Antarctica's Dry Valleys

Podcast transcript

Many places on Earth have extreme climates. However, there is one place on Earth that has a climate so extreme that it is the closest thing to it might be on another planet.

Despite having the most inhospitable and unforgiving climate on Earth, researchers have been shocked at what they’ve found there. Their discoveries might help pave the way to finding life outside our world.

Learn more about the Dry Valleys of Antarctica, how they came to be, and what makes them so unique on this episode of Everything Everywhere Daily.

Antarctica is the continent that people most often forget is there. There is no permanent population. There is no real economic activity to speak of beyond the small number of tourists it gets.

If you envision Antarctica as a land covered in ice and snow…..you wouldn’t be wrong. 98% of Antarctica is covered with ice. In fact, the ice cap over Antarctica has an average thickness of two kilometers. That means that most of the surface of Antarctica is pretty uniform and boring.

However, there is that 2% that isn’t covered with ice.

That is where interesting things can occur.

Of the land that isn’t covered with ice, there isn’t much there either. There are hardly any plants in Antarctica. There are two species of flowering plants, and those never get more than a few centimeters off the ground.

The remaining plants are nothing more than lichens that cover rocks.

There are no land mammals that make their home in Antarctica. Some seals might climb onto the rocks, along with some migratory sea birds and penguins, and that’s about it.

These few life forms that tenuously exist in Antarctica are not the subject of this episode. These stunted plants with tenuous growing seasons actually have it easy because there is a place in Antarctica that is much worse.

Approximately due south of New Zealand is the Ross Sea, which is really a bay in the Southern Ocean off of Antarctica.

This is the home to one place in Antarctica that you might be familiar with, McMurdo Station. McMurdo Station is the largest scientific base in Antarctica and is run by the United States National Science Foundation. It can support a population of up to 1,200 people.

Only 3 kilometers away is the much smaller Scott Base, which is operated by New Zealand.

Both of these bases are located on the McMurdo Sound, which is the southernmost part of the Ross Sea and the southernmost body of navigable water in the world.

The focus of this episode is located directly across McMurdo Sound from the two research stations. Here you will find the largest single section of land in Antarctica that is ice-free, the McMurdo Dry Valleys, also known as the Antarctica Dry Valleys.

They were first discovered in 1903 by the explorer Robert Scott. He looked upon them and called them “a valley of death.”

If you look at Google Earth or some other similar mapping software that uses satellite imagery, you will clearly be able to see it because it is a large patch of dark rock surrounded by ice.

There are several of these valleys in close proximity to each other, each of which has mountains with ice on their peaks surrounding them.

So what makes these valleys which are quite literally in the middle of nowhere and don’t seem to have anything in them, so special?

If you can remember back, I previously did an episode on the Atacama Desert in Chile. The Atacama Desert is often called the driest place on Earth. There are parts of the Atacama that have never had recorded rainfall, and on average, the desert gets only 15 millimeters of rain per year.

The Atacama Desert is a veritable rainforest compared to the McMurdo Dry Valleys.

On average, the dry valleys get zero precipitation. However, just saying they get zero precipitation doesn’t really hammer home the point of just how little precipitation it gets.

Researchers who have studied the dry valleys believe that there has been no precipitation here for the last two million years.

If true, it means that there hasn’t been any precipitation in the dry valleys at any point since humans have existed.

So, what makes these valleys so especially dry compared to everywhere else on Earth?

The first thing is obviously the temperature. Antarctica as a whole is quite dry due to the low temperatures. Antarctica is the driest continent, and the continent, on average, only gets 166 millimeters of precipitation per year. It doesn’t seem like it because everything that does fall never melts and just keeps accumulating.

The cold temperatures mean that there is very little moisture in the air which can precipitate out.

The next thing which causes the unique conditions are the Transantarctic Mountains.

The Transantarctic Mountains are probably one of the lesser-known mountain chains in the world, but they extend across the continent and run right down the coast of the Ross Sea and include the dry valleys.

The mountains, as mountain chains do everywhere in the world, block clouds and precipitation. In the case of Antarctica, it also blocks the flow of the ice sheet, which is why this region isn’t covered in ice like everywhere else on the continent.

The other thing that makes it extremely dry is the Katabatic winds. This is what separates the dry valleys from other arid locations both in Antarctica and on other continents.

A Katabatic wind is an airflow that results from cold, dense air flowing down a slope due to gravity.

As these winds drop in elevation, they pick up speed as well as temperature. Wind speeds in the dry valleys can reach speeds of up to 320 kilometers per hour or 200 miles per hour.

Because Antarctica has an enormous ice cap, it also has the highest average elevation of any continent.

When katabatic winds blow down the valley, they increase the temperature, still cold in the big scheme of things, but warmer than it was at the top of the mountain.

The rapidly moving dry air can then sublimate most ice or snow that happens to be in the way, preventing it from melting and turning into a liquid and seeping into the soil. However, it doesn’t remove all the ice, as we’ll see in a bit.

So it is a set of very unique conditions which doesn’t exist anywhere else, which explains the extreme lack of precipitation in the dry valleys.

However, there is a catch.

The dry valleys actually do have some water. During the very short Antarctica summer, temperatures can get above freezing for a very short period of time.

When this happens, small amounts of ice from glaciers can melt and flow into the valleys. In some of the valleys, this water has actually accumulated in the form of lakes.

You might be wondering how it could be possible for water to accumulate in such an environment. It is because, over time, what little water that has seeped into this area has brought with it minerals, and the water has become incredibly salty.

So you wind up with the seeming paradox of the driest place on Earth having a lake in the middle of it, albeit an extremely salty lake. Lake Vida, one of the largest lakes, is perpetually covered in ice. The ice cap on the lake is 21 meters or 69 feet thick, making it the deepest ice in the world that isn’t part of a glacier. The brine beneath the ice has been locked away from any contact with the atmosphere for thousands of years.

The brine is seven times more salty than the ocean, and some of the lakes have a higher salinity than the Dead Sea. One pool known as Don Juan Pond, has a salinity of 33.8% which means it will only freeze when temperatures reach ?50 °C or ?58 °F.

Everything I’ve just described is interesting. Such an extremely dry place with what little water is there locked away under 21 meters of ice in the form of a hypersaline solution is pretty neat.

However, there is more to the story.

This extremely cold and dry environment seems, at first glance, extremely similar to someplace else. Another dry, cold environment that scientists are very interested in…..Mars.

So, the question is, could life exist in this extremely inhospitable place?

I should note that life has been found almost everywhere on Earth. Even in the Atacama Desert, it is possible to dig beneath the surface and find some microbial life.

In 2013, a team of researchers from the United States and Canada drilled into the permafrost in one of the driest parts of the valleys to test a drill that was considered for use on Mars. In their sample, they found……nothing.

It was the first time absolutely no microbial lifeforms were found in the soil anywhere on Earth.

However, just like the search for life on Mars, you can’t just take one sample and call it a day. You have to check again somewhere else.

Well, they did manage to actually find life in several places in the dry valleys, although they were in places you probably wouldn’t expect, and they were life forms unlike any other found on Earth.

One of the places where microbial life was found was inside some of the rocks.

If you remember, way back to my episode on the deep biosphere, there have been microbes found in rocks far beneath the surface of the Earth. These microbes often live inside the tiny pores inside rocks and have incredibly slow metabolisms.

Such microbes are known as cryptoendolithic life forms (crypto meaning hidden, endo meaning inside, and lithic meaning rock).

Anaerobic bacteria that survive on iron and sulfur have been found underneath one of the glaciers that are near the dry valleys. These microbes are able to use energy without the presence of oxygen

Cyanobacterial mats have been discovered, which use the extremely small window each year where glacial water may melt. They only exhibit metabolism for about eight weeks every year.

In the extremely briny waters of the valleys have been found extremophile microorganisms that are adapted to high levels of salt. Some of them have been found dormant in the ice covering the brine lakes and have been revived after thousands of years.

Despite the researchers who found nothing, which is in itself quite a discovery, it turns out that the dry valleys actually have a wide variety of microorganisms that live there. You just have to look for them very closely.

What does all this mean?

For starters, it means that life can find a way to exist in almost any environment.

However, it also means that if microbial life can exist in such an extremely arid and cold environment, sometimes only showing signs of life a few weeks a year or even less, then perhaps such life could exist someplace like Mars.

We know that there appears to be briny water on Mars that flows infrequently. That might be very similar to the conditions which exist in the dry valleys along McMurdo Sound. If life can exist in the dry valleys, then maybe it might exist on Mars.

The Dry Valleys of Antarctica are an extraordinary and otherworldly landscape characterized by extreme dryness, minimal ice and snow cover, and harsh low temperatures.

Their geological origins, lack of ice, distinctive geology, and scientific significance make them a captivating and critical area of study for scientists seeking to understand both our planet’s past and the potential for life beyond Earth.