Philip H. Abelson, whose early research helped lead to the development of the atomic bomb and the nuclear submarine, and who later influenced scientific thinking during 23 years as the opinionated editor of Science magazine, died Aug. 1 of pneumonia at Suburban Hospital. He was 91 and lived in Washington.

Dr. Abelson was a force in science for more than 60 years, beginning in the 1930s, when he was one of the nation's first nuclear physicists. He was the co-discoverer of the chemical element neptunium and during World War II worked on the Manhattan Project to develop the atomic bomb. Later, he was among the first to analyze the bacteria E. coli.

His scientific expertise knew almost no bounds. Trained in chemistry and physics, he also did groundbreaking research in biology, geology, biochemistry and engineering. When he was elected to the National Academy of Sciences in 1959, he could have been admitted in any of seven disciplines. He chose to be recognized as a geologist.

Dr. Abelson published nine books on such varied subjects as microbiology, energy, food, electronics, health care and earth science -- as well as a collection of his wide-ranging, forcefully written essays that touched on nearly every field in the vast, expanding world of science. An article in The Washington Post in 1980 described him as a "nuclear, geo-, bio-physicist, geo-, paleo-, biochemist, microbiologist and a few other scientific compound specialties."

"He was an iconic figure," said John I. Brauman, a Stanford University chemist who has won the Linus Pauling Award and last year was awarded the National Medal of Science. "He played many roles, and he always found a place of leadership and influence as a scientist and on the public stage."

It's hard to say whether Dr. Abelson left his strongest mark on science as a researcher or as an editor and advocate for science. He had the rare ability to do advanced work and make it understandable to ordinary people. He had several well-known public disputes -- particularly about the space program -- and enjoyed putting science at the center of public debate.

"He wasn't without opinions, that's for sure," Brauman said in a telephone interview from his California office. "It wasn't that he enjoyed being controversial, but he enjoyed the intellectual challenges of solving problems."

Dr. Abelson first gained recognition in the 1930s as a graduate student in the celebrated laboratory of Ernest O. Lawrence at the University of California at Berkeley. In 1938, using money his mother had sent him to buy a suit, he bought uranium at a scientific supply store. Within two months, he had built a spectrometer and devised a way to isolate a fissionable form of uranium.

Abelson and future Nobel prize winner Edwin M. McMillan discovered Neptunium at Berkeley in 1940 by bombarding uranium with neutrons. Previously, there were 92 known chemical elements on Earth. Neptunium was No. 93.

Dr. Abelson then came to Washington as a physicist with the Naval Research Laboratory, where he developed a process to separate isotopes of uranium. This research was applied to development of the atomic bomb in the Manhattan Project at the Oak Ridge National Laboratory in Tennessee. For his work, he received the Navy Distinguished Civilian Service Medal in 1945, the first of many honors.

In 1944, barely past his 30th birthday, Dr. Abelson was put in charge of the Naval Research Laboratory in Philadelphia. Among other things, he devised a way to apply nuclear energy to locomotion. By March 1946, he had written a paper detailing how a nuclear reactor could be installed in a submarine, in effect designing the blueprint for the USS Nautilus, which was launched in 1955 as the Navy's first nuclear-powered submarine.

After World War II, Dr. Abelson turned his attention to biology and geology. His 1955 book on E. coli, which was then little known, was the standard study for decades and pointed out the bacteria's importance in the emerging field of genetic engineering.

During the 1950s, Dr. Abelson also discovered that amino acids can survive in fossils, particularly at low temperatures, for hundreds of millions of years, a finding that would influence biochemists and the study of paleontology.

"He brought this extraordinarily astute mind to every problem he encountered," said Brauman, "whether it was with Science magazine, scientific research or social concerns."

In 1962, Dr. Abelson was named editor of Science magazine, a weekly publication of the American Association for the Advancement of Science that is read by virtually every scientist in the country. He accepted the position on the condition that he be allowed to continue his own outside research.

He made the magazine more timely and more responsive to the latest research by cultivating a network of "bird dogs" across the country to tip him off to new developments. To accommodate the latest breaking news in science, he held the section open until the day before it was shipped.

But he might have been best known for his editorials, in which he often attacked commonly accepted scientific notions and did battle with other scientists. During the 1960s, he had a running feud with NASA Administrator James E. Webb because of his implacable opposition to the manned space program, which he called a waste of time and money that did little but satisfy a sense of adventure.

Dr. Abelson opposed government regulation of science but also warned against eggheaded plans for building a genetically enhanced super race.

"Man is the product of billions of years of hard-won evolution," he told a conference in 1966. "We must not risk permitting zealots, however well-intentioned, to gamble with the future."

Philip Hauge Abelson was born in Tacoma, Wash., the son of Norwegian immigrants. He received a bachelor's degree in chemistry in 1933 and a master's degree in physics in 1935 from what is now Washington State University. He received a doctoral degree in nuclear physics from the University of California in 1939.

Fascinated with science as a boy, he became the city surveyor of Tacoma when he was 17, which helped pay his way through college.

Before he moved permanently to Washington in 1972, Dr. Abelson commuted on weekends to Philadelphia, where his family lived. His wife, Neva, was a physician who helped discover a test for the Rh factor in blood. She died in 2000, after 63 years of marriage.

"He always said my mother was smarter than he was," said Dr. Abelson's daughter, Ellen A. Cherniavsky of Silver Spring. Two grandchildren also survive him.

Dr. Abelson developed adult-onset diabetes in his forties, prompting him to change his diet and to take up exercise. He walked or ran several miles every morning, until his health began to fail in March.

In 1987, Dr. Abelson received the National Medal of Science. He belonged to numerous scientific societies and received dozens of prestigious awards, including the Kalinga Prize from the United Nations Educational, Scientific and Cultural Organization and the Distinguished Public Service Award from National Science Foundation. Affiliated with Carnegie Institution since 1939, he was its president from 1971 to 1978. He received seven honorary degrees.

"He was a very revered figure," said Donald E. Koshland Jr., who succeeded Dr. Abelson as editor of Science. "People knew he had total integrity."

When Dr. Abelson became editor of Science in 1962, it had a circulation of 75,000. By the time he retired at the end of 1984, the circulation was 155,000. Dr. Abelson held many advisory roles with science foundations and stayed on as a contributing editor for Science, writing occasional editorials until the late 1990s. A collection of 100 of his editorials was published in 1985 as "Enough of Pessimism."

"I don't mind people getting mad at Phil Abelson," he once said about his strongly worded opinions, "but I don't want them to get mad at Science or science."

Nuclear physicist Philip H. Abelson did pioneering research in biology, geology, biochemistry and engineering. He edited Science magazine for 23 years.