Courtesy of Wayne Zimmerman at JPL, I've just acquired quite a bit of information on this particular Mars Scout proposal -- which is one of the front-runners (judging from the NASA money provided to study it further after the Mars Scout Workshop early this year), and which uses a prototype of the same cryobot that JPL is proposing for later use on Europa. So here's the goods:
(1) The CryoScout lander is, without a doubt, the most bizarre-looking spacecraft design I have ever seen -- although it's simply the original Mars Surveyor 2001 Lander, rebuilt to fly this mission. The reason is that the 2007 Mars Scouts are not allowed to carry any large amount of plutonium -- so the cryobot has to melt its way through the Martian polar ice using electric heaters that require fully 750 watts, which the lander must provide entirely from solar power despite the fact that it will land only 3 to 5 degrees from the Martian north pole. And so the lander -- in addition to its two original horizontal octagonal solar panels -- will, after landing, erect a gigantic vertical solar panel, fully 2 meters long and 10 meters high, based on the design of the 100-foot solar panel tested on a Shuttle flight back in 1984, and very lightweight but dwarfing the size of the Lander itself. Its mast will be tilted to be completely vertical regardless of what slope the lander comes down on, and the panel will gradually slew around its vertical axis every 24 hours to track the midnight Sun's progress around the polar horizon. The mission lasts 75 days -- well more than enough time for the cryobot to melt the desired 100-200 meters deep. It would seem that such a panel would be very vulnerable to winds -- but Zimmerman tells me that Mars' air is so thin that even the strongest gale would exert only 30 Newtons of force on the huge panel. However -- and despite the fact that y'all know how reluctant I am to fly plutonium unless it's absolutely necessary -- any crucial moving part that big and complex obviously represents a serious point of vulnerability in the spacecraft design. (2) Another vulnerability is that a lander at this landing site cannot communicate directly with Earth, and so CryoScout must depend entirely on relay orbiters -- which means that if the 2005 MRO fails, it would have to depend entirely on Mars Express and (if it's still working) Mars Odyssey. It seems to me that this particular Mars Scout design, while promising, is much more likely to be picked as the 2011 Mars Scout mission, which may be allowed to use plutonium, and which will likely be able to utilize the probable 2009 US Mars comsat. (Of course, that communications problem may also work against selection of any 2007 Mars Scout design that lacks direct-to-Earth communications, such as "Artemis".) (3) As for the cryobot itself, it's extremely similar to the generalized design developed by JPL: about 50 kg, 65-70 cm long and 10-11 cm wide, using 4 big wedge-shaped electric heaters arrayed around its nose plus a separately heated hot-water jet in the center of the nose -- and maybe several other hot-water jets on its sides near the front (as we'll see). It uses two different sonar sensors (one longer-range) to detect embedded rocks, and can modulate the melting rate of its different heaters to swerve to the side at up to a 30-degree angle to steer around them (moreover, tests indicate that it can make such a steep turn in a surprisingly short vertical distance -- only 1-3 cm of vertical descent for each degree of tilt). (4) Since it is scheduled to melt only 200 meters into the ice, it doesn't leave a sequence of separate radio relay transceivers embedded in the ice behind it as the Europa cryobot would -- instead, it unreels a thin tether behind it, containing a copper-beryllium power cable and a fiber-optics communications line. (5) Lab tests indicate that adding water jets in pockets on its sides near its nose would greatly aid it in cutting quickly through ice, by washing dust away to the sides more quickly so it doesn't build up beneath the nose. (Such a system, in lab tests, has easily handled ice 20% contaminated with grit particles 3/4 mm wide.) (6) The cryobot's field test last year in an actual Norwegian glacier penetrated fully 23 meters, at a rate of about 15 meters per day. It punched through several layers of dust whose particle sizes were 10-60 microns. Even with the heaters for the nose water jet turned off, it was able to descend half that fast -- although, with the water jet turned off entirely, the nose heaters alone allowed it to creep downward at only half a meter per day. (Of course, the Europa Cryobot has an major additional problem: since Europa's ice may be briny, this design of cryobot would quickly build up a thick deposit of salt in front of its nose which the water jets alone probably cannot cope with -- so a mechanical drilling head may have to be added to it.) (7) Zimmerman is still rather close-mouthed about Mars CryoScout's science payload. But the cryobot will apparently carry some sensors to analyze the meltwater for minerals dissolved in it from the dust and also for trace isotopes of oxygen and hydrogen relevant to Mars' climatological history, and perhaps also to look for organics. It will also carry a microscopic camera with 10-micron resolution to inspect the thickness and density of the dust layers in the ice, which will also carry a UV fluorescent lamp allowing it to look for organic particles (indeed, the latter might allow it to identify DNA fragments from any microbe remnants frozen into the ice). The lander itself, besides surface cameras and weather sensors, will carry ground-penetrating radar to probe the icecap's structure (and maybe give a better estimate of the cryobot's depth at any time); and it may also carry a Canadian instrument to drill one meter into the ice and measure the precise thickness of the most recent dust layers, which can be associated with known dust storms and thus provide calibration of the timing and intensity of the dust storms which produced the lower layers measured by the cryobot. == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
