NASA MGS TES Press Release, May 27, 1998

Mars Global Surveyor TES Instrument
Identification of Hematite on Mars

The Thermal Emission Spectrometer (TES) instrument on the Mars Global Surveyor mission has discovered a remarkable accumulation of the mineral hematite that covers an area approximately five hundred kilometers (~300 miles) in size. The TES results indicate that the hematite is coarse-grained (sand-sized or larger) and occurs within this localized region with very sharp boundaries (see accompanying figure). Hematite is a ferric iron oxide mineral that forms by a variety of processes that often involve water. Fine-grained (dust-sized) hematite generally forms by the weathering of iron- bearing minerals by oxidation (rusting), which can occur in an atmosphere at low temperatures. This fine-grained material has been previously detected on Mars and is widely thought to be an important component of the materials that give Mars its red color. The coarse-grained hematite discovered by the TES is even more intriguing, however, because it typically forms by crystal growth from hot, iron-rich fluids. Coarse-grained hematite can form when large amounts of hot water move through iron-bearing rocks, dissolving the iron and carrying it away in solution. As the water cools it can no longer hold as much iron and the dissolved iron is then precipitated in cracks and veins in the surrounding rock. On Earth these hydrothermal systems commonly occur around volcanic regions, such as Yellowstone. Coarse-grained hematite deposits can also form when large quantities of iron are dissolved in seas and other large bodies of water. Changes in the water chemistry can cause the iron to precipitate as hematite and collect in large deposits. On Earth these deposits have been highly altered, typically by hot water flowing through them, producing extensive deposits of coarse-grained hematite.

The TES results provide the first evidence that suggests a large-scale hydrothermal system may have operated beneath the Martian surface at some time during the planet's history. Even more intriguing is the possibility that the hematite may have initially precipitated from a large body of water. The accumulation of hematite discovered by the TES occurs near 0 latitude between 0 and 5 W longitude and is the only concentration of hematite that has been found so far. The highly localized occurrence of hematite in this single region provides additional evidence that a unique process has occurred, in contrast to the widespread weathering of iron-rich minerals at the surface that has produced fine-grained, red hematite. A different, and much less common process, such as intense hydrothermal alteration or precipitation, must have created the concentration of hematite observed by the TES. The reason these processes have occurred in this isolated location continues to be investigated.

The search for hydrothermal deposits and other indicators of water at the surface are prime objectives of the TES investigation and the Mars Global Surveyor mission. The existence and location of hydrothermal deposits will provide a positive indication that hot water once existed near the Martian surface, and will provide important information to aid in the selection of future landing sites for exploration and the collection of samples for return to Earth.

The TES instrument is operated at Arizona State University as part of NASA's Mars Global Surveyor mission, and was built by Raytheon Santa Barbara Remote Sensing. The Mars Global Surveyor mission is managed by the Jet Propulsion Laboratory in Pasadena, California.

Figure 1

click on image for full resolution version (428k)

This figure shows the concentration of hematite measured by the Mars Global Surveyor Thermal Emission Spectrometer (TES) instrument. The abundance of hematite is shown in red, with increasing brightness indicating increasing hematite abundance. The location and size of the individual TES observations on the surface are indicated by the individual squares. Black squares indicate observations with no detectable hematite. Data from 11 separate orbits acquired between Nov. 22, 1997 and April 25, 1998 are shown in this image. The TES data are superimposed on a Viking photomosaic for context. The image extends from 10 S to 10 N latitude and 350 W to 15 W longitude, covering an area 1500 km (940 miles) in longitude by 1200 km (750 miles) in latitude.

Contact Information:
Dr. Phil Christensen
Box 871404
Arizona State University
Tempe, AZ 85287-1404
(602) 965-1790

TES Team Members:

  • Dr. Philip Christensen, Arizona State University, AZ (Principal Investigator)
  • Mr. Stillman Chase, Santa Barbara, CA
  • Dr. Todd Clancy, Space Science Institute, CO
  • Dr. Roger Clark, U. S. Geological Survey, CO
  • Dr. Barney Conrath, Goddard Space Flight Center, MD
  • Dr. Hugh Kieffer, U. S. Geological Survey, AZ
  • Dr. Ruslan Kuzmin, Vernadsky Institute, Russia
  • Dr. Mike Malin, Malin Space Science Systems, CA
  • Mr. Greg Mehall, Arizona State University, AZ
  • Dr. John Pearl, Goddard Space Flight Center, MD
  • Dr. Ted Roush, NASA Ames Research Center, CA

    JPL Mars Missions Homepage | WHAT is TES? | Lab Spectroscopy
    K-12 Outreach | ASU Facility & People
    Mars Links |