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
