Overthe course of the past decade, NASA spacecraft have identified severalsites onMars where conditions capable of supporting life existed in the past.
Oneof the most promising of these sites, and a good candidate for afollow-upmission designed explicitly to look for signs of life, is the shallowsubsurface at the Phoenix landing site in the arctic northernplains of Mars. Indeed, some scientists believe the regionwhere Phoenixlanded may still be habitable today.
Asan early step toward developing the technology for a return mission tothe Martianpolar north, members of NASA?sIceBite team will head out this month to explore UniversityValley, inAntarctica?s Dry Valleys.
AstrobiologyMagazine will be following their activity while they?re in the field,regularlyposting blog entries from IceBite team member Margarita Marinova.Visitors tothe Astrobiology Magazine site will be able to ask questions of theIceBiteteam by clicking the Aska Scientist button that will appear in our IceBite storiesand blogentries.
UniversityValley is of interest because it never gets warm enough there forsubsurfaceice to melt, so the overlying layer of soil remains dry year-round.Thisdry-soil-over-ice arrangement, common on Mars but extremely rare onEarth,resembles the near-surface stratigraphy at the Phoenix landing site.
"Everywherein the northern hemisphere where there?s permafrost, it is wet and itgetsmuddy in the summer," says Chris McKay, a planetary scientist at NASA?sAmes Research Center (ARC) in Moffett Field, California, and theprincipalinvestigator of the IceBite team. "In Antarctica, and only inAntarctica,we find a completely different phenomenon called dry permafrost, inwhich wefind ice-cemented ground on top of which we find dry, bone dry soil,and thewhole system never gets warm enough for that ice to turn to liquid.?
Marsdrills on Earth
Lastyear the IceBite team conducted reconnaissance in University Valley andplaceda series of weather stations there to monitor conditions duringthe Antarctic winter. This year, they will return to testIceBreaker, adrill designed and built by Pasadena, Calif.-based Honeybee Robotics.IceBreaker can burrow up to a meter (3 feet) into the ice and frozen soilanddeliver samples to the surface for scientific analysis.
IceBreakeris a rotary-percussive drill: it both rotates and hammers on itstarget. Bycombining percussion with rotary motion, "you get a highly efficientdrillsystem," says Kris Zacny, director of Honeybee?s Drilling andExcavationProgram.
Rotary-percussivedrills are hardly a rarity; you can buy them off the shelf at HomeDepot. ButIceBite has been optimized for the frigid, near-vacuum conditions onMars. Forexample, while most drills are lubricated to prevent their internalparts fromsticking to each other, because Mars is so cold, IceBite?s internalparts areinstead coated with a Teflon-like anti-stick surface.
TheIceBite team will perform three series of tests. The first will be inMcMurdoStation, a research center in Antarctica with ready access to tools,spareparts, electricity, and the Internet. Hopefully the Internet connectionwillenable a group of fifth-grade students in Pleasanton, California tooperate thedrill via remote control.
?Thenwe?re going to pick it up and put it in the back of a truck, and driveit to aremote site near McMurdo, an unaltered site, and drill in the rock ofMcMurdo,which is probably a better Moon analog than Mars analog,? says McKay.The finaltest will be in the still-more-remote University Valley, accessibleonly byhelicopter.
IceBitehas been tested successfully in Honeybee?s Mars SimulationChamber, wherethe temperature and atmospheric conditions can be tuned to approximatethose onMars. But the upcoming tests in the Antarctic will be the first timethe drillwill be subjected to the uncertainties of field operation.
Onething Zacny and his colleagues will monitor closely during these testswill bethe temperature of the drill bit. A temperature sensor in the bit andcontrolsoftware will hopefully guarantee that during drilling operations thebitdoesn?t get too hot. If it does, the subsurface ice can melt, and if itrefreezes before the bit can be pulled out of the hole, the bit willget stuck.If this happens on Mars, says Zacny, ?you?re done. You?ll never be ableto pullthe drill out of the hole.?
They?llalso be looking at how effective the drill is at delivering usefulsamples tothe surface for scientific analysis. In the lab, ?we prepare our own[rock andice] simulants,? says Zacny, "so we kind of understand what can gowrong.In the field, however, ?you have no idea what?s below the surface"untilyou drill and you see the cuttings of samples being conveyed to thesurface."
Zacnyhopes to learn more about how dry permafrost samples behave duringdrilling,?how it behaves when you finally pull it out to the surface, what?s thebestway to transfer it to the instruments. And what happens to the samplewhen itcomes up to the surface, how much mixing there is between samples thatcome upfrom different depths.?
Inaddition to testing IceBreaker, the IceBite team plans to map the depthof thesubsurface ice, both in University Valley and in other nearby valleys.
"Aquestion has arisen as to what sets [the ice] depth," says MargaritaMarinova, a research scientist at ARC. "So a lot of my time will bespenton actually going through the valleys, digging pits or poking holes andtryingto figure out what depth to the ground ice is."
Anotherteam member, Andrew Jackson, an associate professor in the Departmentof Civiland Environmental Engineering at Texas Tech University in Lubbock,Texas, willstudy perchlorate.
Historically,Jackson?s research focus has been on terrestrial perchlorate, inparticular itsimpact on the Earth?s ozone layer. On Earth perchlorate occursprimarily invery dry places, such as the Atacama Desert in Chile. It is known toexist inthe Antarctic Dry Valleys, but no-one has yet studied its presencethere.
Inaddition to shedding light on Earth's climate, perchlorate, which wasfound inthe soil at the Phoenix landing site, is important to understanding thepossibility of life on Mars. Perchlorate acts as a strong anti-freeze,loweringthe freezing point of water.
"Mostsalts do this, but perchlorate is particularly good at it," Jacksonsaid. "Ifwe can see that in Antarctica, if we can show this perchlorate isactuallydoing that."
Jacksonadded that "that?s really important for Mars," where temperaturesrarely get above the freezing point.
Inaddition, many terrestrial microbes can "breathe" perchlorate inplace of oxygen. If perchlorate-respiringmicrobes are found living in tiny pockets of liquid waterwithinAntarctica?s subsurface ice, perhaps the subsurface ice in the frozennorthernplains of Mars could also be considered a viable habitat forpresent-day life.
TheIceBite project is funded by NASA?s ASTEP (Astrobiology Science andTechnologyfor Exploring Planets) program.
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