In the Cold Light of Day
Even one year after landing, nine full months after they were supposed to perish in the frigid distant dust of our solar system, it’s amazing to ponder those twin Mars rovers, Spirit and Opportunity. They are still obeying directions to poke into the geologic secrets of Mars, 207 million miles above their Pasadena control room.
Just getting these twin 384-pound robot carts to Mars last January and landing safely in bouncing air bags with unfolding ramps, wheels, antennas and camera arms was a stellar achievement. There was ground-bound joy among engineers who’d invested years of their lives envisioning, building and launching the probes. But today, these contraptions resembling cluttered coffee tables still radio back research that uncovers the history of Earth and the possibility of other life, past or future, out there somewhere.
Mars, it need not be announced, is a hostile place. About half the size of Earth with the same land area, Mars has one-third our gravity, probably a major reason fierce solar winds could so successfully strip Mars’ atmosphere. But what used to be there? The rovers’ key finding: Mars once had liquid water, more Earth-like. Drilling and brushing rocks during more than a mile’s travel each, they’ve found volcanic rocks and sediment from both water and wind, indicating climate cycles of wet and dry.
They’ve even detected mini-dust devils whirling about, redistributing Martian soil; the same winds apparently wipe clean the rover lenses. One rover found and photographed its own heat shield, jettisoned red-hot when its chutes deployed. This may allow planners to improve, even lighten, the shield for the next Mars mission, in 2009.
Recently, Opportunity found something else. As darkness fell one Mars night shortly after Thanksgiving, putting the rover’s solar generator to sleep, NASA scientist Geoffrey Landis had the camera positioned to look down at a metal post on the rover.
A half-hour before Martian dawn, when temperatures had fallen to minus 60, NASA switched on a camera heater. As a new dawn broke, raising temperatures 110 degrees in minutes, Opportunity’s eye popped open, catching on camera what telescopes and satellites could never spot: a transitory coating of fragile frost. We now know that Mars’ melting ice cap provides enough ambient moisture for the atmosphere to distribute it even 4,000 miles away.
The reliable rovers will rove as long as they’re able. They’ve drilled 34 rocks, brushed 48 and sent back 61,000 photos plus countless hours of data. Each message, traveling at the speed of light, takes 18.5 minutes to get down here from those dutiful little carts way out there, ample time for all of us left behind to shake our heads in joint wonder and whisper to ourselves, “Wow!”
