, Colo. —

Hit or miss … there is already lots of fallout from the anticipation that an

asteroid designated WD5 might

smack into Mars




There already has been some speculation, for example, that WD5 is not a space rock, but an old spacecraft – such as Mars Observer – coming back to haunt the red planet. However, according Donald Yeomans, an

asteroid specialist,

at the Jet Propulsion Laboratory, 2007 WD5 does not have an orbit that is consistent with a Mars spacecraft. When specialists integrate the object’s orbit backward in time, it does not get near Earth within the past few decades, he advised me.

Nevertheless, if Mars does get whacked, scientists will have a field day.

Mark Boslough,

a collision dynamics expert at Sandia National Laboratories in New Mexico, said the

density of Mars’ atmosphere – 20 kilometers or so above the surface – is similar to the density of Earth’s atmosphere.

A stony or chondritic asteroid of the size of WD5 would not explode in Earth’s atmosphere, but at a higher

altitude. “So this won’t be an airburst … it will either hit the ground intact and make a single crater, or break up and generate a cluster of craters,” he added.

said an educated, but speculative, guess is that, if indeed the object strikes Mars, surface material from the red planet would be lofted to a very high altitude as a visible column of dust within an atmospheric plume.

Such a wallop might prove biologically interesting too – given the idea that Mars underground could be a cozy spot for microbial life.

John Rummel, senior scientist for astrobiology in the Science Mission Directorate at NASA headquarters in Washington

, said

an asteroid strike

on Mars would be an event that could be studied by orbiters now circling Mars – particularly by the super-powerful camera onboard NASA’s Mars Reconnaissance Orbiter (MRO).

“An impact that we could witness [and] follow-up with MRO would be truly spectacular, and could tell us much about the hidden subsurface that could help direct a search for life or life-related molecules,” Rummel said.

Depending on the results of such an impact, the impact area

could be a potential landing site

for the Mars Science Laboratory mega-rover, which is

scheduled to be launched toward Mars in 2009.

WD5 is about the size of the object that blasted out Meteor Crater

in northern Arizona

about 50,000 years ago. The asteroid is traveling at an estimated speed of

about 48,000 kilometers

per hour.


WD5 does hit the red planet, the Mars Reconnaissance Orbiter will

have a front-row seat for

surveying the hit. MRO’s

High Resolution Imaging Experiment (HiRISE) is

the most powerful camera ever to orbit another planet.

“If the asteroid hits Mars, we’ll get a great look at the crater within a few days of impact,” said HiRISE principal investigator Alfred McEwen of the University of Arizona’s Lunar and Planetary Laboratory in Tucson.