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A mysterious Martian mineral that has puzzled scientists since its discovery seven years ago may have been ejected in an unusual volcanic eruption, researchers have revealed.This mineral, usually found only in Earthlikely formed on the Red Planet more than 3 billion years ago.
NASA’s curiosity The rover discovered the mineral on July 30, 2015, in a rock at the center of the 96-mile-wide (154-kilometer) Gale Crater. The rover drilled a small hole in the rock and extracted a silver dust sample.Curiosity on board X-ray The Diffraction Lab analyzed the dust and detected tridymite — a rare type of quartz made entirely of silica, or silica, formed by certain types of volcanic activity.
This unusual finding was completely unexpected. “The discovery of scaly quartz in Gale Crater is one of the most surprising observations made by the Curiosity rover in its 10-year exploration of Mars,” said study co-author, a planetary scientist at Rice University in Houston and NASA Kirsten Siebach, the bureau’s mission specialist, Curiosity Team, said in a statement (opens in new tab).
Lead study author Valerie Perret, a planetary scientist at Northern Arizona University and Rice University, told Live Science in an email that the scalyte discovery surprised researchers for two main reasons. First, volcanism on Mars was previously thought to be unsuitable for the production of silica-rich minerals such as tridymite. Second, scientists believe Gale Crater was once an ancient lake with no visible volcanoes nearby, leaving scientists scratching their heads when trying to figure out how the mineral fell to the lake bottom, Payré said.
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In the new study, the researchers propose an explanation that may finally solve the mystery.Researchers suspect unknown explosive eruption volcano Fires scaly quartz-rich ash into the Martian sky and falls into the ancient lakes of Gale Crater.
When the ash falls into the water, it breaks down into its various parts through a combination of physical and chemical processes. The researchers believe this is why the tridymite samples were so pure and uncontaminated by ash. “If the ashes were stored directly where we found [without water]we expect a thick layer of volcanic ash, Payré said.
A similar situation has been observed in only one place on Earth – Lake Tecocomulco in Mexico, where tridymite is found in volcanic rocks rising from the lake floor.
If the striated quartz-rich ash did fall into Gale Crater when it was a lake, the eruption likely occurred 3 billion to 3.5 billion years ago, when researchers suspect the crater was filled with water. “The explosive eruption must have happened within that time frame,” Perey said. However, recent research suggests that Gale Crater may have remained a lake a billion years ago, according to the researchers’ statement.
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Researchers are still unsure of the location on the Red Planet of the volcano that produced the scaly quartz samples. It could have come from a small eruption nearby, or a massive explosion further afield, Perey said. It is difficult to find past volcanoes on Mars because it is difficult to distinguish between impact craters and craters that have eroded over billions of years, she added.
The researchers also had to explain how striated quartz formed on Mars, whose conditions are thought to be very different from those on Earth.
Typically, tridymite forms in extremely high temperatures and silica-rich volcanic environments commonly found on Earth, Payré said. However, previous evidence from Mars suggests that volcanic eruptions on the red planet are basaltic, meaning they have significantly lower levels of silica.This is because Mars does not have tectonic platewhich is the main source of silica-rich eruptions on Earth, Payré added.
Further analysis of the tridymite found on Mars revealed that it is slightly different from the tridymite formed in Earth’s volcanoes. This suggests that the Martian version formed under slightly different conditions, Payré said.
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The researchers propose that the tridymite found in Gale Crater formed over a long period of time in a magma chamber beneath the unknown volcano.This temperature According to the study, the temperature in the chamber may be slightly lower than the conditions on Earth for the volcanoes that form tridymite, but the team believes that this may have allowed the mineral to form slowly as additional silica was present.
Similar mineral formation pathways have been observed on Earth, and this scenario represents “the direct evolution of other volcanic rocks that we find in craters,” Seebach said.
Although less silica is needed to form tridite on Mars than on Earth, the researchers note that the volcanoes where samples were found in Gale Crater may have higher levels of silica than past evidence suggests.
“This work suggests that Mars’ volcanic history may be more complex and interesting than we thought before Curiosity,” Seebach said.
Perey said future discoveries by Curiosity and its successor, the Perseverance rover, and the Martian rocks brought back to Earth by NASA’s proposed Mars sample return mission, could help to learn more about Mars’ ancient volcanic history.
The study will be published in the September 15 issue of the journal Earth and Planetary Science Letters (opens in new tab).
Originally published on Live Science.