archive: SETI [ASTRO] Re: Meteorite Hints At Early Asteroid Furnace

SETI [ASTRO] Re: Meteorite Hints At Early Asteroid Furnace

Larry Klaes ( lklaes@bbn.com )
Tue, 25 May 1999 08:23:43 -0400

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>Date: Tue, 25 May 1999 0:21:21 GMT
>From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>To: astro@lists.mindspring.com
>Subject: [ASTRO] Re: Meteorite Hints At Early Asteroid Furnace
>Sender: owner-astro@brickbat12.mindspring.com
>Reply-To: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>
>>:After a decades-long search for what melted these large
>>:asteroids, researchers report in tomorrow's issue of Science (20 May,
>>:p.1348) that a once-molten 4.57-billion-year-old meteorite bears the
>>:unmistakable signs of radioactive heat. Called Piplia Kalan after a
>>:nearby village, the 42-kilogram meteorite seemed a prime hunting ground
>>:for evidence of 26Al.
>>:
>>:Full story here:
>>:
>>:http://www.academicpress.com/inscight/05201999/grapha.htm
>
>
>>Hi all,
>>
>>This brings up an interesting question, especially since I just purchased a
>>couple of meteorites (not for research; just for "gee-whiz" purposes). What
>>are the chances that these little rocks (one is Canyon Diablo in Arizona,
>>and one is GAO from Africa) have higher than normal levels of radiation? Is
>>this stuff like Kryptonite or what <G>?
>
>Don't worry, no meteorites are radioactive.
>
>The radioactive heat referred to in this article is in reference to
>an isotype called aluminum-26 (or Al-26), which is evidence of a supernova
>from long ago. The theory is that some of the grains
>in our solar system were created from a nearby supernova event, just
>shortly before the solar system formed, and these grains mixed in with the
>solar system material. The supernova also triggered the solar nebula
>collapse (or the beginning of our solar system formation). Al-26 cannot be
>created by the solar nebula collapse, hence the idea they originated from a
>supernova. Since Al-26 has a rapid decay rate with a half life of about
>720,000 years, none of the original Al-26 exists today. However, Al-26 does
>decay into a daughter isotope called magnesium-26 (or Mg-26). The amount
>of Mg-26 in the meteorite is what the scientists are looking at. In this
>particular meteorite, they found Mg-26 to be 3% higher than the amount in
>terrestrial rock, which is a significent excess, and gives evidence
>supporting the supernova theory. This also explains how asteroids
>could have a molten cores as Al-26 puts out a lot of heat as it decays.
>
>Ron Baalke
>