off, but this time we are caught. Sheets of stinging 

 hail bury rocks and impale themselves on spiky 

 plants. Lightning bolts tear horizontally in all direc- 

 tions, striking pinnacles and slopes. Twice they hit a 

 hill the botanists and I have just abandoned for 

 lower ground; nearby, a fire springs up. Anton and 

 Tracie Seimon, dodging bolts on another ridge, feel 

 their scalps and fingers tingle, and their metal 

 trekking poles begin to buzz ominously. Suddenly, 

 routine death by lightning around here seems very 

 plausible indeed. 



Quechua woman harvests potatoes in a river valley in the Cordillera 

 Vilcanota. Domesticated in the Andes, potatoes are well adapted for 

 cultivation in high-altitude and cold regions throughout the world. 



The Himalayas, of course, also hold many 

 records for life at high elevations. On Mount 

 Everest, bacteria are found at 27,500 feet; the 

 jumping spider Euophrys omnisuperstes lives among 

 the rocks at 22,000 feet; and a single woolly flower- 

 ing plant of the species Saussurea gnaphalodes was 

 observed at 2 1 ,000 feet. A lichen, Lecatiora poly- 

 tropa, has been recovered on loose stone at 25,000 

 feet on nearby Mount Makalu. But the record 

 holder for a complex ecosystem lies in the Andes. 



In 1983 Halloy had heard reports of verdant 

 plant communities at the 19,844-foot summit of 

 Socompa, a dormant volcano on the border be- 

 tween Argentina and Chile. Climbing up to a 

 height usually devoid of visible life, he discovered 

 thirty-six species of mosses and bryophytes in mats 

 as much as two inches thick. He also found mites, 

 tiny crablike springtails, flies, a finch, and a leaf- 

 eared mouse, all apparently making a living. The 

 secret? The still-active basement of Socompa re- 

 leases a gentle flow of heat, water vapor, and carbon 



dioxide to its roof. Around small fumaroles, soils 

 are heated to more than a hundred degrees, and 

 plants can take advantage of the moisture and car- 

 bon dioxide that are otherwise in short supply. Hal- 

 loy 's find was all the more astonishing because the 

 plants on Socompa are not alpine species, but mi- 

 grants from remote cloud forests. Socompa's lower 

 slopes lie amid thousands of square miles of salt flats 

 and badlands, and are mostly lifeless. 



Halloy is not able to enjoy a triumphal return 

 visit to Socompa's summit, at least on this trip. 



After traveling for days in the desert and 

 making a brutal near-vertical climb 

 through the loose scree, we establish a 

 base camp halfway up the mountain. But 

 the next morning we are driven down by 

 bad weather and exhaustion. For once, it 

 is too cold for even our chief scientist to 

 sleep outside, and at one point the wind 

 nearly blows me off a crag. Still, against 

 Halloy's advice, three of us press on — 

 Sowell, along with our photographer, 

 Carsten Peter, and David Scott, an athlete 

 helping the team — and manage to reach a 

 small moss garden at 19,160 feet. They 

 find warm gases emanating from several 

 small, circular holes — one covered by a 

 six-inch-wide flap of moss that gently 

 flips open every few seconds once 

 enough pressure has built up. 



Other lightly sleeping volcanoes might 

 host communities even higher up their 

 slopes, but only some may provide the 

 right range of temperature, humidity, and 

 gases required for life. One candidate is Ojos del 

 Salado, on the border between Argentina and 

 Chile — at 22,600 feet, the worlds highest active 

 volcano. From the rim of the summit crater, Halloy 

 has glimpsed fumaroles inside, along with what 

 might be patches of green, though no biologist has 

 yet reached that spot. 



High volcanoes are worth exploring because they 

 are "dead ringers for early Mars," according to 

 Nathalie A. Cabrol, a NASA geologist who heads a 

 new project to investigate such places as 19,400-foot 

 Licancabur on the border between Bolivia and 

 Chile. There, a small lake in the summit crater 

 swarms with strange algae and microcrustaceans, 

 possibly fueled by geothermal springs. She believes 

 even higher lakes remain to be discovered. 



After we straggle back from Socompa, I ask Hal- 

 loy if he feels disappointed at retreating. "Not at all," 

 he says. "Humans don't necessarily belong at the top 

 of the mountain. But the mountain will still be there 

 if we decide to come back some day." □ 



NAT u R A l HISTORY September 2006 



