Renowned planetary scientist/astronomer Tom Gehrels [right, credit UA] passed away in Tucson on Monday at the age of 86. The University of Arizona posted his obituary online and there is another version on Wikipedia.
"Gehrels was among the first members of the fledgling Lunar and Planetary Laboratory when he joined the UA in 1961. During a long and distinguished career Gehrels pioneered new research on asteroids and comets, especially those that pose a collision threat to Earth."
He is credited with discovering several comets and being a member of a small team that discovered more than 4,000 asteroids.
I have numerous volumes on my shelves of the UA Press's Space Science Series of textbooks, that Tom founded and edited.