The Phoenix lander was launched in August 2007, and landed on 25 May 2008 on the icy northern pole of Mars between 65 and 75 north latitude. The region is comparable to the permafrost regions of the Earth. Phoenix is designed to study the history of water and habitability potential in the Martian arctic’s ice-rich soil. Phoenix was NASA’s sixth successful landing out of seven attempts. (Lets hope that Curiosity makes it a nice round number: 10 successful landings).
The mission was named Phoenix because it used the concepts and instruments of two earlier missions: notably the 2001 Mars Surveyor lander (cancelled in 2000) and the Mars Polar Lander (lost on Mars in 1999). Many of the scientific instruments for Phoenix were built or designed for these earlier spacecraft. The 2001 Mars Surveyor lander had been kept in storage at a Lockheed Martin clean room at Sunnyvale, California. Phoenix means ‘rises from ashes’ and is the name for the resilient mythological bird.
It was decided to build Phoenix as a lander and not as a rover, because the area of Mars where Phoenix was going to land was thought to be relatively uniform and thus travelling is of less value. If Phoenix would have been a rover a lot of the weight allowance of this spacecraft would have been needed to make it possible for Phoenix to travel over Mars. As a stationary lander Phoenix could be outfitted with more and better scientific instruments.
The mission had two goals. One was to study the geologic history of water, as that is seen as the key to unlocking the story of past climate change. The second was to evaluate past or potential planetary habitability in the ice-soil boundary. Both goals fitted well in NASA’s ”Follow the water” policy of Mars exploration.
Phoenix had one Robotic Arm (RA) to dig trenches up to half a metre (1.6 feet) into the layers of water ice and scoop up soil and water ice and deliver samples to the TEGA and MECA instruments, the onboard laboratory for geological and chemical analysis. Robotic Arm (RA), built by the Jet Propulsion Laboratory.
The Thermal and Evolved Gas Analyzer (TEGA) was a combination high-temperature furnace and mass spectrometer instrument that scientists used to analyze Martian ice and soil samples.
The Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) is a suit of several scientific instruments including a wet chemistry laboratory, an optical and atomic force microscopes, and a thermal and electrical conductivity probe.
Phoenix had several camera’s on board:
** The Mars Descent Imager (MARDI) – built by Malin Space Science Systems, was in the end not used as it was feared that the operation of this instrument would interfere with the actual landing sequence worked through by the computer on board Phoenix. Late in the Phoenix mission, an attempt was made to acquire sounds through the MARDI microphone, but no data were received and the mission ended shortly therafter.
** The Surface Stereoscopic Imager (SSI), Phoenix’s stereo camera, located on its 2 metre (6.6 foot) mast uses imaging technology inherited from both the Pathfinder and Mars Exploration Rover missions. The camera’s two “eyes” gave a high-resolution perspective of the landing site’s geology. Ofcourse it was meant to take panoramic images of the Martian arctic. They were also meant to provide range maps for the team to choose ideal digging locations. Multi-spectral capability enabled the identification of local minerals.
** The Robotic Arm Camera (RAC) attached to the Robotic Arm (RA) just above the scoop to provide for close up views of the soil to be digged into or scooped up from.
Phoenix also scanned the Martian atmosphere up to 20 kilometres (12.4 miles) in altitude, with its Meteorological Station (MET) obtaining daily data about the formation, duration and movement of clouds, fog and dust plumes. It will also carry temperature and pressure sensors.
The first images of the MARDI, used once the Phoenix had landed, were of clean permafrost underneath the lander. The layer of soil on top of the permafrost had been blown off by the landing rockets. Researchers found later that this was caused by the Lander’s use of pulsed thrusters caused much more extensive digging than a conventional non-pulsed engine. The pulsing thrusters had created shock waves that traveled through the soil and allowed much more gas to be pumped into the ground than the non-pulsed versions. As a result, the rocket plumes flowed through the soil and fluidized it. When the plume flowing through the soil reached an area outside of the engine’s blast zone, it explosively erupted out of the surface, carrying away the soil and causing extensive erosion a rocket plume excavates underlying soil explosively.
Regrettably the Robotic Arm did not reach underneath the lander.
The mission turned out to be quite frustrating for the scientist waiting to analyze a bit of water-ice permafrost on the landing site. Have a one armed lander, that could not move once it had touched down, proved a problem for scooping the soil and ice that people had hoped to examine with the laboratory instruments of Phoenix.
Phoenix landed on the polygon shaped terrain of the polar region. The polygons (multi-cornered tiles) are formed because of the constant freezing and thawing of the upper layer of the terrain. The soil is cracked and buckled to create ice wedges, polygons, with pulverising the edges of the tile-like divisions.
The soil in such regions (on Mars, but also on Earth) is not completely flat as the middle of each polygon is higher than the edges. Phoenix landed its three legs partly on the edge of such a polygon, which made the engineers reluctant to scoop up soil on the left hand side. And it was exactly at that left hand side that ‘white stuff’ presumably water ice was seen to evaporate over the course of 4 days due to sun warmth streaking it.
Next came the scoop of soil that refused to fall through the sieve like it was supposed to do after being deposited there by the robotic arm. You can see that the regolith is rather granular in nature, and it looks clumpy. Now, the clumpiness is not due to water cohesion. It is far too cold here for water to be liquid. It is not as hard as you’d expect if it were permafrost, either. Scientist concluded that the cohesion in the soil sample was probably the result of the salty minerals in the soil, giving it a consistency known as duricrust.
The lander completed its mission in August 2008, and made a last brief communication with Earth on November 2 as available solar power dropped with the Martian winter. The mission was declared concluded on November 10, 2008, after engineers were unable to re-contact the craft. After unsuccessful attempts to contact the lander by the Mars Odyssey orbiter up to and past the Martian summer solstice on May 12, 2010, JPL declared the lander to be dead.
Two images of the Phoenix Mars lander taken from Martian orbit in 2008 and 2010 by MRO. The 2008 lander image (left) shows two relatively blue spots on either side corresponding to the spacecraft’s clean circular solar panels. In the 2010 (right) image scientists see a dark shadow that could be the lander body and eastern solar panel, but no shadow from the western solar panel.
During its mission, Phoenix confirmed and examined patches of the widespread deposits of underground water ice detected by Odyssey and identified a mineral called calcium carbonate that suggested occasional presence of thawed water. The lander also found soil chemistry with significant implications for life and observed falling snow. The mission’s biggest surprise was the discovery of perchlorate, an oxidizing chemical on Earth that is food for some microbes and potentially toxic for others.
Scientists are investigating the implications of the antifreeze properties of perchlorate and its potential use as an energy source by microbes.
Discovery of the ice in the uppermost soil by the Odyssey satellite pointed the way for Phoenix. Since then the Mars Reconnaissance Orbiter detected numerous ice deposits in middle latitudes at greater depth using radar and exposed on the surface by fresh impact craters. As ice-rich environments are an even bigger part of Mars than previously thought, it is likely that Mars will have places that are more habitable than others.