**An Alien World---on Earth**

NASA scientists have discovered a new form of microscopic life in Mono
Lake, California

**July 30, 2003**: Mark Twain didn't think much of California's Mono
Lake.

"It lies in a lifeless, treeless, hideous desert," he wrote in his 1895
travelogue, *Roughing It*. "This solemn, silent, sailless sea\--this
lonely tenant of the loneliest spot on earth\--is little graced with the
picturesque."

Astrobiologist Richard Hoover of NASA's National Science and Technology
Center (NSSTC) in Huntsville, Alabama, has a different view: "It's
beautiful," he says.

Mono Lake looks like an alien world. Strange knobbly spires called
"tufa" jut out of the water a dozen feet in the air. The water itself is
clogged with trillions of floating creatures: brine shrimp. Scoop one
out and look closely; it's a miniature *Alien*. In the middle of the
lake lies an island, covered with ash and spitting hot springs.

Weird.

Mono Lake is actually a volcanic crater about 10 miles wide. Water flows
in from Sierra streams, but there's no way out again except
evaporation---a process which constantly increases the concentration of
salts and minerals. The "venomous waters are nearly pure lye" and twice
as salty as sea water, complained Twain. "There are no fish in Mono
Lake---no frogs, no snakes, no polliwogs---in fact nothing to make life
desirable,"

"In fact," notes Hoover, "many things live there." The shrimp are merely
one example. There's also a species of scuba-diving fly that settles
mostly on the beach but sometimes swims in the water, too, navigating
the lake in tiny submarine air bubbles. The lake also provides a home to
microorganisms such as diatoms, cyanobacteria and filamentious algae.

So much life in such an alien place is bound to attract an
astrobiologist. In March 2000 Hoover, microbiologist Elana Pikuta of the
NSSTC, and colleagues traveled to Mono Lake to discover what else might
be living there.

They were particularly interested in microbes. Many microorganisms are
"extremophiles"---that is, they thrive in places that would kill
ordinary life forms (like people) instantly. \"By studying
microorganisms found in Earth\'s extreme places, like Mono Lake, we
begin to understand how life might exist on Mars or on other worlds,"
Hoover explains.

It was a quick trip---only one day at the lake to collect samples of
water and mud, then back to the lab in Huntsville, Alabama, for
analysis. But that was enough for a discovery. Deep in the lake's salty
alkaline mud where no oxygen could reach, Hoover and Pikuta found a new
species of living bacteria: *Spirochaeta Americana*.

"These extremely thin and graceful bacteria move with an elegant
motion,\" marvels Pikuta. "Their cell walls are very delicate, and it is
difficult to keep them alive for long periods in the laboratory."

The lab is probably too comfortable for anything stubborn enough to live
in Mono Lake. Or so Twain might say.

The genus *Spirochaeta* includes 13 species of bacteria. Not all of them
live in harsh places like Mono Lake. Some thrive in ordinary freshwater
mud---the kind kids love to play in. Most, however, love extreme
environments. *Spirochaeta halophilia*, for instance, can be found in
the high-pressure mud around deep-sea hydrothermal vents. Another
example: *Spirochaeta bajacaliforniensis* thrives without oxygen in the
sulfurous muds of Baja California. All *Spirochaeta* are resistant to
high sulfide concentrations. Hot, salty mud stinking of sulfur seems to
be a good home for these creatures.

Soon Hoover plans to return to Mono Lake to search for more microbes.
It's a timely search because Mono Lake resembles a place on Mars named
Gusev Crater where NASA's Mars rover Spirit will land in 2004. What will
Spirit find there? Mono Lake might be giving us a preview.

There's no water in Gusev Crater today, says Hoover, but there might
have been once. The crater was formed by a meteorite impact more than
3.5 billion years ago. If water was present on Mars at that time, as
some researchers believe, it would have flowed into Gusev Crater through
channels in a huge canyon called Ma\'adim Vallis. Because the crater has
no outlet, it would have become an evaporative lake site like Mono Lake.

It's unlikely---very unlikely\--that microbes like *Spirochaeta
Americana* are living in the dry and barren Gusev Crater now, but their
fossils might be there. A good place to look would be inside tufa
towers, if Gusev Crater has any.

At Mono Lake microfossils are abundant in tufa. These spires are formed
when calcium-rich spring water bubbles up through the lake, which is
rich in bicarbonate. The calcium and bicarbonate combine, precipitating
out as limestone and entombing microbes at the same time.

Tufa towers only grow while underwater, but at Mono Lake they poke above
the surface. That\'s because the lake level has been lowered in recent
years to supply water to Los Angeles, 360 miles to the south. The water
level on Mars has been lowered, too. How no one knows. If Spirit spots
tufa around Gusev Crater it will be a telling discovery\--a clear sign
of ancient water and, perhaps, an environment that once supported life.

After a week at Mono Lake, Mark Twain had had enough of the "ashes,
solitude and heartbreaking silence. The cement excitement is over," he
declared and gladly left.

Maybe if he had known more about Mars, and the hidden forms of life in
Mono Lake, Twain would have felt differently. Richard Hoover and Elena
Pikuta can't wait to get back.