Overview
- The peer-reviewed study, published Wednesday in Physical Review Letters, links tiny amounts of iron-60 in Antarctic archives to changes in our local space environment.
- Researchers found iron-60 in recent surface snow but noticeably lower levels in a 40,000–80,000-year-old ice section, indicating less interstellar dust reached Earth during that period.
- The timing matches independent reconstructions that place our entry into the Local Interstellar Cloud more than 40,000 years ago, suggesting the cloud stores debris from past stellar explosions.
- The team melted and chemically treated hundreds of kilograms of ice, then counted individual iron-60 atoms using accelerator mass spectrometry at the Australian National University, with cross-checks to rule out sample loss.
- The low abundance complicates a simple supernova-origin picture for the cloud, and scientists plan to test the timing and source further by measuring deeper, older Antarctic ice.