Here Be Dragons

GOING TO EXTREMES
the bottom, that's heterotrophic bacteria, they feed off organic compounds
produced in the upper layers. There's not much oxygen down
there, so they're anaerobic. Instead of breathing oxygen they breathe
sulfur, so to speak. They convert sulfate to sulfide, and that's what's
black."
Taking a few strides off the lake bed and across the highway, we
stand under a rocky cliff, among a pile of rocks that have tumbled
down from Dante's View. Here too, the first impression is of total
sterility, but closer inspection reveals the presence of life. An occasional
rock is encrusted with overlapping blotches of yellow or red or
brown or with a branching tracery of black. "Lichen—they're fungi
with algae inside," says McKay. "They can extract moisture from the
air, when the humidity is seventy percent or more. The algae by themselves
need a humidity of at least ninety percent, but the fungus has
some kind of fancy membrane—like Gore-Tex—which lets water
vapor in but doesn't let liquid water out. It's a matter of pore size."
McKay has come to Badwater to install a high-precision thermometer,
which is intended to send a continuous air-temperature reading
back to his office at Ames. The idea is to monitor long-term processes
such as global warming. Badwater held the world's high-temperature
record, at i34°F, until 1922, when a site in the Libyan desert went two
degrees higher. Possibly McKay hopes to wrest the world record back
for the USA.
While he and two junior colleagues attach the device to a post and
program its microprocessor and transmitter, we go off in search of another
ecological niche that McKay has described to us. We soon find
what we're looking for on the pebbly ground north of the lake bed (see
Color Plate i). A small piece of translucent white quartzite looks as
sterile as its darker neighbors, but once flipped on its back, it reveals a
green underbelly—cyanobacteria again. We bring our prize back for
verification. "Yup, hypolith," says McKay. "The stone acts as a moisture
trap. The light comes right through, allowing photosynthesis.
Quartzite stones are a major habitat for life in dry environments all
over the world. They're in the Negev, the Gobi, the Atacama, the outback
of Australia, even Antarctica. If it gets too dry, they go into a dehydrated
vegetative state, and wait it out."
McKay is a biologist whose major interest is in identifying habitats
for life on other planets, especially Mars. Until such time as his employers
provide him with a ticket to the Red Planet, however, he
spends much of his time investigating "extraterrestrial" habitats on
41