Deep Impact, step aside
It seems like yesterday, but it’s already over 13 years ago that a comet, Shoemaker-Levy 9, having been broken up into a couple of dozen fragments on its previous pass, spectacularly slammed into Jupiter. It was the first time ever such an impact had been observed, and it was visible not only from Earth, but also from the spacecraft Voyager 2, which had a close-up view. Last year, NASA launched a mission to slam a large fridge into comet Tempel 1. It was amazingly successful, producing an explosion captured and analysed by astronomers all over the world. Next month, the Mars rover Opportunity could have a ringside seat for a repeat performance by a a newly-discovered asteroid headed for Mars.
Shoemaker-Levy 9 comet had been discovered not long before by Canadian atronomer David Levy, and his more famous American counterparts, champion hunter of comets and asteroids Carolyn Shoemaker, and her late husband, astrogeology poineer and would-be moonwalker Eugene Shoemaker. To date, “the SuperGene”, as he was sometimes referred to, is the only person whose remains are buried on the moon. (Bill Hollenbach, an amateur astronomer with a self-built observatory at the Wondercave in the Cradle of Humankind, northwest of Johannesburg, pointed out where exactly the site is located in the comments to a previous post.) Two of the famous pictures of the Shoemaker-Levy 9 impact, one of the comet string, and another of the impact explosions, are alongside (click on them for larger versions).
The new asteroid, designated 2007 WD5, was discovered by Andrea Boattini of the Catalina Sky Survey. By astronomical standards, the event is very likely. The asteroid has a one in 75 chance of hitting Mars at about 13:00 South African Standard Time (11:00 GMT) on 30 January 2008, and that chance could increase early in January, when more observations of the asteroid’s orbit have been taken. If it misses, it will miss by less than four times the diameter of the earth.
2007 WD5 is estimated to be the same size as the object that is believed to have caused the Tunguska event in Siberia in 1908. William Hartman has created a fascinating page about Tunguska with paintings that reconstruct eyewitness accounts. Wikipedia has lots of links and theories — ranging from likely to lunatic — about the event.
The Jet Propulsion Laboratory’s Ron Baalke modified a Java-application by Osamu Ajiki, which permits you to plot and observe the orbits of WD5, Earth, Mars and Jupiter.
