The decision to use a stationary lander to collect materials and take us closer to answering our most critical questions about Mars was made for two reasons.  The first was that much was already known about the arctic area where Phoenix would land.  Chief among things known was that the surface is relatively uniform and there wasn’t much to be gained by having Phoenix roam and collect samples.  The second reason was that Phoenix would need a number of specialized instruments to take the readings and perform the necessary analysis.  By deploying Phoenix as a stationary craft, the weight that would have been used by mechanisms necessary for movement could instead be devoted to those instruments.

Award-Winning Team

The Phoenix Mission Team was the first of the Scout Class mission teams.  These teams are intended to merge the talents of government, academia, and private industry.  Each Scout Class mission will have a principal investigator who is responsible for all aspects of the mission and works closely with a project manager and a flight system manager.  For the Phoenix Mission, Peter Smith of the University of Arizona served as Principal Investigator (PI).  Barry Goldstein of JPL acted as the Project Manager while Ed Sedivy of Lockheed Martin held the position of Spacecraft Manager.  On March 30 the team will be awarded the 2009 Swigert Award for Space Exploration “in recognition of the technical developments that led to one of the most startling and meaningful discoveries of the new millennium.”  Of course, the confirmation of water on Mars is not the only reason for the award.  It also celebrates the management structure of the project – the first time a project was led by a PI from an academic institution.

Launch to Landing

Phoenix launched from Cape Canaveral, Florida on August 4, 2007 at 5:26 am EDT.  The launch was uneventful and the trajectory was so exact it required only an 18 m/s trajectory course correction burn at its first adjustment on August 10.  The lander made a 10-month voyage of 423 million miles and touched down on Mars on May 25, 2008 at 4:38 pm PDT. The orbits of three satellites around Mars were adjusted to allow views of Phoenix as it entered Mars’ atmosphere, 125 km above the surface, and completed its descent and landing.

The heat shields worked to protect Phoenix as it entered the atmosphere.  When it decelerated to Mach 1.7, the parachutes were to deploy immediately but instead opened after an unanticipated, seven-second delay.  An image of Phoenix, parachute open as it floated to the Martian surface, was captured by one of the satellites.  Shortly after, the heatshield was jettisoned, the legs deployed, and the radar activated.  At 1 km above the surface, the lander separated and the thrusters went into action. At an altitude of 12 m, Phoenix began traveling at a constant velocity until its footpads detected touchdown near the edge of the landing area by Mars’ northern polar cap.

Fifteen minutes of inaction followed as Phoenix waited for any dust to settle.  Her first transmission was received in a euphoric control room at 4:53 pm PDT, signaling to the world that Phoenix was ready to begin its work.

Scientific Instruments

To prove the existence of water, the Phoenix carried a number of specialized instruments.  There was the Robotic Arm (RA), somewhat like a backhoe and designed to extend out from the lander, dig to the subsurface ice layer, scoop samples of the ice and soil, and deliver them to the TEGA and MECA instruments. The Robotic Arm Camera (RAC), mounted just above the scoop, took pictures – close up and in color – of the soil and ice, as well as the sidewalls and interior of the trenches and the area immediately around the lander.  A Thermal and Evolved-Gas Analyzer (TEGA) used 8 tiny ovens to measure the amounts of water vapor, CO₂, and organic compounds given off as the soil samples were heated.  The gasses were then analyzed by the mass spectrometer in this unit.  The Microscopy, Electrochemistry and Conductivity Analyzer (MECA) used several different components to examine the sample mineral grains, measure chemical properties, and check the thermal and electrical properties of the soil.  Some of these experiments used a wet chemistry lab to dissolve small amounts of the soil in water to determine the pH.  Up on the mast, the Surface Stereo Imager (SSI) relayed hi-res, color, stereo, panoramic images of the arctic landscape around the lander.  It also captured info for the positioning of the RA.  The final piece of equipment was the Meterological Station (MET). This weather station was designed to monitor changes in the amount of water and dust, along with temperature and other climate variables.

Guidance /Electrical Power/Telecommunications

On the way to Mars, Phoenix oriented itself by using two sun sensors and a star tracker that compared images of the sky with a catalog of star positions.  Upon landing, none of the instruments onboard would have been useful if Phoenix had not been able to communicate with Earth.  Adequate power was essential for this and other purposes and provided by the solar array, which opened fifteen minutes after touchdown, and kept the batteries charged.  Messages to Earth were relayed by Mars orbiters and broadcast using UHF.

Phoenix Lifetime

The Phoenix was supposed to be operational for 90 Martian days, Sols – the equivalent of 92 Earth days.  Instead, Phoenix lasted a little more than two months longer than expected before the changes in the Martian season cut the hours of sunshine to the point that the arrays could not fully replenish the batteries.  The team cut back on communications and turned off several heaters to maximize battery life, hoping to preserve Phoenix until they could observe the onset of the Martian winter ice.  Ultimately, there was nothing to be done and Phoenix was declared dead on November 10, 2008 after a week with no communication.  It’s unlikely Phoenix will become operational when the Martian winter ends and temperatures rise because the lander will most likely be engulfed in dry ice and will be unable to re-charge.

Mission Accomplished

Phoenix dug two trenches. The dirt from the first was analyzed.  Bright clumps of material in the second were left for observation.  They vanished over the course of four days, implying that the clumps were composed of water ice rather than dry ice.  On July 31, 2008, NASA announced that Phoenix had indeed confirmed the existence of water on Mars.  Unfortunately, as essential as water is, NASA announced soon after that Martian soil might not be friendly to microbial life.  Additional analysis of the Phoenix data is ongoing.

Phoenix didn’t just carry scientific instruments to the Red Planet.  It also brought along an American flag and the Planetary Society’s First Martian Library. This “Phoenix DVD” is made of silica glass that will allow it to last for hundreds of years or more on the Martian surface.  It contains a multimedia collection of literature and art about Mars, messages for future visitors from people like Carl Sagan, and the names of a quarter million people who submitted their names via the Internet to the Planetary Society for inclusion on the disc. Text on the surface of the disc gives instructions for retrieval of the information by those who discover it.

The Phoenix Mars Lander Mission was impressive.  The lander arrived on schedule.  It accomplished every one of its objectives.  It performed all scheduled experiments.  It captured the data it was designed to capture – and more.  It sent back images and it worked for far longer than anyone hoped.  The last message transmitted – in binary – was a fitting one: “Triumph.”