Also Venus is closer (minimum 38.2 million kilometer for Venus vs minimum distance of 55.7 million for Mars).
However I don't know about the microbes, i fear that they might get killed at an average temperature of 737 K (464 C).
https://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.htm... https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.ht...