CSI Mars

Gertrude Weise -- a deposit of silica uncovered by
the wheel of NASA’s Mars Exploration Rover, Spirit.
Credit: NASA/Mars Exploration Rovers.

Watching the unfolding story of the exploration of our solar system's fourth planet is like watching an episode of CSI: Mars. Robotic orbiters, like police helicopters, constantly circle the neighborhood while determined rovers doggedly comb the ground for evidence. Back at the lab (Earth), forensics investigators put all the clues and data through detailed analyses, looking for the smoking gun that will solve the crime….

So what's the crime? In a headline, "Is Mars concealing a wetter, warmer past?"

As the Mars Exploration Rovers, Mars Reconnaissance Orbiter, and other spacecraft have revealed, signs of past liquid water flowing on Mars' surface are abundant -- though scientists still tend to couch the evidence with the caution that there are other processes in nature that can produce these signs. Still, the preponderance of evidence points so strongly to past liquid action on the Red Planet, sometimes you can almost taste the water.

What startling piece of evidence has our forensics team uncovered this week? In a headline, "Gertrude Weise: Scratching the Surface for Pay Dirt." I'll explain. NASA's Mars Exploration Rover Spirit, which has been exploring the giant Gusev Crater for about the past 1,200 Martian days, recently dragged its non-operational wheel through the dirt to reveal a deposit of white material, which it identified as silica (silicon dioxide -- same material that glass is made of). (One of Spirit's six wheels stopped working awhile back -- which has made it a good soil furrowing tool, or plough!)

Gertrude Weise, by the way, is the name given to the silica deposit, named after a player in the All American Girls Professional Baseball League. Yes, naming opportunities abound in our solar system -- dwarf planets, asteroids, craters, mountains, and, yes, small deposits of minerals!

The well-cautioned announcement is that silica deposits like this tend to be formed and concentrated by water--although there are other possible explanations. Whether by the action of standing pools or lakes of water, or geyser-like activity of hot water heated by volcanic activity and bubbling up to the surface, this is yet another strong piece of evidence for the existence of liquid water on Mars, long ago. And, if volcanic heating is what produced the Gertrude Weise deposit, then this spot on Mars once boasted a hot spring -- a warm, mineral rich, watery environment that may have been quite conducive to life...

That's probably the most exciting piece of the Martian puzzle right now: water and life, life and water. As it looks increasingly likely that Mars was indeed warmer and wetter in the past, and as we are finding life forms on Earth that thrive in conditions of extreme heat, cold, and toxicity (extremophiles), the Martian investigation seems to be mounting toward a climax. Is it only a matter of time before we find the fossil of a Martian microbe, or even higher order of life—or, maybe, beneath the frigid, dry, red soils, in an underground aquifer of liquid water, life that is living right now?

Stay tuned to this show. It's hard to say when the "finale" episode will be aired, but it promises to be a good one. For now, it's a real cliff hanger...

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.