A deep-diving robot exploring thedepths of the world'sdeepest water-filled sinkhole has found an amazing diversity ofmicrobial life,even down where sunlight can't reach.
The discovery re-affirms life'sresilience and ability tothrive in extremeenvironments on Earth, and possibly on other planets as well,scientistssay.
The robot, namedDEPTHX, dove about 900 feet (275 m) deep toward the bottom ofthe Zacat?nsinkhole in northeastern Mexico. Over almost 50 dives, thecraft retrievedsamples of water and microbes lining the limestone sinkhole.
Among these samples, researchers wereable to identify morethan 100 types of microbes, including three new phyla of bacteria neverbefore discovered.
The scientists also used datagathered by the robot's 54onboard sonars to create high-resolution three-dimensional maps of theunderground hole, which had never before been explored to such depths.
Sinkholes are depressionsinthe ground that are thought to be formed by the chemicaldissolution ofcarbonate rocks, leaving behind a void that can fill up with water orair.
The Zacat?n sinkhole is about 344feet (105 m) across, andis filled with water that stays about 86 degrees Fahrenheit (30 degreesCelsius)throughout the year. The water contains sulfuric compounds that serveas a foodsource for some of the life within.
"It's a vertical column that goesstraight down intothe Earth," said researcher John Spear of the Colorado School of Mines."We didn?t know how deep before we went down."
Digging up microbes
To collect samples, DEPTHX isequipped with a sipper thatsucks up water and stores it in sealed plastic bags. The craft also hasarobotic arm that reached out and dug into the walls of the sinkhole tocollectsolid samples.
The researchers retrieved thesesamples when DEPTHX cameback to the surface, and brought them back to the lab to do DNAanalysis tofigure out what kind of life was there.
Spear and his colleagues foundmicrobes living both in thewater and in thick mats coating the sinkhole's walls. After a certaindepth,sunlight can no longer penetrate, so instead of getting energy fromlight, theorganisms glean fuel from hydrogen sulfide and other energy-richcompounds.
"Instead of photosynthesis, they'redoingchemosynthesis, pulling carbon off of limestone," Spear said. "In thesubsurface field we call it life in the slow lane ? they have to takeadvantageof whatever's there."
In fact, lifeis teeming in the slow lane, the scientists found.
The researchers were stunned at thewealth of life theydiscovered, including so many species of microbes that they representbetween75 and 80 percent of the known microbial life on Earth, not to mentiona fewunknown types.
"It tells us that we still don't knowthe extent ofdiversity of life, which is an important thing in and of itself," Speartold Astrobiology Magazine. "When you can findthree new phyla ofbacteria without really trying that hard, how much out there are wemissing?"
And if life can survive in thisextreme environment, itoffers hope that some form of life may exist on other planets or moonsthathave similar conditions.
Exploring other worlds
While exploring unknown spots onEarth is incrediblyexciting, the researchers designed DEPTHX with even loftierdestinations inmind. They hope to eventually use a similar robot to explore otherworlds,particularly Jupiter's moon Europa.
That moon is an appealing target forastrobiologists becauseit is thought to host underground oceans of liquid water beneath afrozen icecrust. Since water is thought to be necessary for life, those oceanscould begood spots to look for microbial extraterrestrial life.
"This is a first-generation attemptat something thatcould be used to go underneath the ice on Europa," Spear said.
If a robot were sent to Europa, itwould have toautonomously navigate through space, land on the moon?s surface, digthroughthe ice sheet, explore the ocean underneath for microscopic life, andthentransmit its findings back to Earth.
That's a tall order for currentrobotic technology, but the scientistssee it as a realistic goal.
Spear and his colleagues detailedtheir findings in theMarch 2010 issue of the journal Astrobiology. NASA funds the DEPTHX projectthrough its ASTEP (Astrobiology Science and Technology for ExploringPlanets)program.
