Martian Underground Lakes: Remnants of an Ancient Ocean
Discovery and Confirmation of Underground Lakes
In 2018, scientists made a groundbreaking discovery: a lake hidden beneath the icy surface of Mars’ south pole. This revelation sparked a flurry of questions about its formation and the accuracy of the measurements. A recent study published in Nature Astronomy not only confirms the existence of this lake but also reveals the presence of three additional, smaller water bodies nearby.
The research team conducted extensive radar measurements of the region, adding 100 new data points to their original 29. These measurements paint a clearer picture of the four lakes, which lie a mile below the Martian surface. They are believed to contain salt and sediments, which allow them to remain liquid even in the frigid temperatures of Mars’ south pole.
Implications for Mars’ Past and Present
The discovery of these underground lakes has significant implications for our understanding of Mars’ past and present. The presence of multiple water features at the south pole suggests that they may be the remnants of the planet’s ancient oceans. Erosion patterns on the Martian surface indicate that water once flowed freely across the planet. Observations from the Curiosity rover support the theory that Mars was once covered by a vast ocean.
As the Martian climate cooled, this ocean would have frozen and eventually sublimed away, evaporating from solid ice into water vapor without melting. The water vapor would have traveled in the atmosphere and condensed at the poles, forming vast ice caps. Geothermal energy would have melted the underside of these ice caps, creating groundwater or permafrost. If this water is salty enough, it could persist in the lakes observed today.
Water Characteristics and Habitability
Water needs to be extremely briny to remain liquid at Mars’ south pole, where temperatures can plunge to negative 195 degrees Fahrenheit. Salts and sediments prevent water from freezing by interfering with the alignment of water molecules, which inhibits crystallization.
However, the salts found in Martian water, known as perchlorates, are not suitable for human consumption. The strongest Earth fungus can survive in water with up to 23% sodium perchlorate, while the hardiest bacterium can only tolerate a 12% solution. For water to remain liquid at Mars’ extreme temperatures, it would require a different type of salt, calcium perchlorate, which is even more toxic to Earth microbes.
Earth has its own briny lakes hidden beneath Antarctic ice, but they do not support abundant life. “There’s not much active life in these briny pools in Antarctica,” explains John Priscu, an environmental scientist at Montana State University. “They’re just pickled. And that might be the case [on Mars].”
Research Techniques and Controversies
The research team used the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) to detect the underground lakes. MARSIS shoots radio waves at the Martian surface, which reflect back when they encounter changes in the planet’s makeup. Analyzing the reflection patterns reveals the nature of the material the waves bounced off of.
Some scientists remain skeptical of the study’s conclusions, arguing that the reflective patches could represent slush or sludge rather than liquid water. Additionally, there are discrepancies between the MARSIS observations and measurements from other datasets.
Future Exploration and Perspectives
A Chinese mission called Tianwen-1 is scheduled to orbit Mars in February 2021. This mission may provide a fresh perspective on the observations and shed light on the nature of the underground lakes.
“I’m convinced something funky is going on at this site to cause a spike in the reflection,” says Ali Bramson, a planetary scientist at Purdue University. “Certainly if there is some weird, super-cooled, sludgy salt solution at the base of the polar cap, that’s super cool.”
The discovery of underground lakes on Mars has opened up new avenues for scientific inquiry and speculation. These lakes may hold clues to the planet’s ancient oceans and the potential for past or present life on Mars. Further research and exploration will be crucial in unraveling the mysteries that surround these intriguing water bodies.
