The first study, published May 14 in Nature, introduced a sophisticated gravity model of the Moon that captures tiny variations in its gravitational field as it orbits Earth. These fluctuations, caused by the planet's tidal forces, reveal that the Moon undergoes a slight flexing motion known as tidal deformation, providing crucial clues about its deep interior. Using data from NASA's GRAIL (Gravity Recovery and Interior Laboratory) mission, which orbited the Moon from December 2011 to December 2012, the team created the most detailed lunar gravitational map to date, enhancing navigation and timing for future lunar missions.
The second study, appearing in Nature Astronomy on April 23, examined the interior of Vesta, an asteroid in the main belt between Mars and Jupiter. Researchers utilized radiometric data from NASA's Deep Space Network and imaging from the Dawn spacecraft, which orbited Vesta from July 2011 to September 2012, to assess its internal structure. Contrary to earlier theories suggesting a layered composition, the data indicate that Vesta may have a more uniform interior, potentially lacking a distinct iron core.
Lead author Ryan Park, head of the Solar System Dynamics Group at NASA's Jet Propulsion Laboratory, emphasized the importance of gravity studies in revealing planetary interiors. "Gravity is a unique and fundamental property of a planetary body that can be used to explore its deep interior," he said. "Our technique doesn't need data from the surface; we just need to track the motion of the spacecraft very precisely to get a global view of what's inside."
The lunar study also provided fresh evidence supporting the theory that the Moon's near side is more geologically active than its far side. This side, marked by vast, flat plains of solidified lava known as mare, likely contains heat-generating radioactive elements that influence its internal structure. This finding aligns with the hypothesis that the Moon's near side experienced significant volcanic activity billions of years ago, concentrating these elements deep within its mantle.
Meanwhile, the Vesta analysis revealed surprising findings about the asteroid's formation. Unlike Earth, which developed a dense iron core through gravitational settling, Vesta's interior appears more homogeneous, suggesting it either never fully differentiated or re-formed after a catastrophic impact.
Park's team plans to extend this approach to other planetary bodies, including Jupiter's volcanic moon Io, as they refine their understanding of how these worlds evolved over billions of years.
Research Report:Thermal asymmetry in the Moon's mantle inferred from monthly tidal response
Research Report:A small core in Vesta inferred from Dawn's observations
Related Links
Gravity Recovery and Interior Laboratory GRAIL Mission
The Physics of Time and Space
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