(“We” = humans)
I’ll admit that when I first heard the news, I was skeptical. Although we try to avoid it, scientists can sometimes fall victim to their own wishful thinking just like anyone else can. But I read the report, and the evidence is solid. We really did it this time.
We’ve known for a while that there is H2O on Mars, as water vapor in the atmosphere and as layers of dust and ice near the north and south poles. The question was whether we could find liquid water.
The answer came from the European Space Agency’s Mars Express spacecraft. It carries a radar instrument that broadcasts radio waves at the Martian surface and listens for those waves reflecting back from layers under the surface. When the spacecraft flew over a region near Mars’s south pole – shown below – it picked up echoes from a layer buried below the surface.
The radar echo was so strong that it could only be one thing: liquid water.
There’s a lot more to say about this discovery, but first: