Phoenix set to begin search for water on Mars
by Kathleen Grigg
When looking at Mars through a telescope, the first thing you notice is the red shade of dust covering the surface. Beneath the dust, a span of water ice may contain clues about the planet’s past. The Phoenix Mission may be able to dig up that story.
Phoenix is scheduled to land May 25 in Mars’s northern polar region. Back on Earth, scientists will spend several days preparing its onboard instruments, which include an 8-foot robotic arm, ovens, wet chemistry labs, cameras and a weather station.
Unlike the rovers, Phoenix is a lander and cannot move around on the Martian surface. It will use its robotic arm to scoop up samples of soil and ice. The samples will then be analyzed onboard for composition, pH and other properties.
Phoenix public affairs manager Sara Hammond works out of the University of Arizona Tucson, where the mission is based. She emphasized that while Phoenix is not necessarily searching for life, it is searching for aspects that make a planet habitable, like organic matter and water.
“We expect to be the first to touch water on Mars – water being in the form of ice,�? Hammond said. “Really what we are going to do is to try to study the water and understand its history. Has it ever been liquid? If so, how did it change the properties of the soil?�?
Phoenix’s principle investigator Peter Smith said that because similar ground ice is associated with 25 percent of the Martian surface, it is as if Phoenix will be investigating a quarter of the surface instead of just the robotic arm’s radius. Therefore, if the mission finds organic materials, it’s likely that they will be found elsewhere on the planet too.
“If we find it habitable then it’s really worth sending another mission to do the search for life,�? he said.
One way to determine properties of soil is to heat it up. The onboard Thermal Evolved Gas Analyzer (TEGA) will heat samples to 1800 degrees, maintaining a steady rate of temperature change. Smith said that this helps to determine if something in the sample is changing states – for example, liquid to solid.
“The way we do it is to monitor the power that we’re putting in to it as we’re heating it at a constant temperature ramp,�? Smith said. “Power should have a constant rise, but if you have something that changes states, then you get to a temperature and you figure out it isn’t so easy to heat anymore.�?
TEGA also has a mass spectrometer to analyze which gases are released at those phase changes.
“We do two things,�? Smith said. “We heat up slowly looking at the power profile to see where we’re having trouble heating. We look at gasses that come off when they hit those phase changes.�?
Another onboard instrument, the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA), works like a wet chemistry lab. Soil samples are placed in water to determine properties such as mineral abundance, pH and the presence of dissolved gasses. MECA’s microscope will help determine the origins of the soil and its mineralogy.
Phoenix’s meteorological station will track weather on Mars, sending back a daily report. Smith said that studying the Martian atmosphere can help scientists understand the ground, too.
“You can’t study the surface in isolation from the atmosphere,�? he said.
On Earth, surface pressure and temperature conditions allow water to exist in all three states – solid, liquid and gas. On Mars, the pressures and temperatures are so low that water can only exist as ice or vapor – meaning polar caps, ground ice, clouds, haze and fog.
Robert Burnham, press liaison for the Mars mission THEMIS, said people need to remember that the same rules apply for Earth and Mars alike.
“Physics and chemistry are the same the universe-over,�? Burnham said.
While in graduate school, Cal Poly professor John Keller worked on the Gamma Ray Spectrometer (GRS) that was able to detect the water. GRS was on board the 2001 Mars Odyssey mission, which orbited around Mars and collected signals from certain elements, such as the hydrogen (H) in water (H2O). GRS can collect data up to one meter beneath the surface.
Keller said that the Phoenix Mission was motivated by that discovery of water ice.
“It’s been there ever since we started pointing a telescope at Mars,�? he said. “It’s only in the last seven years that we’ve had this new detection technique to see through the dust and recognize that there’s a hydrogen signal coming from deeper than that.�?
Phoenix may also be able to determine how the water ice ended up where it is – by precipitation from the atmosphere, or from groundwater.
“Climate modelers for both Mars climate models and Earth climate models want to have a better understanding ... and the thing you need for that is data. You need to know where the ice came from,�? Keller said.
Hammond believes that missions like Phoenix speak to human nature’s desire to explore.
“Humans by nature are just kind of explorers and wonderers – whether it’s been the United States from east to west, or looking at stars through telescopes, wondering what’s out there. This is kind of helping answer that question. What’s out there?�? Hammond said “We’re using our technological expertise to go far beyond where we’ve ever gone before.�?