Welcome to Sott.net
Fri, 25 Sep 2020
The World for People who Think

Comets

Bizarro Earth

Did a massive comet kickstart plate tectonics on Earth?

It's such a simple idea that it's surprising no one seems to have thought of it before. Did a massive asteroid or comet impact kick-start plate tectonics on Earth?

For much of our planet's history, rocky plates have been sliding over a viscous, molten mantle, colliding to build mountain ranges or spreading apart to make way for oceans. In a neat piece of recycling, an oceanic plate dives, or "subducts", underneath a less dense continental plate, and eventually melts into the hot mantle.

Geologists estimate that plate tectonics began during the Archean period, between 2.5 and 3.8 billion years ago - but they don't know what triggered it. Ancient Earth was too hot for the crust to solidify completely, and the lightest minerals would have floated to the surface over the entire planet, making the subduction of denser plate material unlikely.

Magnify

A new Polish comet

Michal Kusiak, a student of astronomy at Jagiellonian University in Krakow and an editor of Astronomia.pl has discovered a new comet. This young astronomy enthusiast found the object in images sent back to Earth by the SOHO Solar Observatory. Information on the discovery has been already published on a Web Site of the British Astronomical Association.

©SOHO
Comet belonging to the Kreutz family

Telescope

Evolution of Comet 17P Holmes



©Nicolaus Copernicus University in Toruń.
Sequence of images of Comet 17P/Holmes obtained with the TSC 60/90 telescope in the V filter. They show the increase in the comet's envelope size. The colours are chosen here in order to best show the cometary nucleus (the bright point in the centre) and matter moving away from the nucleus (to the right of the nucleus).

Comet 17P/Holmes has been intriguing astronomers since the end of October, when its sudden outburst in brightness, the biggest in the history of comet research, was observed. Scientists from Nicolaus Copernicus University in Torun in Poland have published a series of images illustrating the evolution of the comet.

Ark

Parody: End of Mayan Calendar Coincides with Impact of Shock Wave from Comet Holmes

Scientists at the Mount Palomar Observatory in California and Caltech have confirmed that the "blast front" from Comet 17P/Holmes will hit the Earth on Dec 21, 2012. By odd coincidence, this is the day that the Mayan Calendar ends, and is predicted by some to correlate with the end of the world.

Telescope

Did a Comet Cause the Great Flood?

The serpent's tails coil together menacingly. A horn juts sharply from its head. The creature looks as if it might be swimming through a sea of stars. Or is it making its way up a sheer basalt cliff? For Bruce Masse, an environmental archaeologist at Los Alamos National Laboratory, there is no confusion as he looks at this ancient petroglyph, scratched into a rock by a Native American shaman. "You can't tell me that isn't a comet," he says.

©Discover
The Fenambosy chevrons at the tip of Madagascar. Image courtesy of Dallas Abbott

Telescope

Hubble Zooms in on Heart of Mystery Comet

NASA's Hubble Space Telescope has probed the bright core of Comet 17P/Holmes, which, to the delight of sky watchers, mysteriously brightened by nearly a millionfold in a 24-hour period beginning Oct. 23, 2007.

Meteor

Comet Holmes and the case of the Disappearing Tail

But what's a Comet, anyway?

©REUTERS/NASA, ESA, and H. Weaver/The Johns Hopkins University Applied Physics Laboratory/Handout
A Hubble image (R), taken November 4, 2007, shows the heart of Comet 17P/Holmes. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a "bow tie" appearance. The composite color image at left, taken on November 1, 2007, by an amateur astronomer shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side. The normally sedate Comet Holmes made a bright splash in the sky about two weeks ago, unexpectedly becoming a million times brighter than normal overnight and causing a stir among astronomers.

Comment: Enjoy our latest Forum's Topic:

Speculations about the Comet 17P/Holmes


Arrow Down

Astronomers unravel a mystery of the Dark Ages: Research blames comet for 6th-century 'nuclear winter'

Scientists at Cardiff University, UK, believe they have discovered the cause of crop failures and summer frosts some 1,500 years ago - a comet colliding with Earth.

The team has been studying evidence from tree rings, which suggests that the Earth underwent a series of very cold summers around 536-540 AD, indicating an effect rather like a nuclear winter.

The scientists in the School of Physics and Astronomy believe this was caused by a comet hitting the earth and exploding in the upper atmosphere. The debris from this giant explosion was such that it enveloped the earth in soot and ash, blocking out the sunlight and causing the very cold weather.

This effect is known as a plume and is similar to that which was seen when comet Shoemaker-Levy-9 hit Jupiter in 1995.

Historical references from this period - known as the Dark Ages - are sparse, but what records there are, tell of crop failures and summer frosts.

Telescope

Comet Holmes' display captivates stargazers

The normally sedate Comet Holmes made a bright splash in the sky about two weeks ago, unexpectedly becoming a million times brighter than normal overnight and causing a stir among astronomers.

©REUTERS/NASA, ESA, and H. Weaver/The Johns Hopkins University Applied Physics Laboratory/Handout
A Hubble image (R), taken November 4, 2007, shows the heart of Comet 17P/Holmes. The central portion of the image has been specially processed to highlight variations in the dust distribution near the nucleus. About twice as much dust lies along the east-west direction (the horizontal direction) as along the north-south direction (the vertical direction), giving the comet a "bow tie" appearance. The composite color image at left, taken on November 1, 2007, by an amateur astronomer shows the complex structure of the entire coma, consisting of concentric shells of dust and a faint tail emanating from the comet's right side.

Ambulance

Look Up! Comet Holmes Bigger Than The Sun

Formerly, the Sun was the largest object in the Solar System. Now, comet 17P/Holmes holds that distinction.

Comment: The same image is available from the University of Hawaii as a 300 dpi tif file.