Just getting whacked by the either the ion tail or the dust/debris tail could be a terrible event. One of the twenty or so Shoemaker-Levy 9 nuclei left a dark spot on Jupiter the size of the Pacific Ocean.
On Wed, Feb 27, 2013 at 4:21 PM, Mark Gibbs <mgi...@gibbs.com> wrote: > > > http://www.universetoday.com/100298/is-a-comet-on-a-collision-course-with-mars/ > > There is an outside chance that a newly discovered comet might be on a > collision course with Mars. Astronomers are still determining the > trajectory of the comet, named C/2013 A1 (Siding Spring), but at the very > least, it is going to come fairly close to the Red Planet in October of > 2014. “Even if it doesn’t impact it will look pretty good from Earth, and > spectacular from Mars,” wrote Australian amateur astronomer Ian > Musgrave<http://astroblogger.blogspot.com/>, > “probably a magnitude -4 comet as seen from Mars’s surface.” > > The comet was discovered in the beginning of 2013 by comet-hunter Robert > McNaught at the Siding Spring Observatory in New South Wales, Australia. > According to a discussion on the IceInSpace amateur astronomy > forum<http://www.iceinspace.com.au/forum/showthread.php?p=950710> when > the discovery was initially made, astronomers at the Catalina Sky Survey in > Arizona looked back over their observations to find “prerecovery” images of > the comet dating back to Dec. 8, 2012. These observations placed the > orbital trajectory of comet C/2013 A1 right through Mars orbit on Oct. 19, > 2014. > > However, now after 74 days of observations, comet specialist Leonid > Elenin<http://spaceobs.org/en/tag/c2013-a1-siding-spring/> notes > that current calculations put the closest approach of the comet at a > distance of 109,200 km, or 0.00073 AU from Mars in October 2014. That close > pass has many wondering if any of the Mars orbiters might be able to > acquire high-resolution images of the comet as is passes by. > > But as Ian O’Neill from Discovery > Space<http://news.discovery.com/space/astronomy/could-a-comet-hit-mars-in-2014-130225.htm> > points > out, since the comet has only been observed for 74 days (so far), so it’s > difficult for astronomers to forecast the comet’s precise location in 20 > months time. “Comet C/2013 A1 may fly past at a very safe distance of 0.008 > AU (650,000 miles),” Ian wrote, “but to the other extreme, its orbital pass > could put Mars directly in its path. At time of Mars close approach (or > impact), the comet will be barreling along at a breakneck speed of 35 miles > per second (126,000 miles per hour).” > > Elenin said that since C/2013 A1 is a hyperbolic comet and moves in a > retrograde orbit, its velocity with respect to the planet will be very > high, approximately 56 km/s. “With the current estimate of the absolute > magnitude of the nucleus M2 = 10.3, which might indicate the diameter up to > 50 km, the energy of impact might reach the equivalent of staggering 2×10¹º > megatons!” > > An impact of this magnitude would leave a crater 500 km across and 2 km > deep, Elenin said. > [image: Fragments of Shoemaker-Levy 9 on approach to Jupiter > (NASA/HST)]<http://ut-images.s3.amazonaws.com/wp-content/uploads/2008/12/shoemaker-levy_9_on_1994-05-17.png> > > Fragments of Shoemaker-Levy 9 on approach to Jupiter (NASA/HST) > > While the massive Comet Shoemaker–Levy 9 (15 km in diameter) that crashed > into Jupiter in 1994 was spectacular as seen from Earth orbit by the Hubble > Space Telescope, an event like C/2013 A1 slamming into Mars would be off > the charts. > > > Read more: > http://www.universetoday.com/100298/is-a-comet-on-a-collision-course-with-mars/#ixzz2M8XbWdrA >
