Icebergs breaking off Antarctica, even massive ones, do not typically concern glaciologists. But the impending birth of a new massive iceberg could be more than business as usual for the frozen continent. The Larsen C ice shelf, the fourth-largest in Antarctica, has attracted worldwide attention in the lead-up to calving an iceberg one-tenth of its area – or about half the area of greater Melbourne. It is still difficult to predict exactly when it will break free.
In the 1970s, scientists subjected newly arrived samples of moon rocks to a barrage of tests. To their surprise, they discovered that some of the rocks were magnetic. When magma cooled and solidified into these rocks, the material had been exposed to a magnetic field. Which was strange because, as far as scientists knew at the time, the moon didn’t have a global magnetic field like the one that envelops Earth, then or ever. But the rocks suggested otherwise, and many studies of the samples since have shown that the moon indeed had a magnetic field billions of years ago, perhaps one as strong as Earth’s today.