Doomsday comet makes closest approach to Earth

ANTICIPATED by doomsayers as a potentially catastrophic event, Comet Elenin traversed the closest point in its trajectory around Earth (35,000km) early Sunday morning just before sunrise. But save for a few keen observers and astronomers, this went largely unnoticed.

When discovered by astronomer Leonid Elenin in December 2010, the passing of the 3-5 km wide chunk of space ice was predicted to be the astronomical event of the year, which in turn inspired an overkill of apocalyptic theories.

Amateur astronomers and conspiracy theorists put forth the idea that Comet Elenin was responsible for a variety of anomalous events seen throughout 2011; from the scattered outbursts of political uprisings to the earthquake in Japan.

Others extrapolated these prophecies to Comet Elenin representing the end of the world.
However, sometime during the middle of August, Comet Elenin began disintegrating as it crossed the solar system and traveled through the sun’s solar flares. And so at around 4 am Sunday morning, the comet passed within view of ground telescopes in an event that astronomers described as “largely uneventful.”

“I could see a hazy group of dim chunks of rock sitting in the sky, moving very slowly,” said Samir Nawar, a professor at the National Research Institute of Astronomy and Geophysics (NRIAG) in Helwan.

“But it was far less interesting than looking at the sun or the moon on any other day of the year, and a lot less noticeable,” he joked, referring to the Earth’s temperate climate and tides.
On the issue of conspiracy theories, Nawar went on to say that there is an obsession with space phenomena, which are far away and little understood; and that even if Comet Elenin had not disintegrated, the event would have still passed largely unnoticed. –AA

“People like to play on the fact that there are a lot of ‘maybes’ with these ‘unknown’ phenomena,” he continued. “But the truth is there are few maybes; there is a lot of accuracy with understanding space science, more than there is an understanding of what’s at the bottom of the oceans. If there was any issue of concern, NASA or any professional astronomer would be the first to raise the issue.”

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New Proof That Comets Watered the Earth

By rights, the earth should not be the cosmic garden it is. In a solar system of planets and moons that are solid rock or mostly gas, shrouded in clouds or atmosphere-free, scorchingly hot or bitterly cold, there's only one that's dripping wet. Earthlings like to refer to our home planet as the solar system's water world, and it's a jolly good thing it's as wet as it is, because without plenty of water, life (at least as we know it) would be impossible.

All the same, it's likely our planet was once a far drier, dustier place. You need only look at two of our nearby rocky neighbors — Mercury and Venus — for a reminder of what living so close to the blast furnace of the sun can do to you. Our atmosphere helps us retain the abundant water we do have, but how did it get to us in the first place?

One popular theory has long been comets. The solar system swarms with these little rogue bodies — perhaps a trillion of them, according to astronomers' back-of-the-envelope estimates — and shortly after the sun and planets formed, they were everywhere, flying randomly and free to collide with anything in their way. Since comets are essentially dirty snowballs made of rock, gas and water ice, a few crash landings on earth could have provided all the water we needed quite nicely.

But there was a problem with that theory. All of the comets astronomers observed were indeed packed with water ice, but a lot of it was what's known as heavy water, in which the hydrogen in the H2O mix is an isotope known as deuterium, with one proton and one neutron in its nucleus. The hydrogen found in ordinary water has no neutron. Since the overwhelming share of the water in earth's oceans is made with the light hydrogen atom, astronomers calculated that comets could have accounted for only about 10% of what's there. Now, according to a new paper published in the journal Nature, it appears that those scientists may have been wrong — and the reason for their error is that they were simply looking at the wrong comets.

The paper, co-authored by researchers at the California Institute of Technology, is based on observations conducted by the Herschel Space Observatory, a spacecraft launched by the European Space Agency in 2009. Herschel looked specifically at comet Hartley 2, a small comet discovered in 1986 with an estimated diameter of .75 to .99 mi. (1.2 to 1.6 km). Analyzing the chemical composition of Hartley 2's corona — or the gassy veil surrounding the main comet body — Herschel discovered that its concentration of heavy water was only about half that of any comets observed before. While that wouldn't entirely explain earth's particular heavy- and light-water mix, it does bring the chemistry a lot more into line — and gives the cometary explanation for earthly water a big boost.

"Our results with Herschel suggest that comets could have played a major role in bringing vast amounts of water to an early earth," says physicist Dariusz Lis of Caltech, a co-author of the paper.

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