Di Gregorio brags about being a serious author. A quick look at the SPIE paper "Rock Varnish As A Habitat For Extant Life On Mars" on the ICASMR website shows him to be a sloppy writer. No doubt he has made similar errors in his other "publications".

BD: "CONCLUSIONS AND RECOMMENDATIONS It is completely plausible that life developed on Mars roughly the same time period as Earth, or perhaps even before. The early exchange of planetary debris during the late bombardment period would have allowed viable microbial spores from the Earth to reach Mars, and vise versa."

The first sentence is missing a word (perhaps 'at') between "Mars" and "roughly." In the second sentence "vise versa" should be spelled "vice versa". No one with any real credentials would submit a sloppy mess like this. Then again SPIE is not exactly picky in what it accepts these days.

Also, I find it odd that Di Gregorio has resisted the notion that life could have travelled from Mars to Earth (as suggested by others in this forum) since he makes a rather specific claim to the contrary in this paper (see above).