Searching for martian life underground
It’s thought that Mars’ frozen layers are mostly composed of water ice. And if the ice melts where these layers meet the crust, then meltwater could form martian analogs of the subglacial lakes that exist beneath the Antarctic ice sheet on Earth.
So far, scientists have found more than 400 subglacial lakes in Antarctica. The largest is Lake Vostok, which is about the size of Lake Ontario and buried beneath more than 2 miles (3 km) of ice.
Some of these lakes are teeming with microorganisms that seem to be feeding on minerals in crushed rock. That suggests that if Mars had surface water in the past, and if life evolved there, then some martian microbes might still survive today in these liquid deposits.
“In Antarctica, there are bacteria everywhere — in the ice, on the surface of the [subglacial] lakes, and in the water of the lakes,” geophysicist Elena Pettinelli of Roma Tre University in Italy and author of the latest study tells Astronomy. “So that is the hope on Mars.”
She says there appear to be several underground bodies of water in Mars Ultimi Scopuli region, with the largest up to 12 miles (20 km) across. But it’s not known how deep the deposits are, or if they’re much more than liquid veins embedded in the ice.
How Mars lakes differ from Earth lakes
In any case, the water deposits are unlikely to be like the subglacial lakes on Earth. That’s because, to remain unfrozen at such extremely low temperatures, the martian lakes would have to be saturated with salts.
Critics, meanwhile, argue Mars is too cold for even hyper-saline brine — water with extremely high levels of dissolved salts — to stay liquid underground. To investigate, Pettinelli’s team studied how radar pulses were absorbed by the layers of ice and dust, which helped them model how heat flows from the planet’s interior through the frozen region.
Their research suggests that temperatures warmer than –100 degrees Fahrenheit (–73 Celsius) beneath the base of the frozen layers — the so-called basal ice — are a “reasonable assumption." And they calculate this location might be as warm as –45 F (–43 C), which would be warm enough for hyper-saline water to exist in liquid form.