Finding the blueberries
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Finding the blueberries

January 4, 2005
Scientists are hunting down the recipe for the "blueberries" they've discovered on Mars. Taken with the front hazard-avoidance camera on the 45th martian day, or sol, of the rover's mission (March 10, 2004), image A shows the area dubbed "Berry Bowl" where many dark and mysterious spherules or "blueberries" collected in a depression on the surface of a rock. Image B is the microscopic image of the same area taken on sol 46 (March 11, 2004) magnifying "Berry Bowl."

To figure out the chemical composition of the blueberries, scientists are currently analyzing the area shown in the microscopic image with the rover's alpha particle X-ray spectrometer and Mössbauer spectrometer. The field of view for the alpha particle X-ray spectrometer is about equal to the field of view of the microscopic image and the field of view for the Mössbauer spectrometer is about half the size of the microscopic image, so the spectrometers will observe a mix of sand, rock, and blueberries. The blueberries are too small to analyze alone. Scientists will discern the blueberry spectra from the observed blend of spectra by subtracting out the known sand and rock spectra. Basically, finding the blueberry recipe is like making a recipe in reverse. Chemical measurements of the sand were taken earlier, and a measurement of the same rock in an area clear of the blueberries will be taken with the spectrometers on sol 48.

The "triple berry" seen in the center of the microscopic image is intriguing to scientists because it reveals a clue about how the blueberries formed. Spheres formed from impacts or volcanoes do not tend to mold together like the spheres seen in the microscopic image. Spheres from impacts or craters are usually round or teardrop-shaped from flying in the air and freezing before hitting the ground. Any droplets of magma that combine with other droplets usually grow into a single mass in a spherical, dumbbell, or teardrop shape. In contrast, concretions could form this triple berry shape. Concretions are spherical mineral structures formed by groundwater percolating through porous rocks. On Earth, as concretions grow in close proximity to each other, their outer edges often intersect each other, giving an appearance like a triple soap bubble.

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