Each statement below represents a feature that has been claimed to exist on Mars. Sort the statements into the correct bin according to whether each is a feature that actually exists, that does not actually exist, or that might exist but about which we cannot yet draw a definitive conclusion.
1. microscopic life
2. abundant water ice
3. underground pockets of liquid water
4. cities built by an ancient civilization
5. surface pools of liquid water
6. minerals of types known to form in liquid water
7. dried-up river beds
8. frequent rainfall and snowfall
9. a network of straight-line canals