Scientists’ hopes of finding liquid water deposits on Mars were dealt a blow this month by a new study that was published in the Nature Astronomy journal.
A team of researchers led by Cornell University astronomer Dan Lalich postulated that a strong reflection spotted by ESA’s Mars Express spacecraft under the Martian South Pole Layered Deposit (SPLD) may not be a liquid water reservoir as some scientists previously speculated.
“On Earth, reflections that bright are often an indication of liquid water, even buried lakes like Lake Vostok,” Lalich remarked. “But on Mars, the prevailing opinion was that it should be too cold for similar lakes to form.”
Through performing a number of computer simulations, the team concluded that interference between geological layers, with no water involved, can produce bright reflections.
Specifically, Lalich and his colleagues ran simulations that established that two layers of carbon dioxide separated by a layer of dusty ice gave off a reflection as bright as the one detected by the ESA mission.
“I used CO2 layers embedded within the water ice because we know it already exists in large quantities near the surface of the ice cap,” Lalich explained. “In principle, though, I could have used rock layers or even particularly dusty water ice and I would have gotten similar results. The point of this paper is really that the composition of the basal layers is less important than the layer thicknesses and separations.”
He did point out, however, that their findings do not disprove “the possible existence of liquid water down there.”
“We just think the interference hypothesis is more consistent with other observations,” Lalich said. “I’m not sure anything short of a drill could prove either side of this debate definitively right or wrong.”