Hexbyte Glen Cove 'Lakes' under Mars' south pole: A muddy picture? thumbnail

Hexbyte Glen Cove ‘Lakes’ under Mars’ south pole: A muddy picture?

Hexbyte Glen Cove

The bright white region of this image shows the icy cap that covers Mars’ south pole, composed of frozen water and frozen carbon dioxide. Credit: ESA/DLR/FU Berlin/Bill Dunford

Two research teams, using data from the European Space Agency’s Mars Express orbiter, have recently published results suggesting that what were thought to be subsurface lakes on Mars may not really be lakes at all.

In 2018, scientists working with data from the Mars Express orbiter announced a surprising discovery: Signals from a reflected off the red planet’s south pole appeared to reveal a liquid subsurface lake. Several more such reflections have been announced since then.

In a new paper published in the American Geophysical Union’s Geophysical Research Letters, lead author and graduate student Aditya Khuller of Arizona State University’s School of Earth and Space Exploration with Jeffrey Plaut of NASA’s Jet Propulsion Laboratory (JPL), describe finding dozens of similar radar reflections around the south pole after analyzing a broader set of Mars Express data. But many are in areas that should be too cold for to remain liquid.

The question of whether the signals are or not is also being considered by a team of scientists led by ASU School of Earth and Space Exploration postdoctoral scholar Carver Bierson. Their research was also recently published in AGU’s Geophysical Research Letters and determined that these bright reflections might be caused by subsurface clays, metal-bearing minerals or saline ice.

Mars Express is the second-longest-surviving continually active spacecraft in orbit around a planet other than Earth, behind only NASA’s still-active 2001 Mars Odyssey. As Mars Express orbits Mars, it continues to provide important data on the red planet’s subsurface, surface and atmosphere.

Onboard this spacecraft is an instrument called the Mars Advanced Radar for Subsurface and Ionosphere Sounding, or MARSIS for short. This instrument uses a radar sounder to assess the composition of the subsurface of Mars.

MARSIS has been collecting data around Mars since 2004, including the south pole, allowing scientists to build a three-dimensional view of the south polar region. “We wanted to look beneath the south polar ice and characterize the old terrain lying underneath using MARSIS data,” said Khuller.

In other recent studies using MARSIS data, researchers have found areas where the reflections below the surface are brighter than that of the surface, which is not what scientists would expect.

“Usually, radar waves lose energy when they travel through a material, so reflections from deeper down should be less bright than those from the surface,” said Khuller, who is concurrently on an internship at JPL under Plaut’s direction. “Although there are a few possible reasons for unusually bright subsurface reflections, these two studies concluded that a liquid water component was the cause of these bright reflections, because liquid water appears bright to radar.”

The colored dots represent sites where bright radar reflections have been spotted by ESA’s Mars Express orbiter at Mars’ south polar cap. Credit: ESA/NASA/JPL-Caltech

Frozen time capsule

The radar signals originally interpreted as liquid water were found in a region of Mars known as the South Polar Layered Deposits, named for the alternating layers of water ice, dry ice (frozen carbon dioxide) and dust that have settled there over millions of years. These layers are believed to hold a record of how the tilt in Mars’ axis has shifted over time, just as changes in Earth’s tilt have created ice ages and warmer periods throughout our planet’s history. When Mars had a lower axial tilt, snowfall and layers of dust accumulated in the region and eventually formed the thick layered ice sheet found there today.

The areas originally hypothesized to contain liquid water span about 6 to 12 miles (10 to 20 kilometers) in a relatively small region of the Martian South Polar Layered Deposits. Khuller and Plaut expanded the search for similar strong radio signals to 44,000 measurements spread across 15 years of MARSIS data over the entirety of the Martian south .

Unexpected ‘lakes’: A muddy picture?

The new, expanded study from Khuller and Plaut revealed dozens of additional bright radar reflections over a far greater range of area and depth than ever before. In some places, they were less than a mile from the surface, where temperatures are estimated to be minus 81 degrees Fahrenheit (minus 63 degrees Celsius)—so cold that water would be frozen, even if it contained salty minerals known as perchlorates, which can lower the freezing point of water.

“We’re not certain whether these signals are liquid water or not, but they appear to be much more widespread than what the original paper found,” said co-author Plaut, who is also the co-principal investigator of the orbiter’s MARSIS instrument. “Either liquid water is common beneath Mars’ south pole, or these signals are indicative of something else.”

Additionally Khuller noted a 2019 paper in which researchers calculated the heat needed to melt subsurface ice in this region, finding that only recent volcanism under the surface could explain the potential presence of liquid water under the south pole.

“They found that it would take double the estimated Martian geothermal heat flow to keep this water liquid,” Khuller said. “One possible way to get this amount of heat is through volcanism. However, we haven’t really seen any strong evidence for recent volcanism at the south pole, so it seems unlikely that volcanic activity would allow subsurface liquid water to be present throughout this region.”

Khuller and Plaut’s next steps in this line of research are to investigate their discovery of a second, deeper layer under parts of the of Mars, which scientists think represents an older buried terrain called the Dorsa Argentea Formation. It is thought to have been modified by ancient glaciers once present across the region, and they intend on trying to more accurately determine its composition and age.



More information:
Aditya R. Khuller et al, Characteristics of the Basal Interface of the Martian South Polar Layered Deposits, Geophysical Research Letters (2021). DOI: 10.1029/2021GL093631

C. J. Bierson et al, Strong MARSIS Radar Reflections from the Base of Martian South Polar Cap may be due to Conductive Ice or Minerals, Geophysical Research Letters (2021). DOI: 10.1029/2021GL093880

Michael M. Sori et al, Water on Mars, With a Grain of Salt: Local Heat Anomalies Are Required for Basal Melting of Ice at the South Pole Today, Geophysical Research Letters (2019). DOI: 10.1029/2018GL080985

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‘Lakes’ under Mars’ south pole: A muddy picture? (2021, July 3)
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Hexbyte Glen Cove Great Lakes advocates hope new administration will take on climate change thumbnail

Hexbyte Glen Cove Great Lakes advocates hope new administration will take on climate change

Hexbyte Glen Cove

Credit: CC0 Public Domain

With the Earth on track to finish out another year among the warmest on record and the impact of climate change mounting around the globe, advocates around the Great Lakes are looking ahead to what a new administration could mean for the Midwest, the region containing one of the world’s largest freshwater sources.

Much is at stake when it comes to the Great Lakes region. Warming temperatures and more precipitation can mean more flooding. Shoreline protections are up against rising levels and million-dollar damage storms. Invasive species threaten to upend ecosystems and toxic algae blooms are intensifying. Human health is at risk if takes a hit.

And yet, Great Lakes advocates say there are reasons for hope.

“This is not shades of gray,” said Howard Learner, executive director of the Environmental Law and Policy Center. “After four years of the Trump administration seeking to roll back more than 100 environmental and public health safeguards, the Biden-Harris administration is a breath of fresh air for those of us who care about protecting the environment.”

One of the first signs of change is likely to come with the rejoining of the Paris climate accord, which aims to curb warming below 2 degrees Celsius from pre-industrial times, and ideally under 1.5 degrees Celsius—the threshold believed to stave off catastrophe.

Almost all countries have signed on to the agreement. The U.S. formally left the agreement this year after years of President Donald Trump criticizing the pact. President-elect Joe Biden pledged this month to rejoin on day one of his presidency.

Biden also pledged to convene world leaders for a climate summit in his first 100 days. The Biden campaign has said it will set a target of net zero emissions by 2050.

“We should never have left it in the first place,” said Don Wuebbles, a University of Illinois professor of atmospheric sciences who served as a White House science adviser, about the accord.

“I would never claim that it is a perfect agreement, but the reason I would say that is not what the existing administration says. I would say it’s because it doesn’t go far enough,” Wuebbles said. “The costs to our society are much greater from not doing something than it would be to tackle this and say, OK, as a society we have to deal with the fact that these energy and transportation-related emissions, yes, they might have some negative impacts on our economy in the short run. But in the long run, we can build a stronger economy because we’ve done something about it.”

As Biden’s climate team comes together, some also expect a shift among toward reemphasizing climate change.

That includes getting “back to basics” with staffing, budget and enforcement capacity at the Environmental Protection Agency, said Joel Brammeier, president and CEO of the Alliance for the Great Lakes.

Brammeier said he also hopes to see the administration prioritize investment in water infrastructure.

“Both Chicagoans and the communities around Chicago have some of the most outmoded, outdated, crumbling water infrastructure in the country,” Brammeier said. “So that needs to be fixed, it needs to be upgraded, it needs to be replaced. And cities, suburbs have varying abilities to do that on their own. Frankly, most of them don’t have the ability to do everything that’s needed on their own.”

Jim Angel, the state’s former climatologist, said the region could certainly benefit from more resources.

“For example, more investment in green infrastructure so we can handle these rainfall events that cause so much flooding and cause so much damage,” Angel said. “We can have structures that can reduce that flooding, as well as reduce the impacts on water quality.”

Advocates have their eye on the Great Lakes Restoration Initiative, a program from federal agencies that funds coastal restoration and cleanup projects. The Trump administration sought to cut funding by 90% and then the president later falsely claimed he was restoring funding for the program, which has generally had strong bipartisan support and was safeguarded by Congress.

Congress authorized the program for another five years, calling for annual funding to increase from $300 million to $475 million by 2026.

“When it comes to protecting the Great Lakes and protecting safe, clean drinking water, here in the Midwest, that’s not a partisan issue,” Learner said.

Now, the incoming administration can reaffirm its commitment to the initiative, Brammeier said. “I think this administration has a real opportunity to put its stamp on that through the lenses of environmental justice and climate change and make sure that it’s addressing the most urgent priorities for the Great Lakes across the region.”

Kristin Murphy, government affairs associate at Audubon Great Lakes, said the initiative is essential to protecting and restoring the Great Lakes.

“And that increased funding will be super crucial,” Murphy said. “It just means we can do more, including protecting habitat, protecting clean drinking water, controlling invasive species, among so many other things.”

Audubon Great Lakes is also looking to the Biden administration to help protect wildlife, especially with the Migratory Bird Treaty Act, threatened during the Trump administration.

“We’ve seen a huge loss of birds, not only in our region but across the United States,” Murphy said. “We know that they’re an indicator species for what’s happening to the environment, so if they’re in trouble, so are we.”

Funding for the Great Lakes Coastal Resiliency Study, headed by the U.S. Army Corps, is a wish list item. The study would search for vulnerable areas along Great Lakes’ coasts.

“And that’s of course top of mind for some communities right now because of the extreme water levels in the Great Lakes,” Brammeier said.

A report reevaluating Chicago’s shoreline could also come into play.

One long-term project likely to be watched closely is the cleanup of contaminated Superfund sites, some of which are susceptible to flooding.

“That’s not something that can be done by the on day one but we believe that it’s a matter of basic civil rights, that people should not have to live in communities with toxic threats,” Learner said. “And one challenge for the incoming will be to find ways to accelerate the cleanups of the old toxic sites that are located around the industrial Midwest.”

Regardless of what happens next with the national approach to climate change, there are already tangible effects, said Trent Ford, the state’s climatologist.

“It’s impactful environmentally, it’s impactful economically, it’s impactful through our health,” Ford said. “As far as being impactful to the Great Lakes region, climate change is impactful right now.”