back to article Comet Siding Spring revealed as flying molehill

The first images of Comet Siding Spring, a celestial body deemed so menacing that humanity cocooned its very best robots, has turned out to be rather smaller than imagined. The first images of the comet, captured by the High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA's Mars Reconnaissance Orbiter, …

  1. Lobstonicus

    m or km?

    "Don't be fooled by those big egg-shaped pics: the real comet is the little eight-bit smudge at the top and what you're seeing is probably about 450kms across."

    Er, I think you mean 450m across?

  2. Voland's right hand Silver badge

    It is is still an E.L.E.

    It is still an E.L.E. if it whacks us on the head. Thankfully this one should be a miss this time.

    1. Duncan Macdonald
      Mushroom

      Re: It is is still an E.L.E. - No it is not

      A 450m diameter comet nucleus is not even close to being large enough to be an extinction level event.

      It could cause local devastation and some global cooling (due to dust) but it is too small to cause major global damage. If (for example) such an object hit in the middle of the UK there would be little damage (if any) to more distant parts of the EU (e.g. Italy and Spain) let alone to the rest of the world.

      This comet masses less than 1/1000 of the dinosaur killer asteroid and therefore has less than 1/1000 of the energy release on impact.

      1. Bunbury

        Re: It is is still an E.L.E. - No it is not

        Yes assuming land impact at 45 degrees the Impact Earth website calculates a 7 km crater. If you were 1000 km away they reckon magnitude 7 earthquake, fine dusting of ejecta and quite a bit of noise but no planet wide issues.

        1. Tom 7

          Re: It is is still an E.L.E. - No it is not

          Assuming the powers that be dont let things disintegrate into a murderous warring mess.

          1. Scroticus Canis

            Re: It is is still an E.L.E. - No it is not

            Assuming it is an aerated slush puppy, as the theory goes, how much would actually make it through the atmosphere to land fall or the more likely sea splash? A more tangential approach would likely not have too much effect 100km or more from the descent path and impact point.

            1. Anonymous Coward
              Anonymous Coward

              Re: It is is still an E.L.E. - No it is not

              California need rain -- maybe we could land it there -- scale 7 earth quake should be nothing very unusual as well, just make sure to land it in a remote area of Califonia

      2. John Brown (no body) Silver badge

        Re: It is is still an E.L.E. - No it is not

        "It could cause local devastation and some global cooling (due to dust) but it is too small to cause major global damage. If (for example) such an object hit in the middle of the UK there would be little damage (if any) to more distant parts of the EU (e.g. Italy and Spain) let alone to the rest of the world."

        What if it hits in the sea? That wet stuff that covers 3/4 of the earths surface. That'd be some pretty big waves. I'd not like to be too close to beach on that day although I'm sure some daft bugger would try to surf it.

  3. frank ly

    First outgassing?

    I've read that this is the first time in a very long time that Sliding Springs has gone for a Sol approach. Would this mean it has lots of volatile compounds and undisturbed dust to give off, hence the large and fat tail?

  4. Blitheringeejit

    450m molehill?

    Very relieved that I don't have moles like that in my garden.

    Unless El Reg is trying to tell us that all comets are really spaceships used by intergalactic mega-moles to travel around the multiverse..? I do hope so.

    1. Muscleguy

      Re: 450m molehill?

      The point is that even compared with actual earthly mountain, that is at best a hill. It is not even a Munro. Everest for e.g. is roughly 7km above sea level and very, very much denser than a dirty snowball. In Mars terms Everest is a tiddler. Olympus Mons is so tall it nudges the edge of space. If it were on Earth you would not just need some oxygen bottles, but a pressure suit to climb it.

      So, molehill is thus entirely appropriate especially in the context of the aphorism it very obviously references. Do you need it spelling out?

      1. Blitheringeejit

        Re: 450m molehill?

        >Do you need it spelling out?

        No. I just wanted to use the phrase "intergalactic mega-moles", because that's exactly the kind of thing the internet was invented for.

        1. Mark 85

          Re: 450m molehill?

          Lends a whole different concept to "Whack-a-Mole" then, doesn't it?

          1. TRT Silver badge
    2. TRT Silver badge

      Re: 450m molehill?

      "Very relieved that I don't have moles like that in my garden."

      What are doing, Carrot?

  5. Christoph

    The size of the comet doesn't matter - the various spacecraft ducked out of the way of any miscellaneous rocks and junk surrounding it. Not only could they be any size, but pretty well anything hitting at that speed is contraindicated for spacecraft health.

    1. Muscleguy

      In the same way that shooting down your neighbour's quadcopter toy with a rifle is a bad bet compared to a shotgun, even one loaded with buckshot. Only one of the low velocity pellets needs to hit a rotor or a wire or a piece of electronics.

      It's also how the missile that took down the Malaysian Airlines jet over Ukraine works. Instead of directly hitting the aircraft it has a proximity fuse and explodes nearby peppering it with shrapnel. A more advances form of old style flak that used best guess altitude fuses.

  6. AndrueC Silver badge
    Unhappy

    “Telescopic observers had modeled the size of the nucleus as about half a mile, or one kilometer, wide,”

    Was it the NASA spokesman or the observers who thought that one kilometer was about half a mile? It seems a rather inaccurate approximation.

    1. cray74

      "Was it the NASA spokesman or the observers who thought that one kilometer was about half a mile? It seems a rather inaccurate approximation."

      The estimate of the comet's nuclear diameter is also rather inaccurate. A kilometer by one guess, a half-mile by another, both are within the error bar and convey some idea of the comet's size to Euro-metric types and metric-challenged 'Muricans alike.

    2. DNTP

      Technically a kilometer can be half a mile, for very small values of the kilometer.

      Anyway it is exponentially easier than explaining "Point Six Two" to lots of people in this country.

      1. Muscleguy

        Fine I'll race you. I'll run 816m and you run 1,000 and we'll see who wins shall we?

        1. DNTP

          Assuming we are equally fit, I could still win, for very small values of winning.

          1. Anonymous Coward
            Anonymous Coward

            @DNTP -- for very small value arguments, I believe you are winning this one :-)

      2. Scroticus Canis
        Facepalm

        explaining "Point Six Two" - ¿Que?

        If you still work in miles then you should know half a mile is 880 yards. Using the rule of thumb estimate of 100m being 110 yds, half a mile is 800m*. Shirley even 'Merkins can grock that one but probably not if they find decimal point confusing.

        * 804.672m for the pedants

  7. Mikel

    Amazing pics

    Still a killer if one like it were to hit us.

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Other stories you might like