What breakthrough discovery did Inge Lehmann make?

Women scientists were involved in the discoveries listed in all four answer options: Marjorie Courtenay-Latimer (the coelacanth); Marie Curie (radium and polonium); Nettie Stevens (sex chromosomes). Inge Lehmann (13 May 1888 – 21 February 1993) discovered the nature of the Earth’s core.

Up until the 1930s seismologists believed the Earth’s core to be a single molten sphere; however, they could not explain careful measurements of seismic waves from earthquakes, which were inconsistent with this idea. In 1936 Inge Lehmann, a Danish seismologist and geophysicist, analysed the seismic wave measurements and concluded that Earth must have a solid inner core and a molten outer core to produce seismic waves that matched the measurements. Other seismologists tested and then accepted Lehmann's explanation.

Inge Lehmann received many honours for her outstanding scientific achievements, including the Gordon Wood Award (1960), the Emil Wiechert Medal (1964), the Gold Medal of the Danish Royal Society of Science and Letters (1965), the Tagea Brandt Rejselegat (1938 and 1967), her election as a Fellow of the Royal Society in 1969, the William Bowie Medal (1971, as the first woman), and the Medal of the Seismological Society of America in 1977.

In the year of her death an asteroid was named after her (5632 Ingelehmann). Twelve years later her life’s work was acknowledged by the naming of a beetle species: “Globicornis (Hadrotoma) ingelehmannae”.