* Astronomy

Comet strikes are an unlikely cause of past mass extinctions on Earth, according to computer simulations.
Scientists used the simulations to model the paths of long-period comets, to determine the likelihood of these "dirty snowballs" striking our planet.
The University of Washington, Seattle, research appears in Science journal.

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Crashing comets not likely the cause of Earth's mass extinctions
Scientists have debated how many mass extinction events in Earth's history were triggered by a space body crashing into the planet's surface. Most agree that an asteroid collision 65 million years ago brought an end to the age of dinosaurs, but there is uncertainty about how many other extinctions might have resulted from asteroid or comet collisions with Earth.
In fact, astronomers know the inner solar system has been protected at least to some degree by Saturn and Jupiter, whose gravitational fields can eject comets into interstellar space or sometimes send them crashing into the giant planets. That point was reinforced last week (July 20) when a huge scar appeared on Jupiter's surface, likely evidence of a comet impact.
New University of Washington research indicates it is highly unlikely that comets have caused any mass extinctions or have been responsible for more than one minor extinction event. The work also shows that many long-period comets that end up in Earth-crossing orbits likely originate from a region astronomers have long believed could not produce observable comets. A long-period comet takes from 200 years to tens of millions of years to make a single orbit of the sun.

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Mission to Mars?
The moon is not enough! That's the thrust of Tom Wolfe's argument in The New York Times, where he laments America's longtime failure to do anything impressive in space. He lays blame for this post-Apollo problem on a lack of big thinkers at NASA.

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Posibilele gauri negre produse de acceleratorul de particule LHC, iarna nucleara si potenialul impact cu asteroidul Apophis în 2029 sunt printre cele mai înfioratoare ameninari apocaliptice iesite din laboratoarele oamenilor de stiina.
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