Ronald Greeley, a prominent planetary geologist and senior NASA adviser, died suddenly Oct. 27 at his home in Tempe, Ariz., his employer, Arizona State University, said in a press release. He was 72.

At the time of his death Greeley was chairman of the NASA Advisory Council’s planetary science subcommittee.

Greeley had taught at Arizona State since 1977. Prior to that, he worked at NASA Ames Research Center in Mountain View, Calif., which he joined in 1967. He contributed to many lunar and martian geology projects and was described by colleagues at Arizona State University as a passionate Mars explorer.

Greeley, at the time of his passing, was a co-investigator for the camera system on the European Space Agency’s Mars Express orbiter. His first Mars project was analyzing data gathered by Mariner 9 — a NASA orbiter that arrived at the red planet in 1971, thereby becoming the first artificial martian satellite.

Greeley contributed to NASA’s Galileo mission to Jupiter. Galileo observed the gas giant for eight years before plunging into its atmosphere in 2003. Greeley also was part of the data analysis program for Voyager 2, studying data gathered by the NASA probe about the moons of Uranus and Neptune.

Greeley was preceded in death by his daughter, Vanessa. He is survived by his wife, Cindy; his son, Randall; and three grandchildren.