What feature of Mars makes it a prime target for astrobiological study when contrasted with Venus or Jupiter?

Answer

Conditions that were once more Earth-like

Mars exhibits habitability potential compared to the super-heated environment of Venus or the deep hydrogen oceans of Jupiter because it once had conditions that were more Earth-like.

What feature of Mars makes it a prime target for astrobiological study when contrasted with Venus or Jupiter?
Spaceexplorationplanetsolar system