Meteorite Masquerade – Part I

The rock at left, found by Lisa Webber of Novato, Cal. is not a meteorite despite its convincing appearance. At right is the first real meteorite from the fall found by Brien Cook from the fall. Credits: Peter Jenniskens (left), Brien Cook

Disappointing news. The rock that Lisa Webber picked up after it bounced off her roof in the wake of the October 17 California fireball wasn’t a meteorite after all. NASA’s Peter Jenniskens, who helped in the identification writes this:

“We examined the rock with a petrographic microscope yesterday and quickly concluded it was not a meteorite. I sincerely thought it was, based on what appeared to me was remnant fusion crust. On closer inspection, that crust was a product of weathering of a natural rock, not from the heat of entry.”

A slice of Brien Cook’s meteorite displays metal and darker, shocked areas – classic meteorite characteristics. Credit: Brien Cook

Another specimen weighing 66 grams was found in the fall zone (Mill Valley area) by meteorite hunter Brien Cook on Monday, October 22.

Cook cut three slices from the rock earlier today, and there’s no doubt it’s the real item. The flecks of metal, the dark, shocked areas – if that’s not a meteorite I’ll eat a rock. To my eye it resembles the Park Forest (IL.)  fall of March 26, 2003 which was classified as an L5 chondrite, a fairly common type of stony meteorite.

Meteorites are tricky. Like a Halloween costume, external appearances can mask a rock’s true identity. The Webber stone appears partially covered in a black fusion crust of melted rock typical of freshly-fallen meteorites. It even stuck to a magnet. Jenniskens peered under its disguise to reveal its real origin – Earth.

While the news is a bit of a let down, it does teach us how science works. Much as we’d like to believe our hunches about this or that aspect of nature, careful analysis may prove otherwise. Scientists and meteorite hunters alike know this is simply part of the process and move on. One question remains. What made the ding in Lisa Webber’s rooftop?

Speaking of roofs and shingles, ever heard of looking for tiny meteorites by sweeping a magnet through the grit that falls on your roof? Tomorrow we’ll explore the possibilities in Part II.

** UPDATE Oct. 25: In light of Brien’s find, Dr. Jenniskens has taken a second look at Lisa’s rock and is now convinced it’s the real thing after all. “An apology may have been too hasty,” said Jenniskens. “Lisa’s find is a genuine meteorite.” Ah, the tortuous path one must walk to find the truth!

15 Responses

    1. astrobob

      Hi Daniel,
      I’ve been reading the met-list closely and have contacted Brien about his find. While I’m very optimistic his is the real thing, I’m waiting for a little more analysis.

    2. astrobob

      Hi Daniel,
      I’ve been following the met-list closely and contacted Brien Cook as well. While his specimen does look like the real thing, I’m waiting for more analysis.

      1. astrobob

        Hi again Daniel,
        Just saw Brien Cook’s slice a minute after I read your comment. Yes, indeed, that’s a meteorite!

  1. Rob Matson

    Hi AstroBob,

    I would not be so sure to dismiss the Lisa Webber specimen as terrestrial. Brien’s find is now confirmed to be a meteorite, was found in the same general area as Lisa Webber’s, and outwardly has a similar appearance. I realize Petrus examined the Webber stone under a petrologic microscope and immediately decided against it being a meteorite, but I haven’t heard on what grounds he made the dismissal. He might want to take another look — especially after windowing a small portion of the stone. –Rob

    1. astrobob

      Hi Rob,
      Thanks for writing. A couple minutes ago I just saw Brien’s photo of a slice he had made and there’s no question about it – that’s a meteorite. I went along with Jenniskens’ assessment given his qualifications. I agree with you – it would probably be best if he had it sliced up like Brien’s. The two stones do bear a more than passing resemblance.

  2. Mike

    With that dent in the roof, they must be searching all over the place on that roof and yard for that piece of space rock, since they say the first thing found wasn’t it. It would be a funny/sad coincidence if that dent wasn’t from a meteorite but something else. It just seems so suspect.

    1. astrobob

      I agree Mike. It’s got to be around somewhere – either that or Dr. Jenniskens will cut into what he no longer thinks is a meteorite only to discover it is … again!

  3. Brien Cook

    Hi all, I emailed Peter this morning a picture of the slice and we spoke a short time later. We both agreed, our meteorites lack the typical fusion crust you would expect. I threw mine away Monday night only to retrieve it Tuesday morning after looking at Lisa Webber’s and re-evaluating it. Meanwhile, he dismissed his to find himself driving back to Novato this morning after seeing my slice. It’s really rather comical if you ask me.

    1. astrobob

      Thanks Brien for sharing your story. Threw it away? Yikes! We’re all glad you retrieved it. Let’s hope Lisa’s rock’s a meteorite too even if might mean some embarrassment for Peter. Bottom line – the more material the better.

  4. Jim

    Simple physics. Compare th trajectory of the meteorite with the angle of the roof and assuming the velocity of the object you should be able to guesstimate where it landed.

  5. Suresh Bansal

    Infect these type of meteorite are seeds of planets out of these very few can germinate in asteroids and out of these asteroids very few can convert in big planets. as one tree is a result of one seed same one planet is a result of one these type of meteor. Earth itself is a single giant living organism like a tree and has been covered with thick bark and producing organic hydrocarbons in the deep origins of earth and fossil fuel is not an option. in my opinion NASA should have observe the interior of earth instead of observing the space. we ourselves can produce new earth like planets and can divert some people there to avoid the global warming on the earth. our understanding about the planet formation would have much much advance if we would have used our funds to observe the interior of earth.even presence of all other minerals like iron, nickel, ci, mn, zn……. etc are also same in all other living organisms including organic hydrocarbons..

Comments are closed.