11.   Frozen water would have been melted by the decay of radioactive elements in the asteroid that spawned the meteorite.

12.   Geologists presume that plate tectonics and continental drift are ultimately driven by heat generated deep within the earth from the decay of radioactive elements.

13.   He says it was not much higher than normal background levels caused by radioactive elements in the earth.

14.   His job was necessary because both spacecraft run on batteries made of plutonium, a potentially deadly radioactive element.

15.   However, some believe it may be able to fashion a crude explosive infused with radioactive elements that could potentially kill thousands of people.

16.   In marked contrast to us, however, citizens of the land of Marie Curie, who isolated the first radioactive element, have embraced the atom.

17.   It is carried to the ground by rain and is used to trace the migration of radioactive elements.

18.   Many of the elements created since plutonium have found important uses in medicine, chemistry and even smoke detectors, which use the radioactive man-made element americium.

19.   Most of the material being taken to the Carlsbad dump is contaminated with plutonium, but the trash will contain other radioactive elements as well.

20.   Other investigators had previously determined the age of the rocks by analyzing the rates at which their radioactive elements decay.