MGS MOC Release No. MOC2-206, 7 February 2000
(A) Daedalia Planum Context, Arsia Mons in upper right.
(C) Compared with Amboy
Based upon observations of Daedalia Planum from the Viking orbiters in the late 1970s, it has been assumed for 20 years that most of Daedalia Planum is a lava flow field that is mantled by bright dust. However, the similarity to the Amboy lava field in California has caused some scientists to re-think the situation on Mars. Instead of bright dust, it now appears that bright sand might be present in this portion of Daedalia Planum.
What's the difference between dust and sand? Observations from the Viking and Mars Pathfinder landers have suggested that martian dust consists of very, very tiny particles of less than 10 micrometers (less than 1/10th the width of a human hair). Sand, on the other hand, is defined by sedimentologists as consisting of particles with sizes in the range 62.5 to 2000 micrometers (2000 micrometers is 2 millimeters, or about 8-hundredths of an inch). In the martian environment, sand moves close to the ground by bouncing and hopping when strong enough gusts of wind come along, this is called saltation. Dust, on the other hand, gets picked up by the wind and travels by being suspended in the air. When dust settles back to the ground, it forms a coating that blankets surfaces in a fairly uniform manner, whereas sand makes drifts, tails, and streaks as it interacts with obstacles such as craters, hills, and the lumpy surfaces of lava flows.
At the Amboy lava field in California, bright sand is being blown across the dark lava from adjacent dry streambeds. When this sand encounters a volcanic cinder cone that rises above the lava field (pictures "B" and "D" in the above, right figure), the sand is deflected around the cone and leaves a dark "shadow" in which very little bright sand gets deposited. A similar situation is seen with respect to craters formed by meteor impact in the Daedalia Planum image AB1-10905 (pictures "A" and "C" in the above, right figure). The spectacular Amboy wind streak, lava flows, and cinder cone can often be seen from an airplane by passengers flying into or out of Los Angeles International Airport (LAX) from points east such as Denver, Colorado.
MOC image AB1-10905 is illuminated from the left. The Amboy lava flows and cinder cone volcano are illuminated from the lower right. The Amboy photographs were taken from an airplane and are from the U.S. Geological Survey. Wind has blown material from right to left in the MOC image, and from upper left toward lower right in the Amboy pictures. North is up in all figures.
For a higher-resolution view of the AB1-10905 MOC image (2.4 MBytes), CLICK HERE.
Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
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