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Tue, 25 Jul 2017
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Bizarro Earth

Scientists Search For A Pulse In Skies Above Earthquake Country

© Unknown
Space-based instruments can image minute Earth movements to within a few centimeters (fractions of an inch), measuring the slow buildup of deformation along faults and mapping ground deformation after earthquakes occur. Among these tools are the Global Positioning System and interferometric synthetic aperture radar, or InSAR.
When a swarm of hundreds of small to moderate earthquakes erupted beneath California's Salton Sea in March, sending spasms rumbling across the desert floor, it set off more than just seismometers. It also raised the eyebrows of quite a few concerned scientists.

The reason: lurking underground, just a few kilometers to the northeast, lays a sleeping giant: the 160-kilometer-(100-mile) long southern segment of the notorious 1,300-kilometer- (800-mile) long San Andreas fault.

Scientists were concerned that the recent earthquake swarm at the Salton Sea's Bombay Beach could perhaps be the straw that broke the camel's back, triggering "the big one," a huge earthquake that could devastate Southern California.

The southern end of the San Andreas has remained silent, at least for now. But the earthquake swarm and more recent, widely felt earthquakes in the Los Angeles area have stirred renewed interest in earthquake research.

Evil Rays

The sound of silence

© physicsworld

From listening in on volcanoes to detecting nuclear explosions, a global network of infrasound detectors is allowing researchers to tune in to our atmosphere, explain Michael Hedlin and Barbara Romanowicz

Our atmosphere is filled with sounds that we cannot hear. The Earth hums; volcanoes howl, pop and whistle; storms roar menacingly; and meteors scream before exploding high above the ground. We are oblivious to this perpetual symphony because it takes place at frequencies below the lower limit of human hearing, otherwise known as infrasound.

The human ear is sensitive to sounds with frequencies between about 20 and 20,000 Hz. These mid-range waves lose energy rapidly, which means we can only hear sounds coming from our immediate surroundings. But sounds exist both above and below the audible range - ultrasound, for example, can have frequencies of several megahertz. Ultrasound decays very quickly and cannot be detected very far from its source, which makes it useful for biological imaging. But with frequencies as low as a few millihertz, infrasound can travel distances of several thousand kilometres.

It was the eruption of the Indonesian volcano Krakatoa in 1883 that showed scientists that what we can hear is just a narrow slice of the full acoustic spectrum. This eruption generated the loudest recorded sound in history, and was distinctly heard some 4800 km away on the island of Mauritius. However, had barometers - which are sensitive to very gradual changes in air pressure - not recorded the cataclysmic event, most of the rest of the world would only have found out about it by word of mouth.


Exploding Stars: Is Earth at Risk?

When stars go pop, a murderous torrent of energy is released. Life on Earth may have been partly extinguished by just such a violent outburst, but there's little hard evidence yet to justify such a claim. A new study plans to fill in the forensic details.

"We are trying to get a better estimate of how dangerous a particular event will be," says Brian Thomas of Washburn University in Topeka, Kansas.

Thomas and his colleagues will be studying the wide-range of astrophysical phenomena that could fling high energy radiation across interstellar space to Earth's doorstep [as occured in a colossal blast detected in 2004]. The team also will radiate different types of phytoplankton to understand how life would be affected by a stellar blast, since life around the globe is highly dependent on these microscopic plants.

Comment: Star explosions are certainly not one of our grave concerns at the moment, as the coming ice age along with a space debris rain and psychopathy are humanity's real threads. For starters read:

Tunguska, Psychopathy and the Sixth Extinction
Fire and Ice: The Day After Tomorrow

Cloud Lightning

Evidence Found Of Lightning On Mars

© Unknown
Illustration only
U.S. scientists say they have detected the first direct evidence of lightning occurring on Mars. University of Michigan researchers said they found signs of electrical discharges during dust storms on the red planet. The bolts were dry lightning, Professor Chris Ruf said.

"What we saw on Mars was a series of huge and sudden electrical discharges caused by a large dust storm," Ruf said. "Clearly, there was no rain associated with the electrical discharges on Mars. However, the implied possibilities are exciting."

Electric activity in Martian dust storms has important implications for Mars science, the researchers said.

"It affects atmospheric chemistry, habitability and preparations for human exploration. It might even have implications for the origin of life, as suggested by experiments in the 1950s," said Professor Nilton Renno of the university's Department of Atmospheric, Oceanic and Space Sciences.


The Sound of One Rock Falling

© Antares Amateur Astronomers Group
A Leonid meteor bursts and sputters over Italy in this false-color computer reconstruction.

Think of it as the extreme-sport version of listening for songbirds: Atmospheric scientists Douglas ReVelle, Rodney Whitaker, and Peter Brown are using microphone arrays to eavesdrop on the baritone rumblings of interplanetary rocks slamming into Earth's atmosphere.

Most of the time nobody sees them hit, but hearing them is much easier. A typical meteor arrives traveling 50 to 300 times the speed of sound, fast enough to create a powerful sonic boom and, if the object is large enough, an explosive flash. These disruptions stir up persistent low-frequency infrasound, similar to the waves from a nuclear test, which can travel thousands of miles without losing significant energy. And infrasound monitoring stations, including four arrays at Los Alamos National Laboratory and a network being built to verify the Comprehensive Test Ban Treaty, already exist to detect such waves anywhere in the world.


The Infrasound Renaissance

On April 23, 2001, scientists manning a network designed to detect covert nuclear tests noticed something unusual - a very "loud" sound coming from above the Pacific Ocean. This global network, consisting of sensitive sound-recording instruments, had picked up on a large meteor slamming into the atmosphere several hundred miles west of Baja California, and exploding with a force comparable to that of the nuclear bomb that was dropped on Hiroshima.

On Feb. 1, 2003, these same instruments heard something else - the Space Shuttle Columbia reentering Earth's atmosphere on its tragic final mission. NASA subsequently used those recordings to rule out potential causes of the mission's demise, including a bolide or missile impact.

The sensitive instruments that recorded the meteor's entrance and the end of the Columbia record a range of low-frequency sound that is inaudible to the human ear called infrasound. "It's sort of like infrared light, which is the part of the electromagnetic spectrum that we can't see, in that it's the part of the sound spectrum that we can't hear," says Michael Hedlin, a geophysicist and infrasound specialist at the University of California, San Diego, and Scripps Institution of Oceanography.

The instruments detect atmospheric noise, such as storms, winds, volcanic eruptions, ocean waves and airplane traffic, and they help scientists understand "just what's going on out there," Hedlin says. "Right now, we're just listening to the world," he says, but soon, the researchers will begin to more fully comprehend the interactions between solid earth, the oceans and the atmosphere.


Noisy end for meteor

© unknown
The burst of very-low frequency sound waves from the meteor explosion over Germany in November 1999.

Belgian scientists have detected ultra-low frequency sound waves - infrasound - from a meteor that exploded over Germany in November 1999.

They were picked up by an observatory more use to searching for the particular infrasound signatures associated with nuclear explosions. It is one of the ways scientists can monitor for compliance with test ban treaties.

This particular meteor would have exploded with a force of 1.5 kilotons of TNT, equivalent to a small nuclear weapon.

The signals were detected by the seismology division of the Royal Netherlands Meteorological Institute.


Military Warning System Also Tracks Bomb-Size Meteors

In the early darkness of April 23, as Washington was beginning to relax after the spy plane crisis in China, alarm bells began to go off on the military system that monitors the globe for nuclear blasts.

Orbiting satellites that keep watch for nuclear attack had detected a blinding flash of light over the Pacific several hundred miles southwest of Los Angeles. On the ground, shock waves were strong enough to register halfway around the world.

Tension reignited until the Pentagon could reassure official Washington that the flash was not a nuclear blast. It was a speeding meteoroid from outer space that had crashed into the earth's atmosphere, where it exploded in an intense fireball.

"There was a big flurry of activity," recalled Dr. Douglas O. ReVelle, a federal scientist who helps run the military detectors. "Events like this don't happen all the time."

Preliminary estimates, Dr. ReVelle said, are that the cosmic intruder was the third largest since the Pentagon began making global satellite observations a quarter century ago. Its explosion in the atmosphere had nearly the force of the atomic bomb dropped on Hiroshima.


Great Red Spot Rival Forming

© Christopher Go (Cebu, Philippines)
Astronomers are monitoring a new red spot forming in Jupiter's northern hemisphere--a brick-red storm nearly as large as the Great Red Spot itself. On June 17th, amateur astronomer Christopher Go of the Philippines photographed it using an 11-inch Celestron telescope.

"I have been monitoring the new spot since mid-April," says Go. "At first it was relatively small. In late May it began to grow rapidly, and just last week John Rogers of the British Astronomical Association issued an alert for everyone to observe it."


Supernova May Be in a New Class

Oddball stellar explosion doesn't match known outbursts

Just in time for July 4, astronomers say they have found a new type of stellar firecracker.

Stars that die an explosive death generally fall into two categories: young, massive stars that collapse under their own weight and hurl their outer layers into space, and older, sun-like stars that undergo a thermonuclear explosion. But the stellar explosion recorded in January 2005 and known as SN 2005E doesn't fit either class, according to a new analysis reported online June 11 at arXiv.org.

The explosion ejected only a small amount of material - the equivalent of 0.3 solar masses - and erupted in the halo of an isolated galaxy, a region devoid of any star formation. These findings suggest that the explosion, or supernova, did not arise from the collapse of a massive star, report study coauthors Hagai-Binyamin Perets and Avishay Gal-Yam of the Weizmann Institute of Science in Rehovot, Israel, and their colleagues. A massive star would have cast off much more material and would have erupted in a star-forming region. Since stellar heavyweights are so short-lived, they can't move far from their birth site.