Asteroid Strike on Mars?

by Paul Gilster on December 21, 2007

Perhaps it’s fortuitous that an object similar to the asteroid that caused the Tunguska event in Siberia may put on a display for us on Mars. It’s only a one in 75 chance that 2007 WD5 will strike the surface, and those odds may change again as further data are analyzed, but if it does hit, the object could strike with much the same force as the Siberian explosion. This news story reports Tunguska as a 15-megaton explosion, though as we saw on Wednesday, new work at Sandia National Laboratories has re-considered that figure and now opts for the 3-5 megaton range.

The potential impact site is near the Martian equator. If we were to witness such a spectacle, it would bring back memories of the 1994 strike of comet Shoemaker/Levy 9, the famous ‘string of pearls’, on Jupiter. The devastation of that event was stunning, far greater than 2007 WD5 would produce, but the latter might deliver enough fireworks to produce a crater the size of Meteor Crater in Arizona. Is the Solar System trying to tell us something? If so, let’s hope the powers that handle the budgetary purse strings for critical planetary radars are listening.

So keep your eyes on this intriguing object. No one wishes Mars ill, but given the equipment we’ve now got orbiting that planet for close-up viewing, the image of what an asteroid strike can do in real time could become a powerful teaching tool. My guess is that as the new observations come in, the chances of an impact will lessen dramatically, but we won’t know for a while. Until we do, this particular game of celestial roulette should make us reflect on the odds as we consider how poorly prepared we would be if 2007 WD5 were coming at us.

Addendum: This asteroid is interesting, and unusual, in being both an Earth crosser and a Mars crosser. Says Steve Chesley (JPL):

“We estimate such impacts occur on Mars every thousand years or so. If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide.”

Opportunity is exploring a crater of approximately this size right now.

Marc L December 21, 2007 at 16:22

It will definitely be an exciting event if it were to happen. However, it does raise some serious issues that must be addressed. If we send a manned crew, or even if we colonize Mars for that matter, we will need to keep not only a close monitor on asteriods coming to Earth or the moon but to Mars as well since Mars has a less dense atmosphere which makes matters worse.

Anyway, despite that troubling issue, this asteriod should spark more exploration and even new discoveries if the rovers survive the impact… imagine all the newly exposed soil this impact will create.

Here’s an article that I wrote about the asteriod that may hit Mars: http://www.simtropolis.com/forum/messageview.cfm?catid=138&threadid=95693&enterthread=y

Robin Goodfellow December 21, 2007 at 19:47

A good percentage of the Earth’s land area is populated. More importantly, most of the Earth’s surface is water, and many coastal areas are densely populated. This means that an impact anywhere on Earth of a certain size or greater is likely to harm human civilization in some way (most likely due to tsunamis). The same is not the case for Mars, even were we to have colonies there, since the planet would still be mostly empty of human influence. To some degree this means that we can be less vigilant concerning Martian impact threats, even when Mars starts gaining a human population. To a first approximation, the risk of a Martian lander mission being hit by an asteroid is comparable to that of being hit in flight through interplanetary space, which is an exceedingly tiny probability. In the long term, of course, we will not want to be surprised by any impacts anywhere in the Solar System.

Moon Saloon December 21, 2007 at 20:13

Too bad there are currently no seismometers on Mars.

The impact could be used to sound out the interior’s properties.

Since we would know the precise location and time of impact, there would be no ambiguity in the source location.

By observing the frequency variations in a MER’s radio carrier wave perhaps we could get measurements of local ground motion and seismic wave arrival times at a Rover.

Ron S December 22, 2007 at 1:00

Robin, the risk of a strike on Mars is higher than in space, so not comparable. Reason being that the impact gets transmitted through the surface, whereas in space you need a direct hit. So it just needs to strike nearby (for a suitable calculation of ‘nearby’). On the other had the risk of smaller objects, which are more numerous, is less of a danger on the surface than in space due to the atmosphere, thin as it is. Nevertheless, you’re right in general that the risk is quite low.

Hans Bausewein December 22, 2007 at 7:08

If we knew earlier about it, we could test deflection techniques to deliberately crash it on Mars. With such a hit probability it’s not so far off. It would also reduce the number of potential earth-impacters by one.

James M. Essig December 22, 2007 at 13:31

Hi Moon Saloon;

It occurred to me that if Mars is actually going to be whacked by a Siberian Tunguska sized asteroid, maybe setting up seismological equipment to measure the resulting shock waves that would travel throughout the Martian Crust and interior might be a very useful way of surveying the inner composition of Mars including its density profile, interior boundary discontinuities, etc.. Such might be a boon to planetary geology and for studying the Martian sub-surface mineral content in support of prospecting and mining operations and also in support of future living infrastructure located deep underground for future Mars colonies.

Regards;

Jim

Donald December 22, 2007 at 16:20

While I am no scientist, I can certainly appreciate the opportunity this potential event presents. What I don’t understand is why no one has questioned the fact that it was only after this object passed within 5 million miles of Earth that it was detected. Sounds like a good argument to up the funding on the various new “Sky Watch” programs to me.

Administrator December 22, 2007 at 16:37

Donald, part of the problem is simply the size of the object. The Catalina Sky Survey, which is the group that spotted this one, is working under a mandate to track objects 140-meters in size and larger. 2007 WD5 is a third that size, and quite a tough catch. When discovered, it was at 20th magnitude, and it’s now sixteen times dimmer. See the follow-up story for more.

James M. Essig December 22, 2007 at 17:44

Hi Folks;

I seem to have been unaware just how close in time the potential encounter of the asteriod with Mars is. So my previous posting on the topic above is irrelevant for the most part. We just could not get the monitering equipment up there fast enough.

Thanks;

Your Friend Jim

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