Mars now has 96% chance of nothing happening

By Phil Plait | December 28, 2007 9:02 pm

Update (January 12, 2008): The odds have now dropped to only 1 in 10,000, so the way to bet is on a clean miss by thousands of kilometers.

You may not see too many blogs phrasing it this way, but the odds of nothing happening with Mars have gone done from 99% to 96%.

2007 WD5 is a 50 or so meter wide rock heading toward Mars, and may impact the Red Planet on January 30. However, the odds of a collision are difficult to get. To find out if the two will collide, the orbit of the asteroid must be very well determined, and that’s hard. Astronomers have to get a precise location of the asteroid as it moves along its orbit, but that’s not really possible. There are errors that crop up from measuring it in the images, from distortion in the detectors, atmospheric distortion, and so on. These add together to make the position of the rock a bit uncertain that far in the future.

The position can be improved by making more observations, finding older ones (thus nailing down a longer arc of its orbit), or by simply waiting until it’s closer to D-Day.

It turns out that some older images were found that coincidentally got the asteroid in their field of view, and NASA’s Near-Earth Object Program Office was able to refine their trajectory for it: the odds of an impact have now improved slightly from 1-in-75 to 1-in-25. That may sound a lot better, but that’s only a 4% impact probability, which means a 96% chance of a miss.

Basically, what this means is that Mars is still somewhere in the fuzzy ellipse of possible asteroid positions on January 30. However, as more observations are made, that ellipse will constrict, and odds are good Mars will be outside of it. But we can’t be sure!

I’d very much like to see this thing hit. It won’t hurt us here, will only do local damage to Mars, won’t hurt the rovers or any other of our robot proxies there, and we’ll get awesome information on what happens when an asteroid impacts a planet. This has never been seen before, and it would improve our knowledge profoundly of such events, and that’s A Good Thing.

CATEGORIZED UNDER: Astronomy, Cool stuff, NASA, Science

Comments (43)

  1. John

    As cool as this would be, I’m not getting my hopes up.

  2. Ken G

    Yeah, I’d like to see it happen for scientific reasons. However, I’m a little concerned about the Earth hysteria if it does– “we’re next” kind of thinking could end up costing NASA tons of money on useless and unnecessary systems for deflecting asteroids, etc. I think NASA’s budget for tracking them is already sufficient, and doesn’t need any help from such an event.

  3. I think it would be cool to see. But I also wonder about the possible “we’re next” hysteria. Things cooled down pretty fast after Shoemaker-Levy whacked Jupiter, but Mars is closer and “a lot more like earth,” so who knows?

    My great burning question is: where will Mars fling it if it doesn’t hit?

    I want to see some HST photo(s) if it does hit. One’s going straight to LOLScience. I’ve got dibs on “im in ur hubble, chekin out ur rubble……..” |-P

    BTW……… How many days’ worth of the $$$$ that’s been burned up in Iraq would it take to give NASA all the toys it wanted but didn’t get for Xmas? My Enquiring Mind wants to know the answer to that, too!

  4. I know my friends who “play” with the rovers and the orbiters are really hoping for an impact.

    And I don’t agree with Ken G on one point: NASA (and other groups) need more funding to find and track NEOs. What is currently going on in that field is woefully insufficient, IMO.

    (FYI, IMO in this case stands for “In My Opinion”, and not “International Meteor Organization.”) :)

  5. Dan

    A buddy of mine recently explained the odds of the potential Mars’ impact thusly:

    “Picture putting a single pool ball on the table in the back of the bar here. Now, take the cue ball, go stand by the front door, and see if you can throw the cue ball and hit the other ball without the cue ball hitting the table first. No bouncies, ya know.”

    Still… I’m keeping my fingers crossed. I just want to see how the debris will interact with Mars’ atmosphere and how vast the dust cloud will be, and whether or not anything green, thorny and screaming gets pitched out of the crater.

  6. Chip

    anomalous4 asked:
    >>>”BTW……… How many days’ worth of the $$$$ that’s been burned up in Iraq would it take to give NASA all the toys it wanted but didn’t get for Xmas? My Enquiring Mind wants to know the answer to that, too!”<<<

    Well here’s a very rough estimate that is surely far from precise:

    Average Cost of Iraq War: $177 million per day – source USA Today

    NASA Budget in 2007: $15.1 billion – a decrease of $2.6 billion (14%) from the previous year. Source:

    Initial NASA Press Release estimate of a manned Mars program: $11 billion over 5 years. Source – flimsy here as there are cost cap statements that don’t site costs and lots of opinions on blogs, but I recall $11 billion being criticized as too low.
    In the USA/UK ‘short scale’ a billion is 1000 million. Approximately $1 billion in 5.64 days in Iraq, so rounding it up to 6 days for $1 billion, in 66 days of the Iraq war NASA would have $11 billion for a manned Mars mission. But they would need more and $11 billion would be really great for several fancy robotic missions.

  7. Michael Lonergan

    anomalous, I get dibs on “I smak ur face”, if it hits Hoagland’s face in Cydonia!

  8. Eric

    Oh dear! It would be amazing to see the impact, but then the underground Martian civilization would be exposed to Earth telescopes!

  9. Michael Lonergan

    When you say odds 1 in 75 chance of it hitting, it sounds much more ominous. I’m laughing at the Google ad underneath the post that asks the question: “Odds of getting pregnant?”

  10. Chip

    It seems that the odds of Mars being hit are greater than the odds of me loosing weight during the holidays.

  11. Not to be glib, but it would be supercool to see the pictures.

    And yes, the science would be fascinating.

  12. Frans Oscar


    Those numbers makes me really sad. Instead of exploring space and expanding the human civilization, they rather spend their money on ape-activities such as war.

  13. What annoys me is these Martian astronomers hoping for a nice big impact on Earth. Have they no sense of responsibility?

  14. tenacious

    One way or the other, using this event will help us narrow the prediction of impact next time. Can’t wait for the results!

  15. andy

    Good way to put it… “96% chance of nothing happening” deflates the hype quite nicely.

  16. LarrySDonald

    >the odds of nothing happening with Mars have gone done from 99% to 96%

    “Down” is misspelled.

    That’s still good news. 1-25 isn’t good odds, but quite better then 1-75. It’s like the first D6 roll did hit 5 or 6 after all and we can keep hoping..

  17. LarrySDonald, perhaps Phil meant to write “the odds of nothing happening with Mars have done gone from 99% to 96%.” Ayup, that sounds more betterer.

    I’m gonna go grab me a d25 and start running some Monte Carlo simulations.

  18. Mark H

    I want to see the Martian Asteroid Defense Grid activated! So far they’ve been allowing our puny little probes to land there, but this will be different.

  19. Sure, it sounds like A Good Thing. Until the asteroid strikes and destroys Mars’s only pool of trilobites.


  20. James B.

    Recent observations have detected a strong smell of coffee coming from the asteroid. It seems to be headed toward what looks like an ancient parking lot behind the only Starbucks yet observed on the red planet. While scientists are slow to say that a Starbucks necessarily implies intelligent life, there are some interesting projections being made regarding the Martian water supply. An object the size of the asteroid, packed with coffee, would indeed suggest there is a considerable amount of available water on Mars.

    However, cautionary scientific advice suggests we not jump to conclusions, as we have no reliable way of determining whether the asteroidal coffee is instant or percolated.

    Meanwhile both of our beloved Martian golf-buggies have independently changed course and are inching toward the same Starbucks. Obviously this raises a serious question: if there is a Martian police force, and if that police force are commandeering our buggies to take them for coffee, can we reasonably postulate that there may also be donuts on Mars?

  21. Nigel Depledge

    James, I do not believe the Mars rovers are permitted to do “doughnuts”. It would wear out their tyres too fast, and they obviously need them to keep rolling, rolling, rolling. :)

  22. Nigel Depledge

    Oh, yeah, and the chances of anything impacting on Mars may be 25-to-1, but still . . .

  23. Jason

    Nitpick: 25-to-1 is not the same as 1-in-25. The first means that for every 25 chances of B happening, there’s one chance that A will instead. So the odds of A happening would be 1-in-26, which is incorrect. The odds of the asteroid hitting Mars are either 1 in 25 (1/25) or 24-to-1 (24:1)

    It’s not a big deal if the mix-up is over 1000:1 vs. 1/1000 but as the numbers get smaller (for example, 2:1 vs 1/2) it’s a big difference!

  24. a 4% chance is nothing to dismiss, but I’m not holding my breath for it to hit, if only because space is a big place with lots of room for stuff to pass by without hitting.

    However, I would really like to see it hit mars. I’m not sure if it would be very visible from earth-based telescopes, although if it hit on the side facing earth it just might be. It would certainly be visible to the orbiters and I would think the hubble telescope.

    It would be quite an opportunity to observe an actual impact on a planet that is not that much different in size and composition than the earth. I think it would be HUGE in terms of understanding past impacts on earth and what the effects may have been and putting theories to the test.

  25. MarkH, please review the success rate for probes sent to Mars actually reaching Mars in working order. The Martian Defense Grid has been very active up to this point, but also somewhat selective. Apparently they like things with wheels. Perhaps H.G. Wells was right about that omission in Martian technology.

  26. Michael L.: If it smacked Mars in the face, now that would be cool! There’d be an awful lot of upset woowoos out there, but wotthehell.

    But no matter where it hits: “im in ur Barsoom, makin big boom!”

    So, anyone…………. any predictions as to where Mars will fling the thing, or is it still too early?

  27. p.s. Thanks for the research, Chip……….. and James B., I hope it nails that Starbuck’s!

  28. geonuc

    I know we’ve determined that an impact would not directly affect the two rovers on Mars, but what about indirect effects? Would it kick up enough dust into the atmosphere to affect Spirit’s power supply?

  29. DenverAstro

    The thing won’t hit. Even if it looks like a dead-on strike, it won’t actually hit the ground. Marvin will simply activate his Iridium U-232 Explosive Space Modulator and vaporize it. Unless of course we can get Duck Dodger out there first….

  30. Am I the only one who thinks that it would be even cooler than an impact if Mars CAPTURES the asteroid and we get to see Mars with three moons? Or has this scenario already been thoroughly ruled out?

  31. Thomas Okken

    Although I’d love to see an impact happen, I’m not sure how much there is to be learned from it. People keep bringing up the Tunguska event, but that appears to have been an explosion caused by a solid object vaporizing in the atmosphere… Given that the Martian atmosphere is so much thinner than Earth’s, I’d expect a Tunguska-sized rock to simply punch straight through to the surface and slam into the ground pretty much unmolested. Nice big crater, ejecta all over the place, but what will it teach us about the effect of a strike on Earth? The hole in the ground and the ejecta field on Mars will be pretty local, but on Earth, the atmospheric impacts, or an ocean strike, can have much more far-reaching effects.

  32. I agree with Charles — Mars adding a moon would be way cool.

  33. Ralf

    A third moon is not gonna happen. Something would have to slow the asteroid down to Mars orbital speed. Unless the Martian Defense Grid has that capability… Maybe they caught Phobos and Deimos in the past and mined them, that’s why they’re so small :)

  34. Minthos

    So what’s the chance of the asteroid hitting phobos or deimos and clusterbombing mars with a shower of rocklets?

    Happy New Year everyone! :)

  35. Schmoo

    However ludicrously small, there must be some chance that it’ll miss Mars by the smallest margin, and hit a spot just right to singshot it towards us, right? Or would that spot be so close to the surface that the atmosphere would interfere? Or something else along those lines that makes it impossible?

    Just out of interest, I monger no doom :)

  36. > Yeah, I’d like to see it happen for scientific reasons.

    I’d like to see the rock hit because I LOVE EXPLOSIONS.



    > However ludicrously small, there must be some chance that it’ll miss Mars by the smallest margin, and hit a spot just right to singshot it towards us, right?

    N-body motion is chaotic (mathematically, not philosophically). It could miss Mars and be nudged into just the right path to hit us in a million or a billion years. The chance of it becoming a DOOM ROCK FROM MARS are a million to one.

    But still, they come…

  37. Hank Roberts

    Will any of the Mars orbiting cameras be trying to get images of this rock? I imagine that might get the best data on it — close vantage point, no atmosphere, presumably the platforms’ location is precisely tracked.

    Where in the sky is this rock coming from, on its approach to Mars? In plane, overtaking, cometary? Do we have even an approximation of its past?

  38. JimC

    The odds WD5 hitting Mars are very low but they aren’t zero. In fact, people play roulette and the lottery with much lower odds.

    It will be interesting to see just how close it gets. If it actually does hit, just imagine the information to be gleaned. The imaging systems we have orbiting Mars could get huge amounts of data on subsurface Mars. Astronomers with an interest in Mars should cross their fingers and hope that it does strike the surface.

    And don’t discount the coolness factor of the big boom when it hits. 😀

  39. So has anyone managed an image of the asteroid AFTER it passed Mars?

    Mind you, I’m not expecting a DEWEY BEATS TRUMAN, but the only recent article I can find is a article (“Asteroid misses Mars, barely”) which was posted… 18 minutes before the asteroid made its closest approach to Mars.


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