October 23, 2013
Impact Crater On Mars Could Actually Be Supervolcano
Lawrence LeBlond for redOrbit.com - Your Universe Online
In a first-of-its-kind discovery, scientists from NASA and the Planetary Science Institute in Tucson, Arizona have identified what could be a supervolcano on a planet, other than Earth, in our Solar System.
The supervolcano in question was discovered on Mars and was previously classified as an impact crater. But after further analysis of the area, scientists believe the basin is actually the remnant landscape of an ancient volcanic eruption. The team’s assessment is based on images and topographical data from NASA’s Mars Odyssey, Mars Global Surveyor and Mars Reconnaissance Orbiter, as well as the ESA’s Mars Express orbiter.
The duo said the basin, recently named Eden Patera, is not an impact crater as previously suggested, but is a volcanic caldera. Because a caldera is a depression, it can look like a crater formed by an impact, rather than a typical volcano, which is usually mountainous.
"On Mars, young volcanoes have a very distinctive appearance that allows us to identify them," said Michalski. "The long-standing question has been what ancient volcanoes on Mars look like. Perhaps they look like this one."
The team also suggest a large body of magma loaded with dissolved gas rose through the thin crust to the surface rapidly. Likening the event to that of a shaken bottle of carbonated soda, the supervolcano would have blown its contents over a wide area if the top suddenly popped off.
"This highly explosive type of eruption is a game-changer, spewing many times more ash and other material than typical, younger Martian volcanoes," said Bleacher. "During these types of eruptions on Earth, the debris may spread so far through the atmosphere and remain so long that it alters the global temperature for years."
They researchers explained that once the material is expelled from the eruption, the depression can collapse even more, causing the ground around it to sink as well. Similar events to this one occurred on Earth in the distant past in Yellowstone National Park in the US, Lake Toba in Indonesia and Lake Taupo in New Zealand.
As for the Red Planet, the region where Michalski and Bleacher are investigating, known as Arabia Terra, is known for its heavily eroded terrain and numerous impact craters. But Michalski noted that Eden Patera was different from other depressions in the region, pointing out that it did not have the typical raised rim seen in other impact craters. He said he also could not find a nearby blanket of “ejecta” – melted rock that splashes outside the crater after an impact is made.
The absences of such evidence led Michalski to suspect volcanic activity. With this evidence in hand, he contacted Bleacher, a volcano expert, who identified the features at Eden Patera as being volcanic in nature.
Bleacher said that a series of rock ledges within the crater looked like “bathtub rings” that were left after a lava lake slowly drained back into the caldera below. He also found faults and valleys outside the area of the caldera that are associated with ground collapse due to activity below the surface. These and other features convinced the team that this depressions should be reclassified as a supervolcanic caldera.
As well as Eden Patera, the team found a few other depressions in the region that should also be reclassified. The team also believe a supervolcano at Eden Patera could have been responsible for volcanic deposits seen elsewhere on Mars that have never been linked to a known volcano.
"If just a handful of volcanoes like these were once active, they could have had a major impact on the evolution of Mars," Bleacher said.