Huge mystery blob found under the moon's far side

The South Pole-Aitken basin, shown here in shades of blue, is the oldest and largest known impact basin in the solar system, spanning some 1,550 miles.PUBLISHED June 11, 2019Researchers have discovered something massive lurking underneath the far side of the moon: a mysterious blob with the mass akin to a pile of metal five times the size of the Big Island of Hawaii.The structure, described in a recent study published in Geophysical Research Letters, sits at least 180 miles beneath the South Pole-Aitken basin—a colossal crater punched into the lunar landscape billions of years ago, when the moon's initially molten surface had cooled just enough for impacts to leave a lasting mark.The team discovered the anomalous blob by combining data from NASA's Gravity Recovery and Interior Laboratory, or GRAIL, mission with topography from the Lunar Reconnaissance Orbiter. (Learn more about strange rocks found in the South Pole-Aitken basin that may have come from deep inside the moon.)“It’s the biggest preserved crater that we know of in the solar system,” James says. “The whole time I was reading [the study], I was thinking about all the different ways we can follow up and try to better understand what is causing this mass anomaly that they've found."In addition to spotting the mysterious blob, the new study retraced the boundary of the basin's inner rim, revealing that scientists previously underestimated the crater's size, a potentially important find as NASA and others prepare to send missions to the basin and the nearby lunar south pole.