NASA's Phoenix Mars Lander: Spacecraft and mission profile

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Mars is a cold desert planet with no liquid water on its surface. But in the Martian arctic, water ice lurks just below ground level.

NASA's Phoenix Mars Lander: During the first 25 seconds after NASA's Phoenix Mars Lander deploys its parachute, the spacecraft will jettison its heat shield and extend its three legs.NASA's Phoenix Mars Lander: During the first 25 seconds after NASA's Phoenix Mars Lander deploys its parachute, the spacecraft will jettison its heat shield and extend its three legs.

Discoveries made by the Mars Odyssey Orbiter in 2002 show large amounts of subsurface water ice in the northern arctic plain. The Phoenix lander targets this circumpolar region using a robotic arm to dig through the protective top soil layer to the water ice below and ultimately, to bring both soil and water ice to the lander platform for sophisticated scientific analysis.

The complement of the Phoenix spacecraft and its scientific instruments are ideally suited to uncover clues to the geologic history and biological potential of the Martian arctic. Phoenix will be the first mission to return data from either polar region providing an important contribution to the overall Mars science strategy "Follow the Water" and will be instrumental in achieving the four science goals of NASA's long-term Mars Exploration Program.

NASA's Phoenix Mars Lander: NASA's Phoenix Mars Lander will open its solar arrays 20 minutes after it touches down on the surface of Mars. This ensures that any dust kicked up during the landing will not settle in on the arrays.   This artist's illustration is part of an animation that can be found at http://www.nasa.gov/mission_pages/phoenix/multimedia/animation.html .   The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.   Image credit: NASA/JPL-Caltech/University of ArizonaNASA's Phoenix Mars Lander: NASA's Phoenix Mars Lander will open its solar arrays 20 minutes after it touches down on the surface of Mars. This ensures that any dust kicked up during the landing will not settle in on the arrays. This artist's illustration is part of an animation that can be found at http://www.nasa.gov/mission_pages/phoenix/multimedia/animation.html . The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. Image credit: NASA/JPL-Caltech/University of Arizona

--Determine whether Life ever arose on Mars

--Characterize the Climate of Mars

--Characterize the Geology of Mars

--Prepare for Human Exploration

The Phoenix Mission has two bold objectives to support these goals, which are to (1) study the history of water in the Martian arctic and (2) search for evidence of a habitable zone and assess the biological potential of the ice-soil boundary.

Objective 1: Study the History of Water in All its Phases

Currently, water on Mars' surface and atmosphere exists in two states: gas and solid. At the poles, the interaction between the solid water ice at and just below the surface and the gaseous water vapor in the atmosphere is believed to be critical to the weather and climate of Mars. Phoenix will be the first mission to collect meteorological data in the Martian arctic needed by scientists to accurately model Mars' past climate and predict future weather processes.

NASA's Phoenix Mars Lander: These color images were acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on the 21st and 25th days of the mission, or Sols 20 and 24 (June 15 and 19, 2008). These images show sublimation of ice in the trench informally called "Dodo-Goldilocks" over the course of four days. In the lower left corner of the left image, a group of lumps is visible. In the right image, the lumps have disappeared, similar to the process of evaporation. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. Image credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University.NASA's Phoenix Mars Lander: These color images were acquired by NASA's Phoenix Mars Lander's Surface Stereo Imager on the 21st and 25th days of the mission, or Sols 20 and 24 (June 15 and 19, 2008). These images show sublimation of ice in the trench informally called "Dodo-Goldilocks" over the course of four days. In the lower left corner of the left image, a group of lumps is visible. In the right image, the lumps have disappeared, similar to the process of evaporation. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. Image credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University.

Liquid water does not currently exist on the surface of Mars, but evidence from Mars Global Surveyor, Odyssey and Exploration Rover missions suggest that water once flowed in canyons and persisted in shallow lakes billions of years ago. However, Phoenix will probe the history of liquid water that may have existed in the arctic as recently as 100,000 years ago. Scientists will better understand the history of the Martian arctic after analyzing the chemistry and mineralogy of the soil and ice using robust instruments.

Objective 2: Search for Evidence of Habitable Zone and Assess the Biological Potential of the Ice-Soil Boundary

Recent discoveries have shown that life can exist in the most extreme conditions. Indeed, it is possible that bacterial spores can lie dormant in bitterly cold, dry, and airless conditions for millions of years and become activated once conditions become favorable. Such dormant microbial colonies may exist in the Martian arctic, where due to the periodic wobbling of the planet, liquid water may exist for brief periods about every 100,000 years making the soil environment habitable.

Phoenix will assess the habitability of the Martian northern environment by using sophisticated chemical experiments to assess the soil's composition of life-giving elements such as carbon, nitrogen, phosphorus, and hydrogen. Identified by chemical analysis, Phoenix will also look at reduction-oxidation (redox) molecular pairs that may determine whether the potential chemical energy of the soil can sustain life, as well as other soil properties critical to determine habitability such as pH and saltiness.

NASA's Phoenix Mars Lander: This image shows a polygonal pattern in the ground near NASA's Phoenix Mars Lander, similar in appearance to icy ground in the arctic regions of Earth.   Phoenix touched down on the Red Planet at 4:53 p.m. Pacific Time (7:53 p.m. Eastern Time), May 25, 2008, in an arctic region called Vastitas Borealis, at 68 degrees north latitude, 234 degrees east longitude.   This is an approximate-color image taken shortly after landing by the spacecraft's Surface Stereo Imager, inferred from two color filters, a violet, 450-nanometer filter and an infrared, 750-nanometer filter.   The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.   Image credit: NASA/JPL-Caltech/University of ArizonaNASA's Phoenix Mars Lander: This image shows a polygonal pattern in the ground near NASA's Phoenix Mars Lander, similar in appearance to icy ground in the arctic regions of Earth. Phoenix touched down on the Red Planet at 4:53 p.m. Pacific Time (7:53 p.m. Eastern Time), May 25, 2008, in an arctic region called Vastitas Borealis, at 68 degrees north latitude, 234 degrees east longitude. This is an approximate-color image taken shortly after landing by the spacecraft's Surface Stereo Imager, inferred from two color filters, a violet, 450-nanometer filter and an infrared, 750-nanometer filter. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. Image credit: NASA/JPL-Caltech/University of Arizona

Despite having the proper ingredients to sustain life, the Martian soil may also contain hazards that prevent biological growth, such as powerful oxidants that break apart organic molecules. Powerful oxidants that can break apart organic molecules are expected in dry environments bathed in UV light, such as the surface of Mars. But a few inches below the surface, the soil could protect organisms from the harmful solar radiation. Phoenix will dig deep enough into the soil to analyze the soil environment potentially protected from UV looking for organic signatures and potential habitability.

Source: NASA

Detailed background:

Source: wikipedia.org

Phoenix was a robotic spacecraft on a space exploration mission on Mars under the Mars Scout Program. The scientists conducting the mission are using instruments aboard the Phoenix lander to search for environments suitable for microbial life on Mars, and to research the history of water there.

The multi-agency program was headed by the Lunar and Planetary Laboratory at the University of Arizona, under the direction of NASA's Jet Propulsion Laboratory. The program was a partnership of universities in the United States, Canada, Switzerland, Denmark, Germany, the United Kingdom, NASA, the Canadian Space Agency, the Finnish Meteorological Institute, Lockheed Martin Space Systems, MacDonald Dettwiler & Associates (MDA) and other aerospace companies. The operational funding for the mission extended through November 10, 2008.

Phoenix is NASA's sixth successful landing on Mars out of the twelve attempts that reached Mars. It is the most recent spacecraft to land successfully on Mars. It is also the first successful landing on a polar region of Mars. The mission was declared concluded on November 10, 2008, after engineers were unable to contact the craft. The lander last made a brief communication with Earth on November 2.

NASA's Phoenix Mars Lander: This image taken by the Surface Stereo Imager on Sol 49, or the 49th Martian day of the mission (July 14, 2008), shows the silver colored rasp protruding from NASA's Phoenix Mars Lander's Robotic Arm scoop. The scoop is inverted and the rasp is pointing up.  Shown with its forks pointing toward the ground is the thermal and electrical conductivity probe, at the lower right. The Robotic Arm Camera is pointed toward the ground.  The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.   Image NASA/JPL-Caltech/University of Arizona/Texas A&M UniversityNASA's Phoenix Mars Lander: This image taken by the Surface Stereo Imager on Sol 49, or the 49th Martian day of the mission (July 14, 2008), shows the silver colored rasp protruding from NASA's Phoenix Mars Lander's Robotic Arm scoop. The scoop is inverted and the rasp is pointing up. Shown with its forks pointing toward the ground is the thermal and electrical conductivity probe, at the lower right. The Robotic Arm Camera is pointed toward the ground. The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. Image NASA/JPL-Caltech/University of Arizona/Texas A&M University

Program overview

The mission had two goals. One was to study the geologic history of water, the key to unlocking the story of past climate change. The second was evaluate past or potential planetary habitability in the ice-soil boundary. Phoenix's instruments were suitable for uncovering information on the geological and possibly biological history of the Martian Arctic. Phoenix was the first mission to return data from either of the poles, and contributed to NASA's main strategy for Mars exploration, "Follow the water."

The primary mission was anticipated to last 90 sols (Martian days) – just over 92 Earth days. However, the craft exceeded its expected operational lifetime by a little over two months before succumbing to the increasing cold and dark of an advancing Martian winter. Researchers had hoped that the lander would survive into the Martian winter so that it could witness polar ice developing at the spacecraft's exploration area. As much as three feet of solid carbon dioxide ice could appear in the area. Even if the lander had survived part way into the winter, it was very unlikely that it would have functioned throughout the entire winter due to the intense cold. The mission was chosen to be a fixed lander rather than a rover because:

1. costs were reduced through reuse of earlier equipment;

2. the area of Mars where Phoenix is landing is thought to be relatively uniform and thus traveling is of less value; and

3. the equipment weight that would be required to allow Phoenix to travel can instead be dedicated to more and better scientific instruments.

The 2003–2004 observations of methane gas on Mars were made remotely by three teams working with separate data. If the methane is truly present in the atmosphere of Mars, then something must be producing it on the planet now, because the gas is broken down by sunlight within 300 years, therefore the importance to search for biological potential or habitability of the Martian arctic's soils. Methane could also be the product of a geochemical process or the result of volcanic or hydrothermal activity. Other future missions may enable us to discover whether life does indeed exist on Mars today.

NASA's Phoenix Mars Lander: This artist's concept depicts NASA's Phoenix Mars Lander a moment before its planned touchdown on the arctic plains of Mars in May 2008. Image credit: NASA/JPL-Calech/University of ArizonaNASA's Phoenix Mars Lander: This artist's concept depicts NASA's Phoenix Mars Lander a moment before its planned touchdown on the arctic plains of Mars in May 2008. Image credit: NASA/JPL-Calech/University of Arizona

History of the program

A comparison of sizes for the Sojourner rover, the Mars Exploration Rovers, the Phoenix lander and the Mars Science Laboratory.

While the proposal for Phoenix was being written, the Mars Odyssey Orbiter used its gamma ray spectrometer and found the distinctive signature of hydrogen on some Martian surface. The only plausible source of hydrogen on Mars would be water in the form of ice, frozen below the surface. The mission was funded on the expectation that Phoenix would find water ice on the arctic plains of Mars. In August 2003 NASA selected the University of Arizona "Phoenix" mission for launch in 2007. It was hoped this would be the first in a new line of smaller, low-cost, Scout missions in the agency's exploration of Mars program. The selection was the result of an intense two-year competition with proposals from other institutions. The $325 million NASA award is more than six times larger than any other single research grant in University of Arizona history.

Peter H. Smith of the University of Arizona Lunar and Planetary Laboratory, as Principal Investigator, along with 24 Co-Investigators, were selected to lead the mission. The mission was named after the Phoenix, a mythological bird that is repeatedly reborn from its own ashes. The Phoenix spacecraft contains several previously built components. The lander used for the 2007–08 mission is the modified Mars Surveyor 2001 Lander (canceled in 2000), along with several of the instruments from both that and the previous unsuccessful Mars Polar Lander mission. Lockheed Martin, which built the lander, had kept the nearly complete lander in an environmentally controlled clean room from 2001 until the mission was funded by the NASA Scout Program.

Phoenix was a partnership of universities, NASA centers, and the aerospace industry. The science instruments and operations were a University of Arizona responsibility. NASA's Jet Propulsion Laboratory in Pasadena, California, managed the project and provided mission design and control. Lockheed Martin Space Systems, Denver, Colorado, built and tested the spacecraft. The Canadian Space Agency provided a meteorological station, including an innovative Laser-based atmospheric sensor. The co-investigator institutions included Malin Space Science Systems (California), Max Planck Institute for Solar System Research (Germany), NASA Ames Research Center (California), NASA Johnson Space Center (Texas), MDA (Canada),Optech Incorporated (Canada), SETI Institute, Texas A&M University, Tufts University, University of Colorado, University of Copenhagen (Denmark), University of Michigan, University of Neuchâtel (Switzerland), University of Texas at Dallas, University of Washington, Washington University in St. Louis, and York University (Canada). Scientists from Imperial College London and Bristol University have provided hardware for the mission and were part of the team operating the microscope station.

On June 2, 2005, following a critical review of the project's planning progress and preliminary design, NASA approved the mission to proceed as planned. The purpose of the review was to confirm NASA's confidence in the mission.

Specifications

Mass

350 kg (770 lb)

Dimensions

About 5.5 m (18 ft) long with the solar panels deployed. The science deck by itself is about 1.5 m (4.9 ft) in diameter. From the ground to the top of the MET mast, the lander measures about 2.2 m (7.2 ft) tall.

Communications

X-band throughout the cruise phase of the mission and for its initial communication after separating from the third stage of the launch vehicle. UHF links, relayed through Mars orbiters during the entry, descent and landing phase and while operating on the surface of Mars. The UHF system on Phoenix is compatible with relay capabilities of NASA’s Mars Odyssey, Mars Reconnaissance Orbiter and with the European Space Agency’s Mars Express. The interconnections use the Proximity-1 protocol.

Power

Power is generated using two gallium arsenide solar array panels (total area 3.1 m2 (33 sq ft)) mounted to the cruise stage during cruise, and via two gallium arsenide solar array panels (total area 2.9 m2 (31 sq ft)) deployed from the lander after touchdown on the Martian surface. NiH2 with 16 A•h.

Lander systems include a RAD6000 based computer system for commanding the spacecraft and handling data. Other parts of the lander are an electrical system containing solar arrays and batteries, a guidance system to land the spacecraft, eight 1.0 lbf (4.4 N) and 5.0 lbf (22 N) monopropellant hydrazine engines built by Aerojet-Redmond Operations for the cruise phase, twelve 68.0 lbf (302 N) Aerojet monopropellant hydrazine thrusters to land the Phoenix, mechanical and structural elements, and a heater system to ensure the spacecraft does not get too cold.

NASA's Phoenix Mars Lander: NASA's Phoenix Mars Lander has launched from Florida's Cape Canaveral Air Force Station aboard a Delta II rocket. Image credit: NASANASA's Phoenix Mars Lander: NASA's Phoenix Mars Lander has launched from Florida's Cape Canaveral Air Force Station aboard a Delta II rocket. Image credit: NASA

Launch

Phoenix was launched on 4 August 2007, at 5:26:34 a.m. EDT (09:26:34 UTC) on a Delta 7925 launch vehicle from Pad 17-A of the Cape Canaveral Air Force Station. The launch was nominal with no significant anomalies. The Phoenix lander was placed on a trajectory of such precision that its first trajectory course correction burn, performed on August 10, 2007 at 7:30 a.m. EDT (11:30 UTC), was only 18 m/s. The launch took place during a launch window extending from August 3, 2007 to August 24, 2007. Due to the small launch window the rescheduled launch of the Dawn mission (originally planned for July 7) had to stand down and was launched after Phoenix in September. The Delta 7925 was chosen due to its successful launch history, which includes launches of the Spirit and Opportunity Mars Exploration Rovers in 2003 and Mars Pathfinder in 1996.

NASA's Phoenix Mars Lander: NASA's Phoenix Mars Lander will enter the Martian atmosphere at hypersonic speeds. Friction will heat the forward-facing surface of the heat shield to a peak of about 1,420 degrees Celsius (2,600 degrees Fahrenheit) at an altitude of 41 kilometers (25.5 miles).   This artist's illustration is part of an animation that can be found at http://www.nasa.gov/mission_pages/phoenix/multimedia/animation.html .   The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.   Image credit: NASA/JPL-Caltech/University of ArizonaNASA's Phoenix Mars Lander: NASA's Phoenix Mars Lander will enter the Martian atmosphere at hypersonic speeds. Friction will heat the forward-facing surface of the heat shield to a peak of about 1,420 degrees Celsius (2,600 degrees Fahrenheit) at an altitude of 41 kilometers (25.5 miles). This artist's illustration is part of an animation that can be found at http://www.nasa.gov/mission_pages/phoenix/multimedia/animation.html . The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver. Image credit: NASA/JPL-Caltech/University of Arizona

Landing

The Jet Propulsion Laboratory made adjustments to the orbits of three satellites around Mars to be in the right place on May 25, 2008 to observe Phoenix as it entered the atmosphere and to monitor it up to one minute after landing. This information will allow for better design for future landers. The projected landing area was an ellipse 100 km by 20 km covering terrain which has been informally named "Green Valley" and contains the largest concentration of water ice outside of the poles.

Phoenix entered the Martian atmosphere at nearly 21,000 km (13,000 miles) per hour, and within 7 minutes had to be able to decrease its speed to 8 kilometres per hour (5.0 mph) before touching down on the surface. Confirmation of atmospheric entry was received at 4:46 p.m. PDT (23:46 UTC). Radio signals received at 4:53:44 p.m. PDT confirmed that Phoenix had survived its difficult descent and landed 15 minutes earlier, thus completing a 680 million km (422 million miles) flight from Earth.

Parachute deployment was about 7 seconds later than expected, leading to a landing position some 25–28 km long (east), near the edge of the predicted 99% landing ellipse. The reason for this delay is not publicly known.

Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera photographed Phoenix suspended from its parachute during its descent through the Martian atmosphere. This marks the first time ever one spacecraft has photographed another in the act of landing on a planet (the Moon not being a planet, but a satellite). The same camera also imaged Phoenix on the surface with enough resolution to distinguish the lander and its two solar cell arrays. Ground controllers used Doppler tracking data from Odyssey and Mars Reconnaissance Orbiter to determine the lander's precise location as 68.218830°N 234.250778°E. The landing site is here on the Google Mars web-based map and here on the NASA World Wind planetary viewer (free installation required; "MOLA Color (ASU)" is the Google image).

Phoenix landed in the Green Valley of Vastitas Borealis on May 25, 2008, in the late Martian northern hemisphere spring (Ls = 76.73), where the Sun shone on its solar panels the whole Martian day. By the Martian northern Summer solstice (June 25, 2008), the Sun appeared at its maximum elevation of 47.0 degrees. Phoenix experienced its first sunset at the start of September 2008.

The landing was made on a flat surface, with the lander reporting only 0.3 degrees of tilt. Just before landing, the craft used its thrusters to orient its solar panels along an east-west axis to maximize power generation. The lander waited 15 minutes before opening its solar panels, to allow dust to settle. The first images from the lander became available around 7:00 p.m. PDT (2008-05-26 02:00 UTC). The images show a surface strewn with pebbles and incised with small troughs into polygons about 5 m across and 10 cm high, with the expected absence of large rocks and hills.

Like the 1970s era Viking spacecraft, Phoenix used rocket motors for its final descent. Experiments conducted by Nilton Renno, mission co-investigator from the University of Michigan, and his students have investigated how much surface dust would be kicked up on landing. Researchers at Tufts University, led by co-investigator Sam Kounaves, conducted additional in-depth experiments to identify the extent of the ammonia contamination from the hydrazine propellant and its possible effects on the chemistry experiments. In 2007, a report to the American Astronomical Society by Washington State University professor Dirk Schulze-Makuch, suggested that Mars might harbor peroxide-based life forms which the Viking landers failed to detect because of the unexpected chemistry. The hypothesis was proposed long after any modifications to Phoenix could be made. One of the Phoenix mission investigators, NASA astrobiologist Chris McKay, stated that the report "piqued his interest" and that ways to test the hypothesis with Phoenix's instruments would be sought.

Surface mission

The robotic arm's first movement was delayed by one day when, on May 27, 2008, commands from Earth were not relayed to the Phoenix lander on Mars. The commands went to NASA's Mars Reconnaissance Orbiter as planned, but the orbiter's Electra UHF radio system for relaying commands to Phoenix temporarily shut off. Without new commands, the lander instead carried out a set of activity commands sent May 26 as a backup. On May 27 the Mars Reconnaissance Orbiter relayed images and other information from those activities back to Earth.

The robotic arm was a critical part of the Phoenix Mars mission. On May 28, scientists leading the mission, sent commands to unstow its robotic arm and take more images of its landing site. The images revealed that the spacecraft landed where it had access to digging down a polygon across the trough and digging into its the center.

The polygonal cracking in this area had previously been observed from orbit, and is similar to patterns seen in permafrost areas in polar and high altitude regions of Earth. A likely formation mechanism is that permafrost ice contracts when the temperature decreases, creating a polygonal pattern of cracks, which are then filled by loose soil falling in from above. When the temperature increases and the ice expands back to its former volume, it thus cannot assume its former shape, but is forced to buckle upwards. (On Earth, liquid water would probably enter at times along with soil, creating additional disruption due to ice wedging when the contents of the cracks freeze.)

The Lander's Robotic Arm touched soil on the red planet for the first time on May 31, 2008. It scooped dirt and started sampling the Martian soil for ice after days of testing. Phoenix's Robotic Arm Camera took an image underneath the lander on sol 5 that shows patches of a smooth bright surface uncovered when thruster exhaust blew off overlying loose soil. It was later shown to be ice. Ray Arvidson of Washington University in St. Louis said: "We could very well be seeing rock, or we could be seeing exposed ice in the retrorocket blast zone."

Presence of shallow subsurface water ice

On June 19, 2008, NASA announced that dice-sized clumps of bright material in the "Dodo-Goldilocks" trench dug by the robotic arm had vaporized over the course of four days, strongly implying that they were composed of water ice which sublimated following exposure. While dry ice also sublimates, under the conditions present it would do so at a rate much faster than observed.

On July 31, 2008, NASA announced that Phoenix confirmed the presence of water ice on Mars, as predicted on 2002 by the Mars Odyssey orbiter. During the initial heating cycle of a new sample, TEGA's mass spectrometer detected water vapor when the sample temperature reached 0 °C. Liquid water cannot exist on the surface of Mars with its present low atmospheric pressure, except at the lowest elevations for short periods.

With Phoenix in good working order, NASA announced operational funding through September 30, 2008. The science team labored to determine whether the water ice ever thaws enough to be available for life processes and if carbon-containing chemicals and other raw materials for life are present.

Wet Chemistry

On June 24, 2008, NASA's scientists launched a major series of tests. The robotic arm scooped up more soil and delivered it to 3 different on-board analyzers: an oven that baked it and tested the emitted gases, a microscopic imager, and a wet chemistry lab. The lander's Robotic Arm scoop was positioned over the Wet Chemistry Lab delivery funnel on Sol 29 (the 29th Martian day after landing, i.e. June 24, 2008). The soil was transferred to the instrument on Sol 30 (June 25, 2008), and Phoenix performed the first wet chemistry tests. On Sol 31 (June 26, 2008) Phoenix returned the wet chemistry test results with information on the salts in the soil, and its acidity. The wet chemistry lab was part of the suite of tools called the Microscopy, Electrochemistry and Conductivity Analyzer (MECA).

Preliminary wet chemistry lab results showed the surface soil is moderately alkaline, between pH 8 and 9. Magnesium, sodium, potassium and chloride ions were found; the overall level of salinity is modest. Chloride levels were low, and thus the bulk of the anions present were not initially identified. The pH and salinity level were viewed as benign from the standpoint of biology. TEGA analysis of its first soil sample indicated the presence of bound water and CO2 that were released during the final (highest-temperature, 1,000°C) heating cycle.

On August 1, 2008, Aviation Week reported that "The White House has been alerted by NASA about plans to make an announcement soon on major new Phoenix lander discoveries concerning the "potential for life" on Mars, scientists tell Aviation Week & Space Technology." This led to a subdued media speculation on whether some evidence of past or present life had been discovered. To quell the speculation, NASA released preliminary and unconfirmed findings which suggest that Mars soil contains perchlorate and thus may not be as earth-like and life-friendly as thought earlier.

Winding down of operations

On October 28, 2008, the spacecraft went into safe mode due to power constraints based on the insufficient amount of sunlight reaching the lander at this time of year. The plan to shut down the four heaters that keep the equipment warm was accelerated. Upon bringing the spacecraft back from safe mode, commands were sent to turn off two of the heaters rather than only one as was originally planned for the first step. The heaters involved provide heat to the robotic arm, TEGA instrument and a pyrotechnic unit on the lander that has been unused since landing, so these three instruments were also shut down.

The Lander was designed to last 90 days, and had been running on bonus time since the successful end of its primary mission in August 2008. On November 10, Phoenix Mission Control reported the loss of contact with the Phoenix lander (the last signal was received on November 2). Immediately prior, Phoenix tweeted its final message: "Triumph" in binary. The demise of the craft occurred three weeks earlier than expected, as a result of a dust storm that reduced power generation even further. While the spacecraft's work has ended, the analysis of data from the instruments is in its earliest stages. There is little chance that Phoenix will survive in this unforgiving environment (it will be encased in dry ice during the Martian winter); however the spacecraft's computer has a safe mode that theoretically, will attempt to reestablish communications when/if the lander can recharge its batteries next spring.

More photos: NASA's Phoenix Mars Lander photo gallery

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