Oh, now you're asking *difficut* questions.

On Earth, we know it's always been *Earth*, even if the rules change a bit with time. And we have phenomenal amounts of data as to ages, processes, and locations.

On Mars, we are all guessing. It's like learning to read in one language, then finding a book in another...

Today, everything seems to be frozen to great depth. This was clearly not always the case. For a few dozens of years (out of 4.6 billion) Mars had spectacular flows of liquid.

Nobody can prove what it was, yet. Pure water, salt water, extreme brine, chlorides, sulphuric or other acids, liquid gasses such as nitrogen, CO2, etc...

We could do with some more independent work here, IMHO...