If you think 1982 looks dicey, consider the rough patch the planet hit 63 million years ago. It is not only consoling, it is germane to goings-on in a Little Rock courtroom, where Arkansas' attorney general is trying to whittle a scientific theory from thin air.

He and the state legislature say "creationism" (the doctrine that the Earth and its life were created a few thousand years ago) is a science, so presenting it as well as evolution theory in public schools does not violate the constitutional separation of church and state. But the Arkansas legislature and others similarly inclined should be less concerned with their constitutional rights and more concerned with their responsibilities toward the idea of science. They should ponder a photograph in the current Scientific American.

It shows two centimeters of brown clay between slices of gray Italian limestone. It also may show why at the end of the Mesozoic Age 75 percent of the previously existing plant and animal species, including dinosaurs, suddenly disappeared, leaving no land animal weighing more than 55 pounds.

The photograph may be evidence for "catastrophism," the scientific doctrine that Earth's history has been emphatically affected by natural catastrophes. The clay may be the residue of one such.

In 1979, scientists announced the discovery of 30 times the normal concentration of the element iridium in a geological formation that once was a seabed and now is in Italy's Apennine mountains. Other concentrations have been found in Denmark, Spain and New Zealand. Dale Russell, a paleontologist, explains that iridium is rarely found in rocks of the Earth's crust, but is abundant in meteorites, and Earth is pelted by a steady rain of it from micrometeorites. Seventy percent of them land in oceans, where iridium accumulates in basins.

One hypothesis is that at the time of that mass extinction of many plants and animals, 500 billion tons of extra-terrestrial material abruptly came to Earth. One idea is that a supernova--a gigantic explosion involving a burst of gamma rays--blew a blizzard of micrometeoric dust off the moon, some of which settled over Earth. A more promising hypothesis is that an asteroid 10 kilometers in diameter struck Earth, perhaps striking an ocean and raising tidal waves eight kilometers high.

The consequence may have been what scientists call, with enchanting understatement, "stresses within the biosphere." They may have included an Earth-blanketing cloud of dust-size particles in the stratosphere that impeded photosynthesis, and hence impeded almost everything else, too.

Research is proceeding, from Spain to the bottom of a seabed now known as North Dakota. If research survives the stressful impact of David Stockman (there are only about 5,000 known fragments of dinosaur skeletons because they are expensive to collect), we may learn more. Meanwhile, consider Russell's thought that the dinosaurs' catastrophe was just what the doctor (perhaps The Doctor?) ordered for mankind:

". . . certain small carnivorous dinosaurs had achieved the ratio of brain weight to body weight that is characteristic of early mammals. If those presumably more intelligent reptiles had survived, their descendants might conceivably have continued to suppress the rise of the mammals, thereby preempting our own position as the brainiest animals on the planet."

Imagine: Earth dominated by clever reptiles that ate our potential ancestors and spared Earth the spectacle of state legislatures endorsing bogus "sciences."

Some creationists embrace catastrophism, at least to the extent that they think it is useful in making plausible such Biblical events as the worldwide flood that fetched Noah up on a mountaintop. But blinkered secularists can be as selective as religious fundamentalists about scientific evidence they consider inconvenient: witness the irrational attempts by "rationalists" to deny that science suggests that the Shroud of Turin was Jesus' burial cloth.

Neither Christianity nor agnosticism depends on any particular conclusion about the archeological artifact, and religion does not stand or fall by any geological finding. If an asteroid cleared away reptilian rivals from the evolutionary path that led to mankind, those who are so inclined can ascribe the event to a benevolent Intelligence. If there is God's will in the fall of a sparrow, there must be also in an asteroid crashing so usefully across space.

As has been said (by an eminent scientist): if all the banging and sloshing of the universe produced, through sheer randomness, mankind, that was an improbability comparable to a typhoon blowing through a junkyard and producing a computer. Call it Providential, call it a miracle--just don't call it that in a public school.