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Close encounters in space

October 19, 2014

A comet scraped past Mars on Sunday in what scientists called a once-in-a-million-years encounter. NASA documented the rare event, and it's hoped the data will shed light on the origins of the solar system.

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Image: picture-alliance/dpa/Nasa

The comet, known as Siding Spring or C/2013 A1, was expected to hurtle past Mars at a close distance of about 140,000 kilometers (90,000 miles) at 18:27 UTC on Sunday night.

The comet is shooting through space at a speed of 196,984 kilometers per hour (120,000 mph) and is thought to have formed billions of years ago in the Oort Cloud, which is made up from material left over from the formation of the solar system.

"Comets such as C/2013 A1 are essentially dirty icy snowballs with rocks and dust embedded in frozen gasses," Dan Brown, an astronomy expert at Nottingham Trent University in the UK, told the news agency AFP.

"It is on its first run towards the center of our solar system and its material is virtually unchanged by the rays of the sun and can give us an insight to the material composition of our early solar system 4.6 billion years ago," he added.

Siding Spring has traveled more than 1 million years to reach the red planet, and another million years will pass before it returns.

Before the event, astronomers predicted that though the comet wouldn't collide with Mars, its tail would likely graze the planet, providing a rare opportunity to gather valuable data. NASA, the US space agency, deployed more than a dozen probes, rovers and telescopes to document the near miss. Its Mars orbiters were also moved to the far side of the planet so that they wouldn't be hit by the comet's flying debris, but it was hoped they would still be able to capture some data from the event.

The US space agency also planned for its two rovers, Curiosity and Opportunity, to turn their cameras skywards and send back pictures of the comet's passing. Data collected by the rovers could measure how the gas and dust interact with the Martian atmosphere, Rebecca Johnson, editor of StarDate magazine, told AFP.

"It gives scientists a chance to see a relic from the distant past - a snowball that preserves the same ingredients that gave birth to our own world," she said.

The comet gets its name from the Siding Spring Observatory in Australia, where it was discovered by Robert McNaught in January 2013.

nm/mkg (dpa, AFP)