In 2018, scientists processing data from the Mars Express spacecraft operated by the European Space Agency THAT announced a surprising discovery: responses from radar signals on board the probe reflected in the pole region of the red planet revealed groundwater lake dripping water. Several other similar echoes have been announced since then.
In a new article published in the journal Geophysical Research Letters, two scientists from NASA’s Jet Propulsion Laboratory in Southern California described the discovery of dozens of similar radar echoes in the South Pole region after analyzing a broader set of data from the Mars Express spacecraft. Many of them are areas that may be too cold for the water to remain in a liquid state.
„We are not sure whether these signals represent the presence of liquid water or not, but they seem to be much more widespread than was published in the original article., ”Says Jeffrey Plaut of JPL, deputy chief scientist for the device MARS (Mars Advanced Radar for Subsurface and Ionospheric Sounding), which was developed in collaboration with the Italian Space Agency and JPL. “Liquid water is common below the surface of the south pole region of Mars, or rather, these signals are a bit of a testament to that.“
Frozen time box
Author: ESA/NASA/JPL-Caltech
Radar signals originally interpreted as liquid water were discovered in the region of Mars known as “South Polar Layered Deposits”, named after alternating layers of water ice, dry ice (frozen carbon dioxide) and dust that settled there. over millions of years. These layers are supposed to provide records of how the inclination of Mars’ rotational axis has changed over time, just as the inclination of Earth’s rotational axis has changed and ice ages and warm periods alternate throughout our planet’s history. When Mars had a small inclination of the axis of rotation, invaded snow and layers of dust accumulated in the region and eventually formed a thick layer of ice sheet as we know it today.
When transmitting a beam of radio waves, scientists can penetrate under these ice layers and map them in detail. Radio waves lose energy as they pass through subsurface material; as they bounce back to the probe, they usually have a weaker signal. However, in some cases, the signals returning from these subsurface regions are stronger than those on the surface. Some scientists have interpreted these signals as confirming the presence of liquid water that strongly reflects radio waves.
Jeffrey Plaut and Aditya Khuller, a doctoral student at Arizona State University who worked on the article as internists at JPL, are not sure what these signals mean. The areas hypothetically contain liquid water in the range of about 10 to 20 kilometers in a relatively small area around the south pole of the planet Mars. Jeffrey Plaut and Aditya Khuller extended the search for similar strong radio signals to 44,000 measurements in MARSIS data spread over a period of 15 years over the entire region of the southern polar cap of Mars.
Unexpected “lakes”
Author: ESA/NASA/JPL-Caltech
Analyzes revealed dozens of additional clear radar echoes over a fairly large area and deeper than ever. In some places, they were less than 1.6 km below the surface, where temperatures are estimated to be around minus 63 ° C – so low that water should freeze if it was not contaminated with salt minerals known as perchlorates, which can lower the freezing point of water.
Aditya Khuller noted in a 2019 article in which astronomers calculated the heat needed to melt subsurface ice in the region and found that only recent subsurface volcanism could explain the potential presence of liquid water below the surface of the South Pole region.
„We found that this would require doubling the estimated geothermal heat of Mars flowing from the interior to retain liquid water, ”Says Aditya Khuller. “One way to obtain this heat is through volcanism. However, in reality we see no strong evidence for recent volcanism in the South Pole area, so it seems unlikely that volcanic activity would provide the conditions for the existence of subsurface liquid water throughout this area..“
What explains the clear echoes if they are not subsurface lakes of liquid water? The authors are not sure. However, their publication offers a detailed map of the region, which contains the key to Mars’ climatic history, including the role of water in its various forms.
Resources and recommended links:
[1] scitechdaily.com
Taken over: Valašské Meziříčí Observatory
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