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Mon, 21 Sep 2020
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Comets

Star

Today in Cape history: Third comet visible in 12 years



Comet 1664
©Unknown

On this day in 1664, as described in the book "Cape Cod Historical Almanac" by Donald G. Trayser, "the people of Cape Cod and other parts of New England saw the last of a great comet which excited fear and awe. It appeared November 8th last, and continued to this date, the third comet witnessed by early settlers in the space of 12 years.

Telescope

Boston University Astronomers Map Full Extent Of Mercury's Comet-Like Tail

Boston University astronomers released new images of Mercury that capture both the source regions of and, for the first time, the extraordinary length of the planet's comet-like tail. Earlier research had mapped-out Mercury's sodium gas tail to approximately 40,000 kilometers, but planetary scientists from BU's Center for Space Physics (CSP) have found that the tail can extend more than 2.5 million kilometers, or 1.5 million miles, from the planet.

mercury comet like tail
©Center for Space Physics, Boston University
Mercury's tail of sodium gas captured by a wide-angle telescope showing an enormous extent of the atoms escaping from the planet's surface. The insert shows the source regions of the tail gases imaged at a different time using a very narrow field of view telescope. The source regions occur at high latitudes, probably related to solar wind access to Mercury's surface along specific magnetic field lines. The impacts of the solar wind ions and electrons result in sputtering sodium from the surface. Since Mercury is close to the Sun, the sputtered atoms are pushed away by the pressure of light, with this photon radiation pressure leading to the long tail. The brightness of the source regions is about 1 million times greater than the faintest part of the distant tail. The sizes of the source regions span about 1/2 of the planet's radius, while the tail extends to about 1500 times the radius of the planet, about 1.5 million miles.

Bizarro Earth

ABC: Man may need to live in space to survive cometary impacts, global disasters

Will humans need to live as space nomads to survive? Possibly, says Neil deGrasse Tyson of the American Museum of Natural History.

"It may be," says Tyson, "that our only insurance policy against extinction is to become a multi-planet, space faring species."

Worries of climate change and unexpected catastrophe on Earth, compounded with humankind's natural curiosity about what lies beyond, compel private industry and NASA alike not only to wonder "what if," but to prepare for the "when."

Telescope

Kamikaze comet ripples Saturn's ring

A smack from a small comet in the 1980s may be responsible for ripples in one of Saturn's rings, images from NASA's Cassini spacecraft suggest. The finding is another indication that the rings are not static and can change on human timescales.

Cassini observations have revealed bright and dark bands in Saturn's innermost ring, called the D ring. The bands are getting more closely spaced as time goes on - Hubble Space Telescope images reveal they were 60 kilometres apart in 1995 and Cassini shows they have been shrinking over the last few years and are just 30 km apart now.

©NASA/JPL/Space Science Institute
The edge of the D ring is seen at the centre of this image, showing a banded structure that has gradually became more finely spaced since it was first detected by Hubble in 1995

Ambulance

The Comet and the Chicago Fire

For nearly one and a half centuries, the cause of the most notorious fire in U.S. history has been a source of "heated" controversy. Some researchers suggest that a disintegrating comet ignited the blaze. But the electrical theorists say that evidence most often ignored offers the best clues.

"With the heat increased the wind, which came howling across the prairie, until at last there arose a perfect hurricane. Mighty flakes of fire, hot cinders, black, stifling smoke, were driven fiercely at the people, and amid the terrible excitement hundreds of them had their very clothes burned off their backs, as they stood there watching with tearful eyes the going down of so many houses". -- James Goodsell's History of the Great Chicago Fire, October 8, 9, and 10, Published 1871 by J.H. and C.M. Goodsell.

Better Earth

Comet Biela and Mrs. O'Leary's Cow



Image
©Unknown
Cometary fire ruins, as seen from the corner of Dearborn and Monroe Streets, Chicago, 1871.


Last night we watched Super Comet - After the Impact, a Discovery Channel special that basically takes the comet that wiped out the dinosaurs and put into modern times. They added some cheesy drama, following the struggles of several individuals or groups, before, during, and after the impact, to show how people would react to such a global cataclysm. They used the same type of cometary body assumed to have caused the extinction of the dinosaurs, the same size, same impact location, and utilized all the computer modeling they have done on this past event to try to show what might happen (and to show what they think happened then). Not terribly creative and suggests that they really don't know all the effects of such an impact and are just putting things together from what little they have been able to figure out about that one impact, some (or much) of which may be just speculation, though I'm sure that there is some good science going on there.

This show highlights what we have already noted in this series of articles: the difference between the American School of Asteroid impacts that happen only at millions of years intervals and the British School which posits that showers of much smaller objects occur with great frequency in between those millions of years events.

The cheesiest part of this "docu-drama" was, of course, the depicted foibles of the humans experiencing the event. But, in a way, even those depictions were useful. The one guy who simply couldn't grasp the nature of the event, kept traveling "home" (which happened to be the site of the impact) even when it was clear that there was no home left. His emotions basically drove him to his own death.

Other people continued to act as if the world was still the same place and suffered thereby, though they learned to cope. What was clearly evident was that it was lack of knowledge about such events that was the chief problem for all of them.

During the course of the show, one of the experts made the remark "WHEN it happens," as though he - and the rest of them - knew for a fact that this was on the agenda for our near future. The very fact that so many scientists are working on these problems, including a large number of them studying the possible human reactions and behaviors and how to deal with masses of people, should warn us that there IS something they aren't telling the masses in the headlines of our daily newspapers, though certainly they are "testing" public reactions with shows such as Super Comet - After the Impact.

On my desk, before me, I have a book out of the more than 30 volumes and scores of papers on the topic of comet and asteroid impacts that I have collected in the course of this study. The title of this book is Hazards due to Comets and Asteroids edited by Tom Gehrels, with 120 contributing authors, published by the University of Arizona Press in 1994.

There is something in this book that I want to bring to your attention before we get on to our main catastrophe of the day: Mrs. O'Leary's Cometary Cow.

Comment: Continue to Part Seven: Tunguska, the Horns of the Moon and Evolution


Umbrella

Comet samples are surprisingly asteroid-like

Samples of Comet Wild 2 suggest it is made of rocky material, like an asteroid, rather than the fluffy dust expected of a comet. The object may be a refugee that formed in the asteroid belt before getting kicked to the chilly fringes of the solar system, or it might have formed in that frigid realm from material thrown out of the inner solar system, scientists say.

©NASA/JPL/Malin Space Science Systems
Comet Wild 2 is shown in close-up above. Beside it is a microscopic view of an EDM (electrical discharge machined) surface. Note the flat-floored depressions with steep scalloped walls and terracing. The small white spots on the comet can then be reasonably identified as the active cathode arcs that produce the cometary jets.

Comment: Read also SOTT's special report on Comets and Catastrophe (links on the left bar)


Better Earth

Thirty Years of Cults and Comets



©Unknown
Comet of 1532


This morning I was thumbing through a newly arrived book: Comet/Asteroid Impacts and Human Society, published by the eminent scientific publishing house, Springer, edited by Peter T. Bobrowsky and Hans Rickman. This book is a collection of scientific papers presented at a workshop under the aegis of the International Council for Science. In the introduction, we read:
The International Council for Science recently recognized that the societal implications (social, cultural, political and economic) of a comet/asteroid impact on Earth warrants an immediate consideration by all countries in the world.
Wow! You think? You mean it's not just us here at SOTT (and a few others on the net) who are keeping track of the increasing number of Fireballs and Meteorites that suggest we are passing through rather dangerous areas of space, or that maybe Something Wicked This Way Comes?

Yes, it seems so. In the chapter entitled "Social Perspectives on Comet/Asteroid Imact (CAI) Hazards: Technocratic Authority and the Geography of Social Vulnerability" we read:
Until quite recently, research into comet and asteroid hazards was focused on establishing the scale and scope of past impacts, credible estimates of their recurrence, and models for physical impact scenarios. ... CAI hazards have moved well beyond the realm of ungrounded speculation and apocalyptic visions. The results represent more than just new findings. They revolutionize, or are about to revolutionize, some basic understandings about the Earth, its history, biological evolution and future. Although human life has had a tiny place in the story so far, our longer term fate seems to be challenged by these forces and may be decided by them.
No kidding.

In a chapter entitled "Social Science and Near-Earth Objects: an Inventory of Issues", we read:
It would have been ridiculous, not too long ago, to admit openly that you were thinking about asteroids and comets slamming into the Earth. Such events could mean the end of the world as we know it - TEOTWAWKI as millenialists call it - and that kind of talk is often ridiculed. ...

Respectable people are pondering the issues. For example, S. Pete Worden, who is a Brigadier General in the US Air Force and Deputy Director for Command and Control Headquarters at the Pentagon, has said that he believes "we should pay more attention to the 'Tunguska-class' objects - 100 meter or so objects which can strike up to several times per century with the destructiveness of a nuclear weapon."
I located the General's comments and they are now in the SOTT database. It seems that the above is not all the general said. In fact, he states quite unequivocally:
I can show people evidence of real strikes inflicting local and regional damage less than a century ago. Even more compelling are the frequent kiloton-level detonations our early warning satellites see in the earth's atmosphere. ... Within the United States space community there is a growing concern over "space situational awareness."
The general was writing back in 2000. "Less than a century ago." That would be after 1900. He said that there were "real strikes inflicting local and regional damage" since 1900?!

Did I miss something? Did all of us miss something?

Comment: Continue to Part Six: Comet Biela and Mrs. O'Leary's Cow


Star

Stardust comet dust resembles asteroid materials

Contrary to expectations for a small icy body, much of the comet dust returned by the Stardust mission formed very close to the young sun and was altered from the solar system's early materials.

When the Stardust mission returned to Earth with samples from the comet Wild 2 in 2006, scientists knew the material would provide new clues about the formation of our solar system, but they didn't know exactly how.

©NASA/JPL
Combined long- and short-exposure images captured during the Stardust flyby of the comet Wild 2.

Star

Electric Comet Theory: The Enduring - Yet Downplayed - Mysteries of Comets

"Mysteries are due to secrecy."
-Francis Bacon


On December 24, 2007, the website Space.com published a report entitled, "The Enduring Mysteries of Comets." The premise is intriguing, since it is rare for science media to acknowledge that "mysteries" of any real significance exist for conventional theories. Unfortunately, the report mentions few of the recent discoveries that have thrown the popular "dirty snowball" model of comets into disarray.

"We have now had four close encounters with comets, and every one of them has thrown astronomers onto their back foot." -Stuart Clark, New Scientist, September 09, 2005.