* Astronomy

On Friday 11 January, leading scientists will gather for a conference at the Royal Astronomical Society (RAS) where they will present new results on how giant impacts have shaped the Earth, other planets, comets and asteroids in the Solar System.
Delegates will consider topics including the consequences of asteroid impacts for the terrestrial environment, the effect of Jupiter on the rates of these collisions and the significance of impacts for life on Earth and elsewhere in the Universe.
The meeting will run from 1030 to 1530 and will take place in the lecture theatre of the Royal Astronomical Society in Burlington House, off Piccadilly in London.

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Mammoth tusks show up meteorite shower
Fossils could provide a new gold mine for micrometeorite hunters.
Bullet-like pieces of what is thought to be an ancient meteorite shower have been found embedded in mammoth tusks and bison bone.
The discovery of the 25 millimetre holes left by meteorites opens a window into a impact event thought to have happened over Alaska and Russia tens of thousands of years ago. And it could provide a whole new way to chart impacts from space.
The fragments, found in seven mammoth tusks and the skull and horns of a Siberian bison, match the geochemical composition of iron meteorites.

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At the end of the Pleistocene era, woolly mammoths roamed North America along with a cast of fantastic creatures giant sloths, sabre-toothed cats, camels, lions, tapirs and the incredible teratorn, a condor with a 16-foot wingspan.
About 12,900 years ago, these megafauna disappeared from the fossil record, as did evidence of human remains. The cause of the mass extinction and the human migration is a mystery. Now a team of scientists, including Brown University planetary geologist Peter Schultz, provides evidence that an asteroid impact likely caused the sudden climate changes that killed off the mammoths and other majestic beasts of prehistory.
In the Proceedings of the National Academy of Sciences, the international team lays out its theory that the mass extinctions in North America were caused by one or more extraterrestrial objects comets or meteorites that exploded over the Earth or slammed into it, triggering catastrophic climate change.
The scientists believe that evidence for these extraterrestrial impacts is hidden in a dark layer of dirt sometimes called a black mat. Found in more than 50 sites around North America, this puzzling slice of geological history is a mere three centimetres deep and filled with carbon, which lends the layer its dark colour. This black mat has been found in archaeological digs in Canada and California, Arizona and South Carolina even in a research site in Belgium.

The formation of this layer dates back 12,900 years and coincides with the abrupt cooling of the Younger Dryas period, sometimes called the Big Freeze. This coincidence intrigued the researchers, led by Richard Firestone of Lawrence Berkeley National Laboratory, who thought that the black mat might be related to the mass extinctions.
So the researchers studied black mat sediment samples from 10 archaeological sites dating back to the Clovis people, the first human inhabitants of the New World. Researchers conducted geochemical analysis of the samples to determine their makeup and also ran carbon dating tests to determine the age of the samples.
Directly beneath the black mat, researchers found high concentrations of magnetic grains containing iridium, charcoal, soot, carbon spherules, glass-like carbon containing nanodiamonds and fullerenes packed with extraterrestrial helium all of which are evidence for an extraterrestrial impact and the raging wildfires that might have followed.
Schultz, professor of geological sciences at Brown and an impact specialist, said the most provocative evidence for an extraterrestrial impact was the discovery of nanodiamonds, microscopic bits of diamond formed only from the kind of intense pressure youd get from a comet or meteorite slamming into the Earth.

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