Recent orbital and rover missions to Mars have turned up ample evidence of clays and other hydrated minerals formed when rocks are altered by the presence of water. Most of that alteration is thought to have happened during the earliest part of Martian history, more than 3.7 billion years ago. But a new study shows that later alteration -- within the last 2 billion years or so -- may be more common than many scientists had thought.
The research, by Brown University geologists Ralph Milliken and Vivian Sun, is in press in the Journal of Geophysical Research: Planets.
Ritchey Crater, located near the Martian equator, has impact melt deposits containing clay minerals. Impact melt forms when rock melted during an impact cools and hardens. The clay minerals found within these deposits are very likely to have formed after the impact event. Most clay minerals on Mars are thought to have formed during the earliest Martian epoch, known as the Noachian. However, evidence from Ritchey crater and other post-Noachian craters, suggests that clay formation after the Noachian was not uncommon.
Credit: NASA/JPL/University of Arizona/Brown University
The lion's share of the clay deposits found on Mars thus far have turned up in terrains that date back to the earliest Martian epoch, known as the Noachian period. Clays also tend to be found in and around large impact craters, where material from deep below the surface has been excavated. Scientists have generally assumed that the clays found at impact sites probably formed in the ancient Noachian, became buried over time, and then were brought back to the surface by the impact.
That assumption is particularly true of clay deposits found in crater central peaks. Central peaks are formed when, in the aftermath of an impact, rocks from within the crust rebound upward, bringing layers to the surface that had been buried many kilometers deep.
"Because central peaks contain rocks uplifted from depth, some previous studies have assumed the clays found within central peak regions are uplifted too," said Milliken, assistant professor of Earth, environmental and planetary sciences. "What we wanted to do was look at lots of these craters in detail to see if that's actually correct."
Milliken and Sun performed a survey of 633 crater central peaks distributed across the Martian surface. They looked at detailed mineralogy data collected by NASA's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), combined with high-resolution stereo images taken by NASA's HiRISE camera. Both instruments fly aboard NASA's Mars Reconnaissance Orbiter.
Of those 633 peaks, Milliken and Sun found 265 that have evidence of hydrated minerals, the majority of which were consistent with clays. The researchers then used HiRISE images to establish a detailed geologic context for each of those craters to help determine if the clays were in rocks that had indeed been excavated from depth. They found that in about 65 percent of cases the clay minerals were indeed associated with uplifted bedrock.
"That's a majority," Milliken said, "but it still leaves a substantial number of craters -- 35 percent -- where these minerals are present and not clearly associated with uplift."
Within those 35 percent, Milliken and Sun found examples where clays exist in dunes, unconsolidated soil, or other formations not associated with bedrock. In other cases, clays were found in impact melt -- deposits of rock that had been melted by the heat of the impact and then re-solidified as it cooled. Both of these scenarios suggest that the clay minerals at these sites are likely "authigenic," meaning they formed in place sometime after impact occurred, rather than being excavated from underground.
In a number of cases, these authigenic clays were found in fairly young craters, ones formed in the last 2 billion years or so.
"What this tells us is that the formation of clays isn't restricted to the most ancient time period on Mars," Milliken said. "You do apparently have a lot of local environments in these crater settings where you can still form clays, and it may have occurred more often than many people had thought."
One mechanism for forming these clays could be related to the impact process itself, the researchers say. Impacts generate heat, which could melt any ice or pre-existing hydrated minerals that may have been present within the nearby crust. Any liberated water could then percolate through surrounding rock to form clays. Some impact simulations suggest that these hydrothermal conditions could persist for perhaps thousands of years, making for potentially habitable conditions.
And that could have implications for the search for evidence of past life on Mars.
"So far, much of our surface exploration by rovers has focused on ancient terrains and whether or not the environments they record were habitable," said Sun, lead author on the study and a graduate student working with Milliken. "But if we wanted to look at an environment that was more recent, we've identified craters that might be possible candidates."
Kevin Stacey | EurekAlert!
New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton
New interactive map shows climate change everywhere in world
22.03.2018 | University of Cincinnati
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
22.03.2018 | Trade Fair News
22.03.2018 | Earth Sciences
22.03.2018 | Earth Sciences