November 18, 1998
Ancient Hydrothermal Activity on Mars
Click on the image for a larger view.
The red areas in this image of the Martian surface correspond to the presence of coarse-grained hematite (see text). Increasing brightness indicates increasing hematite abundance. Black areas indicate areas with no detectable hematite.
The data, which were taken during 11 separate orbits by NASA's Mars Global Surveyor, are superimposed on a photo-mosaic from NASA's Viking program. The image covers an area of about 750 miles by 940 miles, and extends in latitude from 10 degrees south to 10 degrees north, and in longitude from 15 degrees west to 10 degrees east.
Image Credits: Philip Christensen, Arizona State University, Tempe, AZ, and the Thermal Emission Spectrometer instrument team.
It seems that hydrothermal activity, perhaps similar to terrestrial hot springs like those in Yellowstone Park, occurred on Mars some time in the past. The evidence comes from the detection of an iron-bearing mineral, coarse-grained hematite, in highly localized areas on the surface of the red planet.
Hematite is an iron oxide mineral that forms by a variety of processes that often involve water. Coarse-grained hematite, which is a crystal the size of a grain of sand, can form when hot water moves through iron-bearing rocks and dissolves the iron. When the water cools, the dissolved iron precipitates in cracks in the surrounding rock and produces coarse-grained hematite.
Coarse-grained hematite can also form when iron is dissolved in seas and precipitates. On Earth, such deposits have been highly altered, typically by hot water that flowed through them.
The existence of localized, coarse-grained hematite on Mars described here is the only known example of this material on the red planet. However, since our coverage of the planet's surface is not complete, other deposits of coarse-grained hematite may yet be found elsewhere.
The discovery of coarse-grained hematite on Mars constitutes evidence that large-scale hydrothermal activity may have operated on the ancient Martian surface. Even more intriguing is the possibility that the hematite may have initially precipitated from a large body of water.
The discovery of the Martian coarse-grained hematite was made with the Thermal Emission Spectrometer (TES) onboard NASA's Mars Global Surveyor spacecraft, which has been orbiting Mars and collecting data since September 11, 1997.
(Coarse-grained hematite is to be distinguished from fine-grained [i.e., dust-sized] hematite, which forms by the weathering of iron-bearing minerals by oxidation [rusting]. This fine-grained material is widespread on Mars and thought to be partially responsible for Mars' red color.)
More Cool Stuff
- We obtained the above images from the homepage of the Thermal Emission Spectrometer at Arizona State University:
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http://emma.la.asu.edu/webdata/hematitepr.html#fig
- For information about the Mars Global Surveyor, go to its homepage at NASA's Jet Propulsion Laboratory:
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http://mars.jpl.nasa.gov/mgs/
As part of its Learning Technologies Project (LTP), NASA supports a number of educational Web sites that have excellent material on the space sciences:
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http://observe.ivv.nasa.gov/nasa/education/edu/edudocs/topic_space.html