NASA reveals new maps of subsurface water ice on Mars

That’s why NASA has funded the Subsurface Water Ice Mapping (SWIM) project, which aims to locate the best places to access water ice buried under the Martian surface. SWIM has recently released its fourth set of maps, the most detailed and accurate ones since the project started in 2017.

SWIM is led by the Planetary Science Institute in Tucson, Arizona, and managed by NASA’s Jet Propulsion Laboratory in Southern California. The project uses data from several NASA missions, such as the Mars Reconnaissance Orbiter (MRO), the 2001 Mars Odyssey, and the defunct Mars Global Surveyor. By combining different data types, SWIM has identified the most promising regions to find Martian water ice that future missions could reach.

This image shows an impact crater that exposed water ice on Mars. It is one of the features that SWIM uses to map the locations of subsurface water ice on the planet. It is also part of the latest version of SWIM’s maps, which NASA funds. NASA/JPL-Caltech/University of Arizona SWIM has focused on the mid-latitudes of Mars, where instruments on these spacecraft have detected indications of large deposits of frozen water under the surface. The northern mid-latitudes are especially attractive because they have a thicker atmosphere than most other parts of Mars, which can help slow down a landing spacecraft. The ideal landing sites for astronauts would be at the southern edge of this area - close enough to the equator to have warmer temperatures but far enough north to have enough ice.

“If you send humans to Mars, you want to get them as close to the equator as you can,” said Sydney Do, JPL’s SWIM project manager. “The less energy you have to spend on keeping astronauts and their equipment warm, the more you have for other things they’ll need.”

Making a better map

The previous versions of SWIM’s map relied on lower-resolution cameras, radar, thermal mappers, and spectrometers, which can only suggest the presence and amount of buried ice but not confirm it. For this latest version, SWIM used two higher-resolution cameras on MRO. The Context Camera data was used to improve the maps of the Northern Hemisphere. For the first time, the HiRISE (High-Resolution Imaging Science Experiment) data was used to provide the most detailed view of the ice’s edge as close to the equator as possible.

SWIM also uses HiRISE to study fresh impact craters caused by meteoroids that may have dug up chunks of ice. Most of these craters are no more than 33 feet (10 meters) across, but in 2022, HiRISE spotted a 492-foot-wide (150-meter-wide) impact crater that revealed a considerable amount of ice that was hidden under the surface.

This artist’s concept shows NASA astronauts drilling into the Martian subsurface. NASA has created new maps that show where water ice is likely to be easily accessible to future explorers. NASA The new map also includes some other features that indicate the presence of subsurface water ice. One of them is called “polygon terrain,” where seasonal changes in temperature cause cracks in the ground that form polygonal shapes. These polygons can be seen around fresh impact craters filled with ice, suggesting that there is more ice under the surface at these locations.

SWIM’s co-lead at the Planetary Science Institute, Gareth Morgan, said that these impacts reveal locations where there is no doubt about ground ice. He added that these locations can be used to test whether their mapping methods are reliable.

Another mystery that SWIM wants to solve is why there is variation in the amount of water ice across different locations in the Martian mid-latitudes. Some regions have more ice than others, and there is no clear explanation. SWIM’s other co-lead at the Planetary Science Institute, Nathaniel Putzig, said their latest map could help them develop new hypotheses for this phenomenon. He also said it could help them refine their models of how the ancient Martian climate changed, leaving more or less ice in different regions.

SWIM’s scientists hope that their project will pave the way for a proposed Mars Ice Mapper mission, which would be an orbiter with a powerful radar designed to search for near-surface ice beyond where HiRISE has confirmed it. This mission could provide more information about the distribution and depth of water ice on Mars and help future explorers plan their tasks.