Mapping Mars from Wet to Dry

Categories: Mars

New Online Map Reveals Evidence of the Forces that Once Shaped Mars

CRISM breaks sunlight reflected off the Martian surface into a spectrum, from which it measures 544 colors. This wide range helps CRISM determine the mineralogy of the surface. For example, this map was made from only three colors (green, red and infrared) in Mars Pathfinder images and shows iron oxide coatings crusted on rocks.

A new online map lets visitors explore Mars’ past through a collection of high-resolution observations from one of the most powerful spectrometers ever sent to the Red Planet. Evidence of ancient bodies of water, flowing rivers and groundwater peeks out from beneath layers of hardened magma and dust—testaments to Mars’ progression through wet, volcanic and dry eras. Understanding the history of water on Mars will help scientists determine whether or not the planet could have supported life in its past.

The data come from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA’s Mars Reconnaissance Orbiter. CRISM’s primary mission is to search for signs that liquid water once existed on Mars by identifying minerals that form only in the presence of water. Molecules of water trapped in these minerals leave particular patterns in the sunlight that reflects off of them and into CRISM, which senses up to 544 “colors,” or wavelengths, of light.

A team of researchers at The Johns Hopkins University Applied Physics Laboratory (APL), which built and operates the instrument, has converted the complex CRISM data into easy-to-understand composite images. “The images clearly show the distribution of certain minerals, which tells us about the planet’s history,” says Scott Murchie of APL, CRISM’s principal investigator. “This map moves the information out of the domain of specialists and makes the very latest Mars research accessible to anyone with an interest in the planet.” The online collection currently includes more than 900 observations, and more are being added as the team prepares them.

These images are examples of the "browse" products the CRISM instrument obtained of areas on Mars near proposed landing sites for the 2009 Mars Science Laboratory. CRISM is one of six science instruments on the Mars Reconnaissance Orbiter, currently circling the red planet. Click image to enlarge.

The high-resolution map can be found on the “CRISM Data Products: Viewing Features on Mars” Web site, at, and is best viewed with Firefox 2.0, Netscape 7.2, or Internet Explorer 7.0, or better.

Visitors to the site choose from a selection of global background maps made by instruments on NASA’s Viking, Mars Global Surveyor and Mars Odyssey spacecraft. They can zoom in, click on particular CRISM observations that dot the maps, and access a variety of images constructed from the 544-color data. These include versions of each observation that show the locations of water and carbon dioxide ice; iron-containing igneous minerals formed by volcanic activity or cratering; iron minerals that have been altered by oxygen in the atmosphere; and clay-like and sulfate minerals that were formed by past liquid water.

“The images provide good indication of where there are mineral signatures of volcanic deposits or past wet environments,” says APL’s Frank Seelos, CRISM’s science operations lead. “Researchers can browse the map to identify interesting sites and then download the full data from NASA’s Planetary Data System, an archive of data products from NASA planetary missions. Non-scientists can get a sense of the variety of geologic features on Mars, and the variety of processes that created them.”

The high-resolution map can be found on the “CRISM Data Products: Viewing Features on Mars” Web site, at, and is best viewed with Firefox 2.0, Netscape 7.2, or Internet Explorer 7.0, or better.

“This is the first time that these simplified versions of complex spectrometer data have been made easily available to both the science community and public,” says Olivier Barnouin-Jha, a member of the CRISM operations team at APL. “The techniques we used were developed by scientists working on CRISM and a similar instrument, called OMEGA, on the European Space Agency’s Mars Express. OMEGA’s team pioneered some of the techniques that we use, and CRISM provides unprecedented resolution for an imaging spectrometer at Mars.”

Related Web Sites

Astrobiology Roadmap Goal 2: Life in Our Solar System
By the Shores of a Martian Lake
Martian Water, Past and Present
Surf’s Up on Mars
CRISM Opens Its Eyes
Mapping Martian Minerals