Geologically, Mars is very reminiscent of the moon. But it also looks a lot like the Earth. It all depends on who you ask.
Current understanding of Mars’ evolution is based on spacecraft measurements and meteorite analysis. Those meteorites were ejected from Mars and traversed space before landing on Earth, where they were discovered primarily in African deserts and Antarctica. They come in two categories: shergottites and nakhlites. Each paints a distinctly different picture of Mars’ geologic history.
In a study published in the Proceedings of the National Academy of Sciences, LLNL researchers argue that samples retrieved from known locations on Mars by sample return missions could solve this conundrum.