If only it were so simple. The problem is we are not sure of all the genetic diversity of the life we have on Earth, especially the extremophile bacteria and archea [1] that are the most likely to survive the trip to Mars as contaminants.<p>My best guess is we will find organisms related to microbes on Earth. The really interesting thing is we might find organisms that are more distantly related than the our current last common ancestor. This would be amazing as we would then know that life originated on Mars and came to Earth later.<p>1. <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Extremophile" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Extremophile</a>