New high-powered space cameras apparently have confirmed a controversial theory that thousands of house-sized comets are punching holes in the Earth’s upper atmosphere every day.
The comets, made of loose, fluffy snow, pose no danger to human beings but may be the source of most of the water in the oceans. They also may carry organic chemicals that led to the development of life on Earth billions of years ago.
The new evidence was presented in Baltimore on Wednesday by Louis Frank, a University of Iowa physicist who - to much derision from his colleagues - has spent more than a dozen years studying mysterious dark spots captured in NASA satellite images from space.
The holes, eight to 16 miles in diameter, are caused by the breakup of the snowballs which, although they weigh 20 to 40 tons, are small for comets. They crash into the atmosphere 600 to 15,000 miles above the Earth, Frank said.
When Frank first offered his interpretation of the previously undiscovered atmospheric holes to the American Geophysical Union in April 1986, he practically was hooted off stage. Most scientists were skeptical or outright hostile. The controversy raged in geophysical journals without changing many minds.
But Frank’s latest findings were received respectfully at a crowded session of scientists at this week’s union meeting. They were based on images taken by three new cameras he built and put aboard NASA’s Polar spacecraft, which was launched in February 1996.
As evidence, Frank showed photographs of a dark spot over Poland and several small comets diving toward Europe and Asia.
One set of pictures, taken in ultraviolet light, shows the shadows cast by the comets’ water vapor against the Earth’s “dayglow,” the surface of the atmosphere shining in the sunlight.
Other photos, taken in visible light, show the trail left by oxygen and hydrogen molecules stripped from the comets as they streaked through the atmosphere at 5,000 to 8,000 mph.
One of the early skeptics of Frank’s work, Robert Meyer, chief of upper atmospheric physics at the Naval Research Laboratory in Washington, D.C., called the new photos “the smoking gun” that proves the small-comet theory.
“After looking at this data, I’m convinced the phenomena are real,” Meyer told a press briefing in Baltimore. “A lot of the critics are going to go back and take a second look.”
Thomas Donahue, a leading authority on atmospheric science at the University of Michigan in Ann Arbor, also one of Frank’s persistent critics, conceded: “The Polar results definitively demonstrate that there are objects entering the Earth’s upper atmosphere that contain a lot of water.”
By studying his images, Frank estimated that Earth is being bombarded by between 5 and 30 small comets every minute - as many as 16 million a year.
Although they are dumping hundreds of millions of tons of water on Earth every year, scientists said they are nothing to fear. Like fine falling snow, they break up harmlessly in the atmosphere. At worst, one might knock out a communications satellite orbiting at an altitude of 22,000 miles.
“There is no danger for human beings on Earth,” said Robert Hoffman, chief scientist for the Polar project at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Frank said this “cosmic rain” is probably adding about an inch of water to the Earth’s oceans every 10,000 to 20,000 years. Over the 4 billion years of Earth’s history, that would be enough to fill the seas, he said.
If his findings are accepted by the scientific community, the history of the solar system and of Earth’s geology and oceanography will have to be rewritten.
Frank speculated that there is an enormous population of small comets between Earth and Jupiter, left over from the formation of the solar system, and containing enough water to fill the oceans a second time.
Steve Maran, a NASA astronomer and spokesman for the American Astronomical Society, predicted that others will quickly begin work to confirm and expand on Frank’s findings.
“It’s very rare,” Maran said, “for a scientist to make a discovery that is so widely disputed but turns out to be right.”