Mystery on the plains: Who built Woodhenge?

The 54 rough-cut logs impaled in a meadow look like some art student's unfinished abstract sculpture. But archaeological astronomers are using these poles at the edge of a popular recreational lake to mark solar and astral movements. And if their studies are borne out, this stand of carefully arranged timber could prove that Indians operated a early solar research center in what is now Clay County, Mo., while Europeans were still in the Dark Ages.

The scene here is deceptively pastoral. In fact, the strange setting lies just beyond metropolitan Kansas City's northern fringes, only a five-minute drive from hamburger outlets and chlorinated condominium pools. Overhead, jets swoop into and out of busy nearby Kansas City International Airport.

On weekends, the parking lot nearest Woodhenge fills with bass fishermen, not scientists. In all probability, most of them are blissfully unaware of the potential significance of what stands just a few steps away.

Excavation 23-CL-276 - popularly called ''Woodhenge'' - was discovered purely by accident in 1978, when Clay County purchased tracts along the Little Platte River on which the US Army Corps of Engineers was to construct the lake. Since the land would become lake bottom when the river was dammed downstream, by law, archaeological salvage studies had to be conducted first.

A team of specialists was brought in. They walked behind a bulldozer as it scraped six-inch-deep swatches of randomly selected flatland.

According to Milton Perry, curator of historical sites for the county, the team wasn't looking for Woodhenge; in fact, the archaeologists had no idea it was there, since there were no surface indications.

Then they uncovered some of the postholes - circles of off-colored soil made by the original, decomposed logs. They began excavating, assuming it was part of a prehistoric-house site. But the increasingly visible outline of the 35 -square-foot structure indicated it was something else.

Unlike a home, it had large openings at all four corners, contained no storage areas, and had evidently never been covered by a roof. The absence of broken pottery or fire pits indicated a lack of habitation, but the broken bowl of a ceremonial pipe was found.

The structure seemed to have been used for special purposes; stargazing was one guess. Primitive man was intrigued by the heavens, and left traces of observatories in both the Old World and the New. Most all of those were round or arc-shaped; Woodhenge was square.

Whatever it had been, Woodhenge was probably connected with Cahokia, the sacred city of an Indian civilization that flourished at the time Woodhenge was constructed: AD 800-1200.

Among the ruins at Cahokia, near East St. Louis, Ill., is what may have been a circular observatory.

The culture mysteriously vanished long before settlers arrived in mid-America , but Cahokian sites have been discovered in a region bounded by Wisconsin, Alabama, Louisiana and Oklahoma. Sites near Woodhenge include a large mound (possibly a temple) five miles up the Little Platte and the ruins of a town discovered 12 miles downstream from Woodhenge.

At Woodhenge itself, archaeologists found a flat stone the size of a human hand that is engraved with straight lines arranged in angles and geometric shapes. This, Mr. Perry speculates, could be a sort of astronomical ''work manual.''

Woodhenge's positioning offered more convincing hints of prehistoric astronomy. Its north and south walls were at right angles to the North Star - the due-north point that ancients traditionally used to map the skies.

But some things about Woodhenge will never be known, Perry says:

''We're not sure who built it, precisely when it was constructed, or when it ceased to be used. The poles may have been carved, painted, or draped with banners.''

Since the site was soon to be flooded, county officials had a replica built a quarter-mile away on higher ground. Compensations were made to duplicate the original Woodhenge's relationships to the sun and horizon. Based on the size of the now-submerged postholes, the replica was made with 14-foot logs.

It wasn't long before intriguing phenomena came to light.

Temporary poles were in position at the replica last Dec. 22 - or winter solstice, the shortest day of 1982. At dawn, observers stood with their backs to the odd triangle in the center of the maze and saw the sun rise through the opening at the southeast corner. That dusk, the sun fell through the opening at the southwest corner.

On June 22 - summer solstice, the longest day of the year - the sun came up through the northeast corner and descended through the northwest.

That was enough for Milton Perry to order a wooden sign directing visitors to the ''Woodhenge Sun Calendar'' - one similar to plaques pointing the way to the marina and boat launch at the now-ready Smithville Lake.

Upkeep at Woodhenge is minimal, Perry says. The meadow needs occasional mowing, but there has been little litter or vandalism so far.

Perry plans to put cement footings around the logs to preserve Woodhenge's precise dimensions in the event posterity beckons.

But just as archaeo-astronomers can't reach a verdict about Britain's enigmatic Stonehenge ruin, American scholars have reached no consensus about its humble Missouri namesake. Most only agree that Cahokian-period Indians were capable of making sophisticated solar observations.

Later tribes pursued astronomy in a big way. Northern Plains Indians made ''medicine space wheels'' - rock arrangements shaped like spoked wheels used to track the seasons by light and shadow. Many of these have been preserved. And at Chaco Canyon, N.M., the Pueblos built the Great Kiva, a chamber where solstice light enters through carefully placed holes. In such cases, ancient astronomical lore was passed down through time.

A Pueblo can say, ''Yes, this is an observatory.''

But Woodhenge doesn't figure into the legends of the Missouri and Kansas tribes and has no other special significance to them, as far as is known. Its builders vanished before the arrival of Pottawatomie, Kansa, and other Indians occupying this land when white settlers came.

William McHugh, of GAI Consulting in Monroeville, Pa., led the salvage team that unearthed Woodhenge. But while he was the first to hypothesize its use as an observatory, he says flatly that conclusive proof is missing.

Adds John Carlson, director of the University of Maryland Center for Archaeo-Astronomy: ''While it is plausible that Woodhenge was an observatory, that contention is speculative. Then again, I think the 'observatory' at Cahokia is pretty speculative, too.''

The Clay County findings, he says, could merely be ''suggestive asymmetry'' - coincidences fine-tuned by wishful thinkers.

''People play all kinds of statistical and number games,'' Dr. Carlson says. ''There are no simple answers, and you can broaden that to include all things in archaeology.''

Patricia O'Brien-Gorzio, an archaeologist at Kansas State University, thinks that data already available may lessen such skepticism.

''Anthony Aveni at Colgate University put together a computer-generated report showing where in the sky solstices, equinoxes, and celestial bodies were fixed in earlier times,'' Dr. O'Brien-Gorzio says.

''His printout omitted Mars and Venus, because those planets have very irregular patterns and require very complex calculations - but they are important. Mars, the 'Morning Star,' and Venus, the 'Evening Star,' played major roles in Plains Indians' lives. I'm thinking that maybe some posts at Woodhenge marked those planets.''

She has written to Dr. Aveni to find out where in the sky Mars and Venus appeared, in conjunction, between AD 1000 and 1500.

Dr. O'Brien-Gorzio thinks that if the positions of the planets match up with site markers, there could be no question that Woodhenge was an observatory.

If that turns out to be the case, Woodhenge also will be the only square prehistoric observatory archaeologists have found.

One specialist already convinced of Woodhenge's authenticity is James Mavor of Associated Scientists at Woods Hole, Mass., a Cape Cod think tank. Dr. Mavor spent a week at Woodhenge observing the 1982 winter solstice.

''I came away convinced it is a valid astronomical site,'' he says. ''The problem is that the general archaeological community isn't familiar enough with Woodhenge: They have to see it to believe it.''

Mavor said measurements taken during the 1983 spring equinox reveal a telltale ''viewing alley'' in the site that Indians used to make incredibly precise calculations.

Two solstices and two equinoxes form the high points of one complete solar year. Mavor holds that measurements to be made there Sept. 22 - the autumnal equinox, the benchmark completing the first year of research at Woodhenge - will furnish additional proof.

Even so, some basic questions will remain: How many coincidences form a proof? And what will prove this was a solar observatory - beyond a shadow of a doubt?