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Phoenix was an uncrewed space probe that landed on the surface of Mars on May 25, 2008, and operated until November 2, 2008. Phoenix was operational on Mars for sols ( days). Its instruments were used to assess the local habitability and to research the history of water on Mars. The mission was part of the Mars Scout Program; its total cost was $420 million, including the cost of launch.
The multi-agency program was led by the Lunar and Planetary Laboratory at the University of Arizona, with project management by NASA's Jet Propulsion Laboratory. Academic and industrial partners included 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) in partnership with Optech Incorporated (Optech) and other aerospace companies. It was the first NASA mission to Mars led by a public university.
Phoenix was NASA's sixth successful landing on Mars, from seven attempts, and the first in Mars' polar region. 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. The program was considered a success because it completed all planned science experiments and observations.
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 around it – perhaps up to of solid carbon dioxide ice could have appeared. Even had it survived some of the winter, the intense cold would have prevented it from lasting all the way through. The mission was chosen to be a fixed lander rather than a rover because:
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 radiation on Mars within 300 years; therefore, it was considered important to determine the 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.
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 built and tested the spacecraft. The Canadian Space Agency provided a meteorological station, including an innovative laser-based atmospheric sensor. "Certificate of Recognition" Passat Ltd. website. Retrieved October 1, 2012. 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), MacDonald, Dettwiler and Associates (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 the University of Bristol 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.
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 and monopropellant hydrazine engines built by Aerojet-Redmond Operations for the cruise phase, twelve 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.
During EDL, the Atmospheric Structure Experiment was conducted. This used accelerometer and gyroscope data recorded during the lander's descent through the atmosphere to create a vertical profile of the temperature, pressure, and density of the atmosphere above the landing site, at that point in time.
On May 29, 2008 (sol ), electrical tests indicated an intermittent short circuit in TEGA, resulting from a glitch in one of the two filaments responsible for ionizing volatiles. NASA worked around the problem by configuring the backup filament as the primary and vice versa.NASA press conference, June 2, 2008.
In early June, first attempts to get soil into TEGA were unsuccessful as it seemed too "cloddy" for the screens. On June 11 the first of the eight ovens was filled with a soil sample after several tries to get the soil sample through the screen of TEGA. On June 17, it was announced that no water was found in this sample; however, since it had been exposed to the atmosphere for several days prior to entering the oven, any initial water ice it might have contained could have been lost via sublimation.
Before launch, testing of the assembled spacecraft uncovered a potential data corruption problem with an interface card that was designed to route MARDI image data as well as data from various other parts of the spacecraft. The potential problem could occur if the interface card were to receive a MARDI picture during a critical phase of the spacecraft's final descent, at which point data from the spacecraft's Inertial Measurement Unit could have been lost; this data was critical to controlling the descent and landing. This was judged to be an unacceptable risk, and it was decided to not use MARDI during the mission. As the flaw was discovered too late for repairs, the camera remained installed on Phoenix but it was not used to take pictures, nor was its built-in microphone used.
MARDI images had been intended to help pinpoint exactly where the lander landed, and possibly help find potential science targets. It was also to be used to learn if the area where the lander lands is typical of the surrounding terrain. MARDI was built by Malin Space Science Systems. It would have used only 3 of power during the imaging process, less than most other space cameras. It had originally been designed and built to perform the same function on the Mars Surveyor 2001 Lander mission; after that mission was canceled, MARDI spent several years in storage until it was deployed on the Phoenix lander.
Using MECA, researchers examined soil particles as small as 16 μm across; additionally, they attempted to determine the chemical composition of water-soluble ions in the soil. They also measured electrical and thermal conductivity of soil particles using a probe on the robotic arm scoop.
The robotic arm scooped up some soil and put it in one of four wet chemistry lab cells, where water was added, and, while stirring, an array of electrochemical sensors measured a dozen dissolved ions such as sodium, magnesium, calcium, and sulfate that leached out from the soil into the water. This provided information on the biological compatibility of the soil, both for possible indigenous microbes and for possible future Earth visitors.
All of the four wet chemistry labs were identical, each containing 26 chemical sensors and a temperature sensor. The polymer Ion Selective Electrodes (ISE) were able to determine the concentration of ions by measuring the change in electric potential across their ion-selective membranes as a function of concentration. Two gas sensing electrodes for oxygen and carbon dioxide worked on the same principle but with gas-permeable membranes. A gold micro-electrode array was used for the cyclic voltammetry and anodic stripping voltammetry. Cyclic voltammetry is a method to study ions by applying a waveform of varying potential and measuring the current–voltage curve. Anodic stripping voltammetry first deposits the metal ions onto the gold electrode with an applied potential. After the potential is reversed, the current is measured while the metals are stripped off the electrode.
Three of the four probes have tiny heating elements and temperature sensors inside them. One probe uses internal heating elements to send out a pulse of heat, recording the time the pulse is sent and monitoring the rate at which the heat is dissipated away from the probe. Adjacent needles sense when the heat pulse arrives. The speed that the heat travels away from the probe as well as the speed that it travels between probes allows scientists to measure thermal conductivity, specific heat (the ability of the regolith to conduct heat relative to its ability to store heat) and thermal diffusivity (the speed at which a thermal disturbance is propagated in the soil).
The probes also measured the Permittivity and electrical conductivity, which can be used to calculate moisture and salinity of the regolith. Needles 1 and 2 work in conjunction to measure salts in the regolith, heat the soil to measure thermal properties (thermal conductivity, specific heat and thermal diffusivity) of the regolith, and measure soil temperature. Needles 3 and 4 measure liquid water in the regolith. Needle 4 is a reference thermometer for needles 1 and 2.
The TECP humidity sensor is a relative humidity sensor, so it must be coupled with a temperature sensor in order to measure absolute humidity. Both the relative humidity sensor and a temperature sensor are attached directly to the circuit board of the TECP and are, therefore, assumed to be at the same temperature.
The surface wind velocity, pressure, and temperature were also monitored over the mission (from the tell-tale, pressure, and temperature sensors) and show the evolution of the atmosphere with time. To measure dust and ice contribution to the atmosphere, a lidar was employed. The lidar collected information about the time-dependent structure of the planetary boundary layer by investigating the vertical distribution of dust, ice, fog, and clouds in the local atmosphere.
There are three temperature sensors () on a vertical mast (shown in its stowed position) at heights of approximately above the lander deck. The sensors were referenced to a measurement of absolute temperature at the base of the mast. A pressure sensor built by Finnish Meteorological Institute is located in the Payload Electronics Box, which sits on the surface of the deck, and houses the acquisition electronics for the MET payload. The Pressure and Temperature sensors commenced operations on Sol 0 (May 26, 2008) and operated continuously, sampling once every 2 seconds.
The Telltale is a joint Canadian/Danish instrument (right) which provides a coarse estimate of wind speed and direction. The speed is based on the amount of deflection from vertical that is observed, while the wind direction is provided by which way this deflection occurs. A mirror, located under the telltale, and a calibration "cross," above (as observed through the mirror) are employed to increase the accuracy of the measurement. Either camera, SSI or RAC, could make this measurement, though the former was typically used. Periodic observations both day and night aid in understanding the Day variability of wind at the Phoenix landing site.
The wind speeds ranged from . The usual average speed was .
The vertical-pointing lidar was capable of detecting multiple types of backscattering (for example Rayleigh scattering and Mie Scattering), with the delay between laser pulse generation and the return of light scattered by atmospheric particles determining the altitude at which scattering occurs. Additional information was obtained from backscattered light at different wavelengths (colors), and the Phoenix system transmitted both 532 nm and 1064 nm. Such wavelength dependence may make it possible to discriminate between ice and dust, and serve as an indicator of the effective particle size.
The Phoenix lidar's laser was a passive laser with the dual wavelengths of 1064 nm and 532 nm. It operated at 100 Hz with a pulse width of 10 ns. The scattered light was received by two detectors (green and IR) and the green signal was collected in both analog and photon counting modes.
The lidar was operated for the first time at noon on Sol 3 (May 29, 2008), recording the first surface extraterrestrial atmospheric profile. This first profile indicated well-mixed dust in the first few kilometers of the atmosphere of Mars, where the planetary boundary layer was observed by a marked decrease in scattering signal. The contour plot (right) shows the amount of dust as a function of time and altitude, with warmer colors (red, orange) indicating more dust, and cooler colors (blue, green), indicating less dust. There is also an instrumentation effect of the laser warming up, causing the appearance of dust increasing with time. A layer at can be observed in the plot, which could be extra dust, or—less likely, given the time of sol this was acquired—a low altitude ice cloud.
The image on the left shows the lidar laser operating on the surface of Mars, as observed by the SSI looking straight up; the laser beam is the nearly-vertical line just right of center. Overhead dust can be seen both moving in the background, as well as passing through the laser beam in the form of bright sparkles. The fact that the beam appears to terminate is the result of the extremely small angle at which the SSI is observing the laser—it sees farther up along the beam's path than there is dust to reflect the light back down to it.
The laser device discovered snow falling from clouds; this was not known to occur before the mission. NASA Phoenix Results Point to Martian Climate Cycles. July 2, 2009 It was also determined that cirrus clouds formed in the area.
A noctilucent cloud was created by the exhaust gas from the Delta II 7925 rocket used to launch Phoenix. The colors in the cloud formed from the prism-like effect of the ice particles present in the exhaust trail.
Phoenix entered the Martian atmosphere at nearly , and within 7 minutes had decreased its speed to 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.
For unknown reasons, the parachute was deployed about 7 seconds later than expected, leading to a landing position some east, near the edge of the predicted 99% landing ellipse. Mars Reconnaissance Orbiter's HiRISE camera photographed Phoenix suspended from its parachute during its descent through the Martian atmosphere. This marked the first time ever one spacecraft 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 effect tracking data from Odyssey and Mars Reconnaissance Orbiter to determine the lander's precise location as .The landing site is here worldwind://goto/world=Mars&lat=68.21883&lon=234.250778&alt=1200000 on the NASA World Wind planetary viewer (free installation required)
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 across and high, with the expected absence of large rocks and hills.
Like the 1970s era Viking program spacecraft, Phoenix used 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.
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 center.
The lander's robotic arm touched soil on Mars for the first time on May 31, 2008 (sol ). It scooped dirt and started sampling the Martian soil for ice after days of testing its systems.
On June 19, 2008 (sol ), NASA announced that dice-sized clumps of bright material in the "Dodo-Goldilocks" trench dug by the robotic arm had over the course of four days, strongly implying that they were composed of water ice which sublimed following exposure. While dry ice also sublimes, under the conditions present it would do so at a rate much faster than observed.
On July 31, 2008 (sol ), NASA announced that Phoenix confirmed the presence of water ice on Mars, as predicted in 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 (sol ). The science team worked 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.
Additionally during 2008 and early 2009 a debate emerged within NASA over the presence of 'blobs' which appeared on photos of the vehicle's landing struts, which have been variously described as being either water droplets or 'clumps of frost'. Due to the lack of consensus within the Phoenix science project, the issue had not been raised in any NASA news conferences.
One scientist thought that the lander's thrusters splashed a pocket of brine from just below the Martian surface onto the landing strut during the vehicle's landing. The salts would then have absorbed water vapor from the air, which would have explained how they appeared to grow in size during the first 44 sols (Martian days) before slowly evaporating as Mars temperature dropped.
A 360-degree panorama assembled from images taken on sols 1 and 3 after landing. The upper portion has been vertically stretched by a factor of 8 to bring out details. Visible near the horizon at full resolution are the backshell and parachute (a bright speck above the right edge of the left solar array, about distant) and the heat shield and its bounce mark (two end-to-end dark streaks above the center of the left solar array, about distant); on the horizon, left of the weather mast, is a crater.
On November 10, Phoenix Mission Control reported the loss of contact with the Phoenix lander; the last signal was received on November 2. The demise of the craft occurred as a result of a dust storm that reduced power generation even further. While the spacecraft's work ended, the analysis of data from the instruments was in its earliest stages.
Scientists attempted to make contact with Phoenix starting January 18, 2010 (sol ), but were unsuccessful. Further attempts in February and April also failed to pick up any signal from the lander. Frost-Covered Phoenix Lander Seen in Winter Images (November 4, 2009) Project manager Barry Goldstein announced on May 24, 2010, that the project was being formally ended. Images from the Mars Reconnaissance Orbiter showed that its solar panels were apparently irretrievably damaged by freezing during the Martian winter.
The elements detected and measured in the samples are chloride, bicarbonate, magnesium, sodium, potassium, calcium, and sulfate. Further data analysis indicated that the soil contains soluble sulfate (SO42-) at a minimum of 1.1% and provided a refined formulation of the soil.
Analysis of the Phoenix WCL also showed that the Ca(ClO4)2 in the soil has not interacted with liquid water of any form, perhaps for as long as 600 million years. If it had, the highly soluble Ca(ClO4)2 in contact with liquid water would have formed only CaSO4. This suggests a severely arid environment, with minimal or no liquid water interaction. The pH and salinity level were viewed as benign from the standpoint of biology.
Laboratory research published in July 2017 demonstrated that when irradiated with a simulated Martian UV flux, perchlorates become bacteriocidal. Two other compounds of the Martian surface, and hydrogen peroxide, act in synergy with irradiated perchlorates to cause a 10.8-fold increase in cell death when compared to cells exposed to UV radiation after 60 seconds of exposure. It was also found that abraded silicates (quartz and basalt) lead to the formation of toxic reactive oxygen species. The results leaves the question of the presence of organic compounds open-ended since heating the samples containing perchlorate would have broken down any organics present. However, in the cold subsurface of Mars, which provides substantial protection against UV radiation, halotolerant organisms might survive enhanced perchlorate concentrations by physiological adaptations similar to those observed in the yeast Debaryomyces hansenii exposed in lab experiments to increasing NaClO4 concentrations.
Perchlorate (ClO4) is a strong Oxidizing agent, so it has the potential of being used for rocket fuel and as a source of oxygen for future missions. Also, when mixed with water, perchlorate can greatly lower freezing point of water, in a manner similar to how salt is applied to roads to melt ice. So, perchlorate may be allowing small amounts of liquid water to form on the surface of Mars today. Gullies, which are common in certain areas of Mars, may have formed from perchlorate melting ice and causing water to erode soil on steep slopes. Perchlorates have also been detected at the landing site of the Curiosity rover, nearer equatorial Mars, and in the martian meteorite EETA79001, suggesting a "global distribution of these salts". Only highly refractory and/or well-protected are likely to be preserved in the frozen subsurface. Therefore, the MOMA instrument planned to fly on the 2022 ExoMars rover will employ a method that is unaffected by the presence of perchlorates to detect and measure sub-surface organics.
The text just below the center of the disk reads:
A previous CD version was supposed to have been sent with the Russian spacecraft Mars 94, intended to land on Mars in Fall 1995.
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