Reality Rocks: Prospecting on Mars

Close-up of a nickel-iron meteorite discovered on Mars by
the rover Opportunity. Image Courtesy of NASA.

Trundling along the wind-swept plains of Meridiani Planum, NASA's Mars rover Opportunity stumbles upon yet another rock that looks like it could be an iron meteorite. Does the image of a Gold Rush era prospector leading his burro across desert sands and pecking at a rock with a hammer come to mind? Ah, but more precious than gold is common sand and stone when it's on Mars!

Sounds a bit lonely, like the lives of real gold prospectors; right now, Opportunity is the only active explorer on the surface of the entire planet, surrounded by the now eternally sleeping derelicts of the Vikings, Pathfinder, Spirit, Phoenix, and a few lost souls like Beagle and some Soviet landers….

But, it really is an amazing time to be alive. Each new report from our exploration of space—Mars in particular—reminds me of the state of our knowledge of the solar system when I was a starry-eyed child, back in the 1960s. I recall having to imagine what the surface of that planet might look like; I remember poring over pictures in books and posters of artists' concepts of what the Martian desert might be like, or the even more mysterious shrouded surface of Venus, or how a scene of Saturn and it rings from the surface of one of its moons—Titan, Enceladus, Iapetus--might look.

(Speaking of Venus, I remember a page from the old Time-Life book series--I think it was "The Planets" volume--that showed different possibilities of what might lie under the perpetual shroud of cloud: a rocky desert, a vast ocean, a steamy swamps. Isn't imagination great for filling in the gaps in our knowledge? Remember, prior to 1964, we had sent no spacecraft to any planets, so all we had to go on was what we saw through ground-based telescopes.)

But back to Opportunity, lone prospector of Mars now traversing its 15th mile as it marches steadily on to Endurance Crater. NASA sent the rover to the meteorite suspect it spotted from a distance to take a closer look. Why? We sent the rovers to Mars to examine Martian geology, not interplanetary debris that happened to fall from the sky. Sounds a bit like going to Paris to sample French cuisine and running into the McDonalds.

Actually, even a meteorite can tell us something about Mars. Depending on when the meteorite fell, an examination might reveal clues as to the thickness of the atmosphere at the time. And a reading of the content of certain radioactive isotopes (though Opportunity does not possess this capability) might reveal how long ago the meteorite stopped being exposed to interplanetary radiation—see my earlier blog, Mars Rock Talks, Opportunity Listens, for more on that.

Though the highly imaginative ideas about Mars and other places in our solar system are being summarily swept away by the extremely revealing close-up images taken by our robotic explorers, the reality of those places is at least as enthralling. No, no steamy, dinosaur-filled swamps on Venus; no Martian-constructed water-bearing canals on the Red Planet; no strange black obelisks on a Moon of Saturn (that we know of). But, being privileged to stand in the wheels of Opportunity and gaze across real Martian sands at a lump of extra-Martian iron through the rover's eyes is, just, awesome….

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