A study was undertaken to determine if amber, coal and clay samples contain bacteria, in relation to the possibility that rocks ejected from Earth might contain microorganisms capable of colonizing other planets. A technique for isolating bacteria from rocks was developed which excluded the possibility that any of the rock isolates resulted from contamination. Two species of Bacillus were found in the amber sample, and a species of the same genus was found in coal; bacilli were also commonly found in clay. It is concluded that species of the spore-forming genus Bacillus could therefore be ejected from Earth in these geological substrates and possibly be transferred elsewhere.
