Modern glacier remains found near Mars equator suggest water ice possibly present today at low latitudes

At the 54th Lunar and Planetary Science Conference in The Woodlands, Texas, researchers made a ground-breaking statement about the finding of a relict glacier close to Mars' equator. This discovery, which can be found in Eastern Noctis Labyrinthus at 7° 33' S and 93° 14' W, is important because it suggests that Mars once had surface water ice, even close to the equator. This finding suggests the chance that ice may still be present in the region at shallow levels, which could have important repercussions for upcoming human research.

There are numerous light-toned deposits (LTDs) in the area, one of which is the surface structure referred to as a "relict glacier". Although LTDs typically contain mostly light-colored sulfate ions, this deposit also exhibits many characteristics of a glacier, such as crevasse areas and moraine bands. The glacier is thought to be 6 kilometers long, up to 4 kilometers broad, and to have a height of +1.3 to +1.7 kilometers above sea level. This finding raises the possibility that Mars' recent past was wetter than previously believed, which could have consequences for comprehending the planet's habitability.

What we have discovered is a salt accumulation with intricate glacier-like morphology, not ice. According to Dr. Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute and the study's main author, "What we believe occurred here is that salt developed on top of a glacier while retaining the structure of the ice below, down to features like crevasse fields and moraine bands.

A glacier's impression beneath the sulfate salts may have developed and been kept by the volcanic materials that cover the area. Sulfate salts similar to those that typically make up Mars's light-toned deposits may form when newly released pyroclastic materials (combinations of volcanic ash, pumice, and hot lava blocks) come into contact with water ice and eventually solidify into a crusty salt coating.

There has previously been volcano action in this area of Mars. And where some of the volcanic materials came in contact with glacier ice, chemical reactions would have taken place at the boundary between the two to form a hardened layer of sulfate salts," explains Sourabh Shubham, a graduate student at the University of Maryland's Department of Geology, and a co-author of the study. The hydrated and hydroxylated sulfates that we detect in this light-toned deposit have this as their most probable cause.

This would explain how a salt deposit is now visible, showing characteristics specific to glaciers like crevasses and moraine bands. Over time, as weathering removed the blanketing volcanic materials, a crusty coating of sulfates reflecting the glacier ice beneath became revealed.

"Glaciers frequently display unique kinds of characteristics, such as thrust moraine bands and foliation, as well as marginal, splaying, and tic-tac-toe crevasse fields. In terms of shape, location, and size, the characteristics in this light-toned deposit are similar. It's really fascinating," said John Schutt, a geologist at the Mars Institute who has worked as an icefield guide in the Arctic and Antarctica and is also a co-author of this research.

The fine-scale characteristics of the glacier, the sulfate salts deposit that they are linked with, and the volcanic materials that are overlying them are all very sparsely cratered by impacts and must be geologically young. They are probably Amazonian in age, the most recent geologic epoch that encompasses contemporary Mars. "We have knowledge of glacial action on Mars at many places, including more recently close to the equator. Furthermore, recent glacier activity on Mars has been documented, though so far, only at higher altitudes. This location's comparatively new relict glacier informs us that Mars once had surface ice, even close to the equator, which is novel, said Lee.

It is unknown if water ice is still present beneath the light-toned layer or if it has completely vanished. At these altitudes close to the equator, water ice is currently unstable on Mars' very surface. We therefore shouldn't be surprised that we aren't finding any water crystals at the top. It's conceivable that the glacier's entire water ice has already melted away. However, there's also a possibility that some of it is still shielded at modest levels by sulfate salts.

The research compares the prehistoric glacier islands to the saline lakebeds, or salars, of the South American Altiplano. There, under layers of brilliant salts, ancient glacial ice has stayed untouched by melting, evaporation, and sublimation. To explain how sulfate salts on Mars might be able to provide protection to ice that would otherwise be susceptible to sublimation at low latitudes on the planet, Lee and his co-authors propose an analogous scenario.

There would be consequences for science and human travel if there were still water ice on Mars that had been maintained at shallow levels at a low latitude. "Mission managers have been considering higher latitude locations due to the wish to land people somewhere they might be able to extract water ice from the ground. But both people and robots find these latter settings to be generally colder and more difficult. We'd have the best of both worlds: warmer circumstances for human travel and still have access to ice if there were equatorial areas where it might be discovered at shallow depths," said Lee.

Lee points out that more research is necessary to establish whether and how much water ice may truly be present in this extinct glacier as well as whether other light-toned formations may also have had ice-rich substrates.

Provided by SETI Institute