The “microscopy” part of the Microscopy, Electrochemistry and Conductivity Analyzer of NASA's Mars Phoenix Lander was used to take images of dust and sand particles. 

The mission's Optical Microscope observed particles that had fallen onto an exposed surface, revealing grains as small as one-tenth the diameter of a human hair.

The Optical Microscope examines soil particles and possibly ice particles with both an optical microscope and an atomic force microscope. The robotic arm delivers soil samples to a wheel that rotates to present the samples to the microscopes. Along the perimeter of the wheel are substrates with different types of surfaces, such as magnets and sticky silicone. This allows the experiment to get information from the particles’ interaction with the various surfaces, as well as from the sizes, shapes and colors of the particles themselves.

The biggest particles the optical microscope can view are about as long across as the thickness of a dime, just over a millimeter. The smallest it can see are about 500 times smaller - about 2 microns across.

The optical microscope obtains color information by illuminating the sample with any combination of four different light sources. The illumination comes from 12 light-emitting diodes shining in red, blue, green or ultraviolet parts of the spectrum. The atomic force microscope assembles an image of the surface shape of a particle by sensing it with a sharp tip at the end of a spring, which has a strain gauge indicating how far the spring flexes to follow the contour of the surface.

The process is like a much smaller version of a phonograph needle tracking the bumpiness inside the groove of a vinyl record. The shapes and the size distributions of soil particles may tell scientists about environmental conditions the material has experienced. Tumbling rounds the edges. Repeated wetting and freezing causes cracking. Clay minerals formed during long exposure to water have distinctive, plate-shaped particle shapes.

"We have images showing the diversity of mineralogy on Mars at a scale that is unprecedented in planetary exploration," said Michael Hecht of NASA's Jet Propulsion Laboratory, Pasadena. He is the lead scientist for Phoenix's Microscopy.

The Optical Microscope images were taken June 3 of particles that had collected on a sticky surface exposed during the Phoenix landing and for five days after landing. Some of the particles might have come from inside the spacecraft during the forceful events of landing, but many match expectations for Martian particles.

Meanwhile, Phoenix received commands Thursday to collect its first soil sample to be delivered to a laboratory instrument on the lander deck. Commands for that same activity sent on Wednesday did not reach Phoenix because the orbiter intended for relaying the transmission, NASA's Mars Odyssey, had put itself into a safe standby mode shortly before the commands would have reached Odyssey.

On Wednesday, the lander completed a back-up plan of activities that had been sent previously, reported JPL's Chris Lewicki, mission manager for Phoenix surface operations on the lander's 11th Martian day. That plan included weather monitoring and additional imaging for a high-resolution color panorama of the site.

Thursday's commands were relayed to Phoenix via NASA's Mars Reconnaissance Orbiter. The relay radio on that orbiter has been working well in recent days, after intermittently turning itself off last week. Phoenix will continue to do relays via Mars Reconnaissance Orbiter until Odyssey returns to full functioning, and then Phoenix will use both orbiters.