On June 15, the Phoenix Mars Lander, managed by the Jet Propulsion Laboratory here, used its robotic arm to dig down into a trench called â€œDodo-Goldilocks.â€ As the arm scooped out soil samples it came upon dice-size clumps of bright, white material. The arm dropped the clumps to the side and scientists watched. Four days later the clumps had disappeared.
â€œThey had been clearing out the trench area and found these few large clods. They looked light and [scientists thought] they could be ice or salt,â€ said Leslie Tamppari, Phoenix project scientist at JPL.
The clumps were set aside to be watched, and they vanished.
â€œIt was an 'Oh wow! Look at that!' [moment],â€ Tamppari said. â€œMost of us suspected it would turn out to be ice but people were excited. We found what we were looking for. We knew we landed in a good place.â€
Tamppari said that because of the extreme cold temperatures in the northern pole of Mars, where Phoenix landed, the ice didn't melt, but evaporated.
Before the evaporation, there were two basic theories of what the white substance could be: ice or salt. But with the clumps' recent vanishing act it appears that the material was â€œwater ice,â€ Tamppari said.
â€œWe are very excited,â€ she said of the discovery. â€œWe had our suspicions that it was [ice], but being scientists we had to go through the various hypothesis.â€
She added that if it were salt it would not have disappeared.
This disappearing ice may also be the answer to the â€œstickyâ€ soil substance that the robotic arm picked up in one of the lander's first experiments. The soil was to be picked up by the arm, dropped onto the tiny screen that covered the Thermal and Evolved-Gas Analyzer, or TEGA, oven. The soil could not shift through the screen but after several days it filled the oven. At the time, Peter Smith, Phoenix principal investigator, said he thought it there could have been ice that evaporated, allowing the soil to shift through.
Tamppari said that the team would return to the ice clumps but for now they have other experiments to tend to, including viewing soil through the optical microscope from an area called â€œWonderland.â€
â€œWonderland is considered to be one of the best location t search for the history of Mars,â€ she said.
The reason, she added, was because unlike the trench, which is more open to the weather elements, â€œWonderlandâ€ seems undisturbed.
â€œWe delivered a sample [of the 'Wonderland'] soil to the wet-chemistry experiment [on Wednesday],â€ Tamppari said.
This first-ever wet-chemistry experiment will test the soil for salts, acidity and other characteristics.
When the scientists turn back to the icy samples they will not scoop the soil with the robotic arm, but use a drilling-type tool to shave ice. This Martian sno-cone will then be placed into one of the TEGA ovens and tested again. But first the team will continue their research into the surface soil.