<p>A giant mound near the Moon's south pole appears to be a volcanic structure unlike any other found on the lunar surface, according to a new study that used data from the Moon Mineralogy Mapper, which flew aboard India's Chandrayaan-1 spacecraft in 2008.<br /><br /></p>.<p>The formation, known as Mafic Mound, stands about 800 meters tall and 75 kilometres across, smack in the middle of a giant impact crater known as the South Pole-Aitken Basin.<br /><br />The study suggests that the mound is the result of a unique kind of volcanic activity set in motion by the colossal impact that formed the basin.<br /><br />"If the scenarios that we lay out for its formation are correct, it could represent a totally new volcanic process that's never been seen before," said Daniel Moriarty, a PhD student in Brown University's Department of Earth, Environmental and Planetary Sciences and study's lead author.<br /><br />Mafic Mound (mafic is a term for rocks rich in minerals such as pyroxene and olivine) was first discovered in the 1990s by Carle Pieters, a planetary geologist at Brown and Moriarty's adviser.<br /><br />What makes it curious, other than its substantial size, is the fact that it has a different mineralogical composition than the surrounding rock. The mound is rich in high-calcium pyroxene, whereas the surrounding rock is low-calcium.<br /><br />Moriarty and Pieters looked at a rich suite of data from multiple lunar exploration missions. They used detailed mineralogical data from the Moon Mineralogy Mapper, which flew aboard India's Chandrayaan-1 spacecraft.<br /><br />NASA's Lunar Orbiter Laser Altimeter provided precise topographic data, and data from the GRAIL mission characterised gravitational anomalies in the region.<br /><br />Those combined datasets suggested that Mafic Mound was created by one of two unique volcanic processes set in motion by the giant South Pole-Aitken impact.<br /><br />An impact of that size would have created a cauldron of melted rock as much as 50 kilometres deep, some researchers believe.<br /><br />As that sheet of impact melt cooled and crystallised, it would have shrunk. As it did, still-molten material in the middle of the melt sheet may have been squeezed out the top like toothpaste from a tube. Eventually, that erupted material may have formed the mound.<br /><br />Such a process could explain the mound's strange mineralogy. Models of how the South Pole-Aitken melt sheet may have crystallised suggest that the erupting material should be rich in high-calcium pyroxene, which is consistent with the observed mineralogy of the mound.<br /><br />Another scenario that fits the data involves possible melting of the Moon's mantle shortly after the South Pole-Aitken impact. The impact would have blasted tonnes of rock out of the basin, creating a low-gravity region. The research appears in the journal Geophysical Research Letters.</p>
<p>A giant mound near the Moon's south pole appears to be a volcanic structure unlike any other found on the lunar surface, according to a new study that used data from the Moon Mineralogy Mapper, which flew aboard India's Chandrayaan-1 spacecraft in 2008.<br /><br /></p>.<p>The formation, known as Mafic Mound, stands about 800 meters tall and 75 kilometres across, smack in the middle of a giant impact crater known as the South Pole-Aitken Basin.<br /><br />The study suggests that the mound is the result of a unique kind of volcanic activity set in motion by the colossal impact that formed the basin.<br /><br />"If the scenarios that we lay out for its formation are correct, it could represent a totally new volcanic process that's never been seen before," said Daniel Moriarty, a PhD student in Brown University's Department of Earth, Environmental and Planetary Sciences and study's lead author.<br /><br />Mafic Mound (mafic is a term for rocks rich in minerals such as pyroxene and olivine) was first discovered in the 1990s by Carle Pieters, a planetary geologist at Brown and Moriarty's adviser.<br /><br />What makes it curious, other than its substantial size, is the fact that it has a different mineralogical composition than the surrounding rock. The mound is rich in high-calcium pyroxene, whereas the surrounding rock is low-calcium.<br /><br />Moriarty and Pieters looked at a rich suite of data from multiple lunar exploration missions. They used detailed mineralogical data from the Moon Mineralogy Mapper, which flew aboard India's Chandrayaan-1 spacecraft.<br /><br />NASA's Lunar Orbiter Laser Altimeter provided precise topographic data, and data from the GRAIL mission characterised gravitational anomalies in the region.<br /><br />Those combined datasets suggested that Mafic Mound was created by one of two unique volcanic processes set in motion by the giant South Pole-Aitken impact.<br /><br />An impact of that size would have created a cauldron of melted rock as much as 50 kilometres deep, some researchers believe.<br /><br />As that sheet of impact melt cooled and crystallised, it would have shrunk. As it did, still-molten material in the middle of the melt sheet may have been squeezed out the top like toothpaste from a tube. Eventually, that erupted material may have formed the mound.<br /><br />Such a process could explain the mound's strange mineralogy. Models of how the South Pole-Aitken melt sheet may have crystallised suggest that the erupting material should be rich in high-calcium pyroxene, which is consistent with the observed mineralogy of the mound.<br /><br />Another scenario that fits the data involves possible melting of the Moon's mantle shortly after the South Pole-Aitken impact. The impact would have blasted tonnes of rock out of the basin, creating a low-gravity region. The research appears in the journal Geophysical Research Letters.</p>