NASA'S Phoenix Lander Preps to Study Secrets of Mars' Soil

What surprises are hidden in the soils of Mars? To help find out, the Phoenix Lander Phoenix Lander which arrived on Mars two weeks ago has attempted to place a scoop of soil in Phoenix's Thermal and Evolved-Gas Analyzer (TEGA). Once in the oven, a soil material will be baked and the emitted gases categorized by a mass spectrometer.

The arm of NASA's Phoenix Mars Lander released a handful of clumpy Martian soil onto a screened opening of a laboratory instrument on the spacecraft Friday, but the instrument did not confirm that any of the sample passed through the screen.

Quite possibly, some of the light colored material visible in the scoop has the same composition as the light material imaged near the foot of the Lander, which may be ice. Phoenix is scheduled to spend the next three months digging, baking and chemically analyzing its immediate surroundings to better understand Mars and whether the boundary between ice and soil was ever capable of supporting life.

Engineers and scientists on the Phoenix team assembled at the University of Arizona are determining the best approach to get some of that material into the instrument. Meanwhile, the team has developed commands for the spacecraft to use cameras and the Robotic Arm on Saturday to study how strongly the soil from the top layer of the surface clings together into clumps.

Images taken Friday show soil resting on the screen over an open sample-delivery door of Phoenix's Thermal and Evolved-Gas Analyzer, or TEGA, an instrument for identifying some key ingredients. The screen is designed to let through particles up to one-millimeter (0.04 inch) across while keeping out larger particles, in order to prevent clogging a funnel pathway to a tiny oven inside. An infrared beam crossing the pathway checks whether particles are entering the instrument and breaking the beam.

The researchers have not yet determined why none of the sample appears to have gotten past the screen, but they have begun proposing possibilities.

"I think it's the cloddiness of the soil and not having enough fine granular material," said Ray Arvidson of Washington University in St. Louis, the Phoenix team's science lead for Saturday and digging czar for the mission.

"In the future, we may prepare the soil by pushing down on the surface with the arm before scooping up the material to break it up, then sprinkle a smaller amount over the door," he said.

Another strategy under consideration is to use mechanical shakers inside the TEGA instrument differently than the five minutes of shaking that was part of the sample-receiving process on Friday. No activities for the instrument are planned for Saturday, while the team refines plans for diagnostic tests.

Phoenix's planned activities for Saturday include horizontally extending a trench where the lander dug two practice scoops earlier this week, and taking additional images of a small pile of soil that was scooped up and dropped onto the surface during the second of those practice digs.

"We are hoping to learn more about the soil's physical properties at this site," Arvidson said. "It may be more cohesive than what we have seen at earlier Mars landing sites."

The evidence sent back from by two Mars Viking Landers in 1976 and 1977 was inconclusive. In fact, NASA's first press release about the Viking tests announced that the results were positive. The "labeled Release" (LR) experiments had given positive results. But after lengthy discussions in which Carl Sagan participated, NASA reversed its position, mainly because another experiment detected no organics in the soil.

Yet to this day,  Gilbert Levin, the principal designer of the LR experiment, believes the tests pointed to life. When the same two experiments were run on soil from Antarctica, the same conflicting results were obtained (LR - positive; organics - negative.) Soil and ice from Antarctica certainly contains life. The test for organics was negative because it is far less sensitive than the LR experiment. The same problem could have caused the organics test on to give a false negative.

Before oxygen could accumulate in Earth's atmosphere, all the exposed iron had to rust. During that process, lasting hundreds of millions of years, Earth was also a red planet. In the journal Nature, Corinna Wu asked: Could the oxygen that rusted the iron on have been produced biologically? Could life on have simply "run out of steam" after that stage of its development?

The answers to these profound questions will hopefully be made by the Phoenix Probe's Thermal and Evolved Gas Analyzer (TEGA) built by the University of Arizona and University of Texas -a combination high-temperature furnace and mass spectrometer instrument. The robotic arm has delivered samples to a hopper designed to feed a small amount of soil and ice into eight tiny ovens about the size of an ink cartridge in a ballpoint pen. Each of these ovens will be used only once to analyze eight unique samples.

Once a sample is successfully received and sealed in an oven, the temperature is slowly increased at a constant rate, and the power required for heating is carefully and continuously monitored. This process, called scanning calorimetry, shows the transitions from solid to liquid to gas of the different materials in the sample: important information needed by scientists to understand the chemical character of the soil and ice.

As the temperature of the furnace increases up to 1000°C (1800°F), the ice and other volatile materials in the sample are vaporized into a stream of gases. These are called evolved gases and are transported via an inert carrier to a mass spectrometer, a device used to measure the mass and concentrations of specific molecules and atoms in a sample. The mass spectrometer is sensitive to detection levels down to 10 parts per billion, a level that may detect minute quantities of organic molecules potentially existing in the ice and soil.

With these precise measurement capabilities, scientists will be able to determine ratios of various isotopes of hydrogen, oxygen, carbon, and nitrogen, providing clues to origin of the volatile molecules, and possibly, biological processes that occurred in the past.

Posted Casey Kazan.

Related Galaxy posts:

Twittering From Mars -NASA's Tiny URL
Twittering from Mars: The Phoenix on Ice

Story link: http://phoenix.lpl.arizona.edu/06_07_pr.php

Comments

[tin whiskers]

Hi,
It will be fascinating to see if water near the planet's surface might periodically melt enough to sustain a viable environment for microbes.
This will be our first attempt to actually touch and analyze Martian water—water in the form of buried ice,