Understanding Mars

Mars is the fourth planet from the Sun and in many ways displays a "split personality" with respect to its geologic history. On the one hand, the planet retains a thin atmosphere, has large polar caps, and displays evidence that water has flowed and may have ponded on the surface. In these respects, Mars appears to be fairly Earth-like. On the other hand, the planet is variably cratered and large sections have been resurfaced by volcanic activity that give a more Moon-like impression.

Although Mars only has about 11% of the mass of the Earth and only 38% of the surface gravity, it is a strange and diverse planet. For example, the land surface area is approximately equivalent to that exposed above sea level on the Earth and topography ranges some 35 km from the depths of the largest impact basin in the solar system (Hellas basin) to the top of the largest known volcano (Olympus Mons). In addition, there are enormous outflow channels that record the past discharge of floods from the more elevated and ancient southern cratered highlands into the lower and relatively younger northern lowlands. A gigantic canyon stretches thousands of kilometers across the equator of the planet and cuts kilometers into the crust while extensive outpourings of lava have buried broad portions of the surface. Nearly everywhere, a variable density of impact craters provides a means for constraining the relative timing of these events.

Evidence that pulses of water have redistributed sediments on Mars. Arrows show features within a graben (fault-bounded linear valley) that are similar in scale and pattern to features observed in central Australia (by Mary Bourke, University of Oxford and CEPS) that were produced by infrequent massive flood events. (Portion of Mars Orbiter Camera image M04-04068, 20.1°N, 157.1°W, courtesy Malin Space Science Systems/Jet Propulsion Laboratory/NASA).

Martian surface morphology records a complex, changeable geologic history that suggests the planet may have been more hospitable to life during its early history. While the present atmosphere is predominantly CO2 and only about 1% of the density of Earth's atmosphere, some evidence suggests it was denser and warmer in the past. For example, most of the valleys and channels cutting the surface are thought to have been created by flowing water, something that is nearly impossible to sustain under present cold conditions (the average temperature is -23°C). Possible relationships between the atmosphere, the planet's water cycle, and any possible biotic activity on the planet remain the focus of much research.

The Mariner and Viking missions to Mars from the 1960s to the 1980s provided the data needed to determine the global distribution of major terrain types, and to establish the relative age of terrains. The Mars Pathfinder mission in 1997 provided detailed views of the Martian surface near the mouth of Ares and Tiu Valles, as well as the first in situ chemical evaluations of rocks through the use of the first roving vehicle on Mars. The Mars Global Surveyor (MGS) spacecraft went into orbit around Mars in late 1997, and since then it has returned an enormous quantity of data that are revolutionizing our concepts of the planet. The Mars Orbiter Camera has obtained more images of Mars than all previous U.S. orbiting missions combined, including views up to ten times more detailed than any previous orbital image. The Mars Orbiter Laser Altimeter has produced the first well constrained topographic data set for the entire planet through collection of more than 800 million individual elevation measurements. The Thermal Emission Spectrometer has mapped the distribution of two types of volcanic rock across the planet. The Magnetometer and Electron Reflectometer found remnant magnetic signatures in rocks within the cratered highlands of the southern hemisphere, giving the first evidence that early Mars had an active internal dynamo. This wealth of new data is refining many of our Viking-based ideas about the planet.

The next chapters of Mars exploration are already being written with the recent launch of the Mars 2001 Odyssey Orbiter and the upcoming 2003 launch of the twin Mars Exploration Rovers.

Mars Research in CEPS

CEPS personnel are engaged in a variety of Mars related research and activities, ranging from fundamental research in the areas of Planetary Geology and Geophysics to involvement in Mars landing site selection to definition and proposal of future missions and science instrumentation.

Mars research at CEPS makes use of traditional photogeological mapping and image interpretation techniques, aided by quantitative analyses of both landform shapes and dimensions. Our investigations often include measurements of the martian surface obtained from Earth-based radar and spacecraft remote sensing data. Many of these studies also involve investigations of terrestrial analog sites to gain insight into the details of potential processes involved, and to obtain well constrained data of the analog feature for comparison to the landforms on Mars. Descriptions of these research activities can be found by following the links below.

Large crescent-shaped (barchan) sand dunes and barchanoid ridges in the caldera of Nili Patera, Mars (9°N lat., 293°W long.). The sand has moved from upper right to lower left across the scene, based on the dune shapes. The area shown is 2.4 km (1.5 mi) across. (Portion of Mars Orbiter Camera image FHA-00451, courtesy Malin Space Science Systems/Jet Propulsion Laboratory/NASA).

List of Mars research projects