Which planet is considered the most likely to contain evidence of life now or in the past?

• A. Venus
• B. Mars
• C. Jupiter
• D. Mercury

Answer: (B)

The main idea being tested is whether a planet could have supported life and left detectable signs based on its history, especially the presence of liquid water. Mars stands out because decades of exploration show it was once warmer and wetter, with ancient river valleys, lakebeds, and minerals that form in water. These features indicate environments that could have supported microbial life in the past. There’s also the possibility that liquid water exists today underground, offering a potential niche for life even if the surface is dry. In contrast, Venus has extreme heat and atmospheric conditions that would prevent habitability; Jupiter is a gas giant with no solid surface or stable bodies of liquid water; Mercury is extremely hot and arid. Taken together, Mars is the best candidate for having left evidence of life now or in the past.