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-. Most people are aware of the extinction of the dinosaurs caused by a giant asteroid impacting the Earth near the Yucatán 65,000,000 years ago.
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-. But, are you aware that a similar event occurred 252,000,000 years ago. Was it an asteroid impact that wiped out 96 % of life in the oceans and 70 % of all life on land.
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-. The event is called the End- Permian extinction. The extinction event lasted 60,000 years + or -48,000 years.
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-. Science has uncovered evidence of a massive addition of carbon dioxide in the atmosphere 10,000 years before the End -Permian event. This in turn caused acidification of the oceans and a10 C temperature rise that killed 96 % of all sea life.
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-. Where did this spike in the carbon dioxide come from? Was a caused by volcanic eruptions or by an asteroid impact?
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- To answer this question science is studying prehistoric rock in volcanic ash beds. The zircon crystals in the rock contain a mix of lead and uranium. The ratio of the isotopes of lead and uranium are then used to calculate the age of the rock. These isotopes have a predetermined half-life of radioactivity. The ratio of radioactive decay to non-decay can be used to calculate the age.
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-. If the End -Permian extinction lasted 60,000 years proceeded by a sharp increase in the carbon dioxide in the oceans than likely a massive volcanic eruptions triggered the extinctions. If the event was much shorter duration than likely another massive asteroid impact triggered the extinctions. More study is needed.
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- Science has also discovered evidence of a magnetic field on the Moon. This does not seem intuitive, but, astronomers are using precise observations of distant quasars to measure the strength of the Earth's magnetic field.
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-. The answer they get is 25 Gauss.
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-. Gauss is the centimeter- gram- second metric unit of magnetic induction. It is equivalent in other units to 1 Maxwell per square centimeter , or, 0.0001 Webers per square meter.
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-. The magnetic field on the Earth's surface is only 0.5 Gauss. This magnetic strength is 50 times weaker than the core magnetic field some 1,800 miles below the surface.
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-. By using the precise locations of Quasars in the sky astronomers could detect tiny variations in the Earth's axis of rotation caused by the tug of the Moon's gravity. These variations depend on the strength of Earth's core magnetic field.
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-. Quasars are the cores of the most distant galaxies. And, they become instrumental in measuring the Earth's core just 1,800 miles below our feet.
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-. The Moon does not have an iron core like the Earth. And it's core would not be rotating like a giant dynamo generating a magnetic field. Yet, the Moon does have a magnetic field.
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-. This puzzles astronomers. The size the moon is such that it's core should have totally cooled. It should not have a molten core. Yet, moon rocks have a magnetic field measured to be 0.001 milli-Tesla. A refrigerator magnet is 5 milli-Tesla.
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-. A Tesla is a unit of magnetic induction equal to one Weber per square meter.
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-. A Weber is 100,000,000 Maxwells. A Weber is a standard unit of magnetic flux that will produce one volt in a single turn of wire when the flux is removed in one second. Yep, that is how a standard flux is created.
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-. A Maxwell is unit of magnetic flux through 1 square centimeter in a field of 1 Gauss.
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- Magnetic fields are complicated measurements as you can see in the standardization of the units that measure them.
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-. Astronomers estimate that the Moon maintained its magnetic field for over 400,000,000 years. But, how did it produce such a field. The explanations include two theories:
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-. (1) The Earth's wobbly rotation caused a gravitational tidal tug on the Moon in turn causing a wobble in the moon's axis of rotation. This oscillating wobble was enough turbulence and friction to give the Moon a molten core. The interior fluid in the core sloshed around creating a magnetic field much like the Earth has done.
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-. (2). A second theory is that huge asteroid impacts messed up the Moon’s rotation and injected enough energy upon impact to create a liquid core. The calculations show that a reasonably large impact can generate a magnetic field lasting 10,000 years. Enough of these impacts could have done the trick.
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-. The next step is to measure more lunar rocks. Measuring young rocks and old rocks could plot out the evolution of the moon's magnetic field, tracing magnetic intensities over time. The pattern should tell us what caused the moon to have a magnetic field.
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-. Another discovery was to find water in the Moon. Well we think so? But not much, 200 parts per million, or, for every 10,000 molecules of lunar soil there is 1 molecule of water, H2O.
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-. 1998 it was not water directly that was detected. It was the element hydrogen using a neutron spectrometer. Cosmic rays hit the moon's surface and the amount the soil absorbs the neutrons tells the astronomers what the soil is made of.
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-. In 2010 radar measurements found an abundance of water in frozen ice at the bottom of polar craters.
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-. The data is still needed to determine exactly how much water exist on the Moon. And, how much could be practically collected to support a colony living on the Moon.
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-. Over 1,000 planets have been discovered orbiting other stars. Since we tend to detect big planets first most so far are large gaseous planets, like Jupiter and Neptune. These giant planets are hostile to life. However, the planets have moons and their moons may be an ideal environment to find life.
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-. The planet being searched most today is Kepler-22b that is 600 light-years from Earth. Kepler 22b resides in the star’s habitable zone, a region in orbit where liquid water could exist.
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-. Some of the gaseous planets like Jupiter and Saturn are found closer to their star. Some even occupy the habitable zone for liquid water. Some of the moons around these warm giants might have atmospheres and oceans like the Earth.
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-. If a moon was less than 10 % the mass of the Earth it's gravity would not be strong enough to sustain an atmosphere. That would be a Moon smaller than the planet Mars.
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-. How do we get large moons?
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-. The Earth - Moon system was forged out of a cataclysmic collision early in the solar system history. Our Moon was splashed into its orbit.
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-. Another scenario for large moons is when a giant planet encounters a binary pair and in capturing one ejects the other in the space. Action equals reaction. Neptune's biggest moon, Triton, was likely captured in this very fashion.
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-. Tidal heating caused by eccentric orbits about a giant planet would heat the moon comfortably enough for life. A planet and a moon orbiting a common center of gravity would cause the planet to wobble back-and-forth. By detecting the wobbles with transit orbits moons too could be detected. Detecting these slight variations is difficult to analyze. The variations could be caused by sunspots, or star spots, stellar fluctuations, or is instrument measurement errors. To tease out the presence of a moon orbiting a transiting planet is a challenge.
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-. The daily data from Kepler Space Telescope is available on the web. You can hunt for an exomoon yourself. www.cfa.harvard.edu/HEK. HEK is acronym for “Hunt for Exomoons with Kepler.
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-. Moons may be just as good as place for finding life elsewhere. Thus multiplying our chances of not being alone many fold. An announcement will be made shortly, stay tuned.
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RSVP, with comments, suggestions, corrections. Index of reviews available ---
--- Some reviews are at: -------------------- http://jdetrick.blogspot.com -----
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---- www.twitter.com , --- 707-536-3272 ---- Thursday, February 20, 2014 ---
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