A planetary geologist is a scientist who studies the geology of planets other than Earth and their satellites. The field, also known as astrogeology or exogeology, is closely related to traditional geology but focuses on topics such as the internal structure of a planet and volcanic and surface activity. A planetary geologist might look at samples from space missions or meteors that strike the Earth’s surface. Photographs and other data sent from probes about comets, moons, and planets are also of interest to planetary geologists. Many planetary geologists’ research goals include creating accurate planetary and lunar maps and inferring the possibility of life on other planets.
The geological features of celestial bodies such as planets, moons, and comets are all scientifically significant. On Mars, for example, the highest mountain in the solar system is located, and craters on Mercury contain pockets of frozen ice. Data on these features is gathered in a variety of ways, including through telescopes, astronaut samples, and photos and data from space probes. Careful mapping and investigation of these geological features can reveal a great deal about how a body was formed, how its geological composition compares to Earth’s, and whether or not life existed or could exist there.
A planetary geologist studies the composition and structure of geological features and the composition of other planets and their satellites using techniques from other fields of geology, such as geochemistry and geophysics. The primary sources of information are physical analysis of samples and data, as well as photographs. This research can reveal why a planet is a certain color, whether there is or was water on the surface, and whether or not there is volcanic activity. The planet Mars, for example, is red because its surface is covered in iron oxide, which is carried into the atmosphere.
A planetary geologist’s job includes mapping the surface of a planet or one of its satellites. High-resolution photographs of the surface are returned by space probes, revealing craters and other features such as mountains and valleys, as well as color and texture. To enhance the surface image and reveal even minute details, orbital high-resolution photographs can be combined with 3-D modeling. During the spring and summer on Mars, evidence of streaks running down into crater slops can help a planetary geologist infer the presence of liquid rather than frozen water. The environment for life is better in liquid water than it is in frozen water.
A planetary geologist may study impact cratering and planetary atmospheres in addition to mapping. Impact cratering is a major geologic process that shapes the surface of the planet and can produce a variety of geological features. A geologist must differentiate between cratering caused by volcanic activity and cratering caused by a foreign body impact. Planetary atmospheres not only reveal information about gravitational forces, but they also shape planetary surfaces through wind, frost, and precipitation.
A doctoral degree in the subject is required for a career as a planetary geologist. Only a few institutions offer advanced degrees in this field because it is a niche profession within geology. Universities, the United States Geology Survey Astrogeology Science Center, and the National Aeronautics and Space Administration employ the majority of planetary geologists in the United States. They conduct research and create planetary and lunar maps that highlight evidence of past water concentrations, impact craters, and volcanic activity, among other things.