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WASHINGTON — Early this month, James W. Head III treated a class of Brown University freshmen to an encounter with a piece of the “Genesis Rock,” a 4.2-billion-year-old chunk of the moon that he had a role in scavenging just over 37 years ago.

Such extraterrestrial artifacts have become so matter-of-fact a part of the scientific culture that it is easy to lose sight of the extraordinary national endeavor that went into collecting them.

Head, a geologist who was deeply involved in developing the Apollo program’s approach to scientific exploration, will help to celebrate the endeavor this week at a commemoration of the 50th anniversary of the National Aeronautics and Space Administration.

NASA’s crown jewel is Apollo — the program that kept President John F. Kennedy’s pledge to put a man on the moon before the end of the 1960s — but Head emphasized in an interview last week that it was only a part of what has become a permanent enterprise of space exploration. Only last week, for example, Head was at Johns Hopkins University’s Applied Physics Center, in Baltimore, to join others in the space community in observing the first images to be transmitted by the Messenger craft from the heretofore unseen side of Mercury.

In talks he will give at the Langley Space Center in Virginia today, Head will stress how NASA’s exploration of the moon and the solar system beyond has rewritten and expanded our understanding of the origins of the earth beneath our feet.

Head explained that the forces of wind, water and tectonic friction keep the planet’s crust in a state of continuous erosion that has effectively wiped out most of the geological record. One of the wonders of space exploration has been the discovery of large parts of the earth’s missing history.

For example, he said an earlier generation’s theories about the moon’s creation have all become quaint under the illumination of hard science — evidence from space that the moon was flung from the earth during a collision with another object as big as the planet Mars.

Head said the other point he will emphasize in his talks is how the mission of exploration drove the NASA team to surprising types of achievement. “Engineers and scientists accomplished things together that neither group would have even accomplished independently,” he said.

A favorite example: the “moon buggy.” After the first moon landing, in 1969, scientists — especially geologists — pushed for the means to explore far beyond the vicinity of the landing site.

Hence the moon buggy — a marvel of engineering ingenuity that was folded up, secured to the side of the landing craft, unfolded on the moon and deployed to carry astronauts on far-flung lunar adventures.

To make the most of this extraordinary tool, Head was among the scientists who helped to select promising landing sites and to train astronauts — including James Irwin and David Scott of the Apollo 15 mission, in 1971 — to seek out the right mineral treasures.

One such quarry, Head instructed them, would be large rock crystals that could only be created from the action of a transit from relatively deep under the moon’s crust to its surface.

After the Apollo 15 astronauts found exactly such a crystal and brought it home to Houston, Head was among the analysts who promptly examined it and found it to be 4.5 billion years old — and almost certainly earthly in its origins. Thus the “Genesis Rock” offered evidence of the creation of the moon in that planetary crash between the earth and a large, unknown object billions of years ago.

As a fitting bit of preparation for this week’s NASA celebrations, Head treated some of his Brown upperclassmen last Friday to an encounter — via videoconference — with his old friend and onetime protégé in the art of moon rock hunting, astronaut-explorer Dave Scott.

jmulligan@belo-dc.com