McMurdo Dry Valleys of Antarctica: The Driest Place on Earth
Antarctica is covered with ice, but not all of it. The McMurdo
Dry Valleys is almost entirely snow free. Located among mountains by
McMurdo Sound, on the part of Antarctica closest to New Zealand, the
valleys receive the equivalent of only 10 cm of water, on average, each
year in the form of snow. Completely devoid of terrestrial vegetation,
the region is considered one of the most extreme deserts and the driest
place on the planet. At 4,800 square kilometers, the valleys constitute
around 0.03% of the continent, and form the largest ice-free region in
Antarctica.
The Dry Valleys are so different from the rest of
the continent because of its location. The Valleys are nestled between
the mile-high Transantarctic Mountains which block seaward flowing ice
from the East Antarctic ice sheet from reaching the Ross Sea. Several
tongue-like glaciers creep through the gaps, but any ice that breaks off
of the glaciers quickly goes from solid to vapor in the arid
atmosphere. The unique conditions in the Dry Valleys are also caused, in
part, by katabatic winds; these occur when cold, dense air is pulled
downhill by the force of gravity. The winds can reach speeds of 320
kilometers per hour, heating as they descend, and evaporating all water,
ice and snow.
Initially,
the Dry Valleys were thought to be lifeless. Not surprisingly, explorer
Robert Scott, who discovered the Valleys in 1903, looked over one of
them and called it “a valley of death.” But Scott was wrong.
Researchers
have discovered that the Dry Valleys are home to a variety of
extremophiles (organisms that live in extreme environments). Among them
are lichen and mosses, communities of microbes (including
cyanobacteria), and nematodes (microscopic worms). These organisms have
undergone profound changes that allow them to survive in one of the most
punishing environments on the planet.
Bacteria have been found
living in the Dry Valleys, sheltered from the dry air in the relatively
moist interior of rocks. Anaerobic bacteria whose metabolism is based on
iron and sulfur live in sub-freezing temperatures under the Taylor
Glacier, staining red the ice emerging at Blood Falls
Scientists
consider the Dry Valleys perhaps the closest of any terrestrial
environment to the planet Mars, and thus an important source of insights
into possible extraterrestrial life.
The
wind and the gritty groundcover mix, together sculpt some of the rocks
into smooth, oddly shaped formations called ventifacts