A lot of people have had bad days on Mars. They don't call it the death planet for nothing.

The history of Hubble has been a roller coaster, or a trip to Mount Everest and down to Death Valley.

There are a lot of people that are surprised that Hubble can even look at planets in our solar system, because they think of Hubble as looking back to the beginning of time or at things billions of times fainter than the eye can see. But indeed, about 15 percent of the time Hubble spends observing our own planets.

This dramatic confirmation of standing water in Mars' history builds on a progression of discoveries about that most earthlike of alien planets. This result gives us impetus to expand our ambitious program of exploring Mars to learn whether microbes have ever lived there and, ultimately, whether we can.

Everyone on Earth who has ever dreamed of being an explorer on an alien planet will want to go along for the ride.

Life on Earth was not a cosmic fluke but part of a broad imperative. Mars is a lot like Earth. And billions of years ago it had some kind of atmosphere and huge quantities of flowing water.