Is there any natural process on earth that is equivalent to the mass loss of nuclear fission?

Answer 1

The only natural process i can think of is radioactive decay,
it isnt exactly fission, but it is a larger nucleus decaying to a smaller more stable nucleus, while emitting radiation.
Spontaneous fission as you describe it is not a natural process, but a man made process, because we must bombard a heavy nucleus with a neutron to cause fission.

Our Sun however, converts hydrogen to helium, under intense pressure and temperature, releasing enormous amounts of energy, however this process is fusion.

Answer 2

There was simply such a large deposit of uranium present there that it reached critical mass and underwent a fission reaction with natural water acting as a moderator. This was discovered because the uranium mined in Oklo had a lower concentration of U235 than expected, as if the uranium had already been used in a reactor. This is believed to have happened about two billion years ago. Due to the half-life of U235, natural uranium has now decayed to the extent that a natural nuclear fission reaction is no longer possible on Earth.

Answer 3

'Equivalent to mass loss' ? I think the answer to your question is NO. In nuclear fission (and nuclear fusion too, so perhaps that is the answer to your question) the energy change is vast, so vast that the MASS of this ENERGY (from Einstein's equation E = m c^2, or in this case m = E/c^2) can actually be detected.

This happens in ALL cases where there is an energy change, such as burning coal to produce electricity, but usually the change in mass is so small that it is not only unmeasurable but undetectable as well.

Answer 4

There are naturally occuring radioactive substances on Earth. These do loose mass when they split. The splitting is nuclear fission.

Both the natural process and the man-induced process are called nuclear fission.

lots of examples on the web http://www.cancerhelp.org.uk/help/default.asp?page=1830

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fiscon.html#c2 for a Uranium Ore example.