Press Release

Meteoroids help reveal the mesosphere

By SpaceRef Editor
January 24, 2006
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Meteoroids help reveal the mesosphere
meteors.antarctica.jpg

Image: Nikolai Makarov works on a meteor radar antenna at the South Pole. The radar is part of a science project using meteoroid remains to study winds in the upper atmosphere. Credit: James P. Avery / Special to The Antarctic Sun

By Steven Profaizer, Antarctic Sun staff

Bob Dylan wasn’t singing about upper atmospheric dynamics when he wrote the song, but scientists at the South Pole agree that the answer is indeed blowing in the wind.

The group is studying meteoroid remains in the atmosphere, which reveal information about the winds blowing them around 80 to 105 kilometers above the Earth.

“In order to understand the atmosphere as a whole, we have to understand how the layers of the atmosphere are coupled,” said Scott Palo, principal investigator of the project and professor of aerospace engineering at the University of Colorado in Boulder. “We’re trying to get our hands around the fundamental physical processes that are important to this region.”

The group is using a meteor radar at the South Pole to transmit radio waves into the sky and bounce them off trails of electrons left behind by meteoroids traveling through the Earth’s atmosphere. “A meteoroid will be happily flying through the vacuum of space – typically traveling about 10 to 70 kilometers per second,” Palo said. “All of a sudden, it impacts the Earth’s atmosphere, and the atmosphere gets increasingly more dense as it moves down in altitude.”

As this meteoroid streaks toward Earth, it heats very rapidly. When the meteor can no longer take the heat, it is transformed from a solid into a trail of ions and electrons. The radar signals interact with these particles and are reflected back to the receiver.

“We have these trails of electrons left behind, and the wind in the upper atmosphere causes them to drift. It pushes them one direction or another,” Palo said. “We can measure the speed at which those electrons are drifting and infer the wind speed.”

The winds are a basic part of the upper atmosphere and essential to understanding its evolution, yet scientists do not know much about them.

“Very little is known about this region because it hasn’t been well measured, especially in the polar regions,” Palo said.

The group is looking at the upper region of the mesosphere. This area is often referred to as the mesopause, which is the transition area between the mesosphere and the next highest layer, the thermosphere.

Until recently, scientists gave this region very little attention.

“It was referred to as the ëignorosphere’ because there weren’t very many measurements made there,” Palo said. “It’s exciting to be working in an area where no one has made measurements before. It’s all new.”

The project was originally begun to complement NASA’s satellite-based effort to study the upper atmosphere, which is called the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite (TIMED).

The satellite is equipped with an instrument called TIDI, which stands for TIMED Doppler Interferometer, and measures light emission at very specific wavelengths to observe winds in the upper atmosphere.

Palo received the initial grant from the National Science Foundation to provide complementary ground-based data to what NASA was collecting from space. Both the satellite and the South Pole meteor radar went into operation in 2001.

Palo’s instrument at the South Pole provides information that very few science groups are currently equipped to provide.

“There are only a handful of meteor radars around the world – maybe 15 or so,” Palo said. “It’s a very small community. It’s one of those things where I could probably name all the people in the world who have a meteor radar.”

Out of that already small community, Palo said his group is one of only three or four that actually builds its own.

The team operates several other meteor radars they constructed in addition to the one at the South Pole – one in Alaska, one in Russia, and several in Colorado that are used for testing purposes. The other systems are almost identical in both design and purpose to the one at the Pole, and they provide a constant stream of data to the research team via the Internet.

The group travels to Antarctica once a year to perform maintenance and complete upgrades to the system.

“There are always things we are trying to improve,” Palo said. “We always want to make the measurements better. Every year, we take incremental steps so that we have better data quality and a more reliable system. The longer it runs, the more we learn about how to make it better.”

NSF-funded research in this story: Scott Palo, University of Colorado in Boulder.

SpaceRef staff editor.