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Sun, 24 Sep 2017
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Saturn

Sawtooth Shadows On Saturn's Rings

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© NASA/JPL/Space Science Institute
Jagged looking shadows stretch away from vertical structures of ring material created by the moon Daphnis in this image [Full-Res: PIA11547] taken as Saturn approaches its August 2009 equinox.

Daphnis (8 kilometers, or 5 miles across) is a bright dot casting a thin shadow just to the left of the center of the image. The moon has an inclined orbit, and its gravitational pull perturbs the orbits of the particles of the A ring forming the Keeler Gap's edge and sculpting the edge into waves having both horizontal (radial) and out-of-plane components. See Wave Shadows in Motion to learn more and to see a movie of this process.

Meteor

Possible Meteorite Imaged by Opportunity Rover on Mars

This image of "Block Island" was taken on July 28, 2009, with the front hazard-identification camera on NASA's Mars Exploration Rover Opportunity.
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© NASA

The Opportunity rover has eyed an odd-shaped, dark rock, about 0.6 meters (2 feet) across on the surface of Mars, which may be a meteorite. The team spotted the rock called "Block Island," on July 18, 2009, in the opposite direction from which it was driving. The rover then backtracked some 250 meters (820 feet) to study it closer.

Telescope

Experts puzzled by spot on Venus


The existence of the spot was confirmed by Venus Express
Astronomers are puzzled by a strange bright spot which has appeared in the clouds of Venus.

The spot was first identified by an amateur astronomer on 19 July and was later confirmed by the European Space Agency's Venus Express spacecraft.

Meteor

The Perseids Are Coming

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© Space Weather
Looking northeast around midnight on August 11th-12th. The red dot is the Perseid radiant. Although Perseid meteors can appear in any part of the sky, all of their tails will point back to the radiant.
Earth is entering a stream of dusty debris from Comet Swift-Tuttle, the source of the annual Perseid meteor shower. Although the shower won't peak until August 11th and 12th, the show is already getting underway.

Don't get too excited, cautions Bill Cooke of NASA's Meteoroid Environment Office. "We're just in the outskirts of the debris stream now. If you go out at night and stare at the sky, you'll probably only see a few Perseids per hour."

This will change, however, as August unfolds.

"Earth passes through the densest part of the debris stream sometime on August 12th. Then, you could see dozens of meteors per hour."

For sky watchers in North America, the watch begins after nightfall on August 11th and continues until sunrise on the 12th. Veteran observers suggest the following strategy: Unfold a blanket on a flat patch of ground. Lie down and look up. Perseids can appear in any part of the sky, their tails all pointing back to the shower's radiant in the constellation Perseus. Get away from city lights if you can.

Sherlock

Ancient Warrior's Skeleton Found Buried in a Tomb on a Beach Near Rome

Archaeologists have found the skeleton of a warrior from up to 5,000 years ago floating in a tomb filled with sea water on a beach near Rome, Italy's art squad said Friday.

The bones - believed to date from the 3rd millennium B.C. - were discovered in May as art hunters were carrying out routine checks of the region's archaeological areas, Carabinieri art squad official Raffaele Mancino said.

Archaeologists believe the warrior was likely killed by an arrow, part of which was found among his ribs, Mancino said. There was also a hole in the back of the skull, and six vases and two daggers were found buried nearby.

Satellite

Orbiting gas station could refuel lunar missions

Forget huge, expensive rockets. A plan being examined by a US government panel would allow smaller, cheaper rockets to fly to the moon and beyond by stopping off at an "orbiting gas station".

With conventional rockets, many tonnes of fuel are needed on such missions for each tonne of payload. Sending astronauts or the heftiest robotic probes to these distant destinations therefore requires huge launchers.

Telescope

Hawaii: Mauna Kea Selected for World's Largest Telescope

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An artist's rendering shows what the Thirty Meter Telescope observatory would look like atop Mauna Kea. Details of the external structure are tentative.
Mauna Kea was chosen yesterday as the site for what will become the world's largest telescope - a mega-feat of engineering that will cost $1.2 billion, create as many as 440 construction and other jobs and seal the Big Island summit's standing as the premier spot on the planet to study the mysteries of space.

But opposition to the project from environmental and Native Hawaiian groups could still prove a formidable hurdle for making the telescope a reality. Marti Townsend, program director for Kahea: The Hawaiian Environmental Alliance, said opposition groups will go to court to stop the project if needed.

Meteor

Shuttle Plumes Hint at Comet Crash in Siberia

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© NASA
Night-Shining Clouds
Tracking plumes from space shuttle launches provided researchers with one of the strongest pieces of evidence that a comet crash was responsible for flattening a Siberian forest in 1908.

The crash, which leveled trees for hundreds of miles in Siberia, was followed by the appearance of extremely bright clouds, visible by night.

Similar clouds triggered by the flights of space shuttles through atmosphere were found over the planet's poles two days after a launch from Florida, research published in last week's Geophysical Research Letters shows.

Comment: For more in-depth reading on Tunguska read: Tunguska, Psychopathy and the Sixth Extinction


Blackbox

Evolution's third replicator: Genes, memes, and now what?

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© Burneverything
Technological replicators are affecting human nature.
We humans have let loose something extraordinary on our planet - a third replicator - the consequences of which are unpredictable and possibly dangerous.

What do I mean by "third replicator"? The first replicator was the gene - the basis of biological evolution. The second was memes - the basis of cultural evolution. I believe that what we are now seeing, in a vast technological explosion, is the birth of a third evolutionary process. We are Earth's Pandoran species, yet we are blissfully oblivious to what we have let out of the box.

This might sound apocalyptic, but it is how the world looks when we realise that Darwin's principle of evolution by natural selection need not apply just to biology. Given some kind of copying machinery that makes lots of slightly different copies of the same information, and given that only a few of those copies survive to be copied again, an evolutionary process must occur and design will appear out of destruction. You might call it "design by death" since clever designs thrive because of the many failures that don't.

The information that is copied, varied and selected is called the replicator, and the process is well understood when applied to biology. Genes are copied, mutated and selected over and over again. Assemblages of genes are used to build vehicles that carry them around, protect them and propagate them. These vehicles - the lumbering robots, as Richard Dawkins calls them - are animals and plants, the prolific and exquisitely designed products of the first replicator.

Blackbox

Go Back To Sleep - Comet Collisions Won't Spark The End Of The World

© Unknown
Comet Hale-Bopp.
Evidence indicates that it is highly unlikely that a comet crash would result in Earth's demise, researchers at the University of Washington said on Thursday.

Writing in Science Express, the online edition of the journal Science, researchers acknowledged that while most scientists agree that an asteroid collision 65 million years ago caused the mass extinction of the dinosaurs, they tend to differ in opinion on how many other mass extinctions have resulted from similar events.

Researchers used computer models to simulate the formation of comet clouds in the solar system for 1.2 billion years. They pinpointed a body called the Oort Cloud as the source for many long-period comets that find their way into Earth's path.

Formed 4.5 billion years ago from the nebula that formed our solar system, the Oort Cloud spans from about 93 billion miles from the sun to about three light years away. Scientist said the Oort Cloud could contain literally billions of comets, many of which are so small and distant to be seen.

Comment: Regarding the claim that "the gravitational pulls of Jupiter and Saturn act as comet deflectors", let's see what Clube and Napier, British astronomers and writers of The Cosmic Serpent, have to say:
The giant comets normally reside far beyond the planets, in a spherical cloud surrounding the Sun, called the Oort cloud. There is also evidence for a flattened disk of comets closer to the inner solar system, called the Edgeworth/Kuiper belt. What prompts members of either of these comet repositories to enter the realm of the planets? Clube and Napier suggest a galactic influence. The solar system periodically passes through the plane of the galaxy as the Sun (and the solar system with it) orbits the galactic center. Each passage may dislodge giant comets and divert them closer to the Sun. The outer planets, particularly Jupiter, may then perturb some of these giant comets into orbits which enter the inner solar system. These comets, stressed both by gravity and by heat from the sun, may fragment into a cloud of smaller objects with dynamically similar orbits.

Chiron offers a good example of a giant comet as called for by Clube and Napier's giant comet hypothesis. Chiron is somewhere between 148 and 208 kilometers in diameter. Currently Chiron's unstable "parking orbit" lies mostly between Saturn and Uranus. Chiron may end up injected into the inner solar system within a hundred thousand years, or ejected from the solar system on a similar time scale. It is also possible that Chiron has already visited the inner solar system.

The Taurid complex and the Kreutz sungrazer group are two families of objects which most likely represent the fragmented remains of two giant comets in the current era. SOHO has recently discovered many new members of the Kreutz group which were previously unknown.

The Kreutz progenitor was injected into a retrograde orbit and attained the sungrazing state at a high inclination to the ecliptic. Hence the debris of its "children" does not pose a threat to the Earth. The Taurid progenitor on the other hand ended up in a short-period low-inclination prograde orbit. This is why the Earth can encounter its debris with potentially calamitous results.

What would happen should the Earth pass through the orbit of a disintegrating giant comet just before or after the comet passes that same point? Since larger fragments tend to cluster close to the nucleus of the comet, chances would increase that the Earth would be bombarded by these larger fragments. The severity of this comet fragment shower would far exceed any ordinary meteor shower. Not only would "shooting stars" and bright fireballs caused by small debris appear, but so too would large airbursts and possibly ground impacts. These would result in significant destruction should they occur over an inhabited area. If a large enough fragment struck in the ocean -- say, 200 meters or so in diameter -- it would raise tsunamis even at a great distance that would sweep away coastal habitations.

Duncan Steel, a colleague of Clube and Napier, refers to this process as coherent catastrophism. Widespread destruction derives from the coherent arrival of many impactors within a few days, as opposed to the sporadic arrival of objects spread randomly in space. The shower repeats for a period of years until the cometary orbit precesses so that the Earth no longer encounters the dense part of the debris field. (Of course, sporadic debris unrelated to the disintegrating comet may impact at any time as well.)