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Planetary News: Phoenix (2008)Phoenix Scoops Mars and Digs ItBy A.J.S. Rayl
TUCSON -- Phoenix has successfully scooped Mars for the first time. Over the last couple of sols, the Phoenix team made its first test scoop and dig into the Martian surface, wasting no time in moving forward in its mission 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. Phoenix – which is perched in a region of permafrost on Mars's northern plains called Green Valley that is somewhat similar to areas in northern Canada – over the weekend successfully reached out its 7.7-foot robotic arm and dug into the arctic soil, emptying its cache onto a designated dump area on the ground once the robotic arm camera photographed the soil inside the scoop. In those tests, the team found the Martian arctic soil to be crumbly “with some light-toned bits that could be ice or salt,” as Ray Arvidson, of Washington University in St. Louis, co-investigator for the robotic arm, described it this weekend. “There are also some light-toned bits that are in the trench” left after the test, he added. “It’s hard to tell just looking at it what these bits are but they are certainly bright and are something unusual in the soil,” said Peter Smith, Phoenix principal investigator, of the University of Arizona, which is leading the mission for NASA. The robotic arm camera snapped images of the lander's first scoop of Martian soil and the team has produced a color image of the landmark achievement. "The camera has its own red, green and blue lights, and we combine separate images taken with different illumination to create color images," explained the University of Arizona's Pat Woida, senior engineer on the Phoenix team. Today, in addition to taking some more images of the white patches underneath the lander that look like ice and which the team calls Holy Cow, Phoenix was to conduct another dig-and-dump test with its first sample acquisition to be commanded tonight for collection tomorrow.
“It takes two days once you have the sample to get it into the oven,” Smith reminded . Therefore, if all goes as planned, the first sample will be placed in the Thermal and Evolved Gas Analyzer (TEGA) Friday, June 6. The TEGA oven will bake and sniff out the composition of the sample in a process that takes anywhere from 10 to 14 days. The soil is being tested for evidence of water and organics, essentially signs that the area may be or once was habitable. Phoenix does not have the equipment to "read" DNA or find microscopic biological life as we know it. “If you’re trying to make extraordinary claim like -- we found life on Mars -- you’re going to need more than a signature from our oven,” Smith said. However, if an actual Martian bug visible to the naked human eye should pop out of the ice, the lander does have cameras that could easily photograph it. That noted, the team is not expecting any visible Martian bugs on Mars anymore than they would expect a Japanese beetle to crawl out of the Arctic ice on Earth. “We’ll be pulling three samples in a row, just to the right of the divot we took with scoop,” Smith said, confirming the tentative plan announced yesterday. Those three samples will come from targets nearby that have been dubbed Papa Bear, Momma Bear, and Baby Bear, informed Ray Arvidson, of Washington University St. Louis, the co-investigator of the robotic arm. The Bear trio of samples will be “very close together at the surface and very close together to the test dig,” Arvidson said. “We want to get samples into TEGA and then into the MECA optical microscopy lab and the MECA wet chemistry lab that are all from roughly the same area and the same depth so we’ll have a data set that can be inter-compared,” he expounded. “In particular, we’ll want to see if the white chunky bits that are exposed in the initial dig and that we also saw in the scoop are in fact are icy materials or are some salts, like a magnesium sulfate, that we saw at the two Viking sites and that we saw at the [Mars Exploration Rover] Spirit site in Gusev Crater.”
While the plan had been to scoop up the first sample for analysis today, the team decided to take an extra sol to practice its remote operations on the surface of Mars before attempting to collect and deliver a Martian soil sample to the lander’s instruments. Phoenix’s dig and dump is something like what a child does on the beach with a sand pail and shovel, said Smith. “But this is not as easy as it may sound. We’re doing this blind from 170 million miles away, so it’s taking a little more expertise than you might imagine with the child and the pail,” he added. Although the Phoenix team members have been practicing with the robotic arm on Earth for two years, Smith said, taking another day is “prudent,” because of the limited analysis opportunities. The TEGA instrument, for example, can take in and analyze just eight samples, the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA) wet chemistry lab can handle four samples and the optical microscope can examine 10 samples. Other instruments including the atomic force microscope and the stereo surface imager will be used throughout the mission for multiple studies. "We have a real handicap being 170 million miles away," Smith continued. "There’s no joystick here. It's kind of like explaining to someone over the telephone how to tie their shoes. You have to give them all the steps, but you can't see what they’re doing. Doing this slowly and deliberately is really the right thing to do even if it takes an extra sol.” One reason the team decided to spend an extra sol getting more comfortable with scooping and collecting samples of the clumpy soil they’ll be examining is that some of the material stuck in the scoop and some dropped out of the scoop and onto the deck of the Phoenix. Team members had not anticipated either of those events.
Phoenix first tested its scoop on its Sol 7, last Sunday (June 1, 2008), leaving a footprint-like mark on the ground that resembled the telltale big foot allegedly left behind by a Yeti or abominable snowman. “That test was a validation of the ability of the robotic arm to go to a particular place on the surface,” according to Ray Arvidson. The lander next stretched out its arm again and dug into an area just above Yeti, dubbed the Knave of Hearts. “On Sol 7, the downlink showed our first dig and that was a test in which we excavated material just above Yeti and then dumped it to the left in an area we can’t dig,” said Arvidson. The team has set aside an area near the lander that they intend to keep “pristine,” as Arvidson put it. They’re calling it the Humpty Dumpty National Park and it is a no-dig zone for comparative studies and imaging. For the first test dig, Smith said, they began with “an unaltered scene,” then pressed down with it on the back of the robotic arm’s hand, took the scoop and dumped it in another area out of the way. But, the dump actually covered up part of that first touch test, he said. “Yesterday, we had a bit of a mystery because after getting a scoopful we dumped it in the dumpsite, but then the researchers looking for it couldn’t find it,” Smith explained. “It wasn’t until they reviewed before and after images that they found the material that has been emplaced on the surface.”
Since team members were not “really comfortable” with the digging and dumping process – “they haven’t really mastered it” – they wanted to practice for another day, “to dig a little deeper and do some more of the dumping and record it through the robotic arm camera which they neglected to do the first time,” Smith explained. “We really want to feel more comfortable with how material is interacting with scoop and with how the scoop is interacting with the soil and when we deliver our first sample to TEGA we want to be absolutely sure we have what we want and deliver it properly.” The TEGA instrument, meanwhile, looks to be fully restored after suffering an ion filament that was shorting. In order to analyze the sample the TEGA utilizes a mass spectrometer that works by virtue of magnetic fields. Unless you charge sample particles, however, the analysis cannot take place. Basically, the filament puts out a high voltage that induces the charge to ionize particles as they come in. If the filament that ionizes these materials is shorted, you get no charge at all, hence, no analysis. The really good news is the back up filament turns out to be “more sensitive” than the primary,” said Smith. A picture taken of TEGA by one of the analytical instruments received Monday night, however, offered up another “little bit of a surprise,” Smith said and it underscored the need for precise release of samples. The image reveals that one of the two spring-loaded doors on one of TEGA’s tiny ovens opened fully, but the other partially. That was not something they experienced in ground tests.
“This is not what we expected,” said Smith, “however the springs that are trying to open the door are likely to complete their action once we get to the heat of midday on Mars. This is another good reason to take an extra sol.” Whether that TEGA oven door opens fully or not, the instrument team has already tested the delivery process with the partially open doors. “We know that we can get a sample into the oven exactly the way we want to, even with the doors partially open,” Smith assured. “This is not a serious problem of any kind, but we would be surprised if it doesn’t open all the way today,” he added. “We’re taking an extra day to really learn how to operate remotely on the surface of Mars, interact with this soil [of which] we’re just learning its properties,” Smith summed up. “We’ve only touched [the Martian surface] twice, and we’re learning how to collect samples and deliver them to the place we want them to go. We’re very close to that. In another day and we’ll be there.” For more information:
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