1.   Because there is a class of bacteria on Earth that manufacture their own magnetic crystals to orient themselves in dark, muddy pools.

2.   The debate now hangs on the presence of tiny magnetic crystals in the meteorite.

3.   The magnetic crystals act as a sort of compass to allow the bacteria to orient themselves as they move along the lake bottom.

4.   The magnetic crystals act as a sort of compass to allow the bacteria to orient itself as it moves along the lake bottom.