Welcome to Sott.net
Thu, 03 Dec 2020
The World for People who Think

Comets

Bizarro Earth

Proof found of man-made climate change, Scientists fear public won't care after a comet falls on their head

Scientists have been able to say with virtual certainty for the first time that the climate change observed over the past four decades is man made and not the result of natural phenomena.

Umbrella

Comets, dragons & prophets of doom

Ancient myths suggest that a giant comet may have visited the Earth a few thousand years ago, raining fireballs and meteors

Scientists are starting to recognise that the evolution of life on Earth has been affected, if not largely shaped, by its celestial environment. We now recognise that throughout its history the Earth has been bombarded by comets, small asteroids, meteorites (small rocky or iron bodies) and smaller particle and dust (meteor) showers. Over the years, astronomers have detected a substantial population of such small bodies out there in the Solar System, confirming that the threat of their impact with the Earth is a significant one. Current estimates, for example, suggest that between 10 and 30 impacts similar to the one that occurred in Tunguska in Siberia in 1908 have happened over recorded history, with perhaps one or more exploding with a force equivalent to that produced by 500 to 1000 megatonnes of TNT.

Image
©Frontiers
A mediæval representation of a meteorite fall as a serpent in the sky

Frog

High School freshman unearths asteroid, cometary evidence for mammoth extinction

After working countless hours digging soil samples and analyzing them with sophisticated microscopes, Great Falls High School freshman Katelyn Gibbs has come up with evidence that a comet or meteorite crashed to Earth in Montana 13,000 years ago and had major impact on animals living here at the time.

"Bing! She nailed it!" said David Baker of Monarch, a veteran earth science research scientist who mentored Gibbs on the project. "Katelyn found definitive proof - nanodiamonds and iron micrometeorites - for the extraterrestrial impact event that killed the mammoths in Montana.

Telescope

Comets might have caused ancient American extinctions 13,000 years ago

Scientists have come up with a controversial theory which suggests that huge comet impacts wiped out North America's large mammals 13,000 years ago.

According to a report in National Geographic News, the hypothesis, first presented in May 2007, proposes that an onslaught of extraterrestrial bodies caused the mass extinction known as the "Younger Dryas event" and triggered a period of climatic cooling.

Target

Sun's Movement Through Milky Way Regularly Sends Comets Hurtling, Coinciding With Mass Life Extinctions

The sun's movement through the Milky Way regularly sends comets hurtling into the inner solar system -- coinciding with mass life extinctions on earth, a new study claims. The study suggests a link between comet bombardment and the movement through the galaxy.

Star

Study suggests link between comet bombardment and movement through the galaxy, causing mass extinctions on earth

The sun's movement through the Milky Way regularly sends comets hurtling into the inner solar system -- coinciding with mass life extinctions on earth, a new study claims. The study suggests a link between comet bombardment and the movement through the galaxy.

Comets
©Artby Don Davis / Courtesy of NASA
A large body of scientific evidence now exists that support the hypothesis that a major asteroid or comet impact occurred in the Caribbean region at the boundary of the Cretaceous and Tertiary periods in Earth's geologic history. Such an impact is suspected to be responsible for the mass extinction of many floral and faunal species, including the large dinosaurs, that marked the end of the Cretaceous period.

Bizarro Earth

Sorry to ruin the fun, but an ice age cometh

THE scariest photo I have seen on the internet is www.spaceweather.com, where you will find a real-time image of the sun from the Solar and Heliospheric Observatory, located in deep space at the equilibrium point between solar and terrestrial gravity.

What is scary about the picture is that there is only one tiny sunspot.

Image
©SOHO

Comment: Chapman has it only partly right. He excludes the evidence for cometary dust loading that contributed to the last ice age (and most likely previous ones). The increased depositional flux evidenced from Gabrielli's paper shows that it was not the sun alone that caused the last ice age:

Depositional Fluxes
©Nature

And from Victor Clube's talk:
You first take the modern sky accessible to science, especially during the Space Age, and you look at its' darker debris with a view to relating its behavior to the more accessible human history which we can, in principle, really understand. And by this approach you discover from the dynamics of the material in space which I'm talking about that a huge comet must have settled in a Taurid orbit some 20,000 years ago, whose dense meteor stream for 10,000 years almost certainly produced the last Ice Age.
Now the question must be asked, Is there a relationship between the sun's missing spots and a 100,000 year ice age cycle coupled with cometary debris entering the solar system?


Bell

Planetery Protection: Governments reconsider the risk of Near-Earth asteroid and comet impacts

Until very recently, the devastating 1908 explosion of a space rock over the isolated Tunguska region of Siberia was thought to be a once-in-a-millennium event. Based on comparisons to nuclear weapon blast effects, many experts estimated the Tunguska object to be 50 to 100 meters. But new simulations by Mark Boslough at Sandia National Laboratories suggest the Tunguska object was much smaller than previously believed. And since smaller near-Earth objects (NEOs) are more common than larger ones, the implication is that the gap between such impacts may be centuries rather than millennia.

Telescope

The Tagish Lake Meteorite: "Like Sampling the Surface of a Comet"

A scientific consortium of 4 universities and NASA is now trying to uncover the debris and sample the early solar system's unique chemistry.

tagish1
©University Calgary
Close-up of Tagish Lake fragile carbon porousity.

Telescope

Out of the Blue - Group Searches for Evidence of Recurring Cometary Impacts

Magnified 25,000 times under Drexel University's scanning electron microscope, a couple of flecks of dirt offer up a landscape full of crags, valleys, ridges - and, to Dee Breger's eyes, a window back in time.

Microspherule
©Dee Breger
Colorized scanning electron micrograph shows a tiny spherule that is believed to have formed from a vaporized or melted fragment when a piece of a comet slammed into the Indian Ocean an estimated 4,800 years ago. Marine geophysicist Dallas Abbott hypothesizes that such an impact was the source of deluge legends like Noah's ark and Gilgamesh.