Earth Emerges - Element 42, Book 2

The molybdenum cat was out of the bag. Scientists had known the trace metal was essential to plant and animal life, but it was just an esoteric detail until Steve Kowalski encountered the alien Brock in Colorado near one of the largest deposits in the world. It was also one of the largest on all of the million planets Brock's people had explored. Only a handful of worlds had enough molybdenum to support life, but Earth had enough to fertilize over a thousand. And there were other aliens who...