Microscope studies Mars soil up close and personal

William Atkins
Monday, 16 June 2008 20:28

Science - Space

Microsoft Office 365

Phoenix principal investigator Peter Smith (University of Arizona) states, "This is the first time since the Viking missions three decades ago that a sample is being studied inside an instrument on Mars.” [University of Arizona: "NASA's Phoenix Mars Lander Inspects Delivered Soil Samples"]

The composition of the soil was really a puzzle for the scientists and engineers working this mission. Because it is more clumpy and sticky than first thought, the mesh above the oven prevented the soil from reaching the oven on several attempts. However, success was achieved on the seventh try.

The Optical Microscope, along with the Lander’s Atomic Force Microscope, is now imaging these particles. The particles are positioned on a custom silicone substrate that contains different strips, each 0.4 millimeter (about 0.16 inch) wide. Each strip contains different types of pegs and holes to accommodate different sizes of particles.

One of the very important instruments onboard the Mars Lander is its Optical Microscope (OM). It is capable of resolving shapes down to 16 microns (where one micron, or micrometer, is one millionth of a meter)—say like a dust particle on the head of a pin.

So far, the OM has been able to view “nearly 1,000 separate soil particles,” and all of them “down to sizes smaller than one-tenth the diameter of a human hair.”

Smith adds, "Understanding the soil is a major goal of this mission and the soil is a bit different than we expected. There could be real discoveries to come as we analyze this soil with our various instruments. We have just the right instruments for the job." [University of Arizona]

MECA co-investigator Tom Pike (Imperial College London) explains, “It's been more than 11 years since we had the idea to send a microscope to Mars and I'm absolutely gobsmacked that we're now looking at the soil of Mars at a resolution that has never been seen before.”

MECA, which stands for Microscopy, Electrochemistry, and Conductivity Analyzer, is a set of instruments consisting of an Optical Microscope, along with an Atomic Force Microscope (AFM), a wet chemistry lab (WCL), and a thermal and electrical conductivity probe.

So far, the scientists looking at the soil sample say they are “larger, black, glassy” particles, which might be a type of volcanic glass, and others that look “smaller, reddish”—with the smaller ones looking very similar to airborne dust examined earlier in the mission.

Pike comments, "We may be looking at a history of the soil. It appears that original particles of volcanic glass have weathered down to smaller particles with higher concentration of iron." [University of Arizona]

The scientists have also seen yellowish green particles that they think is olivine, a mineral that could mean volcanic eruptions were present earlier in the history of Mars. Very common on Earth, olivine has also been found in meteorites and in lunar dust particles brought back to Earth from Apollo missions.

The soil samples eventually picked up by the robotic arm and scoop and the dust particles in the Martian atmosphere will all help scientists learn more about Mars. Eventually, dust storms are hoped to be examined in more detail. So far, however, dust storms have not been seen by the Lander.

Dust storms are also an important facet for the Phoenix Mars Lander mission. Please read on.