At http://phys.org/print281345356.html … bacteria from the middle and upper troposphere are being studied in a laboratory, micro-organisms that live 6 miles above the surface of the Earth. Long distance transport of bacteria may play a role in disease transmission it is being suggested while the bacteria, and carbon compounds, could play a role in weather. Published by PNAS Feb 28th 2013, the study suggests the bacteria get there from the surface as a result of wind and air movements. No mention is made of diseases and microbes from space. However, at http://phys.org/print281712435.html …is is said there is new evidence that comets could have seeded life on Earth. Of course, this happened at a uniformitarian timescale, at the beginning of life's appearance on our world. This one of those stories that pops up every now and again but does not appear to be universally acceptable.