Mars Past and Present

MARS today is COLD, DRY, and barren. Average temperature: −80°F (−60°C). Atmosphere: thin (1% of Earth's) and mostly CO2. Surface: covered in red iron-oxide dust. But evidence shows Mars was VERY DIFFERENT 3-4 billion years ago — with rivers, lakes, possibly oceans, and a thicker atmosphere. Did life exist then? Could it still hide somewhere today?

Evidence of past water. SATELLITE images show ancient riverbeds, deltas, and lake basins — all carved by liquid water. ROVERS (Curiosity, Perseverance) have found mineral deposits that only form in water — clays, sulfates, hematite. Rocks contain ORGANIC MOLECULES (carbon-based — building blocks of life, though not necessarily from life). Some Mars meteorites that landed on Earth contain controversial structures that some scientists think might be fossilized microbes.

Current missions. PERSEVERANCE rover (NASA, since 2021) is collecting samples for future return to Earth. INGENUITY helicopter has flown small flights — first powered flight on another world. CURIOSITY (since 2012) has analyzed surface chemistry. Future plans: a Mars Sample Return mission could bring samples back to Earth labs by ~2033, where we can analyze them with our most powerful tools. Finding even microbial life — past or present — would change humanity forever.

Mars is humanity's favorite target in the search for life. Whether or not life existed there, the science is teaching us about planetary evolution — including warning signs for Earth's future.