Indians shatter moon myth - Chandrayaan images show volcanism during ‘tranquil’ period

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Indians shatter moon myth - Chandrayaan images show volcanism during 'tranquil' period

G.S. MUDUR

Images of the Tycho crater, the central peak, and the signatures of volcanism on the central peak of the crater. Credit: Prakash Chauhan, Space Applications Centre, Ahmedabad. New Delhi, April 15: Images of a giant crater on the moon's southern highlands have challenged a long-held assumption that the moon has been geologically tranquil for the past 110 million years, Indian space scientists have said. The scientists said the images from India's Chandrayaan-1 spacecraft — relayed before its loss — and a US lunar orbiter have revealed signatures of volcanism during a period when the moon had been assumed to be geologically silent. Space geologists have believed for decades that the last lunar geological activity had occurred about 110 million years ago when an asteroid slammed into the moon and carved out the 90km-wide Tycho crater. But scientists from the Space Applications Centre and the Physical Research Laboratory in Ahmedabad have observed dry lava ponds, lava channels and volcanic vents in the central peak of the Tycho crater. The researchers, who have published their findings last week in the journal Current Science, said their results indicate volcanism long after the crater's formation. "These images may change our view about the geological history of the moon," said Prakash Chauhan, a senior geophysicist at the Space Applications Centre and a member of the team that analysed the images from the two spacecraft. Lunar geologists have suspected since the early 1970s that multiple volcanic eruptions may have marked the formation of the Tycho crater and another, smaller lunar crater named Aristarchus. Tycho is a vast circular valley carved on the lunar surface with a depth of 4km and a central peak region that rises up to 2km. While earlier images of the central peak, captured since the earliest lunar missions, had shown its volcanic features, the new images from Chandrayaan-1 and the US Lunar Reconnaissance Orbiter are the sharpest pictures yet. The images have also revealed several large boulders, including one about 100m in size perched nearly on the summit zone of the central peak. "This is a surprise. We'll have to think about geological mechanisms that might explain how the boulder the size of a jumbo jet is sitting on top of the summit," Chauhan said. This study also provides new data on the mineral make-up of the central peak region, said Jitendra Nath Goswami, the Physical Research Laboratory director. The central peak is dominated by relatively heavy, iron-rich lava-associated minerals that may have oozed out of the lunar interior as lava during volcanic activity. In contrast, the floor of the Tycho crater has more of surface-associated minerals. Scientists hope to learn more about the moon's inner crust through observations of young craters. "Tycho fits this bill nicely," Goswami said. "But, at this point, we are still arguing for possibilities consistent with volcanism in Tycho's central hill." The researchers believe the impact that gave rise to Tycho may itself have activated solidified magma below the surface that led to the volcanic activity. However, similar studies of craters elsewhere on the moon would be needed to draw inferences for other areas of the moon, Goswami told The Telegraph. Planetary geologists believe a planet-sized body had collided with the Earth about 4.5 billion years ago, ejecting enormous material that accreted to form the moon. According to current theory, while the infant moon was covered by an ocean of molten rock, its small size led to the quick cooling of its interior, and lunar volcanism ended within a billion years after its formation. Two years ago, US scientists had used data from the Lunar Reconnaissance Orbiter that they said reveals relatively recent tectonic activity and associated contraction of the lunar interior. The orbiter data suggests that some cliffs in the lunar crust formed less than a billion years ago, and some could be as young as 100 million years old, a news release from the US National Aeronautics and Space Administration had said.