Mounds of ice in craters give new insight into Mars' past climate
Honing the ways Mars' orbit and orientation impacted climate over time
can help scientists find periods of potential habitability
Date:
March 29, 2022
Source:
American Geophysical Union
Summary:
Newly discovered deposits of layered ice in craters scattered
around Mars' southern hemisphere provide insights into how the
planet's orientation controlled the planet's climate over the
past 4 million years, according to a new study. The findings help
scientists understand what controlled Mars' past climate, which is
essential for predicting when the planet could have been habitable.
FULL STORY ========================================================================== Newly discovered deposits of layered ice in craters scattered around Mars' southern hemisphere provide insights into how the planet's orientation controlled the planet's climate over the past 4 million years, according
to a new study. The findings help scientists understand what controlled
Mars' past climate, which is essential for predicting when the planet
could have been habitable.
==========================================================================
The study was published in the AGU journal Geophysical Research Letters,
which publishes short-format, high-impact research with implications
spanning the Earth and space sciences.
Ice deposits on Mars reflect a combination of temperature, hydrology and planetary dynamics, as they do on Earth. The planet's tilt and orbit
impact temperature and sunlight on the surface, which contribute to
climate. Thicker, more pure ice layers generally reflect cold periods
with more ice accumulation, while thin, dusty layers were likely warmer
and less able to build up ice.
The new study matches these ice layers to the tilt of Mars' axis and its orbital precession, or how the planet's elliptical orbit rotates around
the sun over time, with unprecedented resolution and confidence.
The findings give scientists insight into how Mars' climate has changed
over time. While the study is limited to the recent past, establishing
these climate-orbit relationships helps scientists understand Martian
climate deeper in the past, which could help pinpoint periods of potential habitability.
"It was unexpected how cleanly those patterns matched to the orbital
cycles," said lead study author Michael Sori, a planetary scientist at
Purdue University. "It was just such a perfect match, as good as you
can ask for." From caps to craters
========================================================================== Previously, Martian climate scientists have focused on polar ice caps,
which span hundreds of kilometers. But these deposits are old and may
have lost ice over time, losing fine details that are necessary to
confidently establish connections between the planet's orientation and
motion and its climate.
Sori and his colleagues turned to ice mounds in craters, just tens of kilometers wide but much fresher and potentially less complicated. After scouring much of the southern hemisphere, they pinpointed Burroughs
crater, 74 kilometers wide, that has "exceptionally well-preserved"
layers visible from NASA HiRISE imagery, Sori said.
The researchers analyzed the layers' thicknesses and shapes and found
they had strikingly similar patterns to two important Martian orbital
dynamics, the tilt of Mars' axis and orbital precession, over the last
4 to 5 million years.
The findings improve on previous research, which used Mars' polar ice
records of climate to establish tentative connections to orbit. But
those records were too "noisy," or complicated, to confidently connect
the two. Younger, cleaner crater ice preserves less complicated climate records, which the researchers used to match climate changes to orbital precession and tilt with a high level of precision.
Mars as a natural lab Discerning the connections between orbital cycles
and climate is important for understanding both Martian history and
complex climate dynamics on Earth. "Mars is a natural laboratory for
studying orbital controls on climate," Sori said, because many of the complicating factors that exist on Earth -- biology, tectonics -- are negligible on Mars. The whole planet, in essence, isolates the variable
for scientists.
==========================================================================
"If we're ever going to understand climate, we need to go to places that
don't have these interfering factors," said Isaac Smith, a planetary
scientist at the Planetary Science Institute and York University who
was not involved in the study. In that sense, "Mars is a pristine
planet. And there are a lot of potential applications here. Mars has
a lot more in common with Pluto and Triton than you think." Not all
smaller ice deposits have clean, exposed layers at their surface. Some
might be hidden inside the mounds. Eventually, Sori said, the goal is to
sample ice cores like scientists do on Earth, but Mars rovers don't have
that capability yet. Instead, scientists can use ground-penetrating radar
data to "peer inside" the ice and check for layers, making sure visible
layers extend throughout the deposit. It's a necessary quality-control
step in the present study, and the method may help future explorations
of Martian ice without layers visible at the surface.
"Being able to pull a climate signal from a small ice deposit is a
really cool result," said Riley McGlasson, a study co-author from Purdue University who applied this method in the new study. "With radar, we
can get closer to the full story. That's why I'm excited to take this
a step further in the future."
========================================================================== Story Source: Materials provided by American_Geophysical_Union. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Michael M. Sori, Patricio Becerra, Jonathan Bapst, Shane Byrne,
Riley A.
McGlasson. Orbital Forcing of Martian Climate Revealed in a South
Polar Outlier Ice Deposit. Geophysical Research Letters, 2022; 49
(6) DOI: 10.1029/2021GL097450 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220329142530.htm
--- up 4 weeks, 1 day, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)