Which solar system body is most likely to have evidence for past or present life according to the material?

• A. Venus
• B. Mars
• C. Europa
• D. Titan

Answer: (B)

Habitability and the preservation of biosignatures drive where evidence for life is most likely to be found. Mars shows strong signals of past liquid water—valley networks, ancient lakebeds, and minerals that form in watery environments—which means any biosignatures could be well preserved in its rocks for billions of years. That combination makes Mars the most plausible place for past or present life evidence given what’s been observed. Venus, with its extreme heat, corrosive atmosphere, and harsh surface, is unlikely to retain or reveal such evidence. Europa could host a subsurface ocean, but any signs would be hidden beneath thick ice and hard to detect with current data. Titan has intriguing organic chemistry and surface lakes of methane, but no confirmed life signs have been found there yet.