Mars has lots of glaciers located along its mid-latitudes. We’ve known this for years thanks to the Mars Reconnaissance Orbiter’s (MRO’s) SHARAD sounder. But, despite all of the excellent data it’s managed to gather, SHARAD doesn’t have high enough resolution to accurately measure the boundary between the glacier itself and the rocky material that has been deposited on top of it over the course of billions of years. A new study, published in the journal JGR Planets, details a potential method of finding that boundary—by using a drone.
So what exactly does that boundary matter? Debris-covered glaciers (or DCGs) are a common feature on Mars. The debris that rests on top of them stops the sublimation that would otherwise cause the entire glacier to disappear into Mars’ thin atmosphere. But, we aren’t entirely sure how deeply buried these glaciers are. And if we’re to utilize the water they hold, either for direct astrobiological study or in-situ resource utilization (ISRU), we need a better idea of how much rock and dirt we have to dig through in order to access them.
SHARAD is great for tracking big macro features over the surface of the planet. But it’s not great for the nitty-gritty details of how much regolith actually covers a specific glacier. This is largely due to the fact that it’s around 300 kilometers away. In order to get that fine level of detail, we need something closer.
Video describing the plan to use ground-penetrating radar on drones to analyze Martian glaciers. Credit - Breakingspace Youtube ChannelLuckily, plenty of planetary scientists have drawn inspiration from a recent Martian success story. Ingenuity, the helicopter that performed the first powered flight on another planet, has created a rush of enthusiasm for drone-like systems to explore parts of Mars that it would be hard for a rover to access. So why not attach a ground-penetrating radar to one?
That’s exactly the thought process of Roberto Aguilar, the study’s lead author and a graduate student at the University of Arizona’s Lunar and Planetary Laboratory. And what better way to trial that idea for use on the red planet than to run some preliminary tests here on our own.
Glaciers are not known for being easy to get to. Debris-covered glaciers are even less so. But the research team dutifully packed their hiking boots and made their way to two well-studied DCGs - one in Alaska known as Sourdough Rock Glacier, and one in Wyoming known as Galena Creek Rock Glacier. Their key pieces of equipment? A DJI Matrice 600 Pro drone equipped with a MALA Geodrone 80 MHz ground penetrating radar (GPR) module.
Fraser discusses the newest Mars missionAfter braving a swarm of mosquitoes and difficult terrain (which they describe in an associated press release rather than the paper itself), the team did several test flights of the drone-based GPR. They also used an automated terrain-following module rather than trying to manually control the drones over the tricky landscape.
With the data safely collected (and seemingly no drone crashes), the team validated it by ensuring the radar data was actually coming off the sub-surface glacier rather than nearby trees or valley walls—a phenomenon known as “clutter”. After validating the data against 3D simulations of clutter, they then compared their drone-based results to those of surface-based GPR instruments that had been used to previously collect data on these glaciers.
Results from the Sourdough Rock Glacier in Alaska matched well in terms of both the glacier’s thickness and also the debris thickness on top of it, with a measured glacial thickness of 28.5 m and a debris thickness of a mean 1.5 m. In Wyoming, the drone measured the thickness of the glacier to be 48.6 m, and the thickness of debris to range between 0.8 m and 1.3 m in some zones.
Fraser makes the argument for exploring ocean worlds to find life.This study had several advantages, including its integration of the “clutter” modeling, its ability to traverse terrain that was difficult, if not impossible, for a human with ground-penetrating radar to tackle, and the direct validation between its findings and those captured by separate GPR studies. However, the GPR it used on the drone was only 80 MHz, causing it some weakness when detecting the shallowest of debris layers. It also had difficulty detecting some of the deepest bedrock layers, especially compared to a 50 MHz surface-based system.
But ultimately, this study is a proof-of-concept that a ground-penetrating radar attached to a drone is a viable middle ground between orbital-based hardware that is too far away for accurate reading and ground-based hardware that is too hard to place in remote locations. It also fits neatly on the Mars Science Helicopter (MSH), a currently under assessment mission that would be able to carry enough payload to successfully take a GPR to its final destination—the skies above the glacial fields of Mars itself.
Learn More:
University of Arizona - Drone radar reveals buried glaciers on Earth, guiding the search for water on Mars
R.J. Aguilar et al. - Revealing the Internal Structure of Mars-Analog Glaciers From Drone-Based Radar Sounding
UT - Martian Volcanoes Could Be Hiding Massive Glaciers Under A Blanket of Ash
