Asteroid geology, was Re: [OT]Nukes... tunnels.... boom....

Hi,

There are very few inherently radioactive elements. Typically,
one talks about radioactive isotopes. An element is defined by the
number of protons in the nucleus. The difference between isotopes is
the number of neutrons. Whether or not a particular isotope is
radioactive is not entirely dependent on the mass of the isotope.
Some very light isotopes are highly radioactive. Tritium comes to
mind.

Typically, the formation of elements happens in a set way, and the
ratio of stable to radioactive isotopes is mostly fixed at the time
they are created. Geologists use this to estimate the age of rocks.
They find a rock, and measure the ratios of stable and radioactive
isotopes. Knowing the half life of each isotope allows them to
calculate how old the Earth (or other body) was at the time that the
elements in the rock were amalgamated.

What this means is that, wherever a particular element is found, there
will be both radioactive and stable isotopes found in ratios that depend
mostly on the age of the body.

Within our solar system, the composition of the planetoids seems to
be directly related to their distance from the sun, or at least on
the distance they were when they were created. One thing that we
know very well is that the Moon is the geological twin of the Earth.

Therefore, I would conclude that most, if not all, bodies in the solar
system contain radioisotopes.

TTYL,
Tony Christney
On Sunday, March 10, 2002, at 01:55 PM, Brian Burger wrote:
>
> On an SF note: my geology is shaky, so can someone tell us whether
> radioactive elements can be found in asteroids or moons? Or are the 
> heavy
> elements only (probably) going to be found in/on planets?