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Current Science Data

Current Science Data

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One of the first "multispectral spots" obtained by the IMP camera was of the Stripe Rock on Sol 4. A multispectral spot measurement obtains small images of a region of interest in all geology filters with no image compression. Stripe rock is of interest to Mars Pathfinder scientists because of a bright vertical stripe that appears on the center of the rock face. It was thought that this stripe might be an intruded vein of material of different composition than the surrounding rock.

The color image of this rock shows that the stripe is of similar color to the surrounding soils (see arrow). A detailed examination of the rock was conducted to extract preliminary reflectance spectra (that is, the variation of brightness with color) from nearby bright and dark soils, the stripe, and the surrounding rock. Although these data require further calibration (e.g., the lower reflectance at 965 nm is not reliable at this time), they do show that the general spectral characteristic of the stripe is quite similar to the nearby dark soil. This suggests that the "stripe" is actually an accumulation of soil deposited in a crack in the rock face.

Mars Pathfinder Mission
Mineralogy and Geochemistry Science Operations Group

Barnacle Bill Rock

Hypothesis: APXS data show composition of rock is consistent with volcanic andesite, but rough texture of surface suggests it may be a "breccia."

Could it be composed of many different rock fragments that combine to give a similar overall composition?

Method: Target Barnacle Bill with "multispectral spot" (all geology filters at full spatial resolution of about 1-2 cm per picture element)

Goal: Determine variability of reflectance spectra (mineralogy) across the face of the rock

If all spectra are similar: rock is "homogeneous" (composed of the same material)

If spectra vary: rock may be "heterogeneous" (such as an impact melt breccia or sedimentary conglomerate)

Result: Spectra taken from many different locations show only two basic kinds of spectra:

  1. Soil-like deposits
  2. Dark rock face

Implication: At spatial resolution of 1-2 cm, rock composition is homogeneous. However, rock may be composed of fine-grained materials (< 1-2 cm) that cannot be seen with this method.

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This image shows the location of Barnacle Bill rock (left of the Sojourner rover) and the approximate location of the full-resolution "multispectral spot" acquired on Barnacle Bill. Lossless (no compression) images were taken in all geology filters using the IMP camera to study in detail the variation of brightness in each filter, which provides information regarding the mineralogy of the material sampled. Spectra were extracted from several study regions (shown to the right of the high resolution view). The green area represents soil found behind the rock. Red patches represent brighter areas on the rock that are interpreted as accumulations of wind-blown dust found in small holes, or vesicles, on the rock. Blue patches represent darker rock faces not contaminated by a soil deposit. The spectra of these materials are shown in the accompanying figure. Preliminary data acquired from the "multispectral spot" image sequence for Barnacle Bill rock. Images were acquired with no compression in all geology filters. Reflectance spectra (that is, the variation of brightness with wavelength, or color) are shown for background soil (green), soil-like deposits found on and within small holes in the rock (red), and dark portions of the rock face (blue). Comparison of the spectra of these three types of materials demonstrates that the rock has relatively homogeneous composition at the spatial resolution of the patches sampled (about 1-3 cm). That is, all soil-like deposit and rock face spectra cluster in both their overall brightness (reflectance) and shape of their reflectance curves. A more heterogeneous rock would show variable spectral characteristics across its face. Note that the spectra of the soil-like deposit is intermediate to that of the background soil and rock face spectra. This is consistent with the interpretation that the soil-like deposit is a relatively thin layer in which portions of the rock are also sampled within the patches selected.

Also shown are laboratory spectra of oxidized and unoxidized volcanic rocks from Earth. Scientists will compare spectra of terrestrial materials such as these to help determine the composition of the rocks observed at the landing site in combination with data returned by other instruments such as the APXS.

In the foreground of each image is "Flat Top". Each frame was taken by the IMP camera using a different color filter. The color filters alter the appearance of the image. The red filter has enhanced both the textures of the rocks and the dust on the surface of "Flat Top". The Sojourner rover has successfully navigated the rear deployment ramp. This high resolution color image shows the front, left portion of the rover. The micron scale soil beneath the rover was the first specimen examined by the Alpha Proton X-Ray Spectrometer. This image shows the Sojourner rover in its traveling configuration. The rover has since stood up and driven onto the surface of Mars. The red rectangle represents the location of the spectral analysis performed by the Imager for Mars Pathfinder.

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