Antarctica: Window on the Cosmos

A polar research vessel in the Antarctic.
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Antarctica is a frozen, dry desert continent covered with snow in many places. As such, it's one of the least hospitable places on our planet. That actually makes it a perfect place from which to study both the cosmos and the future of Earth's climate. There's a new observatory in place that looks at one type of radio waves from distant star nurseries, giving astronomers a new way to study them.

A Cosmic Mecca for Astronomers

The cold, dry air of Antarctica (which is one of Earth's seven continents) makes it a perfect place to site certain types of telescopes. They need pristine conditions in order to observe and detect light and radio frequency emissions from distant objects in the universe. Over the past few decades, a number of astronomy experiments have been conducted in Antarctica, including infrared observations and balloon-borne missions.

The latest is a place called Dome A, which gives observers a chance to look at something called "terahertz radio frequencies". These are naturally occurring radio emissions coming from cold clouds of interstellar clouds of gas and dust. These are the places where stars form and populate galaxies. Such clouds have existed throughout much of the universe's history, and are what helped our own Milky Way grow its population of stars. Other radio astronomy observatories, such as Atacama Large Millimeter Array (ALMA) in Chile and the VLA in the U.S. southwest also study these regions, but at different frequencies that give different views of the objects. Terahertz frequency observations uncover new knowledge about the same types of star-forming regions.

A Wet Atmosphere Hinders Observations

Terahertz radio frequencies are absorbed by water vapor in Earth's atmosphere. In many regions, very few of these emissions can be observed with radio telescopes in "wetter" climates. However, the air over Antarctica is extremely dry, and those frequencies CAN be detected at Dome A. This observatory is located at the highest point in Antarctic, lying at about 13,000 feet in altitude (4,000 meters). This is about as tall as many of the 14'ers in Colorado (peaks that rise to 14,000 feet or above) and just about the same height as Maunakea in Hawai'i, where a number of the world's best telescopes are located.

To figure out where to locate Dome A, a team of researchers from Harvard Smithsonian Center for Astrophysics and China's Purple Mountain Observatory looked for very dry places on Earth, particularly in Antarctica. For nearly two years, they measured the water vapor in the air over the continent, and the data helped them determine where to place the observatory.

The data indicated that the site of Dome A is frequently arid -- perhaps among the driest "columns" of the atmosphere on the planet. If you could take all the water in a narrow column stretching up from Dome A to the edge of space, it would form a fine film less thick than a human hair. That's not very much water at all. It's actually 10 times less water than in the air over Maunakea, which is a very dry place, indeed.

Implications for Understanding Earth's Climate

Dome A is a very remote place from which to study distant objects in the universe where stars are forming. However, the same conditions that allow astronomers to do that are also giving them more insight into our own planet's greenhouse effect. That's a natural effect of having layers of active gases (so-called "greenhouse gases") that reflect heat coming from Earth's surface back to Earth. It's what keeps the planet warm. Greenhouse gases are also at the heart of climate change studies, and so are important to understanding.

If we didn't have greenhouse gases, our planet would be very cold -- with a surface perhaps even colder than Antarctica. Certainly it wouldn't be as hospitable to life as it is now. Why is the site of Dome A important in climate studies? Because the same water vapor that blocks our view of the cosmos in terahertz frequencies also blocks infrared radiation escaping from Earth's surface toward space. In a region such as Dome A, where there's little water vapor, scientists can study the process of heat escape. Data taken at the site will go into climate models that help scientists understand the processes active in Earth's atmosphere.

Planetary scientists have also used Antarctica as a Mars "analog", basically a stand-in for some of the conditions that future explorers expect to experience on the Red Planet. Its dryness, cold weather, and lack of precipitation in some regions make it a good place to run "practice missions". Mars itself has gone through drastic climate change in the past, from being a wetter, warmer world to a frozen, dry, and dusty desert.

Ice Loss in Antarctica

The icy continent contains other regions where the study of Earth's atmosphere is informing climate models. The West Antarctic Ice Shelf is one of the fastest-warming areas on the planet, along with some regions on the Arctic. In addition to studying the loss of ice in those regions, scientists are taking ice cores on the continent (as well as on Greenland and in the Arctic) to understand the atmosphere as it was when the ice first formed (in the distant past). That information tells them (and the rest of us) just how much our atmosphere has changed over time. Each layer of ice traps atmospheric gases that existed at the time. Ice core studies are one of the main ways we know that our climate has changed, along with the instances of long-term warming that are being experienced around the globe.

Making Dome A Permanent

Over the next few years, astronomers and climate scientists will work to make Dome A into a permanent installation. Its data will significantly help them understand the processes that formed our star and planet, as well as the processes of change that we are experiencing on Earth today. It's a unique spot that looks both up and down for the benefit of scientific understanding.