Lakes of liquid water at Mars’ southern ice cap may be mirages

Perhaps maintain off on that Martian ice fishing journey. Two new research splash chilly water on the concept that doubtlessly liveable lakes of liquid water exist deep underneath the Crimson Planet’s southern polar ice cap.

The potential for a lake roughly 20 kilometers throughout was first raised in 2018, when the European House Company’s Mars Specific spacecraft probed the planet’s southern polar cap with its Mars Superior Radar for Subsurface and Ionosphere Sounding, or MARSIS, instrument. The orbiter detected brilliant spots on radar measurements, hinting at a big physique of liquid water beneath 1.5 kilometers of strong ice that might be an abode to dwelling organisms (SN: 7/25/18). Subsequent work discovered hints of extra swimming pools surrounding the primary lake basin (SN: 9/28/20).

However the planetary science neighborhood has all the time held some skepticism over the lakes’ existence, which might require some type of steady geothermal heating to keep up subglacial circumstances (SN: 2/19/19). Under the ice, temperatures common –68° Celsius, far previous the freezing level of water, even when the lakes are a brine containing a wholesome quantity of salt, which lowers water’s freezing level. An underground magma pool can be wanted to maintain the realm liquid — an unlikely situation given Mars’ lack of present-day volcanism.

“If it’s not liquid water, is there one thing else that would clarify the brilliant radar reflections we’re seeing?” asks planetary scientist Carver Bierson of Arizona State College in Tempe.

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In a examine printed within the July 16 Geophysical Analysis Letters, Bierson and colleagues describe a pair different substances that would clarify the reflections. Radar’s reflectivity is dependent upon {the electrical} conductivity of the fabric the radar sign strikes by means of. Liquid water has a reasonably distinctive radar signature, however analyzing {the electrical} properties of each clay minerals and frozen brine revealed these supplies may mimic this sign.

Including weight to the non-lake rationalization is a examine from an unbiased staff, printed in the identical problem of Geophysical Analysis Letters. The preliminary 2018 watery findings have been based mostly on MARSIS knowledge centered on a small part of the southern ice cap, however the instrument has now constructed up three-dimensional maps of all the south pole, the place lots of to 1000’s of extra brilliant spots seem.

“We discover them actually all around the area,” says planetary scientist Aditya Khuller, additionally of Arizona State College. “These signatures aren’t distinctive. We see them in locations the place we anticipate it to be actually chilly.”

Creating believable eventualities to keep up liquid water in all of those places can be a troublesome train. Each Khuller and Bierson suppose it’s way more doubtless that MARSIS is pointing to some type of widespread geophysical course of that created minerals or frozen brines.

Whereas earlier work had already raised doubts concerning the lake interpretation, these extra knowledge factors may signify the swimming pools’ demise knell. “Placing these two papers along with the opposite present literature, I’d say this places us at 85 p.c confidence that this isn’t a lake,” says Edgard Rivera-Valentín, a planetary scientist on the Lunar and Planetary Institute in Houston who was not concerned in both examine.

The lakes, in the event that they do exist, would doubtless be extraordinarily chilly and comprise as a lot as 50 p.c salt — circumstances during which no recognized organisms on Earth can survive. On condition that, the swimming pools wouldn’t make notably robust astrobiological targets anyway, Rivera-Valentín says. (SN: 5/11/20).

Lab work exploring how substances react to circumstances at Mars’ southern polar ice cap may assist additional constrain what generates the brilliant radar spots, Bierson says.

Within the meantime, Khuller already has his eye on different areas of potential habitability on the Crimson Planet, akin to hotter midlatitude areas the place satellites have seen proof of ice melting within the solar. “I feel there are locations the place liquid water might be on Mars in the present day,” he says. “However I don’t suppose it’s on the south pole.” 

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