Potassium Argon Dating
The Potassium-Argon (K-Ar) dating of the Frass Meteorite was accomplished by Dick Reesman of Geochron Labs in Cambridge, Massachusetts. Three separate samples were tested including a sample of the gray material, a sample of the red material, and a control sample which was a mixture of the other two rocks. I've also included a copy of the cover letter from Dick Reesman. Since the potassium is about the same for each sample, his results clearly show that the meteorite is made of materials created from at least two lava flows.
The gray material was dated a
t
12.9 ma (million years old) +/- 0.5 ma. The gray material makes up most of
the mass of the Frass Meteorite. The red material tested 49 ma +/- 1.3ma,
while the mixture of the two tested 27.9 ma +/- 0.9. Since the red
material was found inside the gray material, the test results seem appropriate
and reliable.
As you can see in the picture, there is a clear difference in the colors of the two materials. From all indications, the gray rock has never been wet, so it has not been oxidized as much as the red rock. I suspect the red rock started out as gray rock, but as it was exposed to both liquid and vapor water, it oxidized over time and turned red. Also notice how much smaller the vesicles appear on the red rock, as opposed to the gray rock. Since everything else would probably have been equal, this difference in vesicle size may indicate the presence of an atmosphere when the red rock was formed. Increased external air pressure could possibly keep the vesicle size smaller. Another possibility is that the lava flowed under water that was on or near the surface of Mars. Again, this increase in external pressure might have kept the vesicles smaller on the older red lava.
