Students in the Division of Geological and Planetary Sciences study the earth and planets to understand their origin, constitution, and development, and the effect of the resulting physical and chemical characteristics on the history of life, on the environment, and on humanity. Students are encouraged to work with complex and often incomplete data sets, to undertake research in natural settings such as in the field or at sea, and to use the many modern laboratory facilities available within the division. Programs of study and research are pursued in environmental science and engineering, geobiology, geochemistry, geology, geophysics, and planetary science.
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The PhD degree is conferred by Caltech primarily in recognition of breadth of scholarship, depth of research, and the power to investigate problems independently and efficiently, rather than for the completion of a definite course of study through a stated period of residence. The work for the degree must consist of research and preparation of a thesis describing it, and of systematic studies of an advanced character, primarily in science or engineering. In addition, candidates must possess clear self-expression in both oral and written English.
Students' work for the degree will be specifically directed by the division in which they have selected their major subject.
For a PhD degree, a student must
Admission to candidacy occurs after the student has satisfied the first two requirements and has been accepted for thesis research by a GPS faculty member, who then becomes the student's thesis adviser.
The qualifying examination consists of an oral and a written defense of two research propositions, supplemented by a written description of one of them. Students are encouraged to consult with various faculty members concerning their ideas on propositions, but the material submitted must represent the work of the student. There must be a different faculty member associated with each of the two propositions.
The exam is normally taken early in the first term of the second year of residence and is administered by the qualifying examination committee, which has members from the six options of the division. A more detailed outline of the examination appears under "PhD Qualifying Oral Examinations" tabbed below.
Before the end of the second year, the thesis advisory committee will be selected, as outlined on the "Advising" page.
The division encourages students to engage in research early in their graduate careers. A student making normal progress will submit to referred journals papers that have been approved by a faculty member of the division.
The final oral examination for the doctorate by the thesis examining committee will be scheduled no sooner than two weeks following submission of the thesis (approved by the thesis adviser), and it must be scheduled at least two weeks before the degree is to be conferred.
Candidates are expected to publish the major results of their thesis work. The published paper should have a California Institute of Technology address. Published papers may be included in the thesis.
The student's program and progress will be reviewed annually by his or her option and by the thesis advisory committee. In cases where, in the opinion of the faculty in the option, the student is clearly not showing adequate progress, they may—based on their overall assessment of the student's performance—recommend to the GPS division chair that the student be denied permission to continue in the PhD program.
The core committee, consisting of five members of the teaching faculty, is charged with the responsibility for administering and overseeing the oral examinations on behalf of the division. The core committee members for the 2024-2025 academic year are Mike Brown (executive chair), Claire Bucholz, Geoff Blake, Nadia Lapusta, Alex Sessions, and Francois Tissot.
Qualifying oral examinations take place in September each academic year. In preparation for this, the core committee will meet with students in the spring to discuss the requirements. Students will be notified of this date.
General Comments
The current formal requirements for the PhD qualifying oral examination are described in the Caltech Catalog. The following comments are intended to be useful to GPS students in preparing for this examination.
The examination's purpose is to provide a structured and, as far as possible, objective basis for determining whether students can successfully complete the requirements for a PhD in GPS in a reasonable period of time. The examination is meant to represent a formidable challenge to students, providing both a test of their general knowledge in their field and of their ability to formulate problems.
The members of the core committee are listed above.
The Examining Committee
The core committee will determine and assign members to the student's examining committee. The examining committee will be composed of four faculty members and will include the two professors involved in supervising the two propositions, and two members of the core committee. The chair of the examining committee will be a core committee member. In special circumstances, where the knowledge or expertise of another professional scientist is crucial to the proper evaluation of the student, the chair of the examining committee, with the approval of the core committee, may invite that person to participate in the examination. Only members of the Caltech professorial faculty may be voting members of the examining committee. One week prior to a student's exam date, the student will submit one-page written abstracts of two propositions on diverse topics and one Written Paper (see below).
The Examination
Julie Lee will organize and coordinate the exam schedule for the division with the core committee.
One week prior to a student's exam date, the student will submit one-page written abstracts of two propositions on diverse topics (see Section D) and a completed Academic Summary. In the exam, the student will be questioned on the two propositions. The student will first present a 10- to 15-minute carefully prepared summary describing the objectives, results, conclusions, and implications that follow from the research to be carried out on each proposition. The presentation of a summary will be followed by detailed and general questions concerning the proposition itself and fundamental questions underlying the proposition or central to the student's option. The format of the exam is flexible. The student will be allowed to answer questions without frequent interruptions. The subject of the questioning may change rapidly when it is apparent that the student knows the material. Inevitably the questions will probe to the limit of the student's knowledge and abilities. The chair will control the discussion to ensure that all major aspects of each proposition and of the student's major interests are aired.
Immediately after the examination, the student will be informed by the chair of the committee as to the outcome of the examination. The examination committee will decide whether the student passes or fails the exam. In the case of failure, the student must petition the core committee to retake the exam. The core committee will decide on the petition at the end of the normal exam period. Unless exceptional circumstances prevent it, oral exams should be retaken before the end of the fall term. Regardless of exam outcome, a student can maintain their student status through the end of the fall term.
In all cases, the examining committee will prepare a written memo to the student and his or her adviser, stating the result of the exam and making recommendations regarding the student's preparation. The response to recommendations will be reviewed by the division faculty when the student applies for admission to candidacy.
Choice of Propositions and the Preparation of Abstracts
A student's propositions are based on small research projects usually carried out during the first year of residence. It is important that the student demonstrate the ability to carry out meaningful research on a given topic, to place the work in the context of previous knowledge, and to recognize the implications and possible interpretations of the proposition.
It is not necessary to have final results, a working computer program, a functioning piece of equipment, or fully analyzed data in order to have a successful proposition. More often, the proposition will be a carefully worded statement based on what has been learned up to the time of the examination, together with a discussion of the implications that might be forthcoming with either more data or more sophisticated analysis. Naturally the proposition may be supported by evidence: maps, graphs, photographs, samples, etc., but these need not be in final form or represent the last word on the subject and should be limited in number.
The student must choose propositions dealing with subjects pertinent to more than one research area within the division. The student should demonstrate versatility by choosing proposition topics that will allow the employment of different types of tools or methods. The propositions defined by the student should not deal with the same topic as investigated by different techniques, nor should they represent different research problems studied with the tools of a single discipline. In the course of developing successful propositions, it is essential that each student seek the advice of faculty. Consultation with postdoctoral scholars and senior graduate students is also encouraged. The name of the faculty member most closely involved should appear on the written abstract of each proposition. The same faculty member should not be the most closely involved with both propositions.
The student's written abstract and the 10-minute presentation summarizing the proposition should be carefully designed by the student to concisely convey to the examining committee the motivation behind the research project, the results of the investigation thus far, and any implications for broader issues in geobiology, geochemistry, geology, geophysics, or planetary science. The organization of the presentation is up to the student, but the student should understand that the presentation is the principal vehicle by which most of the examining committee will be introduced to the proposition, and by which the initial questions are motivated. Some students have found it useful to introduce the proposition by a statement that he or she will defend, but this is not the only acceptable approach.
Requirement of a Written Paper
One of the two propositions must be accompanied by a short, snappy research paper on the subject of the proposition. This requirement aims to provide greater insight into the student's writing ability, scholarship, and general knowledge of the research field involved.
The paper should include an informative and appropriate bibliography. It may be useful to regard the paper as a funding proposal to the National Science Foundation or as a short research note prepared in the format of one of the following five journals: Geology, Science, Nature, Geophysical Research Letters, or Astrophysical Journal Letters. The length of the paper (excluding references, tables, and figures) must not exceed six double-spaced typewritten pages, and the number of figures and tables must not exceed four each. The list of references should give the complete titles and pagination of cited papers.
The complete paper in final form must be in the hands of all members of the student's examination committee and the entire core committee no later than one week prior to the time of the scheduled exam. The paper must be received in the division office by that date, and it will be immediately distributed to the student's examining committee.
Although it is not a requirement, we believe it is desirable that early-stage or preliminary drafts of the paper should be looked at and critiqued by at least one Caltech faculty member. This should be done well in advance of the one week deadline referred to above.
Also, in addition to interactions with and critiques by that faculty member, the student is encouraged to interact with and seek advice from as many other faculty members, graduate students, and postdoctoral scholars as possible, in regard to both this paper and the other research proposition. The student should give proper acknowledgment to these various reviewers.
Both propositions will be treated with equal weight in the oral exam, and the written paper can be attached to either the first or the second proposition. This written proposition will not necessarily be considered the "main" research subject of the student.
Each member of the examining committee will have read and reviewed the student's manuscript. The examining committee's assessment of the quality of the paper will enter into the outcome of the exam and will be noted in the committee's memo to the student.
May 30: The student will deliver two tentative proposition titles to Julie Lee in the division office. Included should be a paragraph or two explaining the general nature of the work planned. The student should indicate the faculty members with whom he or she has discussed the project and who are providing supervision of the work. This information is intended to allow the core committee to assess the student's progress and help the student remedy any potential major problems at an early date.
One week prior to the scheduled exam, the student will submit final typed abstracts of the two propositions and a final typed copy of research paper to the division office for distribution to the examining committee, and a completed Academic Summary. Each abstract should be no more than one page in length.
Meeting with First-Year Students
The core committee will meet with the group of students taking exams to explain and discuss the requirements, and to answer any questions about the examination or the examination procedure. At this meeting we will welcome input from any of the students regarding any aspect of the examination procedure.
To allow time for grades to be finalized and for the processing of option approval, applications for candidacy will be on the agenda for the faculty meeting of the spring academic term. All candidacy applications will be reviewed at the May faculty meeting each year.
By the end of the third year, students should have their Application for Candidacy form completed, approved by their advisers, and delivered to the academic committee representative for their option during the first week of the final term. A copy of the core committee's qualifying-exam letter should be attached to the application, along with a short paragraph describing the student's thesis proposal/research. This should provide sufficient time for the option faculty to review the application package.
The approved application form, signed by the option representative, must reach the division office two weeks before the designated division faculty meeting. These applications will be submitted for the faculty meeting agenda.
The effective dates of the candidacies approved by the division faculty will be the first day of the following term.
Application for Approval of Candidacy Forms
At Least One Month Before the Defense
Remember that each committee has a minimum membership requirement of four Caltech professors. A minimum of three members must be from within the division. Your academic adviser will serve as chair of the committee. According to division policy, other scientists can be committee members in special circumstances. A special circumstance, for example, would be possession of an essential expertise otherwise unrepresented, or a person whose absence might unduly jeopardize adequate assessment of the thesis. Involvement in and partial guidance of the thesis research does not by itself constitute a special circumstance. The division chair and the dean have final discretion on committee membership.
Travel support for external committee members should be taken into consideration when the defense committee chair, the thesis adviser, and the student are in the process of determining committee makeup. If divisional support is proposed, a case should be made to the division chair by the student's thesis adviser or defense committee chair prior to finalizing the committee membership. Any such request will be considered by the division chair on a case-by-case basis.
Two Weeks Before the Defense
One Week Before the Defense
Following the Defense
