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Probe to explore deepest known sinkhole

March 8, 2007
Courtesy University of Texas at Austin
and World Science staff

Sci­en­tists are re­turn­ing this week to the world’s deep­est known wa­ter-filled sink­hole, to re­sume tests of a NASA-funded ro­bot sub­ma­rine. The de­vice is de­signed to seek out life in one of the most ex­treme re­gions of our plan­et, and pos­si­bly on oth­er worlds.

Ce­no­te Za­ca­ton, near Mex­i­co's north­east­ern coast, is the deep­est known water-filled sink­hole. (Cour­te­sy U. Tex­as at Aus­tin)

A sink­hole is a deep pit lead­ing to a nat­u­ral un­der­ground pas­sage. The sink­hole in ques­tion, called Ce­no­te Za­catón, in Mex­i­co, drops more than 1,000 feet (300 me­ters). 

Its gloomy depths—whose mys­ter­ies have lured at least one div­er to his end—form but one part of a lab­y­rin­thine sys­tem of sink­holes called the Za­catón sys­tem.

Re­search­ers from the Uni­ver­si­ty of Tex­as at Aus­tin have found the sys­tem has un­u­su­al char­ac­ter­is­tics, which they think may have sim­i­lar­i­ties to liq­uid oceans un­der the sur­face of Jupiter’s moon Eu­ro­pa.

Tech­nol­o­gy de­vel­oped to ex­plore deep sink­holes, they hope, could serve in fu­ture probes of Eu­ro­pa—whose icy, cracked-lined sur­face, some sci­en­tists be­lieve, may con­ceal life be­neath.

The DEPTHX probe (Courtesy Stone Aerospace)

The up­com­ing work at Za­catón is the sec­ond round of test­ing and ex­plo­ra­tion there with the probe. If it goes well, re­search­ers say they’ll re­turn in May to fully ex­p­lore the sys­tem, which is on­ly par­tially mapped, and its true depth un­known.

Pre­vi­ously un­dis­cov­ered mi­crobes have been found in deep wa­ter and on rocks in Za­catón. Far be­low where sun­light goes, they may live off nu­tri­ents wel­ling up from hot springs at the bot­tom, say the Uni­ver­si­ty of Tex­as in­ves­ti­ga­tors, doc­tor­al stu­dent Mar­cus Gary and pro­fes­sor Jack Sharp. 

They spec­u­late that more new life forms may await dis­cov­ery in the depths.

The ro­bot ex­plo­ra­tion proj­ect is led by Wil­liam Stone of Stone Aer­o­space, a com­pa­ny based in Del Valle, Tex­as. NASA funded the ro­botic probe, called DEPTHX, with $5 mil­lion. The de­vice is in­tend­ed for map­ping un­derwa­ter ca­ves, meas­ur­ing wa­ter chem­is­try, search­ing for mi­crobes and oth­er life forms, and re­turning sam­ples for anal­y­sis.

Re­search­ers con­ducted in­i­tial tests of the probe’s nav­i­ga­tion ca­pa­bil­i­ties last month, map­ping Za­catón’s sec­ond deep­est sink­hole. That mis­sion showed DEPTHX could find its way through unex­plored un­derwa­ter space, col­lect sam­ples and nav­i­gate back to the sur­face, re­search­ers said.

Europa (Courtesy NASA)

Unique in the world of ro­botic ex­plorers, they added, the probe is au­ton­o­mous: it does­n’t re­ly on hu­man in­struc­tions to de­cide where to go or what to do. 

It draws up three-di­men­sion­al maps of pre­vi­ously un­chart­ed ar­eas as it swims along, then uses the maps to nav­i­gate back to the sur­face.

Ce­no­te Za­ca­ton is near the town of Al­dama close to Mex­i­co’s north­east­ern coast. It gained no­to­ri­ety when two div­ers tried to reach the bot­tom in 1994. 

One, Sheck Ex­ley, drowned. The oth­er, Jim Bow­den, sur­vived, reach­ing a rec­ord depth of 925 feet. The trag­e­dy caused sci­en­tists to re­think ways that Za­catón could be ex­plored safe­ly.

Gary be­gan vis­it­ing Ce­no­te Za­catón in 1993 as a com­mer­cial div­ing guide, in­spired by the unique en­vi­ron­ment to pur­sue a doc­tor­ate in ge­ol­o­gy. He has con­tin­ued in­ves­ti­gat­ing the place to un­derstand how it formed and evolved, work­ing with a net­work of ex­plorers and sci­en­tists to pub­li­cize its sci­en­tif­ic val­ue.

“We brought this place in­to in­ter­na­tion­al rec­og­ni­tion with the cave com­mu­ni­ty and now with the sci­en­tif­ic com­mu­ni­ty,” said Gary. “Peo­ple in cave div­ing knew it was there be­cause Sheck died there. He was a pi­o­neer in cave div­ing and leg­end­ary for 30 years, hold­ing pre­vi­ous world depth rec­ords. That’s all it was known for. Now it has po­ten­tial for a lot of fu­ture re­search.”

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Scientists are returning this week to the world’s deepest known water-filled sinkhole to resume tests of a NASA-funded robot submarine. The device is designed to seek out life in one of the most extreme regions of our planet, and possibly on others. A sinkhole is a deep pit leading to a natural underground passage. The sinkhole in question, called Cenote Zacatón, in Mexico, drops more than 1,000 feet (300 meters). Its gloomy depths—whose mysteries have lured at least one diver to his death—form but one part of a whole labyrinthine system of sinkholes known as the Zacatón system. Researchers from the University of Texas at Austin have found that system has unusual character istics, which they think may have similarities to liquid oceans under the icy surface of Jupiter’s moon Europa. Technology developed to explore the sinkholes, they hope, could serve to build probes of Europa—whose icy, cracked-lined surface, some scientists believe, may conceal life beneath. If this second round of testing and exploration at Zacatón goes well, researchers said they plan to return in May for a full-scale exploration of the system, which is only partially mapped, and its true depth unknown. Previously unknown microbes have been found in deep water and on rocks in Zacatón. Far below where sunlight reaches, they may live off nutrients welling up from hot springs at the bottom, say the University of Texas invest igators, doctoral student Marcus Gary and professor Jack Sharp. They speculate that more new life forms may await discovery in the murky depths. The robot exploration project is led by William Stone of Stone Aerospace, a company based in Del Valle, Texas. NASA funded the robotic probe, called DEPTHX, with $5 million. The device is intended for mapping underwater caves, measuring water chemistry, searching for microbes and other life forms, and returning samples for analysis. Researchers conducted initial tests of the probe’s navigation capabilities in February, mapping Zacatón’s second deepest sinkhole. That mission showed DEPTHX could find its way through unexplored underwater space, collect samples and navigate back to the surface, researchers said. Unique in the world of robotic explorers, they added, the probe is autonomous: it doesn’t rely on human instructions to decide where to go or what to do. It draws up three-dimensional maps of previously uncharted areas as it swims along, then uses those maps to navigate back to the surface. Cenote Zacaton is near the town of Aldama close to Mexico’s northeastern coast. It gained notoriety when two divers tried to reach the bottom in 1994. One, Sheck Exley, drowned. The other, Jim Bowden, survived, reaching a record depth of 925 feet. The tragedy caused scientists to rethink ways that Zacatón could be explored safely. Gary began visiting Cenote Zacatón in 1993 as a commercial diving guide, inspired by the unique environment to pursue a doctorate in geology. He has continued invest igating the place to understand how it formed and evolved, working with a network of explorers and scientists to publicize its scientific value. “We brought this place into inter national recognition with the cave community and now with the scientific community,” said Gary. “People in cave diving knew it was there because Sheck died there. He was a pioneer in cave diving and legendary for 30 years, holding previous world depth records. That’s all it was known for. Now it has potential for a lot of future research.”