Apollo astronauts may be garnering another prize from their exploits of more than 3 decades ago. They left seismometers across the face of the moon to probe its interior, but no one had been able to paint a clear picture from the data the sensors collected. Now, two independent groups have reanalyzed the Apollo data using modern but very different techniques, and both teams say they have detected lunar seismologists' prime target: a core of iron that is still molten 4.5 billion years after the moon's formation.
The Apollo seismic experiment was challenging from the start. Moonquakes are sparse and feeble, the moon's impact-shattered crust garbles any seismic signals, and computers of that era couldn't handle the complete data set. Today, computers are faster, and terrestrial seismologists have developed far more powerful analytical techniques, so lunar researchers have taken another crack at the Apollo seismic data, which were recorded by the five sensors and radioed back until the mid-1970s.