While conditions on Mars are no longer favorable for the evolution of life, scientists point out that in many ways Mars resembles portions of Antarctica, which do manage to support colonies of microbes. But these organisms require liquid water, as do all forms of life. And if there is liquid water on Mars at all, it is only seasonal and in small amounts.
If there is life on Mars, then there is liquid water on Mars is the statement that is most strongly supported by the statements above.