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

Citation:
‘Lakes’ under Mars’ south pole: A muddy picture? (2021, July 3)
retrieved 4 July 2021
from https://phys.org/news/2021-07-lakes-mars-south-pole-muddy.html

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Hexbyte Glen Cove 'Nihao Mars': China's Zhurong rover touches down on Red Planet thumbnail

Hexbyte Glen Cove ‘Nihao Mars’: China’s Zhurong rover touches down on Red Planet

Hexbyte Glen Cove

Mars (seen in an image released on March 3, 2021 taken by China’s Tianwen-1 probe which carried the rover) is the the most prestigious of all prizes in the competition for dominion of space

China’s probe to Mars touched down on the Red Planet early Saturday to deploy its Zhurong rover, state media reported, a triumph for Beijing’s increasingly bold space ambitions and a history-making feat for a nation on its first-ever Martian mission.

The lander carrying Zhurong completed the treacherous descent through the Martian atmosphere using a parachute to navigate the “seven minutes of terror” as it is known, aiming for a vast northern lava plain known as the Utopia Planitia.

It “successfully landed in the pre-selected area”, state broadcaster CCTV said, launching a special TV programme dedicated to the mission called “Nihao Mars” (“Hello Mars”).

The official Xinhua news agency cited the China National Space Administration (CNSA) in confirming the touchdown.

It makes China the first country to carry out an orbiting, landing and roving operation during its first mission to Mars—a feat unmatched by the only other two nations to reach the Red Planet so far, the US and Russia.

President Xi Jinping sent his “warm congratulations and sincere greetings to all members who have participated in the Mars exploration mission”, Xinhua reported.

China has now sent astronauts into space, powered probes to the Moon and landed a rover on Mars, the most prestigious of all prizes in the competition for dominion of space.

Three-month mission

Zhurong, named after a Chinese mythical fire god, arrives a few months behind America’s latest probe to Mars—Perseverance—as the show of technological might between the two superpowers plays out beyond the bounds of Earth.

Six-wheeled, solar-powered and weighing roughly 240 kilograms (530 pounds), the Chinese rover is on a quest to collect and analyse rock samples from Mars’ surface.

The launch of China’s Tianwen-1 Mars probe which carried the rover last July marked a major milestone in China’s space programme.

The spacecraft entered Mars’ orbit in February and after a prolonged silence announced it had reached the “crucial touchdown stage” on Friday.

The landing was set to be a nail-biter for the China National Space Administration (CNSA), with state media describing the process of using a parachute to slow descent and buffer legs as “the most challenging part of the mission”.

It is expected to spend around three months there taking photos and harvesting geographical data.

The complicated landing process is called the “seven minutes of terror” because it happens faster than radio signals can reach Earth from Mars, meaning communications are limited.

“The distance was too far away that the spacecraft has to do it totally by itself,” said Chen Lan, an independent analyst specialising in China’s space programme. “If there was something wrong, people on the Earth have no way to help.”

Several US, Russian and European attempts to land rovers on Mars have failed in the past, most recently in 2016 with the crash-landing of the Schiaparelli joint Russian-European spacecraft.

The latest successful arrival came in February, when US space agency NASA landed its rover Perseverance, which has since been exploring the planet.

The US rover launched a small robotic helicopter on Mars which was the first-ever powered flight on another planet.

China has come a long way in its race to catch up with the United States and Russia, whose astronauts and cosmonauts have decades of experience in space exploration.

It successfully launched the first module of its new space station last month with hopes of having it crewed by 2022 and eventually sending humans to the Moon.

Last week a segment of the Chinese Long March 5B rocket disintegrated over the Indian Ocean in an uncontrolled landing back to Earth.

That drew criticism from the United States and other nations for a breach of etiquette governing the return of debris to Earth, with officials saying the remnants had the potential to endanger life and property.



© 2021 AFP

Citation:
‘Nihao Mars’: China’s Zhurong rover touches down on Red Planet (2021, May 15)
retrieved 15 May 2021
from https://phys.org/news/2021-05-nihao-mars-china-zhurong-rover.htm

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