system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we hear that they discovered water on Mars every month? What is different each time?

It seems like once a month or so, evidence of water on Mars makes headlines.

Why is something that has been known for a while newsworthy? What additional information is being discovered each time?

Even just a few examples would be helpful, if possible.
gpt
There are lots of different types of water, and different types of evidence. The evidence can be more or less persuasive, and imply water existed at different times.

So, you can find evidence of ancient, brine like water. Or ancient, acidic water. Or ancient, neutral pH water (note that evidence of all of these have been found). Or modern subsurface ice. Or modern subsurface brine. Or features indicating rare occurrences of liquid on the present day surface. Or clay minerals that are probably formed in water, but we can't be sure. Or evidence of water eroded features like rivers and lakebeds. And so on. Each tells a different facet of the history of water on Mars, and the planet's potential habitability.