Hans Baumhaver, age 11, of Dedham, Massuchusetts, for his question:
What is helium?
Our home planet is made from 92 natural chemical elements and one of the rarest is helium. But it is one of the most plentiful elements out in the universe. In fact, the steps of its discovery are almost all linked with outer space. It was named helium, for the Greek sun god Helios, because it first was identified among the gases on the sun. Later, small quantities were found on earth. Meantime astronomers learned that 24% of the average star is helium. And just recently, surprising amounts of helium were found in those fascinating moon rocks.
The smallest and lightest of all atoms is hydrogen, with one proton in its nucleus and one orbiting electron. Helium is the second smallest atom, with two protons and two electrons. Those two orbiting electrons give the element helium its basic character. Two is the number of electrons required to complete the inner shell around any atomic nucleus. When an atom's electron shell is filled, it has no incentive to combine with other atoms. Helium atoms remain aloof and alone. On the Periodic Table, helium is charted in a family with five other aloof gases neon and argon, krypton, xenon and radon.
They were named the rare gases but maybe that should be changed. They are very rare on the earth where helium is as scarce as gold. But they are not rare out in space. Helium is the second most abundant element in the universe. And space geologists were astonished to find that our so called rare gases are not so rare in the mineral samples brought back from the moon. On earth, helium is given off during the formation of petroleum. Most of the world's supplies are trapped under thick, rocky layers above oil deposits in Texas.
The United States uses about 700 million cubic feet of helium each year but only a fourth of this is used in private industry. The government uses most of its share in the space program for regulating rocket pressures around pumping systems and fuel tanks. Helium is the safest lifting gas for blimps and balloons. Spacecraft, balloons almost everything about light, gaseous helium seems to point up and away. But nobody expected to find it waiting there on the moon. Atoms of helium were identified in several samples of the lunar rocks, especially around the surfaces of small dusty fragments.
Right now, space scientists are trying to figure out why these and atoms of other rare gases are there and they have suggested several theories.
Analysis of the lunar minerals promises to reveal a great deal about the moon's past history. There is plenty of evidence of bombardment by cosmic rays and solar par¬ticles, plus a hint that the lunar landscape suffered some dramatic catastrophe about 3.65 billion years ago. Some experts suspect that the atoms of helium and other rare gases may have reached the moon from the sun. Perhaps they pierce the lunar minerals during outbursts of solar activity and perhaps they did not arrive from the sun at all.