space Flight Center. SETI Institute Explorer
Astrobiology Perseids © Wally Pacholka/ www.astropics.com Tune In! Are We Alone the SETI Institute’s Weekly Science Radio Program by Peter Jenniskens For as long as records exist, the Perseid meteor showers have always been strong. This summer’s Perseid shower will be exceptional. The moon is mostly out of the way later in the night, and higher-thannormal activity rates are expected over the United States. The Perseid shower’s parent body, comet 109P/Swift-Tuttle, is notable in being a comparatively huge comet in an orbit that passes close to Earth’s orbit frequently. It measures 24 - 31 kilometers in diameter, 2 to 3 times the size of comet Halley, and is so big that the continuous ejection of water vapor and dust during its approach to the Sun does not move the comet much off course. It has spewed dust for at least 5,000 years and most likely thirty times longer. It has built a massive meteoroid stream, most of which is located just outside of Earth’s orbit. Earth passes through the outer regions of that stream in July, and hits the center on August 12. At that time, the annual Perseid shower peaks at 80 meteors per hour under ideal circumstances (no clouds or moon, dark sky, stars of magnitude +6.5 just visible). When comet 109P/Swift-Tuttle was rediscovered in 1992, scientists noticed in alarm that a delay of 17 days in the next projected return of the comet in 2126 could cause it to collide with Earth. That fear dissipated when the orbit was recomputed using data from sightings in 188 A.D. and 69 B.C. The more precise orbit has the comet approach Earth in 2126 to within only 23 million kilometers, but there’s no danger of us being hit. In September 4479, the comet will approach Earth even closer, to within about 6 million kilometers. It will then be as bright as Jupiter (-2.1 magnitude) in the sky. The dust released will spread along the comet orbit because some dust grains make wider orbits than others and return later. When Earth encounters these dust trails, a meteor storm may be observed. But only if the very narrow trail is steered smack in Earth’s path by perturbations of the planets. Most dust does wander far from the comet, which is why the best showers are observed in the years following when the comet returns, while lesser outbursts occur when dust further along the comet orbit wanders into Earth’s path. The next big shower is not expected until the next return of the comet. For now, a nice outburst is projected for August 12, 2005, at 08:18h UT (= 04:18 EDT and 01:18 PDT), when Earth will encounter the dust ejected in the return of 1479. Rates can go up four fold to about 240 per hour on top of the 80 per hour annual activity, for a brief period of time (approximately 1.2 hours). In addition, rates may increase again around 13h UT, when Earth is slated to encounter the Filament component, rising to less than 86 per hour on top of normal, annual activity. That Filament is older dust presumably in mean-motion resonance with Jupiter. Dr. Peter Jenniskens Astronomer, SETI Institute Dr. Jenniskens studies meteor showers in order to understand the origins of life on Earth. Listen to Are We Alone Hosted by Dr. Seth Shostak Live Sunday nights at 7pm PST (Check your local listings) or visit www.seti.org/radio for more information Second Quarter 2005 - Celebrating our 20th Anniversary
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Inside the Boardroom with Alan Bagley - SETI Institute

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