Meteorites and Meteor-wrongs

My role as Planetarium Astronomer includes answering astronomy questions from the public over the phone, by email, and in person.  Thus, it is up to me to examine meteorite samples brought in by the public.  Or, I should say, “meteor-wrongs,” as none of the samples brought in since 1996 (when I began doing this) have actually been meteorites. 

First, let’s define some terms.  A rock which is about to enter the Earth’s atmosphere is a meteoroid.  Someone who happens to see it as it is falling, and thus sees a streak of light in the sky, sees a meteor.  Once the rock has landed, it is a meteorite.  Most meteors that we see burn up completely in the atmosphere and therefore never land as meteorites.  A meteorite, then, is a rock which originated in outer space.

which is a meteorite?

Can you tell which of these is a meteorite?

If you have a sample you believe came from outer space, here are 4 simple tests you can do at home.  Note that passing these four tests will not guarantee that your sample is a meteorite; they serve primarily to eliminate ‘meteor-wrongs.’

1) Is the sample heavy for its size?  Meteorites are denser than Earth rocks; they have more mass per volume.  A meteorite will be heavier than an Earth rock of the same size.

2) Does the sample attract a magnet?  Most meteorites found and brought in are iron meteorites.  Even the stony meteorites, which are more common but rarely reported because they superficially resemble Earth rocks, have some iron in them.  A meteorite sample, then, should attract a magnet.  Any magnet, including the ones on your fridge, will suffice for this test.

3) Is there a dark fusion crust? Upon entry into our atmosphere, a meteorite acquires a thin ‘fusion crust’ because its surface melts under the heat of entry.   This crust is black when the meteorite is freshly fallen but may turn brownish due to weathering and rust.  Bright colored or silvery samples are not meteorites.

4) Does the sample have bubble holes?  Many volcanic rocks on Earth have these holes, which form when a bubble of gas or steam expands as the rock solidifies.  A meteorite, however, is never fully molten (only the surface melts on entry into the atmosphere).  Thus, a meteorite sample is a solid hunk, without tiny holes or perforations. 

hole-y

The many large holes in this rock
are a big clue that it is not a meteorite.

So, which of the four is a meteorite? If you go back to the first photo in this post, you should be able to see holes in the top two samples – so those are out. And the bottom right is bright and silvery = not a meteorite. So, the winner is the smallest of all four, in the bottom left.  

For more information, surf to: http://meteorite-identification.com/ ,  http://meteorite.fr/ (the site is in English, too), or http://meteorites.wustl.edu/meteorwrongs/meteorwrongs.htm

Sky Walking: Astronaut Style

tom-at-udvar-hazy-5-03-resizitron.jpeg

Thomas D. Jones, PhD is a veteran NASA astronaut, scientist, speaker, author, and consultant. He holds a doctorate in planetary sciences, and in more than eleven years with NASA, flew on four space shuttle missions to Earth orbit. In 2001, Dr. Jones led three spacewalks to install the centerpiece of the International Space Station, the American Destiny laboratory. He has been privileged to spend fifty-three days working and living in space.

He’s visiting the Houston Museum of Natural Science for  public lecture on May 5 and he was kind enough to give us a preview:

In Sky Walking: An Astronaut’s Memoir, I take readers along for an “inside-the-spacesuit” ride on each of my four space shuttle missions. My most recent was a demanding construction flight to the International Space Station. During the second of three spacewalks outside shuttle Atlantis, I moved carefully along the silvery hull of the Station’s Destiny science lab, hovering by my fingertips some 220 miles above the luminous Earth below.

Creative Commons License photo credit: pingnews.com

My spacewalking partner, Bob Curbeam, and I worked side-by-side on Destiny’s hull, installing the mechanical and electrical foundation for the Station’s robot arm, Canadarm II. We were interrupted by an exuberant call from German astronaut Gerhard Thiele in Mission Control: the robot spacecraft “Near-Earth Asteroid Rendezvous-Shoemaker” (NEAR-Shoemaker) had just landed on asteroid 433 Eros, the first time a machine from Earth had touched down on one of these mountain-sized remnants of the ancient solar system. Falling around Earth beneath the black sky and blazing sun, I tried to imagine what it might be like to walk Eros’ alien surface, held so lightly by its tenuous gravity that an easy leap would toss me aloft for hours. But a hundred million miles away, NEAR/Shoemaker was there, alive and transmitting. How long until an astronaut explorer might follow?

Near-Earth asteroids like Eros should be our next destination beyond the Moon. Their ancient rocks and resources will be key to our efforts to understand and tap the wealth of the solar system. Just as important, astronauts and their robot probes will gather the knowledge we need to keep Eros’ rogue cousins from someday threatening our civilization with a catastrophic impact. We now have the capability to intercept these objects and halt a cosmic force that has often changed the course of evolution on Earth. To survive as a species, we must do so. Only by “Sky Walking” can we ensure that we humans don’t go the way of the dinosaurs.

More details here, and here

Jones is a Distinguished Graduate of the U.S. Air Force Academy. He has engineered intelligence-gathering systems for the CIA, and helped develop advanced mission concepts to explore the solar system prior to joining NASA’s astronaut corps. He writes frequently about space exploration and aviation history in magazines such as Air and Space Smithsonian, Aerospace America, and Popular Mechanics. Tom’s current book is Sky Walking: An Astronaut’s Memoir, published in 2006 by Smithsonian Books-Collins.

Science Doesn’t Sleep (4.17.08)

 

Creative Commons License photo credit: antjeverena

So here’s what went down since you logged off.

You can stop building your asteroid impact shelter - that German kid got it wrong. NASA stands by their estimate of the asteroid Apophis’ chance of colliding with Earth, also denying they ever admitted an error. 1 in 450, 1 in 45,000 – it still seems like “way too likely” to me.

Robot alert! The Carnegi Science Center (those crazy kids that brought us the Robot Hall of Fame) is developing an exhibit called Roboworld, that will “will emphasize three aspects of artificial robotic behavior: sensing, thinking and acting.” Sadly, “taking over the world” is not on the list of behaviors to be featured.

We love nature – but it doesn’t love us back. Humans are more harmful to coral reef than the fallout from an atomic bomb.

Houston, we just keep stacking up the honors. In addition to being named the country’s fattest city, it turns out that Harris County is number one for something else – carbon dioxide emissions.

Are you planning anything for Earth Day? You can check out what people around the world are doing, get some suggestions from Google or, oddly enough, the government.

 

Science Doesn’t Sleep (4.16.08)

Creative Commons License photo credit: goldenrectangle

So here’s what went down since you logged off.

I don’t know what’s more shocking about this story – the fact that there is a 1 in 450 chance that an asteroid will hit Earth in 2036, resulting in fire, brimstone, general chaos and the end of life as we know it – or that a 13-year old corrected NASA’s estimate of the risk (which they put at 1 in 45,000) in a science fair project.

Just add water, bio-sludge, seaweed and a shrimp: Quest and MAKE magazine show us how to make an ecosystem-in-a-jar. Seal it up, and your little eco-naut lives happily ever after.

As if you didn’t already have enough – here’s yet another really great reason to stop smoking.

The meat you eat might be worse for the Earth than the car you drive. In fact, cutting out just 20% of those hamburgers is like trading in your Hummer for a Prius.

Physical anthropologists heart hobbits - even if they can’t decide whether they are human.  

Nerds vs. Jocks: female fruit flies reveal that “there’s more to mating than beating up the competition.”