An engineering and applied science professor received a three-month grant from NASA to explore how radar technology can detect the presence of ice under the soil on Mars.
Roger Lang will use the $35,000 grant to measure how much ice lies beneath Martian Regolith – loose rock debris coating Mars – as part of a larger NASA push to explore the planet. Some engineering experts said ground-penetrating radar is more effective in identifying ice deposits than other techniques, like examining datasets, but others said the radar might be limited in its ability to detect the presence of ice.
“What NASA is thinking about is they are looking to explore Mars, and one of the key elements is to find water,” Lang said. “Past meteors have crashed into the surface and made big holes and they look at the side of the holes.”
Lang said NASA’s long-term goal is to send a satellite to slowly orbit around Mars, sending waves into the regolith – a layer of loose rock – to determine whether water is present. He said he is working in conjunction with NASA researchers, including a planetary geologist, to model the Martian environment and determine which radio wave, L Band or P Band, best penetrates the surface of Mars.
“L band is one gigahertz, that’s cell phone frequency, and P band is approximately 400 megahertz, so 400 megahertz is somewhat lower,” Lang said. “The concern is, which one of these will be able to penetrate through the regolith?”
Lang’s work comes about six months ahead of the Mars 2020 rover mission. The rover is set to launch in mid-July to early August and seeks to address the potential for life on Mars, according to the NASA website.
The rover will be equipped with “The Radar Imager for Mars’ Subsurface Experiment,” an instrument that can detect geologic features, like ice and water, under the surface with a radar, the NASA website states.
Experts who study Mars said researchers must quantify how much water is on Mars to evaluate the possibility of launching long-term missions that will assess the future potential of life on the planet.
Ali Bramson, a postdoctoral researcher at the Lunar and Planetary Laboratory at the University of Arizona, said ground-penetrating radar – or GPR – can look deep underneath the planet’s surface and make more accurate determinations about water quality than tools like thermal and microscopy data.
“Many other datasets like microscopy only looked at like the upper microns,” Bramson said. “And so most datasets really are only looking at what is going on at the surface or in the very near, near surface. With ground penetrating radar we can also look for the bottom of ice, so, ultimately, the different datasets are looking at different depth range.”
Jennifer Buz, a postdoctoral researcher at Northern Arizona University, said frozen water would have to be located “mid-latitude,” or closer to the planet’s warmer equator, to be accessible to future manned missions to the planet.
“Mars’ poles also have ice caps on them, including water ice and carbon dioxide ice, dry ice, but the poles are extremely cold,” Buz said. “And so going to a pole for emissions is incredibly difficult even for robotic missions. And so we need to find ice as a resource at lower latitudes of Mars, closer to the equator.”
Buz said the infrared data she uses in her work produces high-resolution images of the regolith but involves significant calibration steps, or maintenance to ensure the device is working properly. She said the radar technology allows researchers to determine the ice’s permittivity, or it’s ability to store electric potential energy, which the GPR can detect.
“One of the benefits of using radar is how we’ve been able to determine that the ice underneath the subsurface is really pretty pure ice,” Buz said.
But some academics are concerned about the methodology and limited breadth of information GPR can deliver. Robert Grimm, a program director at the Southwestern Research Institute — a scientific research institute based in Texas — said radar technology is more suitable for shallow subsurface imaging.
Grimm said the ice present on Mars is likely scattered in different locations underneath the soil instead of “ice tables,” or large swaths of ice. He said he is concerned that GPR imaging will be unable to detect ice deposits that are not consolidated into large masses and will not yield the most accurate data.
“I am not a fan of GPR for ice discrimination, because there is little difference to the radar between ice and soil,” Grimm said in an email. “An ‘ice table’ that cuts across stratigraphy might be discernible, or a segregated ice lens, but there is no way that pore ice can be distinguished from lesser overall soil porosity.”