During crew planning missions to Mars, the key phrase is “follow the water”. When astronauts land on the Red Planet over the next decade, they will need access to water to meet their basic needs.
Tracking the water is also crucial to our continued exploration of Mars and learning more about its past. While all the water on the surface of Mars exists today as ice (the majority locked in the polar ice caps), rivers, lakes and an ocean are now known to have covered much of the planet there. billions of years ago.
Figuring out where that water went is key to understanding how Mars underwent its historic transformation to become the cold, dry place it is today.
Almost 20 years ago, ESA Mars-Express The orbiter made a huge discovery when it detected what appeared to be a massive deposit of water ice beneath the south polar region. However, recent findings by a team of researchers from Cornell University indicate that radar reflections from the South Pole Layered Deposit (SPLD) may be the result of geological stratification.
The research was led by Daniel Lalich, a research associate at the Cornell Center for Astrophysics and Space Science (CCASS). The article describing their findings, titled Explain the bright radar reflections under the south pole of Mars without liquid waterwas published on September 26 in Natural astronomy.
Mysterious layers
In 2004, the Mars Express orbiter detected the SPLD using the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS). While many astronomers have concluded that the radar reflection was the result of relatively pure water ice formation 1.4 kilometers (0.89 miles) thick, there has been ongoing debate ever since as to know if the SPLD is water ice or something else.
For the purposes of their study, Lalich and his colleagues ran computer simulations on the MARSIS data to investigate what could have caused the strong radar reflections.
As they explained in their paper, radar reflections like this are the result of liquid water on Earth, as indicated by buried lakes like Lake Vostok, located beneath the East Antarctic Ice Sheet. But on Mars, the prevailing view was that conditions are too cold for similar lakes to form.
To investigate this, Lalich and his colleagues used a one-dimensional modeling procedure commonly used to interpret MARSIS observations. It involved simulating layers made up of four materials (atmosphere, water ice, carbon dioxide [CO2] ice and basalt) and assigning each layer a corresponding permittivity.
This describes the interaction between a material and how electromagnetic radiation passes through it instead of being reflected off it. In the end, they found that simulations using three layers (two layers of CO2 ice separated by a layer of dusty ice) produced reflections as bright as the MARSIS observations.
This effectively showed that geologic layers could explain SPLD readings without the presence of water or other rare materials. As Lalich explained in a recent Cornell Chronicle Press release :
“I used layers of CO2 embedded in water ice because we know it already exists in large quantities near the surface of the ice sheet. In principle, however, I could have used layers of rock or even particularly dusty water ice, and I would have gotten similar results.The point of this article is really that the composition of the basal layers is less important than the thicknesses and separations of the layers.
No need for H2O?
From their modeling, the team also determined that layer thickness and spacing have a greater impact on reflectance than their respective composition. Although this does not necessarily mean that there is no liquid water under the Martian south pole, the results indicate that MARSIS readings can be reproduced without water.
This builds on research conducted in 2021 (to which Lalich contributed) which showed that under the right conditions, a class of minerals common to Mars (smectite) could produce a reflection similar to what was observed by MARSIS.
Given its importance for future missions and for understanding the evolution of Mars, it’s vitally important for scientists to figure out where water is on Mars (and where it isn’t). The presence of liquid water under the polar cap could also have important implications for its age, the internal heating of Mars and the evolution of the planet’s climate during recent geological periods.
The same goes for the many other suspicious underground lakes detected in recent years. As Lalich pointed out, he and his colleagues still do not rule out the possibility of liquid water:
“If there is liquid water, maybe there is life, or maybe we could use it for future human missions to Mars. None of the work we have done disproves the possible existence of liquid water there. We just think the interference hypothesis is more consistent with other observations. I’m not sure anything short of an exercise can prove either side of this debate definitively right or wrong.
This article was originally published on Universe today by Matt Williams. Read the original article here.
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