April 26, 2014
Researchers Find New Evidence Of Water In A Martian Crater
April Flowers for redOrbit.com - Your Universe Online
Well preserved gullies and debris flow deposits in a crater on the southern hemisphere of Mars are providing new evidence through their geomorphological attributes that they were formed by the action of liquid water in relatively recent geological times, according to a new study from the University of Gothenburg.On Earth, water becomes a single-phase unit and a flow of debris is created when the sediment on a slope is saturated with water and becomes too heavy to remain in place. Such an event is called a debris flow. These flows often cause significant material destruction and sometimes human casualties if they occur in developed areas. As the debris flow moves rapidly down the slope, a mixture of stones, gravel, clay and water is picked up and taken along. Characteristic surface features, known as landforms, such as lobate deposits and paired levees form along flow channels when the sediment finally stops.
Andreas Johnsson of the Department of Earth Sciences, University of Gothenburg, and his team have identified such landforms on the surface of Mars. By the use of aerial photography and field study, the team has compared the landforms on Mars to known debris flows on Svalbard — a Norwegian archipelago in the Arctic Ocean that has the distinction of being the northernmost location on Earth with a permanent human population. Their findings, reported in the journal Icarus, provide evidence that liquid water has been present in the crater on Mars.
"Our fieldwork on Svalbard confirmed our interpretation of the Martian deposits. What surprised us was that the crater in which these debris flows have formed is so young," said Johnsson.
Johnsson's team was able to use crater statistics to place the age of the crater at approximately 200,000 years, which is long after the most recently proposed ice age on Mars — around 400,000 years ago.
"Gullies are common on Mars, but the ones which have been studied previously are older, and the sediments where they have formed are associated with the most recent ice age. Our study crater on Mars is far too young to have been influenced by the conditions that were prevalent then. This suggests that the meltwater-related processes that formed these deposits have been exceptionally effective also in more recent times," said Johnsson.
The crater in question is in the mid-latitudes of Mars' southern hemisphere. It is superposed on the rampart ejecta — a “flowerlike” form around the host crater believed to have been formed by an impact in wet or ice-rich ground — of a nearby, larger crater.
"My first thought was that the water that formed these debris flows had come from preserved ice within the rampart ejecta. But when we looked more closely, we didn't find any structures such as faults or fractures in the crater that could have acted as conduits for the meltwater. It is more likely that the water has come from melting snow packs, when the conditions were favorable for snow formation. This is possible, since the orbital axis of Mars was more tilted in the past than it is today," Johnsson added.