• Jane Arnault-Factor
    Jane Arnault-Factor

May Greetings from the Associates President

Did you know that the invention of the Richter scale, the development of the field of planetary science, the creation of lunar geology, the design, construction, and deployment of the Curiosity Rover to Mars, and the discovery of evidence for a real ninth planet all came out of Caltech's Division of Geological and Planetary Sciences? Some of these remarkable milestones, and more, will be celebrated at the division's 90th anniversary celebration on May 11.

The Division of Geological and Planetary Sciences (GPS)

Caltech's Division of Geological and Planetary Sciences is one of the six academic divisions, which include Biology and Biological Engineering, Chemistry and Chemical Engineering, Engineering and Applied Science, the Humanities and Social Sciences, and Physics, Mathematics and Astronomy. This month, let's take a closer look at GPS.

The faculty and students working in this division study the earth and other planets in order to understand their origin, composition, and development. John Grotzinger, the current chair of this division and lead project scientist on the Mars Science Laboratory mission, described this division's three main areas of research: exploring earthquake seismology, climate modeling, and investigating planetary evolution.

Drawing on its close relationships with Jet Propulsion Laboratory (JPL), which is managed by Caltech for NASA, and the U.S. Geological Survey, this division for almost a century has been one of the world's leading institutions in earthquake science and engineering, building on basic discoveries about the earth and how it moves and translating those discoveries into practical applications. Caltech is developing early-warning systems, crowd-sourcing earthquake detection, and imaging earthquakes with unprecedented resolution. Since the early days of spaceflight, Caltech and JPL together have been among the first explorers of the solar system and today, Caltech faculty still serve as the scientific leaders of NASA missions. The division's combined excellence in planetary science, geology, and environmental science gives them an ideal set of resources for studying soil, rock, ice, and atmosphere on other planets and moons, as well as on the earth. 


The Division of Geological and Planetary Sciences began as the department of geology at Caltech in 1926. At the same time, the Seismological Laboratory began cooperative operations with the new geology division and was managed jointly by Caltech and the Carnegie Institution of Washington.

The entry into geochemistry around 1950 marked an important transition to a more quantitative approach to earth science. In the 1960s, the division came to include planetary science, taking advantage of the new U.S. space program's unmanned exploration and the proximity of the JPL. At that time, the division adopted its current name.

The Seeley G. Mudd Building of Geophysics and Planetary Science (South Mudd) was built in 1974, and this marked the move of the Seismological Laboratory onto campus. In the 1970s and 1980s, scientists in the division developed and refined isotopic age-dating techniques that are applicable to many meteoric, terrestrial, and lunar materials. During the 1990s, the division expanded in new directions, building strong programs in geobiology and in environmental science, including atmospheric science and oceanographic activities that were previously not represented at Caltech. Today, the division is building a strong program in climate science.

GPS NUMBERS (as of 2016)

  • Professorial faculty: 42
  • Emeritus faculty: 11
  • Undergraduate students: 19
  • Graduate students: 104
  • Postdocs: 49
  • 3 National Medal of Science recipients 
  • 15 National Academy of Sciences members
  • 2 National Academy of Engineering members


  • The Community Seismic Network, developed by GPS faculty, facilitates the block-by-block collection of ground-motion intensity data before, during, and after earthquakes to help with effective emergency response.
  • A GPS mineral museum, also known as the gem room, can be found in the Charles Arms Laboratory of the Geological Sciences, with a beautiful array of rocks and minerals on display.
  • Each year, the GPS division publishes a photo calendar, and proceeds go toward a student-run geology field trip.

(These are just a few chronological examples of the thousands of distinguished faculty and alumni who have worked and studied in GPS.)

  • Geophysicist Charles Richter (PhD '28) developed the Richter scale for measuring earthquakes in the 1930s.
  • Clair Patterson studied the buildup of lead in the environment and in the human body, and his work in this area, which continued into the 1980s, contributed to the removal of lead from gasoline, food containers, and paint.
  • Geology professor emeritus Lee Silver (PhD '55) instructed the Apollo 13, 15, 16, and 17 astronauts on how to perform field geology; he is credited with creating lunar field geology as a new discipline and with significantly improving the Apollo missions' scientific returns.
  • The late geology professor Robert Sharp (BS '34, MS '35) is credited with helping to tie earth science research to the study of other planets, particularly Mars. Research done throughout his career illuminated the nature and origin of planetary surfaces, including basin and range structures, glaciers, sand dunes, and landslides and mud flows. Mars's Mount Sharp, the base of which served as the landing site for the Mars Curiosity rover in 2012, is named after him.
  • John Grotzinger, the Fletcher Jones Professor of Geology, served as the chief project scientist for the Curiosity mission, the Mars Science Laboratory (MSL), which in 2012 achieved an unprecedented landing on the Red Planet. See the short, hair raising video "Seven Minutes of Terror."
  • In 2003, planetary science professor Mike Brown discovered the largest object in the Kuiper Belt—a dwarf planet called Eris—which subsequently led to Pluto's demotion from planet to dwarf planet. More recently, he and his colleague Konstantin Batygin have found evidence for a real ninth planet.
  • The division has also established a nation-leading program in geobiology, the study of the interface between the biosphere and the earth. This new field explores how the earth's history has shaped life and how life has shaped the earth's history. In September, Caltech geobiologists Dianne Newman and Victoria Orphan earned national recognition when both were awarded MacArthur Fellowships. Read about their work in the recently published Caltech Magazine.

Upcoming Associates Events Featuring GPS Faculty

On Tuesday, May 16, 2017, our upcoming luncheon "Virtually Exploring Mars" features Bethany L. Ehlmann, assistant professor of planetary science and Jet Propulsion Laboratory research scientist. Ehlmann will offer insights into the geologic history and the potential habitability of our neighboring planet. She will also talk about her work on robotic explorations led by Caltech and JPL and how the number of potential landing sites shrunk from 50 to the current three for the upcoming Mars 2020 mission. View the invite and RSVP here.

From August 20-24, 2017, Associates will travel with Professors Paul Asimow and Mike Brown on the sold-out President's Circle Great American Eclipse Trip to Oregon. Travelers will chase America's first total solar eclipse of the century and delve into the unique geology of the Columbia River Gorge and Mount Hood.

—Jane Arnault-Factor, PhD, Caltech Associates Board President