Curious Scientists Use ENVI and IDL to Delve into Mysteries on Mars

"What's out there?" is a question that captured our collective imagination long before we actually traveled into space to explore it. With the recent Mars Science Laboratory mission to Mars, once again all eyes are turned skyward. NV5 Geospatial is helping scientists on the Mars Curiosity rover team answer that age old question with its geospatial image and data analysis software that lets scientists dig deeper than ever before into the red planet.

If a Picture = 1000 Words on Earth, How Much is it Worth on Mars?

As it turns out, analyzing geospatial images taken some 179 million miles away isn't as daunting as it sounds. Ralph Milliken, Assistant Professor of Geology at Brown University who is working on the Curiosity rover team as a spectroscopist, used ENVI^® and IDL^® for the spectral analysis that was part of what led to the selection of Gale Crater as the landing site for the rover. "All the sites that were under consideration were good ones," said Milliken. "It was like choosing between different flavors of ice cream." Ultimately it was the diversity of minerals in Gale Crater, the presence of a thick sequence of rocks and evidence of previous water, that led to the Mars Rover landing there on August 5.

The plan for the mission is for the SUV-sized rover to spend at least two years exploring the crater, eventually driving up a 3-mile mountain, Mount Sharp, in the center of the crater. "There are lots of environments present in the crater," according to Milliken. "For example, the rocks near the bottom of the mountain appear to contain hydrated minerals, but these minerals are absent in the overlying strata," said Milliken, referring to the many layers of sediment that form the mountain.

Guess What the Rover Found on the Way to Glenelg?

As the rover was rolling toward Glenelg, what will very likely be its first drilling site, it came across stones in conglomerate rock that indicate water probably flowed there in the past. Scientists made their determination about water on the now dry and dusty planet based on previously-collected satellite images, and now they are able to use the rover's chemistry tools to explore these locations in detail. While there had been speculation from past missions on whether water had flowed in other channels, this was the first direct observation of streambed materials on Mars.

The primary camera system on the rover, the MastCam, has the ability to collect multispectral data via filters (14 in all for geology) for visible and infrared portions of the solar spectrum, out to about 1000 nanometers. Milliken uses ENVI to view and analyze this imagery, looking specifically for subtle differences in the way light is reflected off rocks to help explain Martian minerology. "By using ENVI, I can take full advantage of the spectral data being transmitted from the MastCam, perform PCAs, decorrelation stretches, extraction of reflectance spectra, radiometric and atmospheric calibration," says Milliken.

Don't Try This at Home.

ChemCam is the primary instrument used for remote characterization of the chemical composition of rock and soil on Mars. ChemCam shoots a laser at its target, vaporizing a small amount. The resulting flash is sent down an optical fiber to a spectrometer located in the body of the rover where light intensity from the flash is recorded as a function of wavelength and sent to Earth. Scientists use this data to determine the elemental composition of the vaporized material.

"The team uses IDL as the primary tool for processing ChemCam's emission spectra," said Bethany Ehlmann, Assistant Professor of Planetary Science at California Institute of Technology and a research scientist at NASA's Jet Propulsion Lab, who also uses ENVI in her work with viewing orbital imagery and with image data from the Mars Science Lab.

"We have been looking at the different composition of rocks and soil in relationship to their interaction with water," said Ehlmann. "For example, if large amounts of water have previously flushed through a rock, the rock composition will reflect that with a loss of sodium, calcium, and potassium, which are detected by the examination of spectra and use of IDL code to calculate peak area and do statistical analyses."

Over the next two years, the rover looks poised to uncover many more exciting geological findings on Mars. "Of course, we are also looking for organic carbon. That would be pretty amazing," says Ehlmann, referring to the ever-present question of whether the planet might have at one time supported life. Mission scientists using the geospatial data and image analysis tools from NV5 Geospatial are in the unique and enviable position to find that out.