“Liquid Water” Below Martian Surface Might Be Clay

A brand new research means that clays are a possible reason behind the brilliant radar reflections below the Martian south pole, which had been beforehand thought to point liquid water lakes dwelling deep beneath the floor.   

Previously, scientists used the MARSIS instrument aboard the ESA’s Mars Express Orbiter to find regions of high radar reflectivity coming from the subterranean boundary between deep layers of ice and mud, often known as the south pole layered deposits (SPLD), and Martian bedrock. Liquid water displays radar, however solely salty water may stay liquid within the chilly subsurface. Thus, the case for salty, underground lakes was born.

wavy features appear on the Martian surface indicate smectites
A spectral map taken with the CRISM instrument aboard NASA’s Mars Reconnaissance Orbiter superimposed on a picture of the SPLD edge. Smith’s workforce used CRISM information to determine what is probably going smectite clays surrounding the south pole. Certain colours on this map characterize the presence of smectites, which can clarify the beforehand discovered radar-reflective areas under the SPLD.

However, latest research (lined in this post) of extra radar-bright spots have forged doubt on the liquid water speculation. One of those research, led by Carver Bierson (University of Arizona), used simulations to point out that extremely conductive minerals, like hydrated clays, can mirror radar as a lot as a salty underground lake.

Now, analysis showing within the July Geophysical Research Letters, led by Isaac Smith (Planetary Science Institute), helps the clay principle. Smith’s workforce investigated a specific sort of clay referred to as a smectite, generally discovered on the Martian floor, to point out that these clays may certainly reproduce the MARSIS information with out the necessity for extra water.

Smectites are clay minerals that simply take up water. Smith’s workforce studied the properties of smectites in a laboratory setting below chilly situations (-46°F or -43°C) that mimic these within the Martian subsurface. When smectites are totally hydrated, they create a paste, which then freezes to a brittle state. The scientists discovered that this frozen paste may produce the radar signatures with out the presence of liquid water, salt, or further warmth.

white polar caps on top of the red martian surface, atop an image of smectite clays
Mars South Polar Layered Deposits (SPLD) and Martian Smectites: Top – the kilometers thick south polar ice cap. Bottom – radar measurements of smectite clays.
ESA / DRL / FU Berlin (high), NASA (backside)

Hydrated clays don’t indicate that liquid water at present exists on Mars, solely that it did at one level. Liquid water is assumed to have existed on the base of the SPLD greater than 100 million years in the past, and it may have hydrated floor smectites earlier than layers of ice and mud lined the clays. These layers would have preserved the hydrated state. Since Smith’s workforce found smectites across the south pole, it’s solely logical that they exist under the SPLD as effectively.

Bierson says that his and Smith’s collaboration make comparable arguments, albeit from totally different angles, and he’s excited to see these new outcomes. But, he provides, “this doesn’t rule out other candidates like saline ice or other clays.”

Future research will check whether or not supplies aside from smectite have the fitting properties to breed the Martian radar reflections. Indeed, different research at present below overview counsel that nothing aside from the layers of the SPLD itself is required to mirror radar (preprint accessible here). Whatever the case, one thing geologically attention-grabbing is happening beneath the Martian south pole, and solely time – and science – will uncover its nature.


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