Shaking the Foundations of Solar-System Science
THE touchdown of Stardust in the Utah desert a little over a year ago, after a high-risk, high-velocity flyby of Comet Wild 2, completed the first U.S. sample return from space in more than 30 years. Since then, Stardust particles, mostly nanoscale flakes painstakingly harvested from the spacecraft’s aerogel “catcher’s mitt,” have been analyzed with the world’s most advanced analytic instruments at laboratories around the world, most notably here at Livermore. As described in the article Stardust Results Challenge Astronomical Convention, the initial results of peering for the first time back to the beginning of our solar system using bits of material carried by this periodic, cometary visitor have shaken the foundations of solar-system science. In December 2006, an entire issue of Science magazine was devoted to the findings.
For the National Aeronautics and Space Administration (NASA), it was a high-risk mission. A hit by a single centimeter-size comet particle during the encounter could have destroyed the spacecraft. In addition, debate existed about the use of low-density aerogel for capturing hypervelocity particles. Although similar material had been flown on the European Eureka spacecraft and on Russia’s Mir Space Station to capture particles in low-Earth orbit, its efficacy for collecting comet dust was unknown. Even if individual comet grains could be collected in aerogel, it was unclear how they could be recovered. Debate also existed about the scientific significance of tiny, micrometer-size grains. Some among the “old guard” in planetary sciences worried that such samples would simply be too small to provide useful scientific information.
Immediately following the sample return capsule’s successful touchdown, Livermore scientists were at Johnson Space Center applying techniques developed at the Laboratory to extract particles from the Stardust payload. Within two weeks, a powerful suite of analytic tools—many not even imagined when the mission launched in 1999—was being used at Livermore to recover the secrets of the early solar system locked away in the tiny particles of stardust. Among these unique tools—spread through the Physics and Advanced Technologies; Chemistry, Materials, and Life Sciences; and Energy and Environment directorates—are the world’s most powerful scanning transmission electron microscope (called SuperSTEM), a nanoscale secondary-ion mass spectrometer (called NanoSIMS), a scanning electron microscope, a focused ion beam instrument, and a nuclear ion probe. Each of these tools represents a state-of-the-art Livermore capability; in combination, they have put the Laboratory squarely at the forefront of Stardust sample analysis work.
The Stardust mission has provided a spectacular opportunity for Lawrence Livermore to showcase its capabilities to a global audience. Laboratory staff was on the scene for the first inspection of the Stardust samples in clean rooms at the Curatorial Facility at Johnson Space Center. Livermore-developed technology was used to harvest some of the first comet samples from aerogel collection cells. NASA has recognized Livermore’s unique environment and personnel by purchasing the newest advance in STEM instrumentation—the Titan microscope—for the Laboratory. Titan, representing the next generation of aberration-corrected electron microscopes, has already demonstrated subangstrom spatial resolution and 100-millielectronvolts energy resolution, another world-record feat for the Laboratory.