Frequently Asked Questions The Mission's E/PO team is very grateful for your fantastic questions, comments and reminders that you are out there and eager for more Martian Arctic information! For our Extended Operations Mission, please refer to Phoenix's home page for breaking news as well as the JPL and NASA websites. Thank you for your overwhelmingly positive support of NASA's Phoenix Mars Mission! here to ask the team.

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Science
Why aren’t the images in true color?
To create a color image, multiple images have to be taken with different filters and layered on top of each other. The image processing team has not yet done all of the necessary calibrations to achieve a true color images: The picture of the LIDAR and background landscape from the Sol 2 press released images is the closest approximation we have so far. One reason for this is just time: Our science team has been very busy! Another is that we don’t always request all the color information, because the data we receive is limited by bandwidth, storage and energy requirements. An image might have a “tint” to it because the red and blue information was received and the green information was interpreted to make an approximate color image. Lighting conditions can also affect the result: One layer of the image might have been taken in the morning under direct sunlight, while another layer was taken in the evening under more diffuse lighting conditions.
Is it really possible to plant asparagus on Mars?
The first real soil test on Mars of the type that gardeners or farmers often use to evaluate their soil has shown that the soil is a little alkaline, instead of acidic. One of the scientists on the Phoenix team pointed out that asparagus likes soil that is the same pH (the same level of alkalinity) as this sample of soil in the Martian arctic. (In contrast to other plants, such as strawberries, which grow better in soil that is slightly acidic instead of alkaline.) From preliminary analysis, the soil sample also appears to include some soluble minerals that plants could use. However, the temperature at the site is far below freezing, so no asparagus could grow there, and there may be nutrients needed by asparagus that have not yet been assessed in the Martian soil.
Why do prisms appear in some of the SSI images?
The SSI takes color images by placing a red filter in front of the CCD and taking an image, then a green, then a blue. The three are combined on the ground to make a color image. This has the side effect that the Sun moves between images. This is usually not a problem, but when the camera shadow or lander shadow are in view, they will be in different positions for the three colors. The most interesting shadow is the wiry camera mast--that gives a red, green and blue imprint on the ground.  Consumer digital cameras don't have this problem, because they have filters permanently built onto the CCD. They use some pixels for red, others for green, and other for blue. SSI doesn't do this because we need to use all of the pixels for individual colors sometimes, and also we need to use the camera to look at other colors, including ones the eye cannot see.
What is the best way to stay updated with the Phoenix Mars Mission?
Our website is updated daily and the images taken by the SSI camera stream directly from Mars to our site, so keep checking back for news and images! You can also check out NASA’s Phoenix website, www.nasa.gov/phoenix. Stay tuned for briefings on www.nasa.gov/multimedia/nasatv, and check JPL’s website for news and podcasts at www.jpl.nasa.gov. You can receive Twitter updates to your cellphone at http://twitter.com/MarsPhoenix. Also check out Facebook, iTunes U and YouTube for more neat stuff!
Does Phoenix have a microphone to “hear” the sounds of Mars?
Phoenix, like the 1999 Polar Lander, originally had a microphone to hear the sounds of the descent to Mars. It was part of the MARDI system which was turned off to due the small risk that it could trip a critical landing system. So far, no spacecraft has successfully captured the sounds of Mars. However, the European Space Agency’s orbiter Mars Express captured the sounds of Phoenix’s descent. You can check it out at: http://www.esa.int/SPECIALS/Operations/SEMAWQ1YUFF_1.html. If the mission timeline permits, it is a possibility that the microphone will be activated , so stay tuned!
How long will the mission last?
The Phoenix Mission was designed and funded to accomplish its science goals during the primary mission which will last 90 Sols or about 92 Earth days. Like Earth, Mars has seasons and Phoenix is solar powered to take advantage of the abundant summer sunshine in the Martian Arctic. However, summer will soon turn into the harsh Martian winter and mission management anticipates that the loss of sunlight, extreme arctic cold and accumulation of carbon dioxide frost will prevent operations by December or Jan 2009. There is little chance that Phoenix will survive in this unforgiving landscape, and no plans at this time to try to communicate with it next spring.
What is the schedule of upcoming activities for the lander?
The first phase of the mission process was called the Characterization Phase, where we made sure the spacecraft and instruments were in working order and checked out our landing site. We are now in the Science Phase of the mission, and have a sol by sol planning process. It is designed to be “discovery responsive.” Decisions are made daily about the upcoming sol’s activities, and the science we choose to do often depends on the data Phoenix has relayed to Earth only hours before.
What is the mini-DVD attached to deck of the lander?
The Visions of Mars DVD was developed by the Planetary Society in Pasadena, California. It is made of silica glass for durability and contains the names of approximately 250,000 people from more than 70 nations, as well as selections of literature, art and music. For more information, visit the Planetary Society’s webpage at www.planetary.org/programs/projects/messages/vom.html
Why didn’t we land directly on the northern polar ice cap?
We chose the arctic plains of Mars rather than the ice cap itself for two main reasons. First, it would be very difficult to safely land a spacecraft on solid ice. Second, scientists are interested in studying the interaction of water ice with the Martian dirt, which is responsible for the cracking, polygonal patterns in the surface at our landing site. This is the best place to look for this dirty ice-icy dirt matrix in the arctic highlands.
What test allowed you to understand and prove that you found frozen water ice? Which instrument and what experiment gave you the data?
A combination of coordinated science observations such as SSI spectral characteristics (infrared and visible spectra), RA data of the hardness of the soil/ice, along with MET measurements of the air temperatures and wind speeds allowed the team to explore the three leading hypotheses for the white stuff: Could it be a salt layer? Is it a type of rock? Is it water ice? Given the observations, it was determined that sublimation occurred. Salt or rock can?t vanish, but ice can and does sublimate in the environment conditions present. Remember also that we have previous data from the Mars Odyssey orbiter and the Mars Surveyor orbiter that provides strong evidence for water ice in this region. The TEGA and MECA teams are looking forward to their next observations of the samples.
If the white stuff that disappeared is sublimating ice, why is there still a lot of white stuff there?
Picture a big block of ice that has been buried for a long time. It would melt very slowly if suddenly uncovered in an extremely cold environment. But once it was uncovered, if you could chip little bits of ice off of it, like when the RA began disturbing the areas, the tiny chips land on a "warmer" soil and interact with the atmosphere and sublimate much faster than the big block. So, the chips sublimated quickly and disappeared from view, and the block remains very, very cold for us to observe if and when it changes over time.
How can we tell the disappearing ice chunks are water and not CO2?
The local temperatures are too warm for CO2 to have remained frozen even one day. Sol 21 images showed these chunks took more than a day to sublime.
Why were the first images in black and white?
The early images received from Phoenix are compressed so that we can get them quickly, and they are in black and white so that they can be viewed as soon as they are received. Color images have to be processed (created with multiple layers).
How did you get the HiRISE photo of the lander descending with its parachute?
Phoenix is very grateful to the Mars Reconnaissance Orbiter (MRO) team for that otherworldly picture. It was very, very good math. MRO was moving about 3.4 km/sec (7,344 mph). Phoenix, at the time of parachute deployment, was moving between 700-130 mph. The timing was very precise, and the HiRISE camera swept a wide field of view in preparation to get that shot. To view more HiRISE images and learn more about the MRO mission, visit http://hirise.lpl.arizona.edu.
What advantages does the Thermal and Evolved Gas Analyzer (TEGA) have over the Viking mission's Gas Chromatograph in detecting organics?
The Phoenix mission has two advantages over the Viking mission with respect to organics. The first is that Phoenix is slowly heating the sample to 1000 C, whereas Viking heated very quickly to 500 C. There are many organics thought to be possibly stable on Mars that vaporize in the 700 C to 800 C range. These types of organics are often call kerogens. The other is the location where Phoenix is landing. The Viking mission showed that water can neutralize the effect of the strong oxidant that is hypothesized to be responsible for destroying organics. It is thought that the ice in the polar regions might also protect the sample. In terms of the ultimate sensitivity, the instruments are comparable. It is the nature of the sample the generates the gas that goes to the mass spectrometer that provides the advantage to Phoenix.
Spacecraft
Why is the Phoenix spacecraft a lander instead of a rover?
Despite the success of Mars Pathfinder and the Mars Exploration Rovers, the Phoenix mission will use a lander because it is simply a different type of mission. The rovers were designed to study rocks at different locations, looking for evidence that the liquid water once flowed on the surface of Mars. Unlike the rovers, which were hunting for evidence of water at points along the Martian surface, the Phoenix lander knows exactly where to go to find water. To reach it, however, the spacecraft must dig down below the surface. The Phoenix lander is going to an area of Mars where water is believed to exist in the form of ice just below the surface. This water ice is probably spread fairly uniformly throughout the northern plains so the lander should be able to uncover ice wherever it lands.
How fast will the Phoenix spacecraft travel towards Mars?
The Phoenix spacecraft is traveling at approximately 74,000 mph (120,000 km/h). Another number seen in the media is 14,000 mph (22,500 km/h). The 14,000 mph is the speed Phoenix will be traveling with respect to Mars. As Phoenix approaches Mars next May, Mars will be traveling at about 60,000 mph (96,600 km/h) in its orbit. The resulting difference between the speed of Phoenix and the speed of Mars will be around 14,000 mph (22,500 km/h).
How will the Phoenix spacecraft communicate with engineers on the Earth?
Like all of NASA’s interplanetary missions, Phoenix will rely on the agency’s Deep Space Network to track and communicate with the spacecraft. The network has groups of antennas at three locations: at Goldstone in California’s Mojave Desert; near Madrid, Spain; and near Canberra, Australia. These locations are about one-third of the way around the world from each other so that, whatever time of day it is on Earth, at least one of them will have the spacecraft in view. Each complex is equipped with one antenna 70 meters (230 feet) in diameter, at least two antennas 34 meters (112 feet) in diameter, and smaller antennas. All three complexes communicate directly with the control hub at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. Phoenix will communicate directly with Earth using the X-band portion of the radio spectrum (8 to 12 gigahertz) throughout the cruise phase of the mission and for its initial communication after separating from the third stage of the launch vehicle. The cruise stage carries two copies of its communications equipment, providing redundancy in case of a problem with one of them. The mission will use ultra high frequency (UHF) links (300 megahertz to 1,000 megahertz), relayed through Mars orbiters during the entry, descent and landing phase and while operating on the surface of Mars. A UHF antenna on the back shell will transmit for about six minutes between the time the cruise stage is jettisoned and the time the back shell is jettisoned. From then on, a UHF antenna on the lander deck will handle outgoing and incoming communications. The UHF system on Phoenix is compatible with relay capabilities of NASA’s Mars Odyssey and Mars Reconnaissance Orbiter, and with the European Space Agency’s Mars Express. Phoenix communication relays via orbiters will take advantage of the development of an international standard, called the Proximity-1 protocol, for the data transfer. This protocol was developed by the Consultative Committee for Space Data Systems in an international partnership for standardizing techniques used for handling space data. The Phoenix spacecraft’s UHF signal might also be receivable directly via the Green Bank Telescope in West Virginia. Data transmission is most difficult during the critical sequence of entry, descent and landing activities, but communication from the spacecraft is required during this period in order to diagnose any potential problems that may occur. An antenna on the back shell will transmit during entry and descent. Another, on the lander deck, will transmit and receive during the final moments of descent and throughout the surface operations phase of the mission.
What is the actual full size of the Phoenix lander/spacecraft?
The Phoenix lander is about 18 feet (5.5 meters) long with the solar panels deployed. The science deck by itself is about 5 feet (1.5 meters) in diameter. From the ground to the top of the MET mast, the lander measures about 7 feet (2.2 meters) tall.
Do engineers use metric or english system of units to command the Phoenix spacecraft on its trip to Mars?
NASA uses the metric system to design the Trajectory Correction Maneuver (TCM). They specify the desired maneuver in terms of a change in velocity (delta-V) which is in meters/second. The Lockheed Martin spacecraft team is responsible for implementing the maneuver given the performance characteristics of the Phoenix spacecraft. Lockheed Martin also works in the metric system and ensures that all measures and reference frames are consistent. There will always be some error between the ideal maneuver design and the actual implementation of a TCM. Phoenix's first TCM was on August 10th and the resulting error in total delta-V was less than 1 centimeter/sec for the desired magnitude of approximately 18.5 meters/second. That represents less than 0.054% magnitude error. Five more TCMs are planned to further refine the spacecraft's trajectory.
What is the total weight of the Phoenix Spacecraft?
The total weight of the Phoenix lander is 772 pounds (350 kg).
What is the fuel type and operation mechanism of the in-flight thrusters and course correctors?
The Phoenix spacecraft uses a mono-propellant hydrazine system. The hydrazine passes through a catalyst chamber and decomposes exothermically into hydrogen, nitrogen and ammonia. The propellant is fed to the thrusters by pressure applied above the diaphragms in the tanks.
How big is Phoenix's parachute?
The parachute on Phoenix measures approximately 39 ft (12 meters) in diameter. In comparison, the Viking landers' parachutes measured approximately 52.5 ft (16 meters) in diameter.
Landing
What time did Phoenix land on Mars? What time was the first signal be received from Phoenix?
Phoenix landed at approximately 4:36pm Pacific Daylight Time (7:36pm Eastern Daylight Time). We received the first signal from the lander approximately 17 minutes later at 4:53pm PDT (7:53pm EDT).
Where did Phoenix land in the Martian arctic?
Phoenix's landing site is approximately 68 degree N latitude, 234 degrees E longitude. This same location on the Earth is in the Northwest Territories of northern Canada, very close to the Arctic Ocean.
Will Phoenix's descent thrusters alter the composition of its landing site?
Altering the chemistry of our landing site due to our thruster exhaust is unavoidable. The Phoenix Lander uses hydrazine, a hypergolic propellant that turns into ammonia during combustion. So essentially, we are spraying the surface with ammonia and a small amount of hydrazine that was not combusted. The way we get around that is by 1) knowing that we are going to be producing ammonia and 2) by designing the wet chemistry cells to carefully quantify the amount of ammonia in the regolith. We then use this information to interpret our other results.
Mars
What is the white, vertical object in one of the photos?
Most likely, this is the backshell of the spacecraft. They fell about 300 meters south of Phoenix's landing site. HiRISE imaging shows the backshell projecting up above the surrounding terrain, explaining why it is visible in images from the Phoenix Lander SSI camera. The parachute is flat on the surface and situated in a small depression, making it unseen by the SSI.
Education and Outreach
What do the clocks on the Phoenix and NASA websites represent?
The clock on our website represents the current time on Mars (similar to the clock on your computer telling you the current time on Earth). NASA’s clock is a mission elapse time and represents the number of hours Phoenix has been on Mars. Sol 0 is the day Phoenix landed: Every day the Sol clock will go up by one. For more information on the Phoenix Clock, click on the text “Current Time on Mars.” This link will bring you to a page with more details about calculating Mars time.
Other
How many miles will Phoenix have travelled by the time it gets to Mars?
When Phoenix reaches Mars on May 25, 2008, the spacecraft will have traveled about 423 million miles.