Look to the skies this weekend as an event unfolds that only happens once every million years or so. In fact, this event will be the first ever in recorded history!
CBS reports that a comet as hefty as a small mountain will pass extremely close to Mars on Sunday, approaching within 87,000 miles at a speed of 126,000 mph. NASA’s five robotic explorers at Mars — three orbiters and two rovers — are being repurposed to witness a comet named Siding Spring make its first known visit to the inner solar system. The orbiting craft will attempt to observe the incoming iceball, then hide behind Mars for protection from potentially dangerous dusty debris in the comet tail.
What is so special about the Siding Spring comet? First, according to NASA, the comet will be less than one-tenth the distance of any known previous earthly comet flyby on October 19 at 18:28UTC. In way of contrast, the closest comet to swing by Earth in recorded history was Lexell’s Comet, at six times the moon’s distance from Earth (6 x 384,400 kilometers or 238,855 miles) in the year 1770. Second, this comet is from the Oort cloud. The Oort cloud is located on the extreme fringe of the solar system. It formed during the first million or two years of the solar system’s birth 4.6 billion years ago and, until now, ventured no closer to the sun than perhaps the orbits of Jupiter, Saturn, Uranus or Neptune. It comes around every one or more million years.
Therefore, this is the first time NASA will have the chance to see an Oort cloud comet up close. The close flyby is made all the more exciting since we have rovers and orbiters currently residing on Mars. By studying Siding Spring’s composition and structure, scientists hope to learn more about how the planets formed. Scientists also are keen to spot any changes to the comet or Mars due to the close approach. NASA’s newly arrived Maven spacecraft, for instance, will compare the upper atmosphere before and after it passes. The scientific community will have the opportunity to gain knowledge that was previously impossible to obtain.
The Smithsonian reports that Mars is currently a hotspot of space research. Siding Spring’s close approach, combined with the bevy of telescopes and sensors, means that this weekend will offer astronomers their best look yet at an Oort cloud object. Millions of years ago, says University of Maryland astronomer Michael Kelley, something disturbed the orbit of Siding Spring, sending it hurtling toward the Sun. He notes how extremely rare and unlikely an event like this is to take place again. In fact, he says it may never happen again.
“We may never see another Oort cloud comet breeze past Mars so closely again.”
The comet will be able to be seen from Earth. However, a sky gazer will need a telescope or binoculars to see the fast moving comet. Sadly for those of us in the Northern Hemisphere, the best viewing will be in the south such as Australia and South America.
In other related news, the ESA’s Philae Lander is scheduled to land on a comet next month.