NASA has uncovered a groundbreaking discovery: a massive subsurface reserve of liquid water on Mars. This hidden reservoir is big enough to flood the planet with a mild deep ocean, resolving the long-debated topic of whether Mars still has water. But while we know where the water is, there is still a big problem with future exploration. What is the new challenge preventing further exploration, and how exactly did the water get there in the first place?

Around 3.7 billion years ago, on what is now Mars, a flash flood swept a large boulder into a fast-moving river. The river carried it downstream into a delta where the water met a lake inside a massive 45 km-wide crater, the remnant of an ancient asteroid impact.

Eventually, the boulder sank to the bottom of the lake. Flash floods like this were common on ancient Earth, but this wasn’t Earth—it was Mars during a time when the red planet had vast lakes, a thick atmosphere, a warmer climate, and perhaps even life.

Fast forward to today, and Mars looks nothing like it once did. The lakes have dried, the atmosphere has thinned, and the planet is cold and barren.

But the story doesn’t end there. If you’ve been following this channel, you know Earth’s history is full of radical changes. Similarly, Mars has gone through its own series of transformations, many of which we’re only now beginning to understand.

While we’ve been asking questions about Mars for centuries, it’s only recently, with the help of modern space exploration, that we’re starting to piece together its ancient past. The hunt for water is over—Mars had it. Now the focus shifts to a bigger question: Could life have ever existed on the red planet?

This question can be easily answered if we have access to the water trapped on Mars. But why can’t we explore it?