Transoceanic dust blows out of Afro-Asian deserts

High over the central Pacific, vast dust clouds blowing from Central Asia are reaching their annual peak concentrations. Geochemists recognize this as a regional sign of spring.

It's part of the global dispersion of desert dust which contributes to deep-sea sediments, probably transports living spores of fungi and other organisms between continents, and may have an as-yet-unknown effect on weather and climate.

In a recent report in Science, Josef R. Parrington, William H. Zoller, and Namik K. Aras of the University of Maryland described the dust seen at the Mauna Loa Observatory in Hawaii from Feb. 1979 through Sept. 1982. They found that waves of it blowing past their instruments in the springtime account for 80 percent of the annual air-borne dirt.

These measurements confirm the findings of other geochemists, especially those of Joseph M. Prospero of the University of Miami, which indicate the global importance of desert dust. Working with a variety of colleagues, Prospero has traced masses of African dust blowing across the Atantic to Central and South America, as well as crossing the Pacific from Asia. Several hundred million metric tons of African dust a year are carried eastward in plumes that can be traced in weather-satellite photos. And as Prospero has noted, the size and density of the particles transported suggest that living spores could be carried along with the dirt.

Thus the world's deserts are one of the biggest air polluters known. Prospero says that ''on a global basis, the major sources of mineral aerosols in the atmosphere are found in the vast belt of arid lands and deserts that extends from the west coast of North Africa through the Middle East and Central Asia, and deep into China.''

The source of airborne dust can be determined from its composition. This reflects the distinctive makeup of its native soil. That is how Prospero and colleagues, and now the Maryland research team, have traced the origin of the Pacific springtime dust clouds. Dust storms are at their peak in China at this time of year, both because of seasonal drought and high winds and because of massive ploughing. The dust clouds dim the air's transmission of light. They may have other atmospheric effects. But, so far, meteorologists have not been able to figure out just what the weather and climatic results might be. Cannibal stars

Astronomers have known about cannibal galaxies - star systems that swallow other star systems and grow. Now Albert D. Grauer of the University of Arkansas and Howard E. Bond of Louisiana State University have evidence of cannibal stars.

Stars that swallow other stars have been predicted theoretically. Such a star would be a member of a binary pair. Then, when the star begins to expand as part of its natural evolution, it would engulf its companion.

According to a report by the National Science Foundation, Grauer and Bond have found such pairs within some planetary nebulae. A planetary nebula is a disk-shape gas cloud. Astronomers had thought that such a cloud was expelled by a single star at the center. The new discovery suggested that a nebula can be expelled when one star engulfs another.

As the swallowed star spirals in toward the center of the star that has ''eaten'' it, the process speeds up the rotation of the outer layers of the larger star. Eventually, this outer material is expelled as a planetary nebula. This would leave a pair of closely orbiting stars surrounded by a cloud of gas, just as the two astronomers have found. Europe's new space project

ESA, the European Space Agency, has decided to seek what its Astronomy Working Group hopes will be a commanding position in infrared astronomy. This is the science of studying cosmic objects by the infrared (heat) radiation they emit or absorb.

Some such studies can be done from mountaintop observatories. But, because the atmosphere absorbs many infrared wavelengths heavily, the viewing is better in space. That is why IRAS (InfraRed Astronomy Satellite) - a joint British, Dutch, United States satellite now in orbit - is opening a new frontier.

The 11-nation ESA wants to follow IRAS - and exceed its achievements - with ISO (Infrared Space Observatory), to be launched early in the next decade. ISO instruments would be 100 times more sensitive than those of the IRAS. Thus it could study objects outside our own galaxy.

About these ads
Sponsored Content by LockerDome

We want to hear, did we miss an angle we should have covered? Should we come back to this topic? Or just give us a rating for this story. We want to hear from you.

Loading...

Loading...

Loading...

Save for later

Save
Cancel

Saved ( of items)

This item has been saved to read later from any device.
Access saved items through your user name at the top of the page.

View Saved Items

OK

Failed to save

You reached the limit of 20 saved items.
Please visit following link to manage you saved items.

View Saved Items

OK

Failed to save

You have already saved this item.

View Saved Items

OK