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Planetary News: Phoenix (2008)Holy Cow, Snow Queen! Phoenix Landed on Ice, Team ThinksBy A.J.S. Rayl
TUCSON -- Holy Cow, Snow Queen! Scientists on the Phoenix team are fairly certain the spacecraft’s thrusters uncovered a patch of ice just four to six inches under the surface that may extend all around the area where the lander set down and will soon be digging. Using its robotic arm camera, Phoenix took a picture of a “blind spot” underneath the lander, near a footpad, on Thursday night, which it then photographed again Saturday night, and the smooth, shiny patch they dubbed Snow Queen has convinced most of the scientists that it is ice that was exposed when soil was blown away as the spacecraft touched down Sunday, May 25. Another image that came into the University of Arizona Phoenix Science Operations Center late Friday night showed an even larger, white patch under another part of the lander, so substantial a patch that it had team members exclaiming “Holy Cow,” hence its name. Phoenix is in a region of permafrost on Mars's northern plains, dubbed Green Valley, which is somewhat similar to permafrost areas in northern Canada. Its mission is to study the history of water in the Martian arctic, search for evidence of a habitable zone, and assess the biological potential of the ice-soil boundary. Today, the lander is to conduct a practice dig-and-dump and test a workaround on its oven that is to analyze the soil and ice samples Phoenix collects. “The mood was electric [late Friday night] as we received the first picture from under the lander,” Peter Smith, Phoenix principal investigator told reporters Saturday during a weekend press conference. “The thrusters have interacted with the surface and thrown soil aside revealing a bright hard layer that seems to parallel the surface. The majority opinion, although it is not unanimous, is that we have uncovered ice about four to six inches under the soil,” he said. “But this is an astounding picture.” When the second take of Snow Queen was returned late last night, it offered “no findings contradicting our hypothesis that we’re looking at a slab of ice there,” Uwe Keller, the robotic arm camera lead scientist, of the Max Planck Institute, said earlier today. “But [at the same time] we did not find the ultimate conclusion to confirm that this is really ice,” he added.
In addition to reimaging Snow Queen yesterday, Phoenix had two other priorities, conducting a robotic arm touch test of surface and taking some atmospheric images, both of which it accomplished, David Spencer, Phoenix’s Surface Mission Manager, said earlier today. The touch test involved Phoenix extending its arm and touching the surface with its scoop in preparation for the test dig-and-dump. “That is when we will actually dig down into the surface and get some material, then dump it off to the side, in preparation for the eventual sample acquisition and transfer to an instrument,” Spencer said. “The touch test went well yesterday," he continued. "We got the data down last night and Everything looks great. The robotic arm made a good first impression on the surface and you [can] see that in the image.” On the weather front, the atmospheric science group had indicated there would be a dust storm passing over the landing site before Friday, so Phoenix took additional measurements of the atmosphere yesterday. “It turned out to be less than a big event in terms of the amount of dust in the atmosphere by the time we measured it,” Spencer said. “We think the dust storm already passed over, because it was actually a fairly clear day.” Since Phoenix is a solar-powered lander, the amount of dust in the atmosphere is important, because it impacts how much power the lander can access through its solar arrays and it also affects the exposure of images. The third priority was the reimaging of Snow Queen, in the “blind spot” under the lander. Looking at the image, Keller said, the smooth tabular structure, which is approximately 50 centimeters (about 19.6 inches) in length, features layering, a kind of little ledge in the center, several dark spots or “pits” that may have been created by small pebbles “relocated” by the thrusters during landing, and what appears to be a fracture that could be due to “some contraction,” possibly from a rock. The fracture is, he said, “still in agreement” with the notion that they are looking at an icy layer. “Unfortunately, we did not get as close as we wanted,” Keller said. The attempt to take a color image, as a result, was unsuccessful. “We do see the albedo is brighter than the surroundings, but is slightly reddish,” he added, noting that they will return to Snow Queen in the not too distant future, and perhaps throughout the mission to get more detailed information about the structure.
“The interesting thing is we’re looking at a spot which has the capability of change over time,” Keller continued. “If it’s ice, then in a few sols, we should be able to see some change in the amount of ice there, so I’m pretty sure that we will go back on a regular basis to this spot and observe whether we can find any changes.” Holy Cow, a large “astounding” patch of what looks to be icy snow as we know it here on Earth, knocked most the team members socks off. This patch is highly reflective, “much, much brighter than local soil, like “the reflection you would get off a lake or any bright surface. We thought we might be able to find more of [Snow Queen] and indeed we did, a large amount,” Smith said Saturday, suggesting that Holy Cow, is “a strong indication that we are looking at an icy table covered by just a few centimeters of soil,” even though the patch is “overexposed.” The final determination about what Snow Queen and Holy Cow are revealing "will come with the analysis of the material,” said Keller. “The patches we’re discussing we can’t reach, but we think this extend in all the directions so we’ll be able to dig and do the analysis.” The really good news for this team is, obviously, that Phoenix has in all probability already found what it’s looking for. “Wherever we will be digging, I think we will hit this ice within a few centimeters of soil,” Smith agreed. The ice, he clarified, is like the ice we know and not the carbon dioxide (CO2) ice known to be present on Mars. “The temperatures are not right for CO2 ice,” he noted. “It’s way too cold and CO2 ice would evaporate quickly.”
Since Phoenix team members “never felt the robotic arm had the ability to dig through solid ice” and the Mars polar region is “even colder ice,” they equipped their bird with a rasp or drill-like file that can “throw ice chips in back of scoop,” which can then be analyzed,” Smith pointed out. Another curiosity in the image of Holy Cow, the Phoenix team has noticed, are small particles sticking to the strut to the left. “There is a lot of debate about what is allowing those particles to stick to titanium,” Smith said. Tonight, Phoenix’s highest priority is the “workaround” test for the Thermal and Evolved Gas Analyzer (TEGA) instrument, which is to bake and sniff the samples to detect their composition. “On Friday, we reported we found an intermittent short circuit in the ion source of the instrument,” Spencer said. “The TEGA team has come up with a workaround that uses a backup filament to the filament in the ion source they believe is bad and that is the workaround they will be implementing today." According to Smith, “the team is smiling again.” By Saturday, William Boynton, the TEGA principal investigator, of the University of Arizona, and his crew had “a path laid out to bring the instrument back to full performance using an alternate filament,” Smith elaborated. “They found a way to go to the second filament even with short in first.” The TEGA team suffered a similar filament failure just before launch and though the instrument was diassembled, repaired, and cleaned before it was buttoned up for launch last year, the team now believes “contamination” is the culprit, Spencer said in today’s telecon press conference.
Phoenix is to also open the TEGA cover, a retractable roof over the instrument’s ovens, this evening. “Each of the TEGA ovens has a door in addition to the cover, so tonight we’re going to be retracting the cover in preparation for downstream deliveries of samples to the instrument,” said Spencer. The “final priority” today, Spencer said, “is the robotic arm dig-and-dump.” Since Phoenix had a successful touch test on yesterday, “we’re going ahead with the dig and dump test [Sunday] and we’re targeting an area that’s just a few tenths of centimeters to the north of where we did the touch test on Saturday,” he added. Once Phoenix completes the dig-and-dump test, the team plans on starting the process for sample acquisition and transfer. “We do plan on TEGA being the first instrument to transfer a sample to,” Spencer confirmed. That will mark the end of the characterization phase, the end of the initial checkout of the spacecraft and the instruments, ascertaining that all of the functionality to move forward with the mission is in good shape,” he said. “If everything goes well with our troubleshooting, once TEGA gets a sample, it will shortly thereafter go ahead and do its analysis of that sample,” Spencer said. “If we’re still in troubleshooting mode, then it can hold onto the sample indefinitely. If we do get a successful test dig-and-dump tonight, then we’ll proceed with the start of sample acquisition and transfer.” The plan now is to break the sample acquisition and transfer into two different segments. “First, we’ll acquire a sample with the robotic arm scoop and actually put the arm in position where it has the scoop just over the TEGA receptacle,” Spencer said. “Then, we’ll stop at that point and have ground [team] in the loop review the images and make sure everything looks good before we commit to doing the transfer to TEGA on the following sol. We are taking things very deliberately. We have to base the timetable on how things go day to day.” At that point, Spencer said, the mission will enter a transition phase. “That will be when we will update payloads for our science instruments on the surface and get ready for our sampling cycle, where we deliver samples to the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) wet chemistry laboratory and the TEGA instrument. And that’s when we really get down to business.”
MECA is a combination of several scientific instruments, actually, including a wet chemistry laboratory, optical and atomic force microscopes, and a thermal and electrical conductivity probe. As for the first target Phoenix will be digging into and sampling, perhaps as early as next week, King of Hearts, just to left of National Park Line, is a strong possibility, Smith said. There were – and are – plans to take more pictures of Holy Cow. In fact, that reimaging was planned for Saturday night, but it didn’t happen,” said Keller. The robotic arm was “fully subscribed” today in doing its touch test dig-and-dump with the scoop. Phoenix also is using the robotic arm camera to document the TEGA cover being retracted, so it has a full agenda. “Imaging of Holy Cow will be treated as a drop-in or opportunistic science, meaning we’ll go back to it when we have a gap in the plan and when the arm and robotic arm camera are not being used,” said Spencer. “We don’t have a placeholder on that yet. We’ll have to see how things unfold in the next several sols.” Right now, added Keller, there is “a preference” for Snow Queen. “It’s close and we can look in detail and there we have the chance to see changes,” he said. “If it’s ice and it sublimes, then we have the chance to look at it and detect changes and this is I think very important so I think this is a clear priority.” The Phoenix team is currently relying on Mars Odyssey for uplinking its commands to its charge, since MRO’s Electra UHF radio is still under investigation, according to Spencer, although the MRO communications system is being used to downlink data to the team. “The flight team and the spacecraft continue to perform extremely well and we’re moving ahead with our plans," summed up Spencer today. "Things are going extremely well." The Phoenix Mission is led by the University of Arizona, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory and spacecraft development is by Lockheed Martin Space Systems, Denver. For more information: Emily Lakdawalla's Planetary Weblog
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