Mars is the only known planet aside from Earth that has polar ice caps, but unlike Earth, the ice on Mars is mostly of the “dry” carbon dioxide variety. Naturally, there’s great interest in better understanding the Martian polar regions. A new analysis of Mars using data from NASA’s Mars Reconnaissance Orbiter (MRO) has revealed previously hidden structures under the northern ice cap — as seen above by the Mars Global Surveyor. The researchers found wavy landscapes, impact craters, and even a large canyon all buried under the ice.
The Mars Reconnaissance Orbiter has been observing the red planet from above since 2006. Among its suite of instruments is a special type of penetrating radar called Shallow Subsurface Radar (SHARAD). It emits radar waves between 15 and 25 megahertz, which can pass through up to 4 kilometers of material before bouncing back to the orbiter. It has a depth resolution of about 15 meters. This instrument has been returning data on the ice caps and other regions of Mars for years, but the team from the Planetary Science Institute (PSI) did something new with it.
SHARAD was included on the MRO to complement the MARSIS radar on the Mars Express orbiter. MARSIS can bounce its radar waves deeper into the planet, but SHARAD has a much higher resolution. And with clever data processing, the PSI team boosted the effective resolution. The team processed years of 2D scans from SHARAD using advanced 3D imaging methods to remove noise and interference. The result is a sharper 3D image of the planetary structures below the layers of frozen carbon dioxide. This 3D “radargram” makes it possible to identify things that are difficult or impossible to see otherwise.
The study has been published in the Planetary Science Journal. The image above is a composite, showing a single horizontal slice through the northern polar ice cap (known as Planum Boreum) at the bottom. The other sections are vertical slices. The dark areas near the middle is a 300-kilometer region that MRO cannot see from its orbit. The data reveals surface details like the chasm to the right and the impact crater at the bottom of the horizontal slice.
The team believes this same technique could be used to create 3D representations of structures in other regions of the planet. Next, they plan to scour the Planum Boreum data for more buried impact craters and structures.
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