Phoenix Lander Detects Martian Snow

The Phoenix Mars Lander has detected snow falling from Martian clouds

Doug Smock, Contributing Editor -- Design News, October 2, 2008

In a big breakthrough, the Phoenix Mars Lander has detected snow falling from Martian clouds. "Nothing like this view has ever been seen on Mars," says Jim Whiteway of York University, Toronto, lead scientist for the Canadian-supplied Meteorological Station on Phoenix. "We'll be looking for signs that the snow may even reach the ground."

A laser instrument designed to gather knowledge of how the atmosphere and surface interact on Mars has detected snow from clouds about 2.5 miles above the spacecraft's landing site. The snow vaporizes before reaching the ground.

"We are still collecting data and have lots of analysis ahead, but we are making good progress on the big questions we set out for ourselves," says Phoenix Principle Investigator Peter Smith of the University of Arizona, Tucson.

The Phoenix landed on May 25 and has already confirmed a hard subsurface layer at its far-northern site contains water-ice. Determining whether that ice ever thaws would help answer whether the environment there could ever have supported life of some form.

Scientific investigators also think they have discovered calcium carbonate, the main composition of chalk, and particles that could be clay. That's important because most carbonates and clays on Earth form only in the presence of liquid water. Spacecraft soil experiments also have provided evidence of past interaction between minerals and liquid water, processes that occur on Earth.

The evidence for calcium carbonate in soil samples from trenches dug by the Phoenix robotic arm comes from two laboratory instruments called the Thermal and Evolved Gas Analyzer, or TEGA and the wet chemistry laboratory of the Microscopy, Electrochemistry and Conductivity Analyzer, or MECA. "We have found carbonate," says William Boynton of the University of Arizona, lead scientist for the TEGA. "This points toward episodes of interaction with water in the past."

The TEGA evidence for calcium carbonate came from a high-temperature release of carbon dioxide from soil samples. The temperature of the release matches a temperature known to decompose calcium carbonate and release carbon dioxide gas, which was identified by the instrument's mass spectrometer.

The MECA evidence came from a buffering effect characteristic of calcium carbonate assessed in wet chemistry analysis of the soil. The measured concentration of calcium was exactly what would be expected for a solution buffered by calcium carbonate.

Both TEGA and the microscopy part of MECA have turned up hints of a clay-like substance. "We are seeing smooth-surfaced, platy particles with the atomic-force microscope, not inconsistent with the appearance of clay particles," says Michael Hecht, MECA lead scientist at NASA's Jet Propulsion Laboratory in Pasadena, CA.

The Phoenix mission, originally planned for three months on Mars, is now in its fifth month. However, it faces a decline in solar energy that is expected to curtail and then end the lander's activities before the end of the year. Before power ceases, the Phoenix team will attempt to activate a microphone on the lander to possibly capture sounds on Mars.

"For nearly three months after landing, the sun never went below the horizon at our landing site," says Barry Goldstein, JPL Phoenix project manager. "Now it is gone for more than four hours each night, and the output from our solar panels is dropping each week. Before the end of October, there won't be enough energy to keep using the robotic arm."