CRISM (Compact Reconnaissance Imaging Spectrometer for Mars)
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Looking for a Place to Land

October 25, 2007

Over the past week, the CRISM science team has been releasing one of our largest data sets yet: images covering the 46 candidate sites under consideration for NASA’s Mars Science Laboratory (MSL), now in development and slated to reach Mars in 2010. The releases have been the culmination of an incredible amount of work: planning all of the observations; optimizing the calibration and ground processing of the data; and finally coming up with a way to show the content of 544 wavelengths as red, green and blue. The calibration issues were tackled in September, after months of turning over every stone we could think of, working out the causes of data artifacts and correcting them. Ever since, we've been sprinting to reprocess our terabytes of data and make maps.

We were under a serious crunch to assemble the images and analysis products before the second MSL Landing Site Workshop in Pasadena, taking place this week. To complete a release before the meeting and to get the results of our hard work to the interested community, we've released the data in two batches.

Last Friday, in time for the workshop, we released all of the high-resolution images. They look great, and that's been incredibly satisfying. We settled on seven different red-green-blue versions of the data, each tailored to a different theme – what the eye would see, the igneous rock geology of each site, whether and what kind of hydrated minerals are present. (They've been a big hit!) Scientists finally have a common reference frame to discuss which sites have the rock types that MSL is designed to analyze. Our image release is organized around a Web page with links to the images for each site, in thumbnail form to get the overview, with links to the full-resolution versions. Using these and data from other instruments on the Mars Reconnaissance Orbiter, NASA Mars Program officials and scientists will trim the list of potential MSL landing sites from 46 to just five.

This week we're releasing a map of 180-kilometer squares centered on each site to provide context. These are all shown in similar red-green-blue form, the big difference being that they were assembled from global mapping data. Several hundred individual images were needed to make the maps, so they took a few days longer.

It's been amazing to work with such a talented team of people. Dave, Frank, Kim, Debra, Pete, Chris, Erick, Alysen – everyone brings their own special talents that were needed to get to where we are.

Since MSL will assess whether Mars ever had an environment capable of supporting life, it will have to land in an area with a mineral record indicative of past water. With that in mind, one of our favorite sites is the Nili Fossae region. It would be easily accessible to a spacecraft and it has geochemical diversity – which means you can link the rocks in this area to different periods in Mars’ history, as far back as 3.9 billion years ago!

This is exciting. The biggest revelation from CRISM data is that clay-bearing rocks – that is, rocks altered by water that are good at preserving chemical evidence of past life – are way more common that expected among Mars’ oldest rocks. But no lander has visited a site with rocks of that age; MSL would be a first if it goes to a clay-rich site. Past missions have primarily investigated areas of more recent times. For us, this would be like going back in time and standing on the landscape that formed the bottom layers in the walls of the Grand Canyon, where the oldest rocks are on the bottom. On Mars, these oldest rocks tell the true story of the wet period on the red planet.

Stay tuned!

– Scott Murchie, CRISM Principal Investigator